// File: @openzeppelin/contracts/math/SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @bancor/token-governance/contracts/IClaimable.sol


pragma solidity 0.6.12;

/// @title Claimable contract interface
interface IClaimable {
    function owner() external view returns (address);

    function transferOwnership(address newOwner) external;

    function acceptOwnership() external;
}

// File: @bancor/token-governance/contracts/IMintableToken.sol


pragma solidity 0.6.12;



/// @title Mintable Token interface
interface IMintableToken is IERC20, IClaimable {
    function issue(address to, uint256 amount) external;

    function destroy(address from, uint256 amount) external;
}

// File: @bancor/token-governance/contracts/ITokenGovernance.sol


pragma solidity 0.6.12;


/// @title The interface for mintable/burnable token governance.
interface ITokenGovernance {
    // The address of the mintable ERC20 token.
    function token() external view returns (IMintableToken);

    /// @dev Mints new tokens.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external;

    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external;
}

// File: solidity/contracts/utility/interfaces/ICheckpointStore.sol


pragma solidity 0.6.12;

/**
 * @dev Checkpoint store contract interface
 */
interface ICheckpointStore {
    function addCheckpoint(address _address) external;

    function addPastCheckpoint(address _address, uint256 _time) external;

    function addPastCheckpoints(address[] calldata _addresses, uint256[] calldata _times) external;

    function checkpoint(address _address) external view returns (uint256);
}

// File: solidity/contracts/utility/MathEx.sol


pragma solidity 0.6.12;

/**
 * @dev This library provides a set of complex math operations.
 */
library MathEx {
    uint256 private constant MAX_EXP_BIT_LEN = 4;
    uint256 private constant MAX_EXP = 2**MAX_EXP_BIT_LEN - 1;
    uint256 private constant MAX_UINT128 = 2**128 - 1;

    /**
     * @dev returns the largest integer smaller than or equal to the square root of a positive integer
     *
     * @param _num a positive integer
     *
     * @return the largest integer smaller than or equal to the square root of the positive integer
     */
    function floorSqrt(uint256 _num) internal pure returns (uint256) {
        uint256 x = _num / 2 + 1;
        uint256 y = (x + _num / x) / 2;
        while (x > y) {
            x = y;
            y = (x + _num / x) / 2;
        }
        return x;
    }

    /**
     * @dev returns the smallest integer larger than or equal to the square root of a positive integer
     *
     * @param _num a positive integer
     *
     * @return the smallest integer larger than or equal to the square root of the positive integer
     */
    function ceilSqrt(uint256 _num) internal pure returns (uint256) {
        uint256 x = floorSqrt(_num);
        return x * x == _num ? x : x + 1;
    }

    /**
     * @dev computes a powered ratio
     *
     * @param _n   ratio numerator
     * @param _d   ratio denominator
     * @param _exp ratio exponent
     *
     * @return powered ratio's numerator and denominator
     */
    function poweredRatio(
        uint256 _n,
        uint256 _d,
        uint256 _exp
    ) internal pure returns (uint256, uint256) {
        require(_exp <= MAX_EXP, "ERR_EXP_TOO_LARGE");

        uint256[MAX_EXP_BIT_LEN] memory ns;
        uint256[MAX_EXP_BIT_LEN] memory ds;

        (ns[0], ds[0]) = reducedRatio(_n, _d, MAX_UINT128);
        for (uint256 i = 0; (_exp >> i) > 1; i++) {
            (ns[i + 1], ds[i + 1]) = reducedRatio(ns[i] ** 2, ds[i] ** 2, MAX_UINT128);
        }

        uint256 n = 1;
        uint256 d = 1;

        for (uint256 i = 0; (_exp >> i) > 0; i++) {
            if (((_exp >> i) & 1) > 0) {
                (n, d) = reducedRatio(n * ns[i], d * ds[i], MAX_UINT128);
            }
        }

        return (n, d);
    }

    /**
     * @dev computes a reduced-scalar ratio
     *
     * @param _n   ratio numerator
     * @param _d   ratio denominator
     * @param _max maximum desired scalar
     *
     * @return ratio's numerator and denominator
     */
    function reducedRatio(
        uint256 _n,
        uint256 _d,
        uint256 _max
    ) internal pure returns (uint256, uint256) {
        (uint256 n, uint256 d) = (_n, _d);
        if (n > _max || d > _max) {
            (n, d) = normalizedRatio(n, d, _max);
        }
        if (n != d) {
            return (n, d);
        }
        return (1, 1);
    }

    /**
     * @dev computes "scale * a / (a + b)" and "scale * b / (a + b)".
     */
    function normalizedRatio(
        uint256 _a,
        uint256 _b,
        uint256 _scale
    ) internal pure returns (uint256, uint256) {
        if (_a <= _b) {
            return accurateRatio(_a, _b, _scale);
        }
        (uint256 y, uint256 x) = accurateRatio(_b, _a, _scale);
        return (x, y);
    }

    /**
     * @dev computes "scale * a / (a + b)" and "scale * b / (a + b)", assuming that "a <= b".
     */
    function accurateRatio(
        uint256 _a,
        uint256 _b,
        uint256 _scale
    ) internal pure returns (uint256, uint256) {
        uint256 maxVal = uint256(-1) / _scale;
        if (_a > maxVal) {
            uint256 c = _a / (maxVal + 1) + 1;
            _a /= c; // we can now safely compute `_a * _scale`
            _b /= c;
        }
        if (_a != _b) {
            uint256 n = _a * _scale;
            uint256 d = _a + _b; // can overflow
            if (d >= _a) {
                // no overflow in `_a + _b`
                uint256 x = roundDiv(n, d); // we can now safely compute `_scale - x`
                uint256 y = _scale - x;
                return (x, y);
            }
            if (n < _b - (_b - _a) / 2) {
                return (0, _scale); // `_a * _scale < (_a + _b) / 2 < MAX_UINT256 < _a + _b`
            }
            return (1, _scale - 1); // `(_a + _b) / 2 < _a * _scale < MAX_UINT256 < _a + _b`
        }
        return (_scale / 2, _scale / 2); // allow reduction to `(1, 1)` in the calling function
    }

    /**
     * @dev computes the nearest integer to a given quotient without overflowing or underflowing.
     */
    function roundDiv(uint256 _n, uint256 _d) internal pure returns (uint256) {
        return _n / _d + (_n % _d) / (_d - _d / 2);
    }

    /**
     * @dev returns the average number of decimal digits in a given list of positive integers
     *
     * @param _values  list of positive integers
     *
     * @return the average number of decimal digits in the given list of positive integers
     */
    function geometricMean(uint256[] memory _values) internal pure returns (uint256) {
        uint256 numOfDigits = 0;
        uint256 length = _values.length;
        for (uint256 i = 0; i < length; i++) {
            numOfDigits += decimalLength(_values[i]);
        }
        return uint256(10)**(roundDivUnsafe(numOfDigits, length) - 1);
    }

    /**
     * @dev returns the number of decimal digits in a given positive integer
     *
     * @param _x   positive integer
     *
     * @return the number of decimal digits in the given positive integer
     */
    function decimalLength(uint256 _x) internal pure returns (uint256) {
        uint256 y = 0;
        for (uint256 x = _x; x > 0; x /= 10) {
            y++;
        }
        return y;
    }

    /**
     * @dev returns the nearest integer to a given quotient
     * the computation is overflow-safe assuming that the input is sufficiently small
     *
     * @param _n   quotient numerator
     * @param _d   quotient denominator
     *
     * @return the nearest integer to the given quotient
     */
    function roundDivUnsafe(uint256 _n, uint256 _d) internal pure returns (uint256) {
        return (_n + _d / 2) / _d;
    }

    /**
     * @dev returns the larger of two values
     *
     * @param _val1 the first value
     * @param _val2 the second value
     */
    function max(uint256 _val1, uint256 _val2) internal pure returns (uint256) {
        return _val1 > _val2 ? _val1 : _val2;
    }
}

// File: solidity/contracts/utility/ReentrancyGuard.sol


pragma solidity 0.6.12;

/**
 * @dev This contract provides protection against calling a function
 * (directly or indirectly) from within itself.
 */
contract ReentrancyGuard {
    uint256 private constant UNLOCKED = 1;
    uint256 private constant LOCKED = 2;

    // LOCKED while protected code is being executed, UNLOCKED otherwise
    uint256 private state = UNLOCKED;

    /**
     * @dev ensures instantiation only by sub-contracts
     */
    constructor() internal {}

    // protects a function against reentrancy attacks
    modifier protected() {
        _protected();
        state = LOCKED;
        _;
        state = UNLOCKED;
    }

    // error message binary size optimization
    function _protected() internal view {
        require(state == UNLOCKED, "ERR_REENTRANCY");
    }
}

// File: solidity/contracts/utility/Types.sol


pragma solidity 0.6.12;

/**
 * @dev This contract provides types which can be used by various contracts.
 */

struct Fraction {
    uint256 n; // numerator
    uint256 d; // denominator
}

// File: solidity/contracts/utility/Time.sol


pragma solidity 0.6.12;

/*
    Time implementing contract
*/
contract Time {
    /**
     * @dev returns the current time
     */
    function time() internal view virtual returns (uint256) {
        return block.timestamp;
    }
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;


/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    uint32 internal constant PPM_RESOLUTION = 1000000;

    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // ensures that the portion is valid
    modifier validPortion(uint32 _portion) {
        _validPortion(_portion);
        _;
    }

    // error message binary size optimization
    function _validPortion(uint32 _portion) internal pure {
        require(_portion > 0 && _portion <= PPM_RESOLUTION, "ERR_INVALID_PORTION");
    }

    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address _address) {
        _validExternalAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validExternalAddress(address _address) internal view {
        require(_address != address(0) && _address != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }

    // ensures that the fee is valid
    modifier validFee(uint32 fee) {
        _validFee(fee);
        _;
    }

    // error message binary size optimization
    function _validFee(uint32 fee) internal pure {
        require(fee <= PPM_RESOLUTION, "ERR_INVALID_FEE");
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
 * @dev This contract provides support and utilities for contract ownership.
 */
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
     * @dev triggered when the owner is updated
     *
     * @param _prevOwner previous owner
     * @param _newOwner  new owner
     */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
     * @dev initializes a new Owned instance
     */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
     * @dev allows transferring the contract ownership
     * the new owner still needs to accept the transfer
     * can only be called by the contract owner
     *
     * @param _newOwner    new contract owner
     */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
     * @dev used by a new owner to accept an ownership transfer
     */
    function acceptOwnership() public override {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20 {
    function issue(address _to, uint256 _amount) external;

    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/token/interfaces/IReserveToken.sol


pragma solidity 0.6.12;

/**
 * @dev This contract is used to represent reserve tokens, which are tokens that can either be regular ERC20 tokens or
 * native ETH (represented by the NATIVE_TOKEN_ADDRESS address)
 *
 * Please note that this interface is intentionally doesn't inherit from IERC20, so that it'd be possible to effectively
 * override its balanceOf() function in the ReserveToken library
 */
interface IReserveToken {

}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



pragma solidity >=0.6.0 <0.8.0;




/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: solidity/contracts/token/SafeERC20Ex.sol


pragma solidity 0.6.12;


/**
 * @dev Extends the SafeERC20 library with additional operations
 */
library SafeERC20Ex {
    using SafeERC20 for IERC20;

    /**
     * @dev ensures that the spender has sufficient allowance
     *
     * @param token the address of the token to ensure
     * @param spender the address allowed to spend
     * @param amount the allowed amount to spend
     */
    function ensureApprove(
        IERC20 token,
        address spender,
        uint256 amount
    ) internal {
        if (amount == 0) {
            return;
        }

        uint256 allowance = token.allowance(address(this), spender);
        if (allowance >= amount) {
            return;
        }

        if (allowance > 0) {
            token.safeApprove(spender, 0);
        }
        token.safeApprove(spender, amount);
    }
}

// File: solidity/contracts/token/ReserveToken.sol


pragma solidity 0.6.12;




/**
 * @dev This library implements ERC20 and SafeERC20 utilities for reserve tokens, which can be either ERC20 tokens or ETH
 */
library ReserveToken {
    using SafeERC20 for IERC20;
    using SafeERC20Ex for IERC20;

    // the address that represents an ETH reserve
    IReserveToken public constant NATIVE_TOKEN_ADDRESS = IReserveToken(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);

    /**
     * @dev returns whether the provided token represents an ERC20 or ETH reserve
     *
     * @param reserveToken the address of the reserve token
     *
     * @return whether the provided token represents an ERC20 or ETH reserve
     */
    function isNativeToken(IReserveToken reserveToken) internal pure returns (bool) {
        return reserveToken == NATIVE_TOKEN_ADDRESS;
    }

    /**
     * @dev returns the balance of the reserve token
     *
     * @param reserveToken the address of the reserve token
     * @param account the address of the account to check
     *
     * @return the balance of the reserve token
     */
    function balanceOf(IReserveToken reserveToken, address account) internal view returns (uint256) {
        if (isNativeToken(reserveToken)) {
            return account.balance;
        }

        return toIERC20(reserveToken).balanceOf(account);
    }

    /**
     * @dev transfers a specific amount of the reserve token
     *
     * @param reserveToken the address of the reserve token
     * @param to the destination address to transfer the amount to
     * @param amount the amount to transfer
     */
    function safeTransfer(
        IReserveToken reserveToken,
        address to,
        uint256 amount
    ) internal {
        if (amount == 0) {
            return;
        }

        if (isNativeToken(reserveToken)) {
            payable(to).transfer(amount);
        } else {
            toIERC20(reserveToken).safeTransfer(to, amount);
        }
    }

    /**
     * @dev transfers a specific amount of the reserve token from a specific holder using the allowance mechanism
     * this function ignores a reserve token which represents an ETH reserve
     *
     * @param reserveToken the address of the reserve token
     * @param from the source address to transfer the amount from
     * @param to the destination address to transfer the amount to
     * @param amount the amount to transfer
     */
    function safeTransferFrom(
        IReserveToken reserveToken,
        address from,
        address to,
        uint256 amount
    ) internal {
        if (amount == 0 || isNativeToken(reserveToken)) {
            return;
        }

        toIERC20(reserveToken).safeTransferFrom(from, to, amount);
    }

    /**
     * @dev ensures that the spender has sufficient allowance
     * this function ignores a reserve token which represents an ETH reserve
     *
     * @param reserveToken the address of the reserve token
     * @param spender the address allowed to spend
     * @param amount the allowed amount to spend
     */
    function ensureApprove(
        IReserveToken reserveToken,
        address spender,
        uint256 amount
    ) internal {
        if (isNativeToken(reserveToken)) {
            return;
        }

        toIERC20(reserveToken).ensureApprove(spender, amount);
    }

    /**
     * @dev utility function that converts an IReserveToken to an IERC20
     *
     * @param reserveToken the address of the reserve token
     *
     * @return an IERC20
     */
    function toIERC20(IReserveToken reserveToken) private pure returns (IERC20) {
        return IERC20(address(reserveToken));
    }
}

// File: solidity/contracts/converter/interfaces/IConverter.sol


pragma solidity 0.6.12;





/*
    Converter interface
*/
interface IConverter is IOwned {
    function converterType() external pure returns (uint16);

    function anchor() external view returns (IConverterAnchor);

    function isActive() external view returns (bool);

    function targetAmountAndFee(
        IReserveToken _sourceToken,
        IReserveToken _targetToken,
        uint256 _amount
    ) external view returns (uint256, uint256);

    function convert(
        IReserveToken _sourceToken,
        IReserveToken _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) external payable returns (uint256);

    function conversionFee() external view returns (uint32);

    function maxConversionFee() external view returns (uint32);

    function reserveBalance(IReserveToken _reserveToken) external view returns (uint256);

    receive() external payable;

    function transferAnchorOwnership(address _newOwner) external;

    function acceptAnchorOwnership() external;

    function setConversionFee(uint32 _conversionFee) external;

    function addReserve(IReserveToken _token, uint32 _weight) external;

    function transferReservesOnUpgrade(address _newConverter) external;

    function onUpgradeComplete() external;

    // deprecated, backward compatibility
    function token() external view returns (IConverterAnchor);

    function transferTokenOwnership(address _newOwner) external;

    function acceptTokenOwnership() external;

    function connectors(IReserveToken _address)
        external
        view
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        );

    function getConnectorBalance(IReserveToken _connectorToken) external view returns (uint256);

    function connectorTokens(uint256 _index) external view returns (IReserveToken);

    function connectorTokenCount() external view returns (uint16);

    /**
     * @dev triggered when the converter is activated
     *
     * @param _type        converter type
     * @param _anchor      converter anchor
     * @param _activated   true if the converter was activated, false if it was deactivated
     */
    event Activation(uint16 indexed _type, IConverterAnchor indexed _anchor, bool indexed _activated);

    /**
     * @dev triggered when a conversion between two tokens occurs
     *
     * @param _fromToken       source reserve token
     * @param _toToken         target reserve token
     * @param _trader          wallet that initiated the trade
     * @param _amount          input amount in units of the source token
     * @param _return          output amount minus conversion fee in units of the target token
     * @param _conversionFee   conversion fee in units of the target token
     */
    event Conversion(
        IReserveToken indexed _fromToken,
        IReserveToken indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );

    /**
     * @dev triggered when the rate between two tokens in the converter changes
     * note that the event might be dispatched for rate updates between any two tokens in the converter
     *
     * @param  _token1 address of the first token
     * @param  _token2 address of the second token
     * @param  _rateN  rate of 1 unit of `_token1` in `_token2` (numerator)
     * @param  _rateD  rate of 1 unit of `_token1` in `_token2` (denominator)
     */
    event TokenRateUpdate(address indexed _token1, address indexed _token2, uint256 _rateN, uint256 _rateD);

    /**
     * @dev triggered when the conversion fee is updated
     *
     * @param  _prevFee    previous fee percentage, represented in ppm
     * @param  _newFee     new fee percentage, represented in ppm
     */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);
}

// File: solidity/contracts/converter/interfaces/IConverterRegistry.sol


pragma solidity 0.6.12;



interface IConverterRegistry {
    function getAnchorCount() external view returns (uint256);

    function getAnchors() external view returns (address[] memory);

    function getAnchor(uint256 _index) external view returns (IConverterAnchor);

    function isAnchor(address _value) external view returns (bool);

    function getLiquidityPoolCount() external view returns (uint256);

    function getLiquidityPools() external view returns (address[] memory);

    function getLiquidityPool(uint256 _index) external view returns (IConverterAnchor);

    function isLiquidityPool(address _value) external view returns (bool);

    function getConvertibleTokenCount() external view returns (uint256);

    function getConvertibleTokens() external view returns (address[] memory);

    function getConvertibleToken(uint256 _index) external view returns (IReserveToken);

    function isConvertibleToken(address _value) external view returns (bool);

    function getConvertibleTokenAnchorCount(IReserveToken _convertibleToken) external view returns (uint256);

    function getConvertibleTokenAnchors(IReserveToken _convertibleToken) external view returns (address[] memory);

    function getConvertibleTokenAnchor(IReserveToken _convertibleToken, uint256 _index)
        external
        view
        returns (IConverterAnchor);

    function isConvertibleTokenAnchor(IReserveToken _convertibleToken, address _value) external view returns (bool);

    function getLiquidityPoolByConfig(
        uint16 _type,
        IReserveToken[] memory _reserveTokens,
        uint32[] memory _reserveWeights
    ) external view returns (IConverterAnchor);
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionStore.sol


pragma solidity 0.6.12;





/*
    Liquidity Protection Store interface
*/
interface ILiquidityProtectionStore is IOwned {
    function withdrawTokens(
        IReserveToken _token,
        address _to,
        uint256 _amount
    ) external;

    function protectedLiquidity(uint256 _id)
        external
        view
        returns (
            address,
            IDSToken,
            IReserveToken,
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        );

    function addProtectedLiquidity(
        address _provider,
        IDSToken _poolToken,
        IReserveToken _reserveToken,
        uint256 _poolAmount,
        uint256 _reserveAmount,
        uint256 _reserveRateN,
        uint256 _reserveRateD,
        uint256 _timestamp
    ) external returns (uint256);

    function updateProtectedLiquidityAmounts(
        uint256 _id,
        uint256 _poolNewAmount,
        uint256 _reserveNewAmount
    ) external;

    function removeProtectedLiquidity(uint256 _id) external;

    function lockedBalance(address _provider, uint256 _index) external view returns (uint256, uint256);

    function lockedBalanceRange(
        address _provider,
        uint256 _startIndex,
        uint256 _endIndex
    ) external view returns (uint256[] memory, uint256[] memory);

    function addLockedBalance(
        address _provider,
        uint256 _reserveAmount,
        uint256 _expirationTime
    ) external returns (uint256);

    function removeLockedBalance(address _provider, uint256 _index) external;

    function systemBalance(IReserveToken _poolToken) external view returns (uint256);

    function incSystemBalance(IReserveToken _poolToken, uint256 _poolAmount) external;

    function decSystemBalance(IReserveToken _poolToken, uint256 _poolAmount) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionStats.sol


pragma solidity 0.6.12;




/*
    Liquidity Protection Stats interface
*/
interface ILiquidityProtectionStats {
    function increaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function decreaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function addProviderPool(address provider, IDSToken poolToken) external returns (bool);

    function removeProviderPool(address provider, IDSToken poolToken) external returns (bool);

    function totalPoolAmount(IDSToken poolToken) external view returns (uint256);

    function totalReserveAmount(IDSToken poolToken, IReserveToken reserveToken) external view returns (uint256);

    function totalProviderAmount(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view returns (uint256);

    function providerPools(address provider) external view returns (IDSToken[] memory);
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProvisionEventsSubscriber.sol


pragma solidity 0.6.12;



/**
 * @dev Liquidity provision events subscriber interface
 */
interface ILiquidityProvisionEventsSubscriber {
    function onAddingLiquidity(
        address provider,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function onRemovingLiquidity(
        uint256 id,
        address provider,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionSettings.sol


pragma solidity 0.6.12;




/*
    Liquidity Protection Store Settings interface
*/
interface ILiquidityProtectionSettings {
    function isPoolWhitelisted(IConverterAnchor poolAnchor) external view returns (bool);

    function poolWhitelist() external view returns (address[] memory);

    function subscribers() external view returns (address[] memory);

    function isPoolSupported(IConverterAnchor poolAnchor) external view returns (bool);

    function minNetworkTokenLiquidityForMinting() external view returns (uint256);

    function defaultNetworkTokenMintingLimit() external view returns (uint256);

    function networkTokenMintingLimits(IConverterAnchor poolAnchor) external view returns (uint256);

    function addLiquidityDisabled(IConverterAnchor poolAnchor, IReserveToken reserveToken) external view returns (bool);

    function minProtectionDelay() external view returns (uint256);

    function maxProtectionDelay() external view returns (uint256);

    function minNetworkCompensation() external view returns (uint256);

    function lockDuration() external view returns (uint256);

    function averageRateMaxDeviation() external view returns (uint32);
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionSystemStore.sol


pragma solidity 0.6.12;



/*
    Liquidity Protection System Store interface
*/
interface ILiquidityProtectionSystemStore {
    function systemBalance(IERC20 poolToken) external view returns (uint256);

    function incSystemBalance(IERC20 poolToken, uint256 poolAmount) external;

    function decSystemBalance(IERC20 poolToken, uint256 poolAmount) external;

    function networkTokensMinted(IConverterAnchor poolAnchor) external view returns (uint256);

    function incNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;

    function decNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ITransferPositionCallback.sol


pragma solidity 0.6.12;

/**
 * @dev Transfer position event callback interface
 */
interface ITransferPositionCallback {
    function onTransferPosition(
        uint256 newId,
        address provider,
        bytes calldata data
    ) external;
}

// File: solidity/contracts/utility/interfaces/ITokenHolder.sol


pragma solidity 0.6.12;



/*
    Token Holder interface
*/
interface ITokenHolder is IOwned {
    receive() external payable;

    function withdrawTokens(
        IReserveToken reserveToken,
        address payable to,
        uint256 amount
    ) external;

    function withdrawTokensMultiple(
        IReserveToken[] calldata reserveTokens,
        address payable to,
        uint256[] calldata amounts
    ) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtection.sol


pragma solidity 0.6.12;









/*
    Liquidity Protection interface
*/
interface ILiquidityProtection {
    function store() external view returns (ILiquidityProtectionStore);

    function stats() external view returns (ILiquidityProtectionStats);

    function settings() external view returns (ILiquidityProtectionSettings);

    function systemStore() external view returns (ILiquidityProtectionSystemStore);

    function wallet() external view returns (ITokenHolder);

    function addLiquidityFor(
        address owner,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    ) external payable returns (uint256);

    function addLiquidity(
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    ) external payable returns (uint256);

    function removeLiquidity(uint256 id, uint32 portion) external;

    function transferPosition(uint256 id, address newProvider) external returns (uint256);

    function transferPositionAndNotify(
        uint256 id,
        address newProvider,
        ITransferPositionCallback callback,
        bytes calldata data
    ) external returns (uint256);
}

// File: solidity/contracts/liquidity-protection/LiquidityProtection.sol


pragma solidity 0.6.12;

















interface ILiquidityPoolConverter is IConverter {
    function addLiquidity(
        IReserveToken[] memory reserveTokens,
        uint256[] memory reserveAmounts,
        uint256 _minReturn
    ) external payable;

    function removeLiquidity(
        uint256 amount,
        IReserveToken[] memory reserveTokens,
        uint256[] memory _reserveMinReturnAmounts
    ) external;

    function recentAverageRate(IReserveToken reserveToken) external view returns (uint256, uint256);
}

/**
 * @dev This contract implements the liquidity protection mechanism.
 */
contract LiquidityProtection is ILiquidityProtection, Utils, Owned, ReentrancyGuard, Time {
    using SafeMath for uint256;
    using ReserveToken for IReserveToken;
    using SafeERC20 for IERC20;
    using SafeERC20 for IDSToken;
    using SafeERC20Ex for IERC20;
    using MathEx for *;

    struct Position {
        address provider; // liquidity provider
        IDSToken poolToken; // pool token address
        IReserveToken reserveToken; // reserve token address
        uint256 poolAmount; // pool token amount
        uint256 reserveAmount; // reserve token amount
        uint256 reserveRateN; // rate of 1 protected reserve token in units of the other reserve token (numerator)
        uint256 reserveRateD; // rate of 1 protected reserve token in units of the other reserve token (denominator)
        uint256 timestamp; // timestamp
    }

    // various rates between the two reserve tokens. the rate is of 1 unit of the protected reserve token in units of the other reserve token
    struct PackedRates {
        uint128 addSpotRateN; // spot rate of 1 A in units of B when liquidity was added (numerator)
        uint128 addSpotRateD; // spot rate of 1 A in units of B when liquidity was added (denominator)
        uint128 removeSpotRateN; // spot rate of 1 A in units of B when liquidity is removed (numerator)
        uint128 removeSpotRateD; // spot rate of 1 A in units of B when liquidity is removed (denominator)
        uint128 removeAverageRateN; // average rate of 1 A in units of B when liquidity is removed (numerator)
        uint128 removeAverageRateD; // average rate of 1 A in units of B when liquidity is removed (denominator)
    }

    uint256 internal constant MAX_UINT128 = 2**128 - 1;
    uint256 internal constant MAX_UINT256 = uint256(-1);

    ILiquidityProtectionSettings private immutable _settings;
    ILiquidityProtectionStore private immutable _store;
    ILiquidityProtectionStats private immutable _stats;
    ILiquidityProtectionSystemStore private immutable _systemStore;
    ITokenHolder private immutable _wallet;
    IERC20 private immutable _networkToken;
    ITokenGovernance private immutable _networkTokenGovernance;
    IERC20 private immutable _govToken;
    ITokenGovernance private immutable _govTokenGovernance;
    ICheckpointStore private immutable _lastRemoveCheckpointStore;

    /**
     * @dev initializes a new LiquidityProtection contract
     *
     * @param settings liquidity protection settings
     * @param store liquidity protection store
     * @param stats liquidity protection stats
     * @param systemStore liquidity protection system store
     * @param wallet liquidity protection wallet
     * @param networkTokenGovernance network token governance
     * @param govTokenGovernance governance token governance
     * @param lastRemoveCheckpointStore last liquidity removal/unprotection checkpoints store
     */
    constructor(
        ILiquidityProtectionSettings settings,
        ILiquidityProtectionStore store,
        ILiquidityProtectionStats stats,
        ILiquidityProtectionSystemStore systemStore,
        ITokenHolder wallet,
        ITokenGovernance networkTokenGovernance,
        ITokenGovernance govTokenGovernance,
        ICheckpointStore lastRemoveCheckpointStore
    )
        public
        validAddress(address(settings))
        validAddress(address(store))
        validAddress(address(stats))
        validAddress(address(systemStore))
        validAddress(address(wallet))
        validAddress(address(lastRemoveCheckpointStore))
    {
        _settings = settings;
        _store = store;
        _stats = stats;
        _systemStore = systemStore;
        _wallet = wallet;
        _networkTokenGovernance = networkTokenGovernance;
        _govTokenGovernance = govTokenGovernance;
        _lastRemoveCheckpointStore = lastRemoveCheckpointStore;

        _networkToken = networkTokenGovernance.token();
        _govToken = govTokenGovernance.token();
    }

    // ensures that the pool is supported and whitelisted
    modifier poolSupportedAndWhitelisted(IConverterAnchor poolAnchor) {
        _poolSupported(poolAnchor);
        _poolWhitelisted(poolAnchor);

        _;
    }

    // ensures that add liquidity is enabled
    modifier addLiquidityEnabled(IConverterAnchor poolAnchor, IReserveToken reserveToken) {
        _addLiquidityEnabled(poolAnchor, reserveToken);

        _;
    }

    // error message binary size optimization
    function _poolSupported(IConverterAnchor poolAnchor) internal view {
        require(_settings.isPoolSupported(poolAnchor), "ERR_POOL_NOT_SUPPORTED");
    }

    // error message binary size optimization
    function _poolWhitelisted(IConverterAnchor poolAnchor) internal view {
        require(_settings.isPoolWhitelisted(poolAnchor), "ERR_POOL_NOT_WHITELISTED");
    }

    // error message binary size optimization
    function _addLiquidityEnabled(IConverterAnchor poolAnchor, IReserveToken reserveToken) internal view {
        require(!_settings.addLiquidityDisabled(poolAnchor, reserveToken), "ERR_ADD_LIQUIDITY_DISABLED");
    }

    // error message binary size optimization
    function verifyEthAmount(uint256 value) internal view {
        require(msg.value == value, "ERR_ETH_AMOUNT_MISMATCH");
    }

    /**
     * @dev returns the LP store
     *
     * @return the LP store
     */
    function store() external view override returns (ILiquidityProtectionStore) {
        return _store;
    }

    /**
     * @dev returns the LP stats
     *
     * @return the LP stats
     */
    function stats() external view override returns (ILiquidityProtectionStats) {
        return _stats;
    }

    /**
     * @dev returns the LP settings
     *
     * @return the LP settings
     */
    function settings() external view override returns (ILiquidityProtectionSettings) {
        return _settings;
    }

    /**
     * @dev returns the LP system store
     *
     * @return the LP system store
     */
    function systemStore() external view override returns (ILiquidityProtectionSystemStore) {
        return _systemStore;
    }

    /**
     * @dev returns the LP wallet
     *
     * @return the LP wallet
     */
    function wallet() external view override returns (ITokenHolder) {
        return _wallet;
    }

    /**
     * @dev accept ETH
     */
    receive() external payable {}

    /**
     * @dev transfers the ownership of the store
     * can only be called by the contract owner
     *
     * @param newOwner the new owner of the store
     */
    function transferStoreOwnership(address newOwner) external ownerOnly {
        _store.transferOwnership(newOwner);
    }

    /**
     * @dev accepts the ownership of the store
     * can only be called by the contract owner
     */
    function acceptStoreOwnership() external ownerOnly {
        _store.acceptOwnership();
    }

    /**
     * @dev transfers the ownership of the wallet
     * can only be called by the contract owner
     *
     * @param newOwner the new owner of the wallet
     */
    function transferWalletOwnership(address newOwner) external ownerOnly {
        _wallet.transferOwnership(newOwner);
    }

    /**
     * @dev accepts the ownership of the wallet
     * can only be called by the contract owner
     */
    function acceptWalletOwnership() external ownerOnly {
        _wallet.acceptOwnership();
    }

    /**
     * @dev adds protected liquidity to a pool for a specific recipient
     * also mints new governance tokens for the caller if the caller adds network tokens
     *
     * @param owner position owner
     * @param poolAnchor anchor of the pool
     * @param reserveToken reserve token to add to the pool
     * @param amount amount of tokens to add to the pool
     *
     * @return new position id
     */
    function addLiquidityFor(
        address owner,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    )
        external
        payable
        override
        protected
        validAddress(owner)
        poolSupportedAndWhitelisted(poolAnchor)
        addLiquidityEnabled(poolAnchor, reserveToken)
        greaterThanZero(amount)
        returns (uint256)
    {
        return addLiquidity(owner, poolAnchor, reserveToken, amount);
    }

    /**
     * @dev adds protected liquidity to a pool
     * also mints new governance tokens for the caller if the caller adds network tokens
     *
     * @param poolAnchor anchor of the pool
     * @param reserveToken reserve token to add to the pool
     * @param amount amount of tokens to add to the pool
     *
     * @return new position id
     */
    function addLiquidity(
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    )
        external
        payable
        override
        protected
        poolSupportedAndWhitelisted(poolAnchor)
        addLiquidityEnabled(poolAnchor, reserveToken)
        greaterThanZero(amount)
        returns (uint256)
    {
        return addLiquidity(msg.sender, poolAnchor, reserveToken, amount);
    }

    /**
     * @dev adds protected liquidity to a pool for a specific recipient
     * also mints new governance tokens for the caller if the caller adds network tokens
     *
     * @param owner position owner
     * @param poolAnchor anchor of the pool
     * @param reserveToken reserve token to add to the pool
     * @param amount amount of tokens to add to the pool
     *
     * @return new position id
     */
    function addLiquidity(
        address owner,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    ) private returns (uint256) {
        if (isNetworkToken(reserveToken)) {
            verifyEthAmount(0);
            return addNetworkTokenLiquidity(owner, poolAnchor, amount);
        }

        // verify that ETH was passed with the call if needed
        verifyEthAmount(reserveToken.isNativeToken() ? amount : 0);
        return addBaseTokenLiquidity(owner, poolAnchor, reserveToken, amount);
    }

    /**
     * @dev adds network token liquidity to a pool
     * also mints new governance tokens for the caller
     *
     * @param owner position owner
     * @param poolAnchor anchor of the pool
     * @param amount amount of tokens to add to the pool
     *
     * @return new position id
     */
    function addNetworkTokenLiquidity(
        address owner,
        IConverterAnchor poolAnchor,
        uint256 amount
    ) internal returns (uint256) {
        IDSToken poolToken = IDSToken(address(poolAnchor));
        IReserveToken networkToken = IReserveToken(address(_networkToken));

        // get the rate between the pool token and the reserve
        Fraction memory poolRate = poolTokenRate(poolToken, networkToken);

        // calculate the amount of pool tokens based on the amount of reserve tokens
        uint256 poolTokenAmount = amount.mul(poolRate.d).div(poolRate.n);

        // remove the pool tokens from the system's ownership (will revert if not enough tokens are available)
        _systemStore.decSystemBalance(poolToken, poolTokenAmount);

        // add the position for the recipient
        uint256 id = addPosition(owner, poolToken, networkToken, poolTokenAmount, amount, time());

        // burns the network tokens from the caller. we need to transfer the tokens to the contract itself, since only
        // token holders can burn their tokens
        _networkToken.safeTransferFrom(msg.sender, address(this), amount);
        burnNetworkTokens(poolAnchor, amount);

        // mint governance tokens to the recipient
        _govTokenGovernance.mint(owner, amount);

        return id;
    }

    /**
     * @dev adds base token liquidity to a pool
     *
     * @param owner position owner
     * @param poolAnchor anchor of the pool
     * @param baseToken the base reserve token of the pool
     * @param amount amount of tokens to add to the pool
     *
     * @return new position id
     */
    function addBaseTokenLiquidity(
        address owner,
        IConverterAnchor poolAnchor,
        IReserveToken baseToken,
        uint256 amount
    ) internal returns (uint256) {
        IDSToken poolToken = IDSToken(address(poolAnchor));
        IReserveToken networkToken = IReserveToken(address(_networkToken));

        // get the reserve balances
        ILiquidityPoolConverter converter = ILiquidityPoolConverter(payable(ownedBy(poolAnchor)));
        (uint256 reserveBalanceBase, uint256 reserveBalanceNetwork) =
            converterReserveBalances(converter, baseToken, networkToken);

        require(reserveBalanceNetwork >= _settings.minNetworkTokenLiquidityForMinting(), "ERR_NOT_ENOUGH_LIQUIDITY");

        // calculate and mint the required amount of network tokens for adding liquidity
        uint256 newNetworkLiquidityAmount = amount.mul(reserveBalanceNetwork).div(reserveBalanceBase);

        // verify network token minting limit
        uint256 mintingLimit = _settings.networkTokenMintingLimits(poolAnchor);
        if (mintingLimit == 0) {
            mintingLimit = _settings.defaultNetworkTokenMintingLimit();
        }

        uint256 newNetworkTokensMinted = _systemStore.networkTokensMinted(poolAnchor).add(newNetworkLiquidityAmount);
        require(newNetworkTokensMinted <= mintingLimit, "ERR_MAX_AMOUNT_REACHED");

        // issue new network tokens to the system
        mintNetworkTokens(address(this), poolAnchor, newNetworkLiquidityAmount);

        // transfer the base tokens from the caller and approve the converter
        networkToken.ensureApprove(address(converter), newNetworkLiquidityAmount);

        if (!baseToken.isNativeToken()) {
            baseToken.safeTransferFrom(msg.sender, address(this), amount);
            baseToken.ensureApprove(address(converter), amount);
        }

        // add the liquidity to the converter
        addLiquidity(converter, baseToken, networkToken, amount, newNetworkLiquidityAmount, msg.value);

        // transfer the new pool tokens to the wallet
        uint256 poolTokenAmount = poolToken.balanceOf(address(this));
        poolToken.safeTransfer(address(_wallet), poolTokenAmount);

        // the system splits the pool tokens with the caller
        // increase the system's pool token balance and add the position for the caller
        _systemStore.incSystemBalance(poolToken, poolTokenAmount - poolTokenAmount / 2); // account for rounding errors

        return addPosition(owner, poolToken, baseToken, poolTokenAmount / 2, amount, time());
    }

    /**
     * @dev returns the single-side staking limits of a given pool
     *
     * @param poolAnchor anchor of the pool
     *
     * @return maximum amount of base tokens that can be single-side staked in the pool
     * @return maximum amount of network tokens that can be single-side staked in the pool
     */
    function poolAvailableSpace(IConverterAnchor poolAnchor)
        external
        view
        poolSupportedAndWhitelisted(poolAnchor)
        returns (uint256, uint256)
    {
        return (baseTokenAvailableSpace(poolAnchor), networkTokenAvailableSpace(poolAnchor));
    }

    /**
     * @dev returns the base-token staking limits of a given pool
     *
     * @param poolAnchor anchor of the pool
     *
     * @return maximum amount of base tokens that can be single-side staked in the pool
     */
    function baseTokenAvailableSpace(IConverterAnchor poolAnchor) internal view returns (uint256) {
        // get the pool converter
        ILiquidityPoolConverter converter = ILiquidityPoolConverter(payable(ownedBy(poolAnchor)));

        // get the base token
        IReserveToken networkToken = IReserveToken(address(_networkToken));
        IReserveToken baseToken = converterOtherReserve(converter, networkToken);

        // get the reserve balances
        (uint256 reserveBalanceBase, uint256 reserveBalanceNetwork) =
            converterReserveBalances(converter, baseToken, networkToken);

        // get the network token minting limit
        uint256 mintingLimit = _settings.networkTokenMintingLimits(poolAnchor);
        if (mintingLimit == 0) {
            mintingLimit = _settings.defaultNetworkTokenMintingLimit();
        }

        // get the amount of network tokens already minted for the pool
        uint256 networkTokensMinted = _systemStore.networkTokensMinted(poolAnchor);

        // get the amount of network tokens which can minted for the pool
        uint256 networkTokensCanBeMinted = MathEx.max(mintingLimit, networkTokensMinted) - networkTokensMinted;

        // return the maximum amount of base token liquidity that can be single-sided staked in the pool
        return networkTokensCanBeMinted.mul(reserveBalanceBase).div(reserveBalanceNetwork);
    }

    /**
     * @dev returns the network-token staking limits of a given pool
     *
     * @param poolAnchor anchor of the pool
     *
     * @return maximum amount of network tokens that can be single-side staked in the pool
     */
    function networkTokenAvailableSpace(IConverterAnchor poolAnchor) internal view returns (uint256) {
        // get the pool token
        IDSToken poolToken = IDSToken(address(poolAnchor));
        IReserveToken networkToken = IReserveToken(address(_networkToken));

        // get the pool token rate
        Fraction memory poolRate = poolTokenRate(poolToken, networkToken);

        // return the maximum amount of network token liquidity that can be single-sided staked in the pool
        return _systemStore.systemBalance(poolToken).mul(poolRate.n).add(poolRate.n).sub(1).div(poolRate.d);
    }

    /**
     * @dev returns the expected/actual amounts the provider will receive for removing liquidity
     * it's also possible to provide the remove liquidity time to get an estimation
     * for the return at that given point
     *
     * @param id position id
     * @param portion portion of liquidity to remove, in PPM
     * @param removeTimestamp time at which the liquidity is removed
     *
     * @return expected return amount in the reserve token
     * @return actual return amount in the reserve token
     * @return compensation in the network token
     */
    function removeLiquidityReturn(
        uint256 id,
        uint32 portion,
        uint256 removeTimestamp
    )
        external
        view
        validPortion(portion)
        returns (
            uint256,
            uint256,
            uint256
        )
    {
        Position memory pos = position(id);

        // verify input
        require(pos.provider != address(0), "ERR_INVALID_ID");
        require(removeTimestamp >= pos.timestamp, "ERR_INVALID_TIMESTAMP");

        // calculate the portion of the liquidity to remove
        if (portion != PPM_RESOLUTION) {
            pos.poolAmount = pos.poolAmount.mul(portion) / PPM_RESOLUTION;
            pos.reserveAmount = pos.reserveAmount.mul(portion) / PPM_RESOLUTION;
        }

        // get the various rates between the reserves upon adding liquidity and now
        PackedRates memory packedRates = packRates(pos.poolToken, pos.reserveToken, pos.reserveRateN, pos.reserveRateD);

        uint256 targetAmount =
            removeLiquidityTargetAmount(
                pos.poolToken,
                pos.reserveToken,
                pos.poolAmount,
                pos.reserveAmount,
                packedRates,
                pos.timestamp,
                removeTimestamp
            );

        // for network token, the return amount is identical to the target amount
        if (isNetworkToken(pos.reserveToken)) {
            return (targetAmount, targetAmount, 0);
        }

        // handle base token return

        // calculate the amount of pool tokens required for liquidation
        // note that the amount is doubled since it's not possible to liquidate one reserve only
        Fraction memory poolRate = poolTokenRate(pos.poolToken, pos.reserveToken);
        uint256 poolAmount = targetAmount.mul(poolRate.d).div(poolRate.n / 2);

        // limit the amount of pool tokens by the amount the system/caller holds
        uint256 availableBalance = _systemStore.systemBalance(pos.poolToken).add(pos.poolAmount);
        poolAmount = poolAmount > availableBalance ? availableBalance : poolAmount;

        // calculate the base token amount received by liquidating the pool tokens
        // note that the amount is divided by 2 since the pool amount represents both reserves
        uint256 baseAmount = poolAmount.mul(poolRate.n / 2).div(poolRate.d);
        uint256 networkAmount = networkCompensation(targetAmount, baseAmount, packedRates);

        return (targetAmount, baseAmount, networkAmount);
    }

    /**
     * @dev removes protected liquidity from a pool
     * also burns governance tokens from the caller if the caller removes network tokens
     *
     * @param id position id
     * @param portion portion of liquidity to remove, in PPM
     */
    function removeLiquidity(uint256 id, uint32 portion) external override protected validPortion(portion) {
        removeLiquidity(msg.sender, id, portion);
    }

    /**
     * @dev removes a position from a pool
     * also burns governance tokens from the caller if the caller removes network tokens
     *
     * @param provider liquidity provider
     * @param id position id
     * @param portion portion of liquidity to remove, in PPM
     */
    function removeLiquidity(
        address payable provider,
        uint256 id,
        uint32 portion
    ) internal {
        // remove the position from the store and update the stats and the last removal checkpoint
        Position memory removedPos = removePosition(provider, id, portion);

        // add the pool tokens to the system
        _systemStore.incSystemBalance(removedPos.poolToken, removedPos.poolAmount);

        // if removing network token liquidity, burn the governance tokens from the caller. we need to transfer the
        // tokens to the contract itself, since only token holders can burn their tokens
        if (isNetworkToken(removedPos.reserveToken)) {
            _govToken.safeTransferFrom(provider, address(this), removedPos.reserveAmount);
            _govTokenGovernance.burn(removedPos.reserveAmount);
        }

        // get the various rates between the reserves upon adding liquidity and now
        PackedRates memory packedRates =
            packRates(removedPos.poolToken, removedPos.reserveToken, removedPos.reserveRateN, removedPos.reserveRateD);

        // verify rate deviation as early as possible in order to reduce gas-cost for failing transactions
        verifyRateDeviation(
            packedRates.removeSpotRateN,
            packedRates.removeSpotRateD,
            packedRates.removeAverageRateN,
            packedRates.removeAverageRateD
        );

        // get the target token amount
        uint256 targetAmount =
            removeLiquidityTargetAmount(
                removedPos.poolToken,
                removedPos.reserveToken,
                removedPos.poolAmount,
                removedPos.reserveAmount,
                packedRates,
                removedPos.timestamp,
                time()
            );

        // remove network token liquidity
        if (isNetworkToken(removedPos.reserveToken)) {
            // mint network tokens for the caller and lock them
            mintNetworkTokens(address(_wallet), removedPos.poolToken, targetAmount);
            lockTokens(provider, targetAmount);

            return;
        }

        // remove base token liquidity

        // calculate the amount of pool tokens required for liquidation
        // note that the amount is doubled since it's not possible to liquidate one reserve only
        Fraction memory poolRate = poolTokenRate(removedPos.poolToken, removedPos.reserveToken);
        uint256 poolAmount = targetAmount.mul(poolRate.d).div(poolRate.n / 2);

        // limit the amount of pool tokens by the amount the system holds
        uint256 systemBalance = _systemStore.systemBalance(removedPos.poolToken);
        poolAmount = poolAmount > systemBalance ? systemBalance : poolAmount;

        // withdraw the pool tokens from the wallet
        IReserveToken poolToken = IReserveToken(address(removedPos.poolToken));
        _systemStore.decSystemBalance(removedPos.poolToken, poolAmount);
        _wallet.withdrawTokens(poolToken, address(this), poolAmount);

        // remove liquidity
        removeLiquidity(
            removedPos.poolToken,
            poolAmount,
            removedPos.reserveToken,
            IReserveToken(address(_networkToken))
        );

        // transfer the base tokens to the caller
        uint256 baseBalance = removedPos.reserveToken.balanceOf(address(this));
        removedPos.reserveToken.safeTransfer(provider, baseBalance);

        // compensate the caller with network tokens if still needed
        uint256 delta = networkCompensation(targetAmount, baseBalance, packedRates);
        if (delta > 0) {
            // check if there's enough network token balance, otherwise mint more
            uint256 networkBalance = _networkToken.balanceOf(address(this));
            if (networkBalance < delta) {
                _networkTokenGovernance.mint(address(this), delta - networkBalance);
            }

            // lock network tokens for the caller
            _networkToken.safeTransfer(address(_wallet), delta);
            lockTokens(provider, delta);
        }

        // if the contract still holds network tokens, burn them
        uint256 networkBalance = _networkToken.balanceOf(address(this));
        if (networkBalance > 0) {
            burnNetworkTokens(removedPos.poolToken, networkBalance);
        }
    }

    /**
     * @dev returns the amount the provider will receive for removing liquidity
     * it's also possible to provide the remove liquidity rate & time to get an estimation
     * for the return at that given point
     *
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param poolAmount pool token amount when the liquidity was added
     * @param reserveAmount reserve token amount that was added
     * @param packedRates see `struct PackedRates`
     * @param addTimestamp time at which the liquidity was added
     * @param removeTimestamp time at which the liquidity is removed
     *
     * @return amount received for removing liquidity
     */
    function removeLiquidityTargetAmount(
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount,
        PackedRates memory packedRates,
        uint256 addTimestamp,
        uint256 removeTimestamp
    ) internal view returns (uint256) {
        // get the rate between the pool token and the reserve token
        Fraction memory poolRate = poolTokenRate(poolToken, reserveToken);

        // get the rate between the reserves upon adding liquidity and now
        Fraction memory addSpotRate = Fraction({ n: packedRates.addSpotRateN, d: packedRates.addSpotRateD });
        Fraction memory removeSpotRate = Fraction({ n: packedRates.removeSpotRateN, d: packedRates.removeSpotRateD });
        Fraction memory removeAverageRate =
            Fraction({ n: packedRates.removeAverageRateN, d: packedRates.removeAverageRateD });

        // calculate the protected amount of reserve tokens plus accumulated fee before compensation
        uint256 total = protectedAmountPlusFee(poolAmount, poolRate, addSpotRate, removeSpotRate);

        // calculate the impermanent loss
        Fraction memory loss = impLoss(addSpotRate, removeAverageRate);

        // calculate the protection level
        Fraction memory level = protectionLevel(addTimestamp, removeTimestamp);

        // calculate the compensation amount
        return compensationAmount(reserveAmount, MathEx.max(reserveAmount, total), loss, level);
    }

    /**
     * @dev transfers a position to a new provider
     *
     * @param id position id
     * @param newProvider the new provider
     *
     * @return new position id
     */
    function transferPosition(uint256 id, address newProvider)
        external
        override
        protected
        validAddress(newProvider)
        returns (uint256)
    {
        return transferPosition(msg.sender, id, newProvider);
    }

    /**
     * @dev transfers a position to a new provider and optionally notifies another contract
     *
     * @param id position id
     * @param newProvider the new provider
     * @param callback the callback contract to notify
     * @param data custom data provided to the callback
     *
     * @return new position id
     */
    function transferPositionAndNotify(
        uint256 id,
        address newProvider,
        ITransferPositionCallback callback,
        bytes calldata data
    ) external override protected validAddress(newProvider) validAddress(address(callback)) returns (uint256) {
        uint256 newId = transferPosition(msg.sender, id, newProvider);

        callback.onTransferPosition(newId, msg.sender, data);

        return newId;
    }

    /**
     * @dev transfers a position to a new provider
     *
     * @param provider the existing provider
     * @param id position id
     * @param newProvider the new provider
     *
     * @return new position id
     */
    function transferPosition(
        address provider,
        uint256 id,
        address newProvider
    ) internal returns (uint256) {
        // remove the position from the store and update the stats and the last removal checkpoint
        Position memory removedPos = removePosition(provider, id, PPM_RESOLUTION);

        // add the position to the store, update the stats, and return the new id
        return
            addPosition(
                newProvider,
                removedPos.poolToken,
                removedPos.reserveToken,
                removedPos.poolAmount,
                removedPos.reserveAmount,
                removedPos.timestamp
            );
    }

    /**
     * @dev allows the caller to claim network token balance that is no longer locked
     * note that the function can revert if the range is too large
     *
     * @param startIndex start index in the caller's list of locked balances
     * @param endIndex end index in the caller's list of locked balances (exclusive)
     */
    function claimBalance(uint256 startIndex, uint256 endIndex) external protected {
        // get the locked balances from the store
        (uint256[] memory amounts, uint256[] memory expirationTimes) =
            _store.lockedBalanceRange(msg.sender, startIndex, endIndex);

        uint256 totalAmount = 0;
        uint256 length = amounts.length;
        assert(length == expirationTimes.length);

        // reverse iteration since we're removing from the list
        for (uint256 i = length; i > 0; i--) {
            uint256 index = i - 1;
            if (expirationTimes[index] > time()) {
                continue;
            }

            // remove the locked balance item
            _store.removeLockedBalance(msg.sender, startIndex + index);
            totalAmount = totalAmount.add(amounts[index]);
        }

        if (totalAmount > 0) {
            // transfer the tokens to the caller in a single call
            _wallet.withdrawTokens(IReserveToken(address(_networkToken)), msg.sender, totalAmount);
        }
    }

    /**
     * @dev returns the ROI for removing liquidity in the current state after providing liquidity with the given args
     * the function assumes full protection is in effect
     * return value is in PPM and can be larger than PPM_RESOLUTION for positive ROI, 1M = 0% ROI
     *
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param reserveAmount reserve token amount that was added
     * @param poolRateN rate of 1 pool token in reserve token units when the liquidity was added (numerator)
     * @param poolRateD rate of 1 pool token in reserve token units when the liquidity was added (denominator)
     * @param reserveRateN rate of 1 reserve token in the other reserve token units when the liquidity was added (numerator)
     * @param reserveRateD rate of 1 reserve token in the other reserve token units when the liquidity was added (denominator)
     *
     * @return ROI in PPM
     */
    function poolROI(
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 reserveAmount,
        uint256 poolRateN,
        uint256 poolRateD,
        uint256 reserveRateN,
        uint256 reserveRateD
    ) external view returns (uint256) {
        // calculate the amount of pool tokens based on the amount of reserve tokens
        uint256 poolAmount = reserveAmount.mul(poolRateD).div(poolRateN);

        // get the various rates between the reserves upon adding liquidity and now
        PackedRates memory packedRates = packRates(poolToken, reserveToken, reserveRateN, reserveRateD);

        // get the current return
        uint256 protectedReturn =
            removeLiquidityTargetAmount(
                poolToken,
                reserveToken,
                poolAmount,
                reserveAmount,
                packedRates,
                time().sub(_settings.maxProtectionDelay()),
                time()
            );

        // calculate the ROI as the ratio between the current fully protected return and the initial amount
        return protectedReturn.mul(PPM_RESOLUTION).div(reserveAmount);
    }

    /**
     * @dev adds the position to the store and updates the stats
     *
     * @param provider the provider
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param poolAmount amount of pool tokens to protect
     * @param reserveAmount amount of reserve tokens to protect
     * @param timestamp the timestamp of the position
     *
     * @return new position id
     */
    function addPosition(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount,
        uint256 timestamp
    ) internal returns (uint256) {
        // verify rate deviation as early as possible in order to reduce gas-cost for failing transactions
        (Fraction memory spotRate, Fraction memory averageRate) = reserveTokenRates(poolToken, reserveToken);
        verifyRateDeviation(spotRate.n, spotRate.d, averageRate.n, averageRate.d);

        notifyEventSubscribersOnAddingLiquidity(provider, poolToken, reserveToken, poolAmount, reserveAmount);

        _stats.increaseTotalAmounts(provider, poolToken, reserveToken, poolAmount, reserveAmount);
        _stats.addProviderPool(provider, poolToken);

        return
            _store.addProtectedLiquidity(
                provider,
                poolToken,
                reserveToken,
                poolAmount,
                reserveAmount,
                spotRate.n,
                spotRate.d,
                timestamp
            );
    }

    /**
     * @dev removes the position from the store and updates the stats and the last removal checkpoint
     *
     * @param provider the provider
     * @param id position id
     * @param portion portion of the position to remove, in PPM
     *
     * @return a Position struct representing the removed liquidity
     */
    function removePosition(
        address provider,
        uint256 id,
        uint32 portion
    ) private returns (Position memory) {
        Position memory pos = providerPosition(id, provider);

        // verify that the pool is whitelisted
        _poolWhitelisted(pos.poolToken);

        // verify that the position is not removed on the same block in which it was added
        require(pos.timestamp < time(), "ERR_TOO_EARLY");

        if (portion == PPM_RESOLUTION) {
            notifyEventSubscribersOnRemovingLiquidity(
                id,
                pos.provider,
                pos.poolToken,
                pos.reserveToken,
                pos.poolAmount,
                pos.reserveAmount
            );

            // remove the position from the provider
            _store.removeProtectedLiquidity(id);
        } else {
            // remove a portion of the position from the provider
            uint256 fullPoolAmount = pos.poolAmount;
            uint256 fullReserveAmount = pos.reserveAmount;
            pos.poolAmount = pos.poolAmount.mul(portion) / PPM_RESOLUTION;
            pos.reserveAmount = pos.reserveAmount.mul(portion) / PPM_RESOLUTION;

            notifyEventSubscribersOnRemovingLiquidity(
                id,
                pos.provider,
                pos.poolToken,
                pos.reserveToken,
                pos.poolAmount,
                pos.reserveAmount
            );

            _store.updateProtectedLiquidityAmounts(
                id,
                fullPoolAmount - pos.poolAmount,
                fullReserveAmount - pos.reserveAmount
            );
        }

        // update the statistics
        _stats.decreaseTotalAmounts(pos.provider, pos.poolToken, pos.reserveToken, pos.poolAmount, pos.reserveAmount);

        // update last liquidity removal checkpoint
        _lastRemoveCheckpointStore.addCheckpoint(provider);

        return pos;
    }

    /**
     * @dev locks network tokens for the provider and emits the tokens locked event
     *
     * @param provider tokens provider
     * @param amount amount of network tokens
     */
    function lockTokens(address provider, uint256 amount) internal {
        uint256 expirationTime = time().add(_settings.lockDuration());
        _store.addLockedBalance(provider, amount, expirationTime);
    }

    /**
     * @dev returns the rate of 1 pool token in reserve token units
     *
     * @param poolToken pool token
     * @param reserveToken reserve token
     */
    function poolTokenRate(IDSToken poolToken, IReserveToken reserveToken)
        internal
        view
        virtual
        returns (Fraction memory)
    {
        // get the pool token supply
        uint256 poolTokenSupply = poolToken.totalSupply();

        // get the reserve balance
        IConverter converter = IConverter(payable(ownedBy(poolToken)));
        uint256 reserveBalance = converter.getConnectorBalance(reserveToken);

        // for standard pools, 50% of the pool supply value equals the value of each reserve
        return Fraction({ n: reserveBalance.mul(2), d: poolTokenSupply });
    }

    /**
     * @dev returns the spot rate and average rate of 1 reserve token in the other reserve token units
     *
     * @param poolToken pool token
     * @param reserveToken reserve token
     *
     * @return spot rate
     * @return average rate
     */
    function reserveTokenRates(IDSToken poolToken, IReserveToken reserveToken)
        internal
        view
        returns (Fraction memory, Fraction memory)
    {
        ILiquidityPoolConverter converter = ILiquidityPoolConverter(payable(ownedBy(poolToken)));
        IReserveToken otherReserve = converterOtherReserve(converter, reserveToken);

        (uint256 spotRateN, uint256 spotRateD) = converterReserveBalances(converter, otherReserve, reserveToken);
        (uint256 averageRateN, uint256 averageRateD) = converter.recentAverageRate(reserveToken);

        return (Fraction({ n: spotRateN, d: spotRateD }), Fraction({ n: averageRateN, d: averageRateD }));
    }

    /**
     * @dev returns the various rates between the reserves
     *
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param addSpotRateN add spot rate numerator
     * @param addSpotRateD add spot rate denominator
     *
     * @return see `struct PackedRates`
     */
    function packRates(
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 addSpotRateN,
        uint256 addSpotRateD
    ) internal view returns (PackedRates memory) {
        (Fraction memory removeSpotRate, Fraction memory removeAverageRate) =
            reserveTokenRates(poolToken, reserveToken);

        assert(
            addSpotRateN <= MAX_UINT128 &&
                addSpotRateD <= MAX_UINT128 &&
                removeSpotRate.n <= MAX_UINT128 &&
                removeSpotRate.d <= MAX_UINT128 &&
                removeAverageRate.n <= MAX_UINT128 &&
                removeAverageRate.d <= MAX_UINT128
        );

        return
            PackedRates({
                addSpotRateN: uint128(addSpotRateN),
                addSpotRateD: uint128(addSpotRateD),
                removeSpotRateN: uint128(removeSpotRate.n),
                removeSpotRateD: uint128(removeSpotRate.d),
                removeAverageRateN: uint128(removeAverageRate.n),
                removeAverageRateD: uint128(removeAverageRate.d)
            });
    }

    /**
     * @dev verifies that the deviation of the average rate from the spot rate is within the permitted range
     * for example, if the maximum permitted deviation is 5%, then verify `95/100 <= average/spot <= 100/95`
     *
     * @param spotRateN spot rate numerator
     * @param spotRateD spot rate denominator
     * @param averageRateN average rate numerator
     * @param averageRateD average rate denominator
     */
    function verifyRateDeviation(
        uint256 spotRateN,
        uint256 spotRateD,
        uint256 averageRateN,
        uint256 averageRateD
    ) internal view {
        uint256 ppmDelta = PPM_RESOLUTION - _settings.averageRateMaxDeviation();
        uint256 min = spotRateN.mul(averageRateD).mul(ppmDelta).mul(ppmDelta);
        uint256 mid = spotRateD.mul(averageRateN).mul(ppmDelta).mul(PPM_RESOLUTION);
        uint256 max = spotRateN.mul(averageRateD).mul(PPM_RESOLUTION).mul(PPM_RESOLUTION);
        require(min <= mid && mid <= max, "ERR_INVALID_RATE");
    }

    /**
     * @dev utility to add liquidity to a converter
     *
     * @param converter converter
     * @param reserveToken1 reserve token 1
     * @param reserveToken2 reserve token 2
     * @param reserveAmount1 reserve amount 1
     * @param reserveAmount2 reserve amount 2
     * @param value ETH amount to add
     */
    function addLiquidity(
        ILiquidityPoolConverter converter,
        IReserveToken reserveToken1,
        IReserveToken reserveToken2,
        uint256 reserveAmount1,
        uint256 reserveAmount2,
        uint256 value
    ) internal {
        IReserveToken[] memory reserveTokens = new IReserveToken[](2);
        uint256[] memory amounts = new uint256[](2);
        reserveTokens[0] = reserveToken1;
        reserveTokens[1] = reserveToken2;
        amounts[0] = reserveAmount1;
        amounts[1] = reserveAmount2;
        converter.addLiquidity{ value: value }(reserveTokens, amounts, 1);
    }

    /**
     * @dev utility to remove liquidity from a converter
     *
     * @param poolToken pool token of the converter
     * @param poolAmount amount of pool tokens to remove
     * @param reserveToken1 reserve token 1
     * @param reserveToken2 reserve token 2
     */
    function removeLiquidity(
        IDSToken poolToken,
        uint256 poolAmount,
        IReserveToken reserveToken1,
        IReserveToken reserveToken2
    ) internal {
        ILiquidityPoolConverter converter = ILiquidityPoolConverter(payable(ownedBy(poolToken)));

        IReserveToken[] memory reserveTokens = new IReserveToken[](2);
        uint256[] memory minReturns = new uint256[](2);
        reserveTokens[0] = reserveToken1;
        reserveTokens[1] = reserveToken2;
        minReturns[0] = 1;
        minReturns[1] = 1;
        converter.removeLiquidity(poolAmount, reserveTokens, minReturns);
    }

    /**
     * @dev returns a position from the store
     *
     * @param id position id
     *
     * @return a position
     */
    function position(uint256 id) internal view returns (Position memory) {
        Position memory pos;
        (
            pos.provider,
            pos.poolToken,
            pos.reserveToken,
            pos.poolAmount,
            pos.reserveAmount,
            pos.reserveRateN,
            pos.reserveRateD,
            pos.timestamp
        ) = _store.protectedLiquidity(id);

        return pos;
    }

    /**
     * @dev returns a position from the store
     *
     * @param id position id
     * @param provider authorized provider
     *
     * @return a position
     */
    function providerPosition(uint256 id, address provider) internal view returns (Position memory) {
        Position memory pos = position(id);
        require(pos.provider == provider, "ERR_ACCESS_DENIED");

        return pos;
    }

    /**
     * @dev returns the protected amount of reserve tokens plus accumulated fee before compensation
     *
     * @param poolAmount pool token amount when the liquidity was added
     * @param poolRate rate of 1 pool token in the related reserve token units
     * @param addRate rate of 1 reserve token in the other reserve token units when the liquidity was added
     * @param removeRate rate of 1 reserve token in the other reserve token units when the liquidity is removed
     *
     * @return protected amount of reserve tokens plus accumulated fee = sqrt(removeRate / addRate) * poolRate * poolAmount
     */
    function protectedAmountPlusFee(
        uint256 poolAmount,
        Fraction memory poolRate,
        Fraction memory addRate,
        Fraction memory removeRate
    ) internal pure returns (uint256) {
        uint256 n = MathEx.ceilSqrt(addRate.d.mul(removeRate.n)).mul(poolRate.n);
        uint256 d = MathEx.floorSqrt(addRate.n.mul(removeRate.d)).mul(poolRate.d);

        uint256 x = n * poolAmount;
        if (x / n == poolAmount) {
            return x / d;
        }

        (uint256 hi, uint256 lo) = n > poolAmount ? (n, poolAmount) : (poolAmount, n);
        (uint256 p, uint256 q) = MathEx.reducedRatio(hi, d, MAX_UINT256 / lo);
        uint256 min = (hi / d).mul(lo);

        if (q > 0) {
            return MathEx.max(min, (p * lo) / q);
        }
        return min;
    }

    /**
     * @dev returns the impermanent loss incurred due to the change in rates between the reserve tokens
     *
     * @param prevRate previous rate between the reserves
     * @param newRate new rate between the reserves
     *
     * @return impermanent loss (as a ratio)
     */
    function impLoss(Fraction memory prevRate, Fraction memory newRate) internal pure returns (Fraction memory) {
        uint256 ratioN = newRate.n.mul(prevRate.d);
        uint256 ratioD = newRate.d.mul(prevRate.n);

        uint256 prod = ratioN * ratioD;
        uint256 root =
            prod / ratioN == ratioD ? MathEx.floorSqrt(prod) : MathEx.floorSqrt(ratioN) * MathEx.floorSqrt(ratioD);
        uint256 sum = ratioN.add(ratioD);

        // the arithmetic below is safe because `x + y >= sqrt(x * y) * 2`
        if (sum % 2 == 0) {
            sum /= 2;
            return Fraction({ n: sum - root, d: sum });
        }
        return Fraction({ n: sum - root * 2, d: sum });
    }

    /**
     * @dev returns the protection level based on the timestamp and protection delays
     *
     * @param addTimestamp time at which the liquidity was added
     * @param removeTimestamp time at which the liquidity is removed
     *
     * @return protection level (as a ratio)
     */
    function protectionLevel(uint256 addTimestamp, uint256 removeTimestamp) internal view returns (Fraction memory) {
        uint256 timeElapsed = removeTimestamp.sub(addTimestamp);
        uint256 minProtectionDelay = _settings.minProtectionDelay();
        uint256 maxProtectionDelay = _settings.maxProtectionDelay();
        if (timeElapsed < minProtectionDelay) {
            return Fraction({ n: 0, d: 1 });
        }

        if (timeElapsed >= maxProtectionDelay) {
            return Fraction({ n: 1, d: 1 });
        }

        return Fraction({ n: timeElapsed, d: maxProtectionDelay });
    }

    /**
     * @dev returns the compensation amount based on the impermanent loss and the protection level
     *
     * @param amount protected amount in units of the reserve token
     * @param total amount plus fee in units of the reserve token
     * @param loss protection level (as a ratio between 0 and 1)
     * @param level impermanent loss (as a ratio between 0 and 1)
     *
     * @return compensation amount
     */
    function compensationAmount(
        uint256 amount,
        uint256 total,
        Fraction memory loss,
        Fraction memory level
    ) internal pure returns (uint256) {
        uint256 levelN = level.n.mul(amount);
        uint256 levelD = level.d;
        uint256 maxVal = MathEx.max(MathEx.max(levelN, levelD), total);
        (uint256 lossN, uint256 lossD) = MathEx.reducedRatio(loss.n, loss.d, MAX_UINT256 / maxVal);
        return total.mul(lossD.sub(lossN)).div(lossD).add(lossN.mul(levelN).div(lossD.mul(levelD)));
    }

    function networkCompensation(
        uint256 targetAmount,
        uint256 baseAmount,
        PackedRates memory packedRates
    ) internal view returns (uint256) {
        if (targetAmount <= baseAmount) {
            return 0;
        }

        // calculate the delta in network tokens
        uint256 delta =
            (targetAmount - baseAmount).mul(packedRates.removeAverageRateN).div(packedRates.removeAverageRateD);

        // the delta might be very small due to precision loss
        // in which case no compensation will take place (gas optimization)
        if (delta >= _settings.minNetworkCompensation()) {
            return delta;
        }

        return 0;
    }

    // utility to mint network tokens
    function mintNetworkTokens(
        address owner,
        IConverterAnchor poolAnchor,
        uint256 amount
    ) private {
        _systemStore.incNetworkTokensMinted(poolAnchor, amount);
        _networkTokenGovernance.mint(owner, amount);
    }

    // utility to burn network tokens
    function burnNetworkTokens(IConverterAnchor poolAnchor, uint256 amount) private {
        _systemStore.decNetworkTokensMinted(poolAnchor, amount);
        _networkTokenGovernance.burn(amount);
    }

    /**
     * @dev notify event subscribers on adding liquidity
     *
     * @param provider liquidity provider
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param poolAmount amount of pool tokens to protect
     * @param reserveAmount amount of reserve tokens to protect
     */
    function notifyEventSubscribersOnAddingLiquidity(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) private {
        address[] memory subscribers = _settings.subscribers();
        uint256 length = subscribers.length;
        for (uint256 i = 0; i < length; i++) {
            ILiquidityProvisionEventsSubscriber(subscribers[i]).onAddingLiquidity(
                provider,
                poolToken,
                reserveToken,
                poolAmount,
                reserveAmount
            );
        }
    }

    /**
     * @dev notify event subscribers on removing liquidity
     *
     * @param id position id
     * @param provider liquidity provider
     * @param poolToken pool token
     * @param reserveToken reserve token
     * @param poolAmount amount of pool tokens to protect
     * @param reserveAmount amount of reserve tokens to protect
     */
    function notifyEventSubscribersOnRemovingLiquidity(
        uint256 id,
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) private {
        address[] memory subscribers = _settings.subscribers();
        uint256 length = subscribers.length;
        for (uint256 i = 0; i < length; i++) {
            ILiquidityProvisionEventsSubscriber(subscribers[i]).onRemovingLiquidity(
                id,
                provider,
                poolToken,
                reserveToken,
                poolAmount,
                reserveAmount
            );
        }
    }

    // utility to get the reserve balances
    function converterReserveBalances(
        IConverter converter,
        IReserveToken reserveToken1,
        IReserveToken reserveToken2
    ) private view returns (uint256, uint256) {
        return (converter.getConnectorBalance(reserveToken1), converter.getConnectorBalance(reserveToken2));
    }

    // utility to get the other reserve
    function converterOtherReserve(IConverter converter, IReserveToken thisReserve)
        private
        view
        returns (IReserveToken)
    {
        IReserveToken otherReserve = converter.connectorTokens(0);
        return otherReserve != thisReserve ? otherReserve : converter.connectorTokens(1);
    }

    // utility to get the owner
    function ownedBy(IOwned owned) private view returns (address) {
        return owned.owner();
    }

    /**
     * @dev returns whether the provided reserve token is the network token
     *
     * @return whether the provided reserve token is the network token
     */
    function isNetworkToken(IReserveToken reserveToken) private view returns (bool) {
        return address(reserveToken) == address(_networkToken);
    }
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.6.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/AccessControl.sol



pragma solidity ^0.6.0;




/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;

    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }

    mapping (bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");

        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");

        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }

    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }

    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



pragma solidity ^0.6.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: solidity/contracts/token/interfaces/IERC20Token.sol


pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address _owner) external view returns (uint256);

    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool);

    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionSystemStore.sol


pragma solidity 0.6.12;



/*
    Liquidity Protection System Store interface
*/
interface ILiquidityProtectionSystemStore {
    function systemBalance(IERC20Token poolToken) external view returns (uint256);

    function incSystemBalance(IERC20Token poolToken, uint256 poolAmount) external;

    function decSystemBalance(IERC20Token poolToken, uint256 poolAmount) external;

    function networkTokensMinted(IConverterAnchor poolAnchor) external view returns (uint256);

    function incNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;

    function decNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;

/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }

    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }

    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address _address) {
        _validExternalAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validExternalAddress(address _address) internal view {
        require(_address != address(0) && _address != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }
}

// File: solidity/contracts/liquidity-protection/LiquidityProtectionSystemStore.sol


pragma solidity 0.6.12;






/**
 * @dev This contract aggregates the system balances of the liquidity protection mechanism.
 */
contract LiquidityProtectionSystemStore is ILiquidityProtectionSystemStore, AccessControl, Utils {
    using SafeMath for uint256;

    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    bytes32 public constant ROLE_OWNER = keccak256("ROLE_OWNER");

    // system balances
    mapping(IERC20Token => uint256) private _systemBalances;

    // network tokens minted
    mapping(IConverterAnchor => uint256) private _networkTokensMinted;

    // allows execution only by an owner
    modifier ownerOnly {
        _hasRole(ROLE_OWNER);
        _;
    }

    // error message binary size optimization
    function _hasRole(bytes32 role) internal view {
        require(hasRole(role, msg.sender), "ERR_ACCESS_DENIED");
    }

    /**
     * @dev triggered when the system balance for a given token is updated
     *
     * @param token         token address
     * @param prevAmount    previous amount
     * @param newAmount     new amount
     */
    event SystemBalanceUpdated(IERC20Token indexed token, uint256 prevAmount, uint256 newAmount);

    /**
     * @dev triggered when the amount of network tokens minted into a specific pool is updated
     *
     * @param poolAnchor    pool anchor
     * @param prevAmount    previous amount
     * @param newAmount     new amount
     */
    event NetworkTokensMintedUpdated(IConverterAnchor indexed poolAnchor, uint256 prevAmount, uint256 newAmount);

    constructor() public {
        // set up administrative roles
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_OWNER, ROLE_SUPERVISOR);

        // allow the deployer to initially govern the contract
        _setupRole(ROLE_SUPERVISOR, msg.sender);
    }

    /**
     * @dev returns the system balance for a given token
     *
     * @param token token address
     * @return system balance
     */
    function systemBalance(IERC20Token token) external view override returns (uint256) {
        return _systemBalances[token];
    }

    /**
     * @dev increases the system balance for a given token
     * can be executed only by an owner
     *
     * @param token     token address
     * @param amount    token amount
     */
    function incSystemBalance(IERC20Token token, uint256 amount)
        external
        override
        ownerOnly
        validAddress(address(token))
    {
        uint256 prevAmount = _systemBalances[token];
        uint256 newAmount = prevAmount.add(amount);
        _systemBalances[token] = newAmount;

        emit SystemBalanceUpdated(token, prevAmount, newAmount);
    }

    /**
     * @dev decreases the system balance for a given token
     * can be executed only by an owner
     *
     * @param token     token address
     * @param amount    token amount
     */
    function decSystemBalance(IERC20Token token, uint256 amount)
        external
        override
        ownerOnly
        validAddress(address(token))
    {
        uint256 prevAmount = _systemBalances[token];
        uint256 newAmount = prevAmount.sub(amount);
        _systemBalances[token] = newAmount;

        emit SystemBalanceUpdated(token, prevAmount, newAmount);
    }

    /**
     * @dev returns the amount of network tokens minted into a specific pool
     *
     * @param poolAnchor    pool anchor
     * @return amount of network tokens
     */
    function networkTokensMinted(IConverterAnchor poolAnchor) external view override returns (uint256) {
        return _networkTokensMinted[poolAnchor];
    }

    /**
     * @dev increases the amount of network tokens minted into a specific pool
     * can be executed only by an owner
     *
     * @param poolAnchor    pool anchor
     * @param amount        amount to increase the minted tokens by
     */
    function incNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount)
        external
        override
        ownerOnly
        validAddress(address(poolAnchor))
    {
        uint256 prevAmount = _networkTokensMinted[poolAnchor];
        uint256 newAmount = prevAmount.add(amount);
        _networkTokensMinted[poolAnchor] = newAmount;

        emit NetworkTokensMintedUpdated(poolAnchor, prevAmount, newAmount);
    }

    /**
     * @dev decreases the amount of network tokens minted into a specific pool
     * can be executed only by an owner
     *
     * @param poolAnchor    pool anchor
     * @param amount        amount to decrease the minted tokens by
     */
    function decNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount)
        external
        override
        ownerOnly
        validAddress(address(poolAnchor))
    {
        uint256 prevAmount = _networkTokensMinted[poolAnchor];
        uint256 newAmount = prevAmount > amount ? prevAmount - amount : 0;
        _networkTokensMinted[poolAnchor] = newAmount;

        emit NetworkTokensMintedUpdated(poolAnchor, prevAmount, newAmount);
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;
    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {
}

// File: solidity/contracts/token/interfaces/IERC20Token.sol


pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address _owner) external view returns (uint256);
    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);
    function transferFrom(address _from, address _to, uint256 _value) external returns (bool);
    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20Token {
    function issue(address _to, uint256 _amount) external;
    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionStore.sol


pragma solidity 0.6.12;





/*
    Liquidity Protection Store interface
*/
interface ILiquidityProtectionStore is IOwned {
    function addPoolToWhitelist(IConverterAnchor _anchor) external;
    function removePoolFromWhitelist(IConverterAnchor _anchor) external;
    function isPoolWhitelisted(IConverterAnchor _anchor) external view returns (bool);

    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) external;

    function protectedLiquidity(uint256 _id)
        external
        view
        returns (address, IDSToken, IERC20Token, uint256, uint256, uint256, uint256, uint256);

    function addProtectedLiquidity(
        address _provider,
        IDSToken _poolToken,
        IERC20Token _reserveToken,
        uint256 _poolAmount,
        uint256 _reserveAmount,
        uint256 _reserveRateN,
        uint256 _reserveRateD,
        uint256 _timestamp
    ) external returns (uint256);

    function updateProtectedLiquidityAmounts(uint256 _id, uint256 _poolNewAmount, uint256 _reserveNewAmount) external;
    function removeProtectedLiquidity(uint256 _id) external;
    
    function lockedBalance(address _provider, uint256 _index) external view returns (uint256, uint256);
    function lockedBalanceRange(address _provider, uint256 _startIndex, uint256 _endIndex) external view returns (uint256[] memory, uint256[] memory);

    function addLockedBalance(address _provider, uint256 _reserveAmount, uint256 _expirationTime) external returns (uint256);
    function removeLockedBalance(address _provider, uint256 _index) external;

    function systemBalance(IERC20Token _poolToken) external view returns (uint256);
    function incSystemBalance(IERC20Token _poolToken, uint256 _poolAmount) external;
    function decSystemBalance(IERC20Token _poolToken, uint256 _poolAmount ) external;
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
  * @dev Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
      * @dev triggered when the owner is updated
      *
      * @param _prevOwner previous owner
      * @param _newOwner  new owner
    */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
      * @dev initializes a new Owned instance
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
      * @dev allows transferring the contract ownership
      * the new owner still needs to accept the transfer
      * can only be called by the contract owner
      *
      * @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
      * @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() override public {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/utility/SafeMath.sol


pragma solidity 0.6.12;

/**
  * @dev Library for basic math operations with overflow/underflow protection
*/
library SafeMath {
    /**
      * @dev returns the sum of _x and _y, reverts if the calculation overflows
      *
      * @param _x   value 1
      * @param _y   value 2
      *
      * @return sum
    */
    function add(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        require(z >= _x, "ERR_OVERFLOW");
        return z;
    }

    /**
      * @dev returns the difference of _x minus _y, reverts if the calculation underflows
      *
      * @param _x   minuend
      * @param _y   subtrahend
      *
      * @return difference
    */
    function sub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_x >= _y, "ERR_UNDERFLOW");
        return _x - _y;
    }

    /**
      * @dev returns the product of multiplying _x by _y, reverts if the calculation overflows
      *
      * @param _x   factor 1
      * @param _y   factor 2
      *
      * @return product
    */
    function mul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        // gas optimization
        if (_x == 0)
            return 0;

        uint256 z = _x * _y;
        require(z / _x == _y, "ERR_OVERFLOW");
        return z;
    }

    /**
      * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
      *
      * @param _x   dividend
      * @param _y   divisor
      *
      * @return quotient
    */
    function div(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_y > 0, "ERR_DIVIDE_BY_ZERO");
        uint256 c = _x / _y;
        return c;
    }
}

// File: solidity/contracts/utility/TokenHandler.sol


pragma solidity 0.6.12;


contract TokenHandler {
    bytes4 private constant APPROVE_FUNC_SELECTOR = bytes4(keccak256("approve(address,uint256)"));
    bytes4 private constant TRANSFER_FUNC_SELECTOR = bytes4(keccak256("transfer(address,uint256)"));
    bytes4 private constant TRANSFER_FROM_FUNC_SELECTOR = bytes4(keccak256("transferFrom(address,address,uint256)"));

    /**
      * @dev executes the ERC20 token's `approve` function and reverts upon failure
      * the main purpose of this function is to prevent a non standard ERC20 token
      * from failing silently
      *
      * @param _token   ERC20 token address
      * @param _spender approved address
      * @param _value   allowance amount
    */
    function safeApprove(IERC20Token _token, address _spender, uint256 _value) internal {
        (bool success, bytes memory data) = address(_token).call(abi.encodeWithSelector(APPROVE_FUNC_SELECTOR, _spender, _value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'ERR_APPROVE_FAILED');
    }

    /**
      * @dev executes the ERC20 token's `transfer` function and reverts upon failure
      * the main purpose of this function is to prevent a non standard ERC20 token
      * from failing silently
      *
      * @param _token   ERC20 token address
      * @param _to      target address
      * @param _value   transfer amount
    */
    function safeTransfer(IERC20Token _token, address _to, uint256 _value) internal {
       (bool success, bytes memory data) = address(_token).call(abi.encodeWithSelector(TRANSFER_FUNC_SELECTOR, _to, _value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'ERR_TRANSFER_FAILED');
    }

    /**
      * @dev executes the ERC20 token's `transferFrom` function and reverts upon failure
      * the main purpose of this function is to prevent a non standard ERC20 token
      * from failing silently
      *
      * @param _token   ERC20 token address
      * @param _from    source address
      * @param _to      target address
      * @param _value   transfer amount
    */
    function safeTransferFrom(IERC20Token _token, address _from, address _to, uint256 _value) internal {
       (bool success, bytes memory data) = address(_token).call(abi.encodeWithSelector(TRANSFER_FROM_FUNC_SELECTOR, _from, _to, _value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'ERR_TRANSFER_FROM_FAILED');
    }
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;

/**
  * @dev Utilities & Common Modifiers
*/
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }

    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }
}

// File: solidity/contracts/liquidity-protection/LiquidityProtectionStore.sol


pragma solidity 0.6.12;






/**
  * @dev The Liquidity Protection Store contract serves as the storage of the liquidity protection
  * mechanism. It holds the data and tokens and is non upgradable.
  *
*/
contract LiquidityProtectionStore is ILiquidityProtectionStore, Owned, TokenHandler, Utils {
    using SafeMath for uint256;

    struct PoolIndex {
        bool isValid;
        uint256 value;
    }

    struct ProtectedLiquidity {
        address provider;           // liquidity provider
        uint256 index;              // index in the provider liquidity ids array
        IDSToken poolToken;         // pool token address
        IERC20Token reserveToken;   // reserve token address
        uint256 poolAmount;         // pool token amount
        uint256 reserveAmount;      // reserve token amount
        uint256 reserveRateN;       // rate of 1 protected reserve token in units of the other reserve token (numerator)
        uint256 reserveRateD;       // rate of 1 protected reserve token in units of the other reserve token (denominator)
        uint256 timestamp;          // timestamp
    }

    struct LockedBalance {
        uint256 amount;         // amount of network tokens
        uint256 expirationTime; // lock expiration time
    }

    // list of whitelisted pools and mapping of pool anchor address -> index in the pool whitelist for quick access
    IConverterAnchor[] private poolWhitelist;
    mapping(IConverterAnchor => PoolIndex) private poolWhitelistIndices;

    // protected liquidity by provider
    uint256 private nextProtectedLiquidityId;
    mapping (address => uint256[]) private protectedLiquidityIdsByProvider;
    mapping (uint256 => ProtectedLiquidity) private protectedLiquidities;

    // user locked network token balances
    mapping (address => LockedBalance[]) private lockedBalances;

    // system balances
    mapping (IERC20Token => uint256) private systemBalances;

    // total protected pool supplies / reserve amounts
    mapping (IDSToken =>    uint256) private totalProtectedPoolAmounts;
    mapping (IDSToken =>    mapping (IERC20Token => uint256)) private totalProtectedReserveAmounts;

    /**
      * @dev triggered when the pool whitelist is updated
      *
      * @param _poolAnchor  pool anchor
      * @param _added       true if the pool was added to the whitelist, false if it was removed
    */
    event PoolWhitelistUpdated(
        IConverterAnchor indexed _poolAnchor,
        bool _added
    );

    /**
      * @dev triggered when liquidity protection is added
      *
      * @param _provider        liquidity provider
      * @param _poolToken       pool token address
      * @param _reserveToken    reserve token address
      * @param _poolAmount      amount of pool tokens
      * @param _reserveAmount   amount of reserve tokens
    */
    event ProtectionAdded(
        address indexed _provider,
        IDSToken indexed    _poolToken,
        IERC20Token indexed _reserveToken,
        uint256 _poolAmount,
        uint256 _reserveAmount
    );

    /**
      * @dev triggered when liquidity protection is updated
      *
      * @param _provider            liquidity provider
      * @param _prevPoolAmount      previous amount of pool tokens
      * @param _prevReserveAmount   previous amount of reserve tokens
      * @param _newPoolAmount       new amount of pool tokens
      * @param _newReserveAmount    new amount of reserve tokens
    */
    event ProtectionUpdated(
        address indexed _provider,
        uint256 _prevPoolAmount,
        uint256 _prevReserveAmount,
        uint256 _newPoolAmount,
        uint256 _newReserveAmount
    );

    /**
      * @dev triggered when liquidity protection is removed
      *
      * @param _provider        liquidity provider
      * @param _poolToken       pool token address
      * @param _reserveToken    reserve token address
      * @param _poolAmount      amount of pool tokens
      * @param _reserveAmount   amount of reserve tokens
    */
    event ProtectionRemoved(
        address indexed _provider,
        IDSToken indexed    _poolToken,
        IERC20Token indexed _reserveToken,
        uint256 _poolAmount,
        uint256 _reserveAmount
    );

    /**
      * @dev triggered when network tokens are locked
      *
      * @param _provider        provider of the network tokens
      * @param _amount          amount of network tokens
      * @param _expirationTime  lock expiration time
    */
    event BalanceLocked(
        address indexed _provider,
        uint256 _amount,
        uint256 _expirationTime
    );

    /**
      * @dev triggered when network tokens are unlocked
      *
      * @param _provider    provider of the network tokens
      * @param _amount      amount of network tokens
    */
    event BalanceUnlocked(
        address indexed _provider,
        uint256 _amount
    );

    /**
      * @dev triggered when the system balance for a given token is updated
      *
      * @param _token       token address
      * @param _prevAmount  previous amount
      * @param _newAmount   new amount
    */
    event SystemBalanceUpdated(
        IERC20Token _token,
        uint256 _prevAmount,
        uint256 _newAmount
    );

    /**
      * @dev adds a pool to the whitelist
      * can only be called by the contract owner
      *
      * @param _poolAnchor pool anchor
    */
    function addPoolToWhitelist(IConverterAnchor _poolAnchor)
        external
        override
        ownerOnly
        validAddress(address(_poolAnchor))
        notThis(address(_poolAnchor))
    {
        // validate input
        PoolIndex storage poolIndex = poolWhitelistIndices[_poolAnchor];
        require(!poolIndex.isValid, "ERR_POOL_ALREADY_WHITELISTED");

        poolIndex.value = poolWhitelist.length;
        poolWhitelist.push(_poolAnchor);
        poolIndex.isValid = true;

        emit PoolWhitelistUpdated(_poolAnchor, true);
    }

    /**
      * @dev removes a pool from the whitelist
      * can only be called by the contract owner
      *
      * @param _poolAnchor pool anchor
    */
    function removePoolFromWhitelist(IConverterAnchor _poolAnchor)
        external
        override
        ownerOnly
        validAddress(address(_poolAnchor))
        notThis(address(_poolAnchor))
    {
        // validate input
        PoolIndex storage poolIndex = poolWhitelistIndices[_poolAnchor];
        require(poolIndex.isValid, "ERR_POOL_NOT_WHITELISTED");

        uint256 index = poolIndex.value;
        uint256 length = poolWhitelist.length;
        assert(length > 0);

        uint256 lastIndex = length - 1;
        if (index < lastIndex) {
            IConverterAnchor lastAnchor = poolWhitelist[lastIndex];
            poolWhitelistIndices[lastAnchor].value = index;
            poolWhitelist[index] = lastAnchor;
        }

        poolWhitelist.pop();
        delete poolWhitelistIndices[_poolAnchor];

        emit PoolWhitelistUpdated(_poolAnchor, false);
    }

    /**
      * @dev returns the number of whitelisted pools
      *
      * @return number of whitelisted pools
    */
    function whitelistedPoolCount() external view returns (uint256) {
        return poolWhitelist.length;
    }

    /**
      * @dev returns the list of whitelisted pools
      *
      * @return list of whitelisted pools
    */
    function whitelistedPools() external view returns (IConverterAnchor[] memory) {
        return poolWhitelist;
    }

    /**
      * @dev returns the whitelisted pool at a given index
      *
      * @param _index index
      * @return whitelisted pool anchor
    */
    function whitelistedPool(uint256 _index) external view returns (IConverterAnchor) {
        return poolWhitelist[_index];
    }

    /**
      * @dev checks whether a given pool is whitelisted
      *
      * @param _poolAnchor pool anchor
      * @return true if the given pool is whitelisted, false otherwise
    */
    function isPoolWhitelisted(IConverterAnchor _poolAnchor) external view override returns (bool) {
        return poolWhitelistIndices[_poolAnchor].isValid;
    }

    /**
      * @dev withdraws tokens held by the contract
      * can only be called by the contract owner
      *
      * @param _token   token address
      * @param _to      recipient address
      * @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        external
        override
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        safeTransfer(_token, _to, _amount);
    }

    /**
      * @dev returns the number of protected liquidities for the given provider
      *
      * @param _provider    liquidity provider
      * @return number of protected liquidities
    */
    function protectedLiquidityCount(address _provider) external view returns (uint256) {
        return protectedLiquidityIdsByProvider[_provider].length;
    }

    /**
      * @dev returns the list of protected liquidity ids for the given provider
      *
      * @param _provider    liquidity provider
      * @return protected liquidity ids
    */
    function protectedLiquidityIds(address _provider) external view returns (uint256[] memory) {
        return protectedLiquidityIdsByProvider[_provider];
    }

    /**
      * @dev returns the id of a protected liquidity for the given provider at a specific index
      *
      * @param _provider    liquidity provider
      * @param _index       protected liquidity index
      * @return protected liquidity id
    */
    function protectedLiquidityId(address _provider, uint256 _index) external view returns (uint256) {
        return protectedLiquidityIdsByProvider[_provider][_index];
    }

    /**
      * @dev returns an existing protected liquidity details
      *
      * @param _id  protected liquidity id
      *
      * @return liquidity provider
      * @return pool token address
      * @return reserve token address
      * @return pool token amount
      * @return reserve token amount
      * @return rate of 1 protected reserve token in units of the other reserve token (numerator)
      * @return rate of 1 protected reserve token in units of the other reserve token (denominator)
      * @return timestamp
    */
    function protectedLiquidity(uint256 _id)
        external
        view
        override
        returns (address, IDSToken,    IERC20Token, uint256, uint256, uint256, uint256, uint256) 
    {
        ProtectedLiquidity storage liquidity = protectedLiquidities[_id];
        return (
            liquidity.provider,
            liquidity.poolToken,
            liquidity.reserveToken,
            liquidity.poolAmount,
            liquidity.reserveAmount,
            liquidity.reserveRateN,
            liquidity.reserveRateD,
            liquidity.timestamp
        );
    }

    /**
      * @dev adds protected liquidity
      * can only be called by the contract owner
      *
      * @param _provider        liquidity provider
      * @param _poolToken       pool token address
      * @param _reserveToken    reserve token address
      * @param _poolAmount      pool token amount
      * @param _reserveAmount   reserve token amount
      * @param _reserveRateN    rate of 1 protected reserve token in units of the other reserve token (numerator)
      * @param _reserveRateD    rate of 1 protected reserve token in units of the other reserve token (denominator)
      * @param _timestamp       timestamp
      * @return new protected liquidity id
    */
    function addProtectedLiquidity(
        address _provider,
        IDSToken _poolToken,   
        IERC20Token _reserveToken,
        uint256 _poolAmount,
        uint256 _reserveAmount,
        uint256 _reserveRateN,
        uint256 _reserveRateD,
        uint256 _timestamp
    ) external override ownerOnly returns (uint256) {
        // validate input
        require(
            _provider != address(0) &&
            _provider != address(this) &&
            address(_poolToken) != address(0) &&
            address(_poolToken) != address(this) &&
            address(_reserveToken) != address(0) &&
            address(_reserveToken) != address(this),
            "ERR_INVALID_ADDRESS"
        );
        require(
            _poolAmount > 0 &&
            _reserveAmount > 0 &&
            _reserveRateN > 0 &&
            _reserveRateD > 0 &&
            _timestamp > 0,
            "ERR_ZERO_VALUE"
        );


        // add the protected liquidity
        uint256[] storage ids = protectedLiquidityIdsByProvider[_provider];
        uint256 id = nextProtectedLiquidityId;
        nextProtectedLiquidityId += 1;

        protectedLiquidities[id] = ProtectedLiquidity({
            provider: _provider,
            index: ids.length,
            poolToken: _poolToken,
            reserveToken: _reserveToken,
            poolAmount: _poolAmount,
            reserveAmount: _reserveAmount,
            reserveRateN: _reserveRateN,
            reserveRateD: _reserveRateD,
            timestamp: _timestamp
        });

        ids.push(id);

        // update the total amounts
        totalProtectedPoolAmounts[_poolToken] = totalProtectedPoolAmounts[_poolToken].add(_poolAmount);
        totalProtectedReserveAmounts[_poolToken][_reserveToken] = totalProtectedReserveAmounts[_poolToken][_reserveToken].add(_reserveAmount);

        emit ProtectionAdded(_provider, _poolToken, _reserveToken, _poolAmount, _reserveAmount);
        return id;
    }

    /**
      * @dev updates an existing protected liquidity pool/reserve amounts
      * can only be called by the contract owner
      *
      * @param _id                  protected liquidity id
      * @param _newPoolAmount       new pool tokens amount
      * @param _newReserveAmount    new reserve tokens amount
    */
    function updateProtectedLiquidityAmounts(uint256 _id, uint256 _newPoolAmount, uint256 _newReserveAmount)
        external
        override
        ownerOnly
        greaterThanZero(_newPoolAmount)
        greaterThanZero(_newReserveAmount)
    {
        // update the protected liquidity
        ProtectedLiquidity storage liquidity = protectedLiquidities[_id];

        // validate input
        address provider = liquidity.provider;
        require(provider != address(0), "ERR_INVALID_ID");

        IDSToken poolToken    = liquidity.poolToken;
        IERC20Token reserveToken = liquidity.reserveToken;
        uint256 prevPoolAmount = liquidity.poolAmount;
        uint256 prevReserveAmount = liquidity.reserveAmount;
        liquidity.poolAmount = _newPoolAmount;
        liquidity.reserveAmount = _newReserveAmount;

        // update the total amounts
        totalProtectedPoolAmounts[poolToken] = totalProtectedPoolAmounts[poolToken].add(_newPoolAmount).sub(prevPoolAmount);
        totalProtectedReserveAmounts[poolToken][reserveToken] = totalProtectedReserveAmounts[poolToken][reserveToken].add(_newReserveAmount).sub(prevReserveAmount);

        emit ProtectionUpdated(provider, prevPoolAmount, prevReserveAmount, _newPoolAmount, _newReserveAmount);
    }

    /**
      * @dev removes protected liquidity
      * can only be called by the contract owner
      *
      * @param _id  protected liquidity id
    */
    function removeProtectedLiquidity(uint256 _id) external override ownerOnly {
        // remove the protected liquidity
        ProtectedLiquidity storage liquidity = protectedLiquidities[_id];

        // validate input
        address provider = liquidity.provider;
        require(provider != address(0), "ERR_INVALID_ID");

        uint256 index = liquidity.index;
        IDSToken poolToken    = liquidity.poolToken;
        IERC20Token reserveToken = liquidity.reserveToken;
        uint256 poolAmount = liquidity.poolAmount;
        uint256 reserveAmount = liquidity.reserveAmount;
        delete protectedLiquidities[_id];

        uint256[] storage ids = protectedLiquidityIdsByProvider[provider];
        uint256 length = ids.length;
        assert(length > 0);

        uint256 lastIndex = length - 1;
        if (index < lastIndex) {
            uint256 lastId = ids[lastIndex];
            ids[index] = lastId;
            protectedLiquidities[lastId].index = index;
        }

        ids.pop();

        // update the total amounts
        totalProtectedPoolAmounts[poolToken] = totalProtectedPoolAmounts[poolToken].sub(poolAmount);
        totalProtectedReserveAmounts[poolToken][reserveToken] = totalProtectedReserveAmounts[poolToken][reserveToken].sub(reserveAmount);

        emit ProtectionRemoved(provider, poolToken, reserveToken, poolAmount, reserveAmount);
    }

    /**
      * @dev returns the number of network token locked balances for a given provider
      *
      * @param _provider    locked balances provider
      * @return the number of network token locked balances
    */
    function lockedBalanceCount(address _provider) external view returns (uint256) {
        return lockedBalances[_provider].length;
    }

    /**
      * @dev returns an existing locked network token balance details
      *
      * @param _provider    locked balances provider
      * @param _index       start index
      * @return amount of network tokens
      * @return lock expiration time
    */
    function lockedBalance(address _provider, uint256 _index) external view override returns (uint256, uint256) {
        LockedBalance storage balance = lockedBalances[_provider][_index];
        return (
            balance.amount,
            balance.expirationTime
        );
    }

    /**
      * @dev returns a range of locked network token balances for a given provider
      *
      * @param _provider    locked balances provider
      * @param _startIndex  start index
      * @param _endIndex    end index (exclusive)
      * @return locked amounts
      * @return expiration times
    */
    function lockedBalanceRange(address _provider, uint256 _startIndex, uint256 _endIndex)
        external
        view
        override
        returns (uint256[] memory, uint256[] memory)
    {
        // limit the end index by the number of locked balances
        if (_endIndex > lockedBalances[_provider].length) {
            _endIndex = lockedBalances[_provider].length;
        }

        // ensure that the end index is higher than the start index
        require(_endIndex > _startIndex, "ERR_INVALID_INDICES");

        // get the locked balances for the given range and return them
        uint256 length = _endIndex - _startIndex;
        uint256[] memory amounts = new uint256[](length);
        uint256[] memory expirationTimes = new uint256[](length);

        for (uint256 i = 0; i < length; i++) {
            LockedBalance storage balance = lockedBalances[_provider][_startIndex + i];
            amounts[i] = balance.amount;
            expirationTimes[i] = balance.expirationTime;
        }

        return (amounts, expirationTimes);
    }

    /**
      * @dev adds new locked network token balance
      * can only be called by the contract owner
      *
      * @param _provider        liquidity provider
      * @param _amount          token amount
      * @param _expirationTime  lock expiration time
      * @return new locked balance index
    */
    function addLockedBalance(address _provider, uint256 _amount, uint256 _expirationTime)
        external
        override
        ownerOnly
        validAddress(_provider)
        notThis(_provider)
        greaterThanZero(_amount)
        greaterThanZero(_expirationTime)
        returns (uint256)
    {
        lockedBalances[_provider].push(LockedBalance({
            amount: _amount,
            expirationTime: _expirationTime
        }));

        emit BalanceLocked(_provider, _amount, _expirationTime);
        return lockedBalances[_provider].length - 1;
    }

    /**
      * @dev removes a locked network token balance
      * can only be called by the contract owner
      *
      * @param _provider    liquidity provider
      * @param _index       index of the locked balance
    */
    function removeLockedBalance(address _provider, uint256 _index)
        external
        override
        ownerOnly
        validAddress(_provider)
    {
        LockedBalance[] storage balances = lockedBalances[_provider];
        uint256 length = balances.length;
        
        // validate input
        require(_index < length, "ERR_INVALID_INDEX");

        uint256 amount = balances[_index].amount;
        uint256 lastIndex = length - 1;
        if (_index < lastIndex) {
            balances[_index] = balances[lastIndex];
        }

        balances.pop();

        emit BalanceUnlocked(_provider, amount);
    }

    /**
      * @dev returns the system balance for a given token
      *
      * @param _token   token address
      * @return system balance
    */
    function systemBalance(IERC20Token _token) external view override returns (uint256) {
        return systemBalances[_token];
    }

    /**
      * @dev increases the system balance for a given token
      * can only be called by the contract owner
      *
      * @param _token   token address
      * @param _amount  token amount
    */
    function incSystemBalance(IERC20Token _token, uint256 _amount)
        external
        override
        ownerOnly
        validAddress(address(_token))
    {
        uint256 prevAmount = systemBalances[_token];
        uint256 newAmount = prevAmount.add(_amount);
        systemBalances[_token] = newAmount;

        emit SystemBalanceUpdated(_token, prevAmount, newAmount);
    }

    /**
      * @dev decreases the system balance for a given token
      * can only be called by the contract owner
      *
      * @param _token   token address
      * @param _amount  token amount
    */
    function decSystemBalance(IERC20Token _token, uint256 _amount)
        external
        override
        ownerOnly
        validAddress(address(_token))
    {
        uint256 prevAmount = systemBalances[_token];
        uint256 newAmount = prevAmount.sub(_amount);
        systemBalances[_token] = newAmount;

        emit SystemBalanceUpdated(_token, prevAmount, newAmount);
    }

    /**
      * @dev returns the total protected pool token amount for a given pool
      *
      * @param _poolToken   pool token address
      * @return total protected amount
    */
    function totalProtectedPoolAmount(IDSToken _poolToken)    external view returns (uint256) {
        return totalProtectedPoolAmounts[_poolToken];
    }

    /**
      * @dev returns the total protected reserve amount for a given pool
      *
      * @param _poolToken       pool token address
      * @param _reserveToken    reserve token address
      * @return total protected amount
    */
    function totalProtectedReserveAmount(IDSToken _poolToken,    IERC20Token _reserveToken) external view returns (uint256) {
        return totalProtectedReserveAmounts[_poolToken][_reserveToken];
    }
}

pragma solidity ^0.4.11;

/*
    Overflow protected math functions
*/
contract SafeMath {
    /**
        constructor
    */
    function SafeMath() {
    }

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
} 

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public constant returns (address owner) { owner; }

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address _prevOwner, address _newOwner);

    /**
        @dev constructor
    */
    function Owned() {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        assert(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still need to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = 0x0;
    }
}

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned {
    /**
        @dev constructor
    */
    function TokenHolder() {
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public constant returns (string name) { name; }
    function symbol() public constant returns (string symbol) { symbol; }
    function decimals() public constant returns (uint8 decimals) { decimals; }
    function totalSupply() public constant returns (uint256 totalSupply) { totalSupply; }
    function balanceOf(address _owner) public constant returns (uint256 balance) { _owner; balance; }
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) { _owner; _spender; remaining; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

/**
    ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, SafeMath {
    string public standard = 'Token 0.1';
    string public name = '';
    string public symbol = '';
    uint8 public decimals = 0;
    uint256 public totalSupply = 0;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
        @dev constructor

        @param _name        token name
        @param _symbol      token symbol
        @param _decimals    decimal points, for display purposes
    */
    function ERC20Token(string _name, string _symbol, uint8 _decimals) {
        require(bytes(_name).length > 0 && bytes(_symbol).length > 0); // validate input

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        validAddress(_to)
        returns (bool success)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        validAddress(_from)
        validAddress(_to)
        returns (bool success)
    {
        allowance[_from][msg.sender] = safeSub(allowance[_from][msg.sender], _value);
        balanceOf[_from] = safeSub(balanceOf[_from], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(_from, _to, _value);
        return true;
    }

    /**
        @dev allow another account/contract to spend some tokens on your behalf
        throws on any error rather then return a false flag to minimize user errors

        also, to minimize the risk of the approve/transferFrom attack vector
        (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), approve has to be called twice
        in 2 separate transactions - once to change the allowance to 0 and secondly to change it to the new allowance value

        @param _spender approved address
        @param _value   allowance amount

        @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        validAddress(_spender)
        returns (bool success)
    {
        // if the allowance isn't 0, it can only be updated to 0 to prevent an allowance change immediately after withdrawal
        require(_value == 0 || allowance[msg.sender][_spender] == 0);

        allowance[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
}

/*
    Smart Token interface
*/
contract ISmartToken is ITokenHolder, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

/*
    Smart Token v0.2

    'Owned' is specified here for readability reasons
*/
contract SmartToken is ISmartToken, ERC20Token, Owned, TokenHolder {
    string public version = '0.2';

    bool public transfersEnabled = true;    // true if transfer/transferFrom are enabled, false if not

    // triggered when a smart token is deployed - the _token address is defined for forward compatibility, in case we want to trigger the event from a factory
    event NewSmartToken(address _token);
    // triggered when the total supply is increased
    event Issuance(uint256 _amount);
    // triggered when the total supply is decreased
    event Destruction(uint256 _amount);

    /**
        @dev constructor

        @param _name       token name
        @param _symbol     token short symbol, 1-6 characters
        @param _decimals   for display purposes only
    */
    function SmartToken(string _name, string _symbol, uint8 _decimals)
        ERC20Token(_name, _symbol, _decimals)
    {
        require(bytes(_symbol).length <= 6); // validate input
        NewSmartToken(address(this));
    }

    // allows execution only when transfers aren't disabled
    modifier transfersAllowed {
        assert(transfersEnabled);
        _;
    }

    /**
        @dev disables/enables transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTransfers(bool _disable) public ownerOnly {
        transfersEnabled = !_disable;
    }

    /**
        @dev increases the token supply and sends the new tokens to an account
        can only be called by the contract owner

        @param _to         account to receive the new amount
        @param _amount     amount to increase the supply by
    */
    function issue(address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        totalSupply = safeAdd(totalSupply, _amount);
        balanceOf[_to] = safeAdd(balanceOf[_to], _amount);

        Issuance(_amount);
        Transfer(this, _to, _amount);
    }

    /**
        @dev removes tokens from an account and decreases the token supply
        can only be called by the contract owner

        @param _from       account to remove the amount from
        @param _amount     amount to decrease the supply by
    */
    function destroy(address _from, uint256 _amount)
        public
        ownerOnly
    {
        balanceOf[_from] = safeSub(balanceOf[_from], _amount);
        totalSupply = safeSub(totalSupply, _amount);

        Transfer(_from, this, _amount);
        Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra functionality

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors
        note that when transferring to the smart token's address, the coins are actually destroyed

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transfer(_to, _value));

        // transferring to the contract address destroys tokens
        if (_to == address(this)) {
            balanceOf[_to] -= _value;
            totalSupply -= _value;
            Destruction(_value);
        }

        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors
        note that when transferring to the smart token's address, the coins are actually destroyed

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transferFrom(_from, _to, _value));

        // transferring to the contract address destroys tokens
        if (_to == address(this)) {
            balanceOf[_to] -= _value;
            totalSupply -= _value;
            Destruction(_value);
        }

        return true;
    }
}

// File: solidity/contracts/token/interfaces/IERC20Token.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address _owner) external view returns (uint256);
    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);
    function transferFrom(address _from, address _to, uint256 _value) external returns (bool);
    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;

/**
  * @dev Utilities & Common Modifiers
*/
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }

    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }
}

// File: solidity/contracts/utility/SafeMath.sol


pragma solidity 0.6.12;

/**
  * @dev Library for basic math operations with overflow/underflow protection
*/
library SafeMath {
    /**
      * @dev returns the sum of _x and _y, reverts if the calculation overflows
      *
      * @param _x   value 1
      * @param _y   value 2
      *
      * @return sum
    */
    function add(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        require(z >= _x, "ERR_OVERFLOW");
        return z;
    }

    /**
      * @dev returns the difference of _x minus _y, reverts if the calculation underflows
      *
      * @param _x   minuend
      * @param _y   subtrahend
      *
      * @return difference
    */
    function sub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_x >= _y, "ERR_UNDERFLOW");
        return _x - _y;
    }

    /**
      * @dev returns the product of multiplying _x by _y, reverts if the calculation overflows
      *
      * @param _x   factor 1
      * @param _y   factor 2
      *
      * @return product
    */
    function mul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        // gas optimization
        if (_x == 0)
            return 0;

        uint256 z = _x * _y;
        require(z / _x == _y, "ERR_OVERFLOW");
        return z;
    }

    /**
      * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
      *
      * @param _x   dividend
      * @param _y   divisor
      *
      * @return quotient
    */
    function div(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_y > 0, "ERR_DIVIDE_BY_ZERO");
        uint256 c = _x / _y;
        return c;
    }
}

// File: solidity/contracts/token/ERC20Token.sol


pragma solidity 0.6.12;




/**
  * @dev ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, Utils {
    using SafeMath for uint256;


    string public override name;
    string public override symbol;
    uint8 public override decimals;
    uint256 public override totalSupply;
    mapping (address => uint256) public override balanceOf;
    mapping (address => mapping (address => uint256)) public override allowance;

    /**
      * @dev triggered when tokens are transferred between wallets
      *
      * @param _from    source address
      * @param _to      target address
      * @param _value   transfer amount
    */
    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    /**
      * @dev triggered when a wallet allows another wallet to transfer tokens from on its behalf
      *
      * @param _owner   wallet that approves the allowance
      * @param _spender wallet that receives the allowance
      * @param _value   allowance amount
    */
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
      * @dev initializes a new ERC20Token instance
      *
      * @param _name        token name
      * @param _symbol      token symbol
      * @param _decimals    decimal points, for display purposes
      * @param _totalSupply total supply of token units
    */
    constructor(string memory _name, string memory _symbol, uint8 _decimals, uint256 _totalSupply) public {
        // validate input
        require(bytes(_name).length > 0, "ERR_INVALID_NAME");
        require(bytes(_symbol).length > 0, "ERR_INVALID_SYMBOL");

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        totalSupply = _totalSupply;
        balanceOf[msg.sender] = _totalSupply;
    }

    /**
      * @dev transfers tokens to a given address
      * throws on any error rather then return a false flag to minimize user errors
      *
      * @param _to      target address
      * @param _value   transfer amount
      *
      * @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        virtual
        override
        validAddress(_to)
        returns (bool)
    {
        balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);
        balanceOf[_to] = balanceOf[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
      * @dev transfers tokens to a given address on behalf of another address
      * throws on any error rather then return a false flag to minimize user errors
      *
      * @param _from    source address
      * @param _to      target address
      * @param _value   transfer amount
      *
      * @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        virtual
        override
        validAddress(_from)
        validAddress(_to)
        returns (bool)
    {
        allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);
        balanceOf[_from] = balanceOf[_from].sub(_value);
        balanceOf[_to] = balanceOf[_to].add(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
      * @dev allows another account/contract to transfers tokens on behalf of the caller
      * throws on any error rather then return a false flag to minimize user errors
      *
      * @param _spender approved address
      * @param _value   allowance amount
      *
      * @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        virtual
        override
        validAddress(_spender)
        returns (bool)
    {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;
    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {
}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20Token {
    function issue(address _to, uint256 _amount) external;
    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
  * @dev Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
      * @dev triggered when the owner is updated
      *
      * @param _prevOwner previous owner
      * @param _newOwner  new owner
    */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
      * @dev initializes a new Owned instance
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
      * @dev allows transferring the contract ownership
      * the new owner still needs to accept the transfer
      * can only be called by the contract owner
      *
      * @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
      * @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() override public {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/token/DSToken.sol


pragma solidity 0.6.12;




/**
  * @dev DSToken represents a token with dynamic supply.
  * The owner of the token can mint/burn tokens to/from any account.
  *
*/
contract DSToken is IDSToken, ERC20Token, Owned {
    using SafeMath for uint256;

    /**
      * @dev triggered when the total supply is increased
      *
      * @param _amount  amount that gets added to the supply
    */
    event Issuance(uint256 _amount);

    /**
      * @dev triggered when the total supply is decreased
      *
      * @param _amount  amount that gets removed from the supply
    */
    event Destruction(uint256 _amount);

    /**
      * @dev initializes a new DSToken instance
      *
      * @param _name       token name
      * @param _symbol     token short symbol, minimum 1 character
      * @param _decimals   for display purposes only
    */
    constructor(string memory _name, string memory _symbol, uint8 _decimals)
        public
        ERC20Token(_name, _symbol, _decimals, 0)
    {
    }

    /**
      * @dev increases the token supply and sends the new tokens to the given account
      * can only be called by the contract owner
      *
      * @param _to      account to receive the new amount
      * @param _amount  amount to increase the supply by
    */
    function issue(address _to, uint256 _amount)
        public
        override
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        totalSupply = totalSupply.add(_amount);
        balanceOf[_to] = balanceOf[_to].add(_amount);

        emit Issuance(_amount);
        emit Transfer(address(0), _to, _amount);
    }

    /**
      * @dev removes tokens from the given account and decreases the token supply
      * can only be called by the contract owner
      *
      * @param _from    account to remove the amount from
      * @param _amount  amount to decrease the supply by
    */
    function destroy(address _from, uint256 _amount) public override ownerOnly {
        balanceOf[_from] = balanceOf[_from].sub(_amount);
        totalSupply = totalSupply.sub(_amount);

        emit Transfer(_from, address(0), _amount);
        emit Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra functionality

    /**
      * @dev send coins
      * throws on any error rather then return a false flag to minimize user errors
      * in addition to the standard checks, the function throws if transfers are disabled
      *
      * @param _to      target address
      * @param _value   transfer amount
      *
      * @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        override(IERC20Token, ERC20Token)
        returns (bool)
    {
        return super.transfer(_to, _value);
    }

    /**
      * @dev an account/contract attempts to get the coins
      * throws on any error rather then return a false flag to minimize user errors
      * in addition to the standard checks, the function throws if transfers are disabled
      *
      * @param _from    source address
      * @param _to      target address
      * @param _value   transfer amount
      *
      * @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        override(IERC20Token, ERC20Token)
        returns (bool) 
    {
        return super.transferFrom(_from, _to, _value);
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol



pragma solidity ^0.6.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.6.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/AccessControl.sol



pragma solidity ^0.6.0;




/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;

    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }

    mapping (bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");

        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");

        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }

    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }

    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/token/interfaces/IERC20Token.sol


pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address _owner) external view returns (uint256);

    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool);

    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionEventsSubscriber.sol


pragma solidity 0.6.12;



/**
 * @dev Liquidity protection events subscriber interface
 */
interface ILiquidityProtectionEventsSubscriber {
    function onAddingLiquidity(
        address provider,
        IConverterAnchor poolAnchor,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function onRemovingLiquidity(
        uint256 id,
        address provider,
        IConverterAnchor poolAnchor,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionSettings.sol


pragma solidity 0.6.12;




/*
    Liquidity Protection Store Settings interface
*/
interface ILiquidityProtectionSettings {
    function isPoolWhitelisted(IConverterAnchor poolAnchor) external view returns (bool);

    function poolWhitelist() external view returns (address[] memory);

    function subscribers() external view returns (address[] memory);

    function isPoolSupported(IConverterAnchor poolAnchor) external view returns (bool);

    function minNetworkTokenLiquidityForMinting() external view returns (uint256);

    function defaultNetworkTokenMintingLimit() external view returns (uint256);

    function networkTokenMintingLimits(IConverterAnchor poolAnchor) external view returns (uint256);

    function addLiquidityDisabled(IConverterAnchor poolAnchor, IERC20Token reserveToken) external view returns (bool);

    function minProtectionDelay() external view returns (uint256);

    function maxProtectionDelay() external view returns (uint256);

    function minNetworkCompensation() external view returns (uint256);

    function lockDuration() external view returns (uint256);

    function averageRateMaxDeviation() external view returns (uint32);
}

// File: solidity/contracts/converter/interfaces/IConverter.sol


pragma solidity 0.6.12;




/*
    Converter interface
*/
interface IConverter is IOwned {
    function converterType() external pure returns (uint16);

    function anchor() external view returns (IConverterAnchor);

    function isActive() external view returns (bool);

    function targetAmountAndFee(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount
    ) external view returns (uint256, uint256);

    function convert(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) external payable returns (uint256);

    function conversionFee() external view returns (uint32);

    function maxConversionFee() external view returns (uint32);

    function reserveBalance(IERC20Token _reserveToken) external view returns (uint256);

    receive() external payable;

    function transferAnchorOwnership(address _newOwner) external;

    function acceptAnchorOwnership() external;

    function setConversionFee(uint32 _conversionFee) external;

    function withdrawTokens(
        IERC20Token _token,
        address _to,
        uint256 _amount
    ) external;

    function withdrawETH(address payable _to) external;

    function addReserve(IERC20Token _token, uint32 _ratio) external;

    // deprecated, backward compatibility
    function token() external view returns (IConverterAnchor);

    function transferTokenOwnership(address _newOwner) external;

    function acceptTokenOwnership() external;

    function connectors(IERC20Token _address)
        external
        view
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        );

    function getConnectorBalance(IERC20Token _connectorToken) external view returns (uint256);

    function connectorTokens(uint256 _index) external view returns (IERC20Token);

    function connectorTokenCount() external view returns (uint16);

    /**
     * @dev triggered when the converter is activated
     *
     * @param _type        converter type
     * @param _anchor      converter anchor
     * @param _activated   true if the converter was activated, false if it was deactivated
     */
    event Activation(uint16 indexed _type, IConverterAnchor indexed _anchor, bool indexed _activated);

    /**
     * @dev triggered when a conversion between two tokens occurs
     *
     * @param _fromToken       source ERC20 token
     * @param _toToken         target ERC20 token
     * @param _trader          wallet that initiated the trade
     * @param _amount          input amount in units of the source token
     * @param _return          output amount minus conversion fee in units of the target token
     * @param _conversionFee   conversion fee in units of the target token
     */
    event Conversion(
        IERC20Token indexed _fromToken,
        IERC20Token indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );

    /**
     * @dev triggered when the rate between two tokens in the converter changes
     * note that the event might be dispatched for rate updates between any two tokens in the converter
     *
     * @param  _token1 address of the first token
     * @param  _token2 address of the second token
     * @param  _rateN  rate of 1 unit of `_token1` in `_token2` (numerator)
     * @param  _rateD  rate of 1 unit of `_token1` in `_token2` (denominator)
     */
    event TokenRateUpdate(IERC20Token indexed _token1, IERC20Token indexed _token2, uint256 _rateN, uint256 _rateD);

    /**
     * @dev triggered when the conversion fee is updated
     *
     * @param  _prevFee    previous fee percentage, represented in ppm
     * @param  _newFee     new fee percentage, represented in ppm
     */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);
}

// File: solidity/contracts/converter/interfaces/IConverterRegistry.sol


pragma solidity 0.6.12;



interface IConverterRegistry {
    function getAnchorCount() external view returns (uint256);

    function getAnchors() external view returns (address[] memory);

    function getAnchor(uint256 _index) external view returns (IConverterAnchor);

    function isAnchor(address _value) external view returns (bool);

    function getLiquidityPoolCount() external view returns (uint256);

    function getLiquidityPools() external view returns (address[] memory);

    function getLiquidityPool(uint256 _index) external view returns (IConverterAnchor);

    function isLiquidityPool(address _value) external view returns (bool);

    function getConvertibleTokenCount() external view returns (uint256);

    function getConvertibleTokens() external view returns (address[] memory);

    function getConvertibleToken(uint256 _index) external view returns (IERC20Token);

    function isConvertibleToken(address _value) external view returns (bool);

    function getConvertibleTokenAnchorCount(IERC20Token _convertibleToken) external view returns (uint256);

    function getConvertibleTokenAnchors(IERC20Token _convertibleToken) external view returns (address[] memory);

    function getConvertibleTokenAnchor(IERC20Token _convertibleToken, uint256 _index)
        external
        view
        returns (IConverterAnchor);

    function isConvertibleTokenAnchor(IERC20Token _convertibleToken, address _value) external view returns (bool);
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
 * @dev This contract provides support and utilities for contract ownership.
 */
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
     * @dev triggered when the owner is updated
     *
     * @param _prevOwner previous owner
     * @param _newOwner  new owner
     */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
     * @dev initializes a new Owned instance
     */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
     * @dev allows transferring the contract ownership
     * the new owner still needs to accept the transfer
     * can only be called by the contract owner
     *
     * @param _newOwner    new contract owner
     */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
     * @dev used by a new owner to accept an ownership transfer
     */
    function acceptOwnership() public override {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;

/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }

    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }

    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address _address) {
        _validExternalAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validExternalAddress(address _address) internal view {
        require(_address != address(0) && _address != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }
}

// File: solidity/contracts/utility/interfaces/IContractRegistry.sol


pragma solidity 0.6.12;

/*
    Contract Registry interface
*/
interface IContractRegistry {
    function addressOf(bytes32 _contractName) external view returns (address);
}

// File: solidity/contracts/utility/ContractRegistryClient.sol


pragma solidity 0.6.12;




/**
 * @dev This is the base contract for ContractRegistry clients.
 */
contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant BANCOR_FORMULA = "BancorFormula";
    bytes32 internal constant CONVERTER_FACTORY = "ConverterFactory";
    bytes32 internal constant CONVERSION_PATH_FINDER = "ConversionPathFinder";
    bytes32 internal constant CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";
    bytes32 internal constant LIQUIDITY_PROTECTION = "LiquidityProtection";

    IContractRegistry public registry; // address of the current contract-registry
    IContractRegistry public prevRegistry; // address of the previous contract-registry
    bool public onlyOwnerCanUpdateRegistry; // only an owner can update the contract-registry

    /**
     * @dev verifies that the caller is mapped to the given contract name
     *
     * @param _contractName    contract name
     */
    modifier only(bytes32 _contractName) {
        _only(_contractName);
        _;
    }

    // error message binary size optimization
    function _only(bytes32 _contractName) internal view {
        require(msg.sender == addressOf(_contractName), "ERR_ACCESS_DENIED");
    }

    /**
     * @dev initializes a new ContractRegistryClient instance
     *
     * @param  _registry   address of a contract-registry contract
     */
    constructor(IContractRegistry _registry) internal validAddress(address(_registry)) {
        registry = IContractRegistry(_registry);
        prevRegistry = IContractRegistry(_registry);
    }

    /**
     * @dev updates to the new contract-registry
     */
    function updateRegistry() public {
        // verify that this function is permitted
        require(msg.sender == owner || !onlyOwnerCanUpdateRegistry, "ERR_ACCESS_DENIED");

        // get the new contract-registry
        IContractRegistry newRegistry = IContractRegistry(addressOf(CONTRACT_REGISTRY));

        // verify that the new contract-registry is different and not zero
        require(newRegistry != registry && address(newRegistry) != address(0), "ERR_INVALID_REGISTRY");

        // verify that the new contract-registry is pointing to a non-zero contract-registry
        require(newRegistry.addressOf(CONTRACT_REGISTRY) != address(0), "ERR_INVALID_REGISTRY");

        // save a backup of the current contract-registry before replacing it
        prevRegistry = registry;

        // replace the current contract-registry with the new contract-registry
        registry = newRegistry;
    }

    /**
     * @dev restores the previous contract-registry
     */
    function restoreRegistry() public ownerOnly {
        // restore the previous contract-registry
        registry = prevRegistry;
    }

    /**
     * @dev restricts the permission to update the contract-registry
     *
     * @param _onlyOwnerCanUpdateRegistry  indicates whether or not permission is restricted to owner only
     */
    function restrictRegistryUpdate(bool _onlyOwnerCanUpdateRegistry) public ownerOnly {
        // change the permission to update the contract-registry
        onlyOwnerCanUpdateRegistry = _onlyOwnerCanUpdateRegistry;
    }

    /**
     * @dev returns the address associated with the given contract name
     *
     * @param _contractName    contract name
     *
     * @return contract address
     */
    function addressOf(bytes32 _contractName) internal view returns (address) {
        return registry.addressOf(_contractName);
    }
}

// File: solidity/contracts/liquidity-protection/LiquidityProtectionSettings.sol


pragma solidity 0.6.12;









/**
 * @dev Liquidity Protection Settings contract
 */
contract LiquidityProtectionSettings is ILiquidityProtectionSettings, AccessControl, ContractRegistryClient {
    using SafeMath for uint256;
    using EnumerableSet for EnumerableSet.AddressSet;

    // the owner role is used to update the settings
    bytes32 public constant ROLE_OWNER = keccak256("ROLE_OWNER");

    uint32 private constant PPM_RESOLUTION = 1000000;

    IERC20Token private immutable _networkToken;

    // list of whitelisted pools
    EnumerableSet.AddressSet private _poolWhitelist;

    // list of subscribers
    EnumerableSet.AddressSet private _subscribers;

    // network token minting limits
    uint256 private _minNetworkTokenLiquidityForMinting = 1000e18;
    uint256 private _defaultNetworkTokenMintingLimit = 20000e18;
    mapping(IConverterAnchor => uint256) private _networkTokenMintingLimits;

    // permission of adding liquidity for a given reserve on a given pool
    mapping(IConverterAnchor => mapping(IERC20Token => bool)) private _addLiquidityDisabled;

    // number of seconds until any protection is in effect
    uint256 private _minProtectionDelay = 30 days;

    // number of seconds until full protection is in effect
    uint256 private _maxProtectionDelay = 100 days;

    // minimum amount of network tokens that the system can mint as compensation for base token losses
    uint256 private _minNetworkCompensation = 1e16; // = 0.01 network tokens

    // number of seconds from liquidation to full network token release
    uint256 private _lockDuration = 24 hours;

    // maximum deviation of the average rate from the spot rate
    uint32 private _averageRateMaxDeviation = 5000; // PPM units

    /**
     * @dev triggered when the pool whitelist is updated
     *
     * @param poolAnchor    pool anchor
     * @param added         true if the pool was added to the whitelist, false if it was removed
     */
    event PoolWhitelistUpdated(IConverterAnchor indexed poolAnchor, bool added);

    /**
     * @dev triggered when a subscriber is added or removed
     *
     * @param subscriber    subscriber
     * @param added         true if the subscriber was added, false if it was removed
     */
    event SubscriberUpdated(ILiquidityProtectionEventsSubscriber indexed subscriber, bool added);

    /**
     * @dev triggered when the minimum amount of network token liquidity to allow minting is updated
     *
     * @param prevMin   previous minimum amount of network token liquidity for minting
     * @param newMin    new minimum amount of network token liquidity for minting
     */
    event MinNetworkTokenLiquidityForMintingUpdated(uint256 prevMin, uint256 newMin);

    /**
     * @dev triggered when the default network token minting limit is updated
     *
     * @param prevDefault   previous default network token minting limit
     * @param newDefault    new default network token minting limit
     */
    event DefaultNetworkTokenMintingLimitUpdated(uint256 prevDefault, uint256 newDefault);

    /**
     * @dev triggered when a pool network token minting limit is updated
     *
     * @param poolAnchor    pool anchor
     * @param prevLimit     previous limit
     * @param newLimit      new limit
     */
    event NetworkTokenMintingLimitUpdated(IConverterAnchor indexed poolAnchor, uint256 prevLimit, uint256 newLimit);

    /**
     * @dev triggered when the protection delays are updated
     *
     * @param prevMinProtectionDelay    previous seconds until the protection starts
     * @param newMinProtectionDelay     new seconds until the protection starts
     * @param prevMaxProtectionDelay    previous seconds until full protection
     * @param newMaxProtectionDelay     new seconds until full protection
     */
    event ProtectionDelaysUpdated(
        uint256 prevMinProtectionDelay,
        uint256 newMinProtectionDelay,
        uint256 prevMaxProtectionDelay,
        uint256 newMaxProtectionDelay
    );

    /**
     * @dev triggered when the minimum network token compensation is updated
     *
     * @param prevMinNetworkCompensation    previous minimum network token compensation
     * @param newMinNetworkCompensation     new minimum network token compensation
     */
    event MinNetworkCompensationUpdated(uint256 prevMinNetworkCompensation, uint256 newMinNetworkCompensation);

    /**
     * @dev triggered when the network token lock duration is updated
     *
     * @param prevLockDuration  previous network token lock duration, in seconds
     * @param newLockDuration   new network token lock duration, in seconds
     */
    event LockDurationUpdated(uint256 prevLockDuration, uint256 newLockDuration);

    /**
     * @dev triggered when the maximum deviation of the average rate from the spot rate is updated
     *
     * @param prevAverageRateMaxDeviation   previous maximum deviation of the average rate from the spot rate
     * @param newAverageRateMaxDeviation    new maximum deviation of the average rate from the spot rate
     */
    event AverageRateMaxDeviationUpdated(uint32 prevAverageRateMaxDeviation, uint32 newAverageRateMaxDeviation);

    /**
     * @dev triggered when adding liquidity is disabled or enabled for a given reserve on a given pool
     *
     * @param poolAnchor    pool anchor
     * @param reserveToken  reserve token
     * @param disabled      true if disabled, false otherwise
     */
    event AddLiquidityDisabled(IConverterAnchor indexed poolAnchor, IERC20Token indexed reserveToken, bool disabled);

    /**
     * @dev initializes a new LiquidityProtectionSettings contract
     *
     * @param registry  contract registry
     * @param token     the network token
     */
    constructor(IERC20Token token, IContractRegistry registry)
        public
        ContractRegistryClient(registry)
        validAddress(address(token))
        notThis(address(token))
    {
        // set up administrative roles.
        _setRoleAdmin(ROLE_OWNER, ROLE_OWNER);

        // allow the deployer to initially govern the contract.
        _setupRole(ROLE_OWNER, msg.sender);

        _networkToken = token;
    }

    modifier onlyOwner() {
        _onlyOwner();
        _;
    }

    // error message binary size optimization
    function _onlyOwner() internal view {
        require(hasRole(ROLE_OWNER, msg.sender), "ERR_ACCESS_DENIED");
    }

    // ensures that the portion is valid
    modifier validPortion(uint32 portion) {
        _validPortion(portion);
        _;
    }

    // error message binary size optimization
    function _validPortion(uint32 portion) internal pure {
        require(portion > 0 && portion <= PPM_RESOLUTION, "ERR_INVALID_PORTION");
    }

    /**
     * @dev returns the network token
     *
     * @return the network token
     */
    function networkToken() external view returns (IERC20Token) {
        return _networkToken;
    }

    /**
     * @dev returns the minimum network token liquidity for minting
     *
     * @return the minimum network token liquidity for minting
     */
    function minNetworkTokenLiquidityForMinting() external view override returns (uint256) {
        return _minNetworkTokenLiquidityForMinting;
    }

    /**
     * @dev returns the default network token minting limit
     *
     * @return the default network token minting limit
     */
    function defaultNetworkTokenMintingLimit() external view override returns (uint256) {
        return _defaultNetworkTokenMintingLimit;
    }

    /**
     * @dev returns the network token minting limit for a given pool
     *
     * @param poolAnchor    pool anchor
     * @return the network token minting limit for a given pool
     */
    function networkTokenMintingLimits(IConverterAnchor poolAnchor) external view override returns (uint256) {
        return _networkTokenMintingLimits[poolAnchor];
    }

    /**
     * @dev returns the permission of adding liquidity for a given reserve on a given pool
     *
     * @param poolAnchor    pool anchor
     * @param reserveToken  reserve token
     * @return true if adding liquidity is disabled, false otherwise
     */
    function addLiquidityDisabled(IConverterAnchor poolAnchor, IERC20Token reserveToken)
        external
        view
        override
        returns (bool)
    {
        return _addLiquidityDisabled[poolAnchor][reserveToken];
    }

    /**
     * @dev returns the minimum number of seconds until any protection is in effect
     *
     * @return the minimum number of seconds until any protection is in effect
     */
    function minProtectionDelay() external view override returns (uint256) {
        return _minProtectionDelay;
    }

    /**
     * @dev returns the maximum number of seconds until full protection is in effect
     *
     * @return the maximum number of seconds until full protection is in effect
     */
    function maxProtectionDelay() external view override returns (uint256) {
        return _maxProtectionDelay;
    }

    /**
     * @dev returns the minimum amount of network tokens that the system can mint as compensation for base token losses
     *
     * @return the minimum amount of network tokens that the system can mint as compensation for base token losses
     */
    function minNetworkCompensation() external view override returns (uint256) {
        return _minNetworkCompensation;
    }

    /**
     * @dev returns the number of seconds from liquidation to full network token release
     *
     * @return the number of seconds from liquidation to full network token release
     */
    function lockDuration() external view override returns (uint256) {
        return _lockDuration;
    }

    /**
     * @dev returns the maximum deviation of the average rate from the spot rate
     *
     * @return the maximum deviation of the average rate from the spot rate
     */
    function averageRateMaxDeviation() external view override returns (uint32) {
        return _averageRateMaxDeviation;
    }

    /**
     * @dev adds a pool to the whitelist
     * can only be called by the contract owner
     *
     * @param poolAnchor    pool anchor
     */
    function addPoolToWhitelist(IConverterAnchor poolAnchor)
        external
        onlyOwner
        validAddress(address(poolAnchor))
        notThis(address(poolAnchor))
    {
        require(_poolWhitelist.add(address(poolAnchor)), "ERR_POOL_ALREADY_WHITELISTED");

        emit PoolWhitelistUpdated(poolAnchor, true);
    }

    /**
     * @dev removes a pool from the whitelist
     * can only be called by the contract owner
     *
     * @param poolAnchor    pool anchor
     */
    function removePoolFromWhitelist(IConverterAnchor poolAnchor)
        external
        onlyOwner
        validAddress(address(poolAnchor))
        notThis(address(poolAnchor))
    {
        require(_poolWhitelist.remove(address(poolAnchor)), "ERR_POOL_NOT_WHITELISTED");

        emit PoolWhitelistUpdated(poolAnchor, false);
    }

    /**
     * @dev checks whether a given pool is whitelisted
     *
     * @param poolAnchor    pool anchor
     * @return true if the given pool is whitelisted, false otherwise
     */
    function isPoolWhitelisted(IConverterAnchor poolAnchor) external view override returns (bool) {
        return _poolWhitelist.contains(address(poolAnchor));
    }

    /**
     * @dev returns pools whitelist
     *
     * @return pools whitelist
     */
    function poolWhitelist() external view override returns (address[] memory) {
        uint256 length = _poolWhitelist.length();
        address[] memory list = new address[](length);
        for (uint256 i = 0; i < length; i++) {
            list[i] = _poolWhitelist.at(i);
        }
        return list;
    }

    /**
     * @dev adds a subscriber
     * can only be called by the contract owner
     *
     * @param subscriber    subscriber address
     */
    function addSubscriber(ILiquidityProtectionEventsSubscriber subscriber)
        external
        onlyOwner
        validAddress(address(subscriber))
        notThis(address(subscriber))
    {
        require(_subscribers.add(address(subscriber)), "ERR_SUBSCRIBER_ALREADY_SET");

        emit SubscriberUpdated(subscriber, true);
    }

    /**
     * @dev removes a subscriber
     * can only be called by the contract owner
     *
     * @param subscriber    subscriber address
     */
    function removeSubscriber(ILiquidityProtectionEventsSubscriber subscriber)
        external
        onlyOwner
        validAddress(address(subscriber))
        notThis(address(subscriber))
    {
        require(_subscribers.remove(address(subscriber)), "ERR_INVALID_SUBSCRIBER");

        emit SubscriberUpdated(subscriber, false);
    }

    /**
     * @dev returns subscribers list
     *
     * @return subscribers list
     */
    function subscribers() external view override returns (address[] memory) {
        uint256 length = _subscribers.length();
        address[] memory list = new address[](length);
        for (uint256 i = 0; i < length; i++) {
            list[i] = _subscribers.at(i);
        }
        return list;
    }

    /**
     * @dev updates the minimum amount of network token liquidity to allow minting
     * can only be called by the contract owner
     *
     * @param amount   the minimum amount of network token liquidity to allow minting
     */
    function setMinNetworkTokenLiquidityForMinting(uint256 amount) external onlyOwner() {
        emit MinNetworkTokenLiquidityForMintingUpdated(_minNetworkTokenLiquidityForMinting, amount);

        _minNetworkTokenLiquidityForMinting = amount;
    }

    /**
     * @dev updates the default amount of network token that the system can mint into each pool
     * can only be called by the contract owner
     *
     * @param amount    the default amount of network token that the system can mint into each pool
     */
    function setDefaultNetworkTokenMintingLimit(uint256 amount) external onlyOwner() {
        emit DefaultNetworkTokenMintingLimitUpdated(_defaultNetworkTokenMintingLimit, amount);

        _defaultNetworkTokenMintingLimit = amount;
    }

    /**
     * @dev updates the amount of network tokens that the system can mint into a specific pool
     * can only be called by the contract owner
     *
     * @param poolAnchor    pool anchor
     * @param amount        the amount of network tokens that the system can mint into a specific pool
     */
    function setNetworkTokenMintingLimit(IConverterAnchor poolAnchor, uint256 amount)
        external
        onlyOwner()
        validAddress(address(poolAnchor))
    {
        emit NetworkTokenMintingLimitUpdated(poolAnchor, _networkTokenMintingLimits[poolAnchor], amount);

        _networkTokenMintingLimits[poolAnchor] = amount;
    }

    /**
     * @dev updates the protection delays
     * can only be called by the contract owner
     *
     * @param minDelay   seconds until the protection starts
     * @param maxDelay   seconds until full protection
     */
    function setProtectionDelays(uint256 minDelay, uint256 maxDelay) external onlyOwner() {
        require(minDelay < maxDelay, "ERR_INVALID_PROTECTION_DELAY");

        emit ProtectionDelaysUpdated(_minProtectionDelay, minDelay, _maxProtectionDelay, maxDelay);

        _minProtectionDelay = minDelay;
        _maxProtectionDelay = maxDelay;
    }

    /**
     * @dev updates the minimum amount of network token compensation
     * can only be called by the contract owner
     *
     * @param amount    the minimum amount of network token compensation
     */
    function setMinNetworkCompensation(uint256 amount) external onlyOwner() {
        emit MinNetworkCompensationUpdated(_minNetworkCompensation, amount);

        _minNetworkCompensation = amount;
    }

    /**
     * @dev updates the network token lock duration
     * can only be called by the contract owner
     *
     * @param duration  network token lock duration, in seconds
     */
    function setLockDuration(uint256 duration) external onlyOwner() {
        emit LockDurationUpdated(_lockDuration, duration);

        _lockDuration = duration;
    }

    /**
     * @dev sets the maximum deviation of the average rate from the spot rate
     * can only be called by the contract owner
     *
     * @param deviation maximum deviation of the average rate from the spot rate
     */
    function setAverageRateMaxDeviation(uint32 deviation) external onlyOwner() validPortion(deviation) {
        emit AverageRateMaxDeviationUpdated(_averageRateMaxDeviation, deviation);

        _averageRateMaxDeviation = deviation;
    }

    /**
     * @dev disables or enables adding liquidity for a given reserve on a given pool
     * can only be called by the contract owner
     *
     * @param poolAnchor    pool anchor
     * @param reserveToken  reserve token
     * @param disable       true to disable, false otherwise
     */
    function disableAddLiquidity(
        IConverterAnchor poolAnchor,
        IERC20Token reserveToken,
        bool disable
    ) external onlyOwner() {
        emit AddLiquidityDisabled(poolAnchor, reserveToken, disable);

        _addLiquidityDisabled[poolAnchor][reserveToken] = disable;
    }

    /**
     * @dev checks if protection is supported for the given pool
     * only standard pools are supported (2 reserves, 50%/50% weights)
     * note that the pool should still be whitelisted
     *
     * @param poolAnchor    anchor of the pool
     * @return true if the pool is supported, false otherwise
     */
    function isPoolSupported(IConverterAnchor poolAnchor) external view override returns (bool) {
        IERC20Token tmpNetworkToken = _networkToken;

        // verify that the pool exists in the registry
        IConverterRegistry converterRegistry = IConverterRegistry(addressOf(CONVERTER_REGISTRY));
        require(converterRegistry.isAnchor(address(poolAnchor)), "ERR_INVALID_ANCHOR");

        // get the converter
        IConverter converter = IConverter(payable(poolAnchor.owner()));

        // verify that the converter has 2 reserves
        if (converter.connectorTokenCount() != 2) {
            return false;
        }

        // verify that one of the reserves is the network token
        IERC20Token reserve0Token = converter.connectorTokens(0);
        IERC20Token reserve1Token = converter.connectorTokens(1);
        if (reserve0Token != tmpNetworkToken && reserve1Token != tmpNetworkToken) {
            return false;
        }

        // verify that the reserve weights are exactly 50%/50%
        if (
            converterReserveWeight(converter, reserve0Token) != PPM_RESOLUTION / 2 ||
            converterReserveWeight(converter, reserve1Token) != PPM_RESOLUTION / 2
        ) {
            return false;
        }

        return true;
    }

    // utility to get the reserve weight (including from older converters that don't support the new converterReserveWeight function)
    function converterReserveWeight(IConverter converter, IERC20Token reserveToken) private view returns (uint32) {
        (, uint32 weight, , , ) = converter.connectors(reserveToken);
        return weight;
    }
}

pragma solidity ^0.4.24;

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/ContractIds.sol

/**
    Id definitions for bancor contracts

    Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // Ids of BNT converter and BNT token
    bytes32 public constant BNT_TOKEN = "BNTToken";
    bytes32 public constant BNT_CONVERTER = "BNTConverter";

    // Id of BancorX contract
    bytes32 public constant BANCOR_X = "BancorX";
}

// File: contracts/utility/ContractRegistry.sol

/**
    Contract Registry

    The contract registry keeps contract addresses by name.
    The owner can update contract addresses so that a contract name always points to the latest version
    of the given contract.
    Other contracts can query the registry to get updated addresses instead of depending on specific
    addresses.

    Note that contract names are limited to 32 bytes UTF8 encoded ASCII strings to optimize gas costs
*/
contract ContractRegistry is IContractRegistry, Owned, Utils, ContractIds {
    struct RegistryItem {
        address contractAddress;    // contract address
        uint256 nameIndex;          // index of the item in the list of contract names
        bool isSet;                 // used to tell if the mapping element is defined
    }

    mapping (bytes32 => RegistryItem) private items;    // name -> RegistryItem mapping
    string[] public contractNames;                      // list of all registered contract names

    // triggered when an address pointed to by a contract name is modified
    event AddressUpdate(bytes32 indexed _contractName, address _contractAddress);

    /**
        @dev constructor
    */
    constructor() public {
        registerAddress(ContractIds.CONTRACT_REGISTRY, address(this));
    }

    /**
        @dev returns the number of items in the registry

        @return number of items
    */
    function itemCount() public view returns (uint256) {
        return contractNames.length;
    }

    /**
        @dev returns the address associated with the given contract name

        @param _contractName    contract name

        @return contract address
    */
    function addressOf(bytes32 _contractName) public view returns (address) {
        return items[_contractName].contractAddress;
    }

    /**
        @dev registers a new address for the contract name in the registry

        @param _contractName     contract name
        @param _contractAddress  contract address
    */
    function registerAddress(bytes32 _contractName, address _contractAddress)
        public
        ownerOnly
        validAddress(_contractAddress)
    {
        require(_contractName.length > 0); // validate input

        // update the address in the registry
        items[_contractName].contractAddress = _contractAddress;

        if (!items[_contractName].isSet) {
            // mark the item as set
            items[_contractName].isSet = true;
            // add the contract name to the name list
            uint256 i = contractNames.push(bytes32ToString(_contractName));
            // update the item's index in the list
            items[_contractName].nameIndex = i - 1;
        }

        // dispatch the address update event
        emit AddressUpdate(_contractName, _contractAddress);
    }

    /**
        @dev removes an existing contract address from the registry

        @param _contractName contract name
    */
    function unregisterAddress(bytes32 _contractName) public ownerOnly {
        require(_contractName.length > 0); // validate input

        // remove the address from the registry
        items[_contractName].contractAddress = address(0);

        // if there are multiple items in the registry, move the last element to the deleted element's position
        // and modify last element's registryItem.nameIndex in the items collection to point to the right position in contractNames
        if (contractNames.length > 1) {
            string memory lastContractNameString = contractNames[contractNames.length - 1];
            uint256 unregisterIndex = items[_contractName].nameIndex;

            contractNames[unregisterIndex] = lastContractNameString;
            bytes32 lastContractName = stringToBytes32(lastContractNameString);
            RegistryItem storage registryItem = items[lastContractName];
            registryItem.nameIndex = unregisterIndex;
        }

        // remove the last element from the name list
        contractNames.length--;
        // zero the deleted element's index
        items[_contractName].nameIndex = 0;

        // dispatch the address update event
        emit AddressUpdate(_contractName, address(0));
    }

    /**
        @dev utility, converts bytes32 to a string
        note that the bytes32 argument is assumed to be UTF8 encoded ASCII string

        @return string representation of the given bytes32 argument
    */
    function bytes32ToString(bytes32 _bytes) private pure returns (string) {
        bytes memory byteArray = new bytes(32);
        for (uint256 i; i < 32; i++) {
            byteArray[i] = _bytes[i];
        }

        return string(byteArray);
    }

    // @dev utility, converts string to bytes32
    function stringToBytes32(string memory _string) private pure returns (bytes32) {
        bytes32 result;
        assembly {
            result := mload(add(_string,32))
        }
        return result;
    }

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address) {
        return addressOf(_contractName);
    }
}

// File: solidity/contracts/token/interfaces/IERC20Token.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address _owner) external view returns (uint256);

    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool);

    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/utility/TokenHandler.sol


pragma solidity 0.6.12;


contract TokenHandler {
    bytes4 private constant APPROVE_FUNC_SELECTOR = bytes4(keccak256("approve(address,uint256)"));
    bytes4 private constant TRANSFER_FUNC_SELECTOR = bytes4(keccak256("transfer(address,uint256)"));
    bytes4 private constant TRANSFER_FROM_FUNC_SELECTOR = bytes4(keccak256("transferFrom(address,address,uint256)"));

    /**
     * @dev executes the ERC20 token's `approve` function and reverts upon failure
     * the main purpose of this function is to prevent a non standard ERC20 token
     * from failing silently
     *
     * @param _token   ERC20 token address
     * @param _spender approved address
     * @param _value   allowance amount
     */
    function safeApprove(
        IERC20Token _token,
        address _spender,
        uint256 _value
    ) internal {
        (bool success, bytes memory data) = address(_token).call(
            abi.encodeWithSelector(APPROVE_FUNC_SELECTOR, _spender, _value)
        );
        require(success && (data.length == 0 || abi.decode(data, (bool))), "ERR_APPROVE_FAILED");
    }

    /**
     * @dev executes the ERC20 token's `transfer` function and reverts upon failure
     * the main purpose of this function is to prevent a non standard ERC20 token
     * from failing silently
     *
     * @param _token   ERC20 token address
     * @param _to      target address
     * @param _value   transfer amount
     */
    function safeTransfer(
        IERC20Token _token,
        address _to,
        uint256 _value
    ) internal {
        (bool success, bytes memory data) = address(_token).call(
            abi.encodeWithSelector(TRANSFER_FUNC_SELECTOR, _to, _value)
        );
        require(success && (data.length == 0 || abi.decode(data, (bool))), "ERR_TRANSFER_FAILED");
    }

    /**
     * @dev executes the ERC20 token's `transferFrom` function and reverts upon failure
     * the main purpose of this function is to prevent a non standard ERC20 token
     * from failing silently
     *
     * @param _token   ERC20 token address
     * @param _from    source address
     * @param _to      target address
     * @param _value   transfer amount
     */
    function safeTransferFrom(
        IERC20Token _token,
        address _from,
        address _to,
        uint256 _value
    ) internal {
        (bool success, bytes memory data) = address(_token).call(
            abi.encodeWithSelector(TRANSFER_FROM_FUNC_SELECTOR, _from, _to, _value)
        );
        require(success && (data.length == 0 || abi.decode(data, (bool))), "ERR_TRANSFER_FROM_FAILED");
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
 * @dev This contract provides support and utilities for contract ownership.
 */
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
     * @dev triggered when the owner is updated
     *
     * @param _prevOwner previous owner
     * @param _newOwner  new owner
     */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
     * @dev initializes a new Owned instance
     */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
     * @dev allows transferring the contract ownership
     * the new owner still needs to accept the transfer
     * can only be called by the contract owner
     *
     * @param _newOwner    new contract owner
     */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
     * @dev used by a new owner to accept an ownership transfer
     */
    function acceptOwnership() public override {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;

/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }

    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }
}

// File: solidity/contracts/utility/interfaces/IContractRegistry.sol


pragma solidity 0.6.12;

/*
    Contract Registry interface
*/
interface IContractRegistry {
    function addressOf(bytes32 _contractName) external view returns (address);
}

// File: solidity/contracts/utility/ContractRegistryClient.sol


pragma solidity 0.6.12;




/**
 * @dev This is the base contract for ContractRegistry clients.
 */
contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant BANCOR_FORMULA = "BancorFormula";
    bytes32 internal constant CONVERTER_FACTORY = "ConverterFactory";
    bytes32 internal constant CONVERSION_PATH_FINDER = "ConversionPathFinder";
    bytes32 internal constant CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";

    IContractRegistry public registry; // address of the current contract-registry
    IContractRegistry public prevRegistry; // address of the previous contract-registry
    bool public onlyOwnerCanUpdateRegistry; // only an owner can update the contract-registry

    /**
     * @dev verifies that the caller is mapped to the given contract name
     *
     * @param _contractName    contract name
     */
    modifier only(bytes32 _contractName) {
        _only(_contractName);
        _;
    }

    // error message binary size optimization
    function _only(bytes32 _contractName) internal view {
        require(msg.sender == addressOf(_contractName), "ERR_ACCESS_DENIED");
    }

    /**
     * @dev initializes a new ContractRegistryClient instance
     *
     * @param  _registry   address of a contract-registry contract
     */
    constructor(IContractRegistry _registry) internal validAddress(address(_registry)) {
        registry = IContractRegistry(_registry);
        prevRegistry = IContractRegistry(_registry);
    }

    /**
     * @dev updates to the new contract-registry
     */
    function updateRegistry() public {
        // verify that this function is permitted
        require(msg.sender == owner || !onlyOwnerCanUpdateRegistry, "ERR_ACCESS_DENIED");

        // get the new contract-registry
        IContractRegistry newRegistry = IContractRegistry(addressOf(CONTRACT_REGISTRY));

        // verify that the new contract-registry is different and not zero
        require(newRegistry != registry && address(newRegistry) != address(0), "ERR_INVALID_REGISTRY");

        // verify that the new contract-registry is pointing to a non-zero contract-registry
        require(newRegistry.addressOf(CONTRACT_REGISTRY) != address(0), "ERR_INVALID_REGISTRY");

        // save a backup of the current contract-registry before replacing it
        prevRegistry = registry;

        // replace the current contract-registry with the new contract-registry
        registry = newRegistry;
    }

    /**
     * @dev restores the previous contract-registry
     */
    function restoreRegistry() public ownerOnly {
        // restore the previous contract-registry
        registry = prevRegistry;
    }

    /**
     * @dev restricts the permission to update the contract-registry
     *
     * @param _onlyOwnerCanUpdateRegistry  indicates whether or not permission is restricted to owner only
     */
    function restrictRegistryUpdate(bool _onlyOwnerCanUpdateRegistry) public ownerOnly {
        // change the permission to update the contract-registry
        onlyOwnerCanUpdateRegistry = _onlyOwnerCanUpdateRegistry;
    }

    /**
     * @dev returns the address associated with the given contract name
     *
     * @param _contractName    contract name
     *
     * @return contract address
     */
    function addressOf(bytes32 _contractName) internal view returns (address) {
        return registry.addressOf(_contractName);
    }
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/converter/interfaces/IConverter.sol


pragma solidity 0.6.12;




/*
    Converter interface
*/
interface IConverter is IOwned {
    function converterType() external pure returns (uint16);

    function anchor() external view returns (IConverterAnchor);

    function isActive() external view returns (bool);

    function targetAmountAndFee(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount
    ) external view returns (uint256, uint256);

    function convert(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) external payable returns (uint256);

    function conversionFee() external view returns (uint32);

    function maxConversionFee() external view returns (uint32);

    function reserveBalance(IERC20Token _reserveToken) external view returns (uint256);

    receive() external payable;

    function transferAnchorOwnership(address _newOwner) external;

    function acceptAnchorOwnership() external;

    function setConversionFee(uint32 _conversionFee) external;

    function withdrawTokens(
        IERC20Token _token,
        address _to,
        uint256 _amount
    ) external;

    function withdrawETH(address payable _to) external;

    function addReserve(IERC20Token _token, uint32 _ratio) external;

    // deprecated, backward compatibility
    function token() external view returns (IConverterAnchor);

    function transferTokenOwnership(address _newOwner) external;

    function acceptTokenOwnership() external;

    function connectors(IERC20Token _address)
        external
        view
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        );

    function getConnectorBalance(IERC20Token _connectorToken) external view returns (uint256);

    function connectorTokens(uint256 _index) external view returns (IERC20Token);

    function connectorTokenCount() external view returns (uint16);

    /**
     * @dev triggered when the converter is activated
     *
     * @param _type        converter type
     * @param _anchor      converter anchor
     * @param _activated   true if the converter was activated, false if it was deactivated
     */
    event Activation(uint16 indexed _type, IConverterAnchor indexed _anchor, bool indexed _activated);

    /**
     * @dev triggered when a conversion between two tokens occurs
     *
     * @param _fromToken       source ERC20 token
     * @param _toToken         target ERC20 token
     * @param _trader          wallet that initiated the trade
     * @param _amount          input amount in units of the source token
     * @param _return          output amount minus conversion fee in units of the target token
     * @param _conversionFee   conversion fee in units of the target token
     */
    event Conversion(
        IERC20Token indexed _fromToken,
        IERC20Token indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );

    /**
     * @dev triggered when the rate between two tokens in the converter changes
     * note that the event might be dispatched for rate updates between any two tokens in the converter
     *
     * @param  _token1 address of the first token
     * @param  _token2 address of the second token
     * @param  _rateN  rate of 1 unit of `_token1` in `_token2` (numerator)
     * @param  _rateD  rate of 1 unit of `_token1` in `_token2` (denominator)
     */
    event TokenRateUpdate(IERC20Token indexed _token1, IERC20Token indexed _token2, uint256 _rateN, uint256 _rateD);

    /**
     * @dev triggered when the conversion fee is updated
     *
     * @param  _prevFee    previous fee percentage, represented in ppm
     * @param  _newFee     new fee percentage, represented in ppm
     */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);
}

// File: solidity/contracts/converter/interfaces/ITypedConverterCustomFactory.sol


pragma solidity 0.6.12;

/*
    Typed Converter Custom Factory interface
*/
interface ITypedConverterCustomFactory {
    function converterType() external pure returns (uint16);
}

// File: solidity/contracts/converter/interfaces/IConverterFactory.sol


pragma solidity 0.6.12;





/*
    Converter Factory interface
*/
interface IConverterFactory {
    function createAnchor(
        uint16 _type,
        string memory _name,
        string memory _symbol,
        uint8 _decimals
    ) external returns (IConverterAnchor);

    function createConverter(
        uint16 _type,
        IConverterAnchor _anchor,
        IContractRegistry _registry,
        uint32 _maxConversionFee
    ) external returns (IConverter);

    function customFactories(uint16 _type) external view returns (ITypedConverterCustomFactory);
}

// File: solidity/contracts/converter/interfaces/IConverterRegistry.sol


pragma solidity 0.6.12;



interface IConverterRegistry {
    function getAnchorCount() external view returns (uint256);

    function getAnchors() external view returns (address[] memory);

    function getAnchor(uint256 _index) external view returns (IConverterAnchor);

    function isAnchor(address _value) external view returns (bool);

    function getLiquidityPoolCount() external view returns (uint256);

    function getLiquidityPools() external view returns (address[] memory);

    function getLiquidityPool(uint256 _index) external view returns (IConverterAnchor);

    function isLiquidityPool(address _value) external view returns (bool);

    function getConvertibleTokenCount() external view returns (uint256);

    function getConvertibleTokens() external view returns (address[] memory);

    function getConvertibleToken(uint256 _index) external view returns (IERC20Token);

    function isConvertibleToken(address _value) external view returns (bool);

    function getConvertibleTokenAnchorCount(IERC20Token _convertibleToken) external view returns (uint256);

    function getConvertibleTokenAnchors(IERC20Token _convertibleToken) external view returns (address[] memory);

    function getConvertibleTokenAnchor(IERC20Token _convertibleToken, uint256 _index)
        external
        view
        returns (IConverterAnchor);

    function isConvertibleTokenAnchor(IERC20Token _convertibleToken, address _value) external view returns (bool);
}

// File: solidity/contracts/converter/interfaces/IConverterRegistryData.sol


pragma solidity 0.6.12;



interface IConverterRegistryData {
    function addSmartToken(IConverterAnchor _anchor) external;

    function removeSmartToken(IConverterAnchor _anchor) external;

    function addLiquidityPool(IConverterAnchor _liquidityPoolAnchor) external;

    function removeLiquidityPool(IConverterAnchor _liquidityPoolAnchor) external;

    function addConvertibleToken(IERC20Token _convertibleToken, IConverterAnchor _anchor) external;

    function removeConvertibleToken(IERC20Token _convertibleToken, IConverterAnchor _anchor) external;

    function getSmartTokenCount() external view returns (uint256);

    function getSmartTokens() external view returns (address[] memory);

    function getSmartToken(uint256 _index) external view returns (IConverterAnchor);

    function isSmartToken(address _value) external view returns (bool);

    function getLiquidityPoolCount() external view returns (uint256);

    function getLiquidityPools() external view returns (address[] memory);

    function getLiquidityPool(uint256 _index) external view returns (IConverterAnchor);

    function isLiquidityPool(address _value) external view returns (bool);

    function getConvertibleTokenCount() external view returns (uint256);

    function getConvertibleTokens() external view returns (address[] memory);

    function getConvertibleToken(uint256 _index) external view returns (IERC20Token);

    function isConvertibleToken(address _value) external view returns (bool);

    function getConvertibleTokenSmartTokenCount(IERC20Token _convertibleToken) external view returns (uint256);

    function getConvertibleTokenSmartTokens(IERC20Token _convertibleToken) external view returns (address[] memory);

    function getConvertibleTokenSmartToken(IERC20Token _convertibleToken, uint256 _index)
        external
        view
        returns (IConverterAnchor);

    function isConvertibleTokenSmartToken(IERC20Token _convertibleToken, address _value) external view returns (bool);
}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20Token {
    function issue(address _to, uint256 _amount) external;

    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/converter/ConverterRegistry.sol


pragma solidity 0.6.12;








/**
 * @dev This contract maintains a list of all active converters in the Bancor Network.
 *
 * Since converters can be upgraded and thus their address can change, the registry actually keeps
 * converter anchors internally and not the converters themselves.
 * The active converter for each anchor can be easily accessed by querying the anchor's owner.
 *
 * The registry exposes 3 differnet lists that can be accessed and iterated, based on the use-case of the caller:
 * - Anchors - can be used to get all the latest / historical data in the network
 * - Liquidity pools - can be used to get all liquidity pools for funding, liquidation etc.
 * - Convertible tokens - can be used to get all tokens that can be converted in the network (excluding pool
 *   tokens), and for each one - all anchors that hold it in their reserves
 *
 *
 * The contract fires events whenever one of the primitives is added to or removed from the registry
 *
 * The contract is upgradable.
 */
contract ConverterRegistry is IConverterRegistry, ContractRegistryClient, TokenHandler {
    uint32 private constant PPM_RESOLUTION = 1000000;

    /**
     * @dev triggered when a converter anchor is added to the registry
     *
     * @param _anchor anchor token
     */
    event ConverterAnchorAdded(IConverterAnchor indexed _anchor);

    /**
     * @dev triggered when a converter anchor is removed from the registry
     *
     * @param _anchor anchor token
     */
    event ConverterAnchorRemoved(IConverterAnchor indexed _anchor);

    /**
     * @dev triggered when a liquidity pool is added to the registry
     *
     * @param _liquidityPool liquidity pool
     */
    event LiquidityPoolAdded(IConverterAnchor indexed _liquidityPool);

    /**
     * @dev triggered when a liquidity pool is removed from the registry
     *
     * @param _liquidityPool liquidity pool
     */
    event LiquidityPoolRemoved(IConverterAnchor indexed _liquidityPool);

    /**
     * @dev triggered when a convertible token is added to the registry
     *
     * @param _convertibleToken convertible token
     * @param _smartToken associated anchor token
     */
    event ConvertibleTokenAdded(IERC20Token indexed _convertibleToken, IConverterAnchor indexed _smartToken);

    /**
     * @dev triggered when a convertible token is removed from the registry
     *
     * @param _convertibleToken convertible token
     * @param _smartToken associated anchor token
     */
    event ConvertibleTokenRemoved(IERC20Token indexed _convertibleToken, IConverterAnchor indexed _smartToken);

    /**
     * @dev deprecated, backward compatibility, use `ConverterAnchorAdded`
     */
    event SmartTokenAdded(IConverterAnchor indexed _smartToken);

    /**
     * @dev deprecated, backward compatibility, use `ConverterAnchorRemoved`
     */
    event SmartTokenRemoved(IConverterAnchor indexed _smartToken);

    /**
     * @dev initializes a new ConverterRegistry instance
     *
     * @param _registry address of a contract registry contract
     */
    constructor(IContractRegistry _registry) public ContractRegistryClient(_registry) {}

    /**
     * @dev creates a zero supply liquid token / empty liquidity pool and adds its converter to the registry
     *
     * @param _type                converter type, see ConverterBase contract main doc
     * @param _name                token / pool name
     * @param _symbol              token / pool symbol
     * @param _decimals            token / pool decimals
     * @param _maxConversionFee    maximum conversion-fee
     * @param _reserveTokens       reserve tokens
     * @param _reserveWeights      reserve weights
     *
     * @return new converter
     */
    function newConverter(
        uint16 _type,
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        uint32 _maxConversionFee,
        IERC20Token[] memory _reserveTokens,
        uint32[] memory _reserveWeights
    ) public virtual returns (IConverter) {
        uint256 length = _reserveTokens.length;
        require(length == _reserveWeights.length, "ERR_INVALID_RESERVES");

        // for standard pools, change type 1 to type 3
        if (_type == 1 && isStandardPool(_reserveWeights)) {
            _type = 3;
        }

        require(
            getLiquidityPoolByConfig(_type, _reserveTokens, _reserveWeights) == IConverterAnchor(0),
            "ERR_ALREADY_EXISTS"
        );

        IConverterFactory factory = IConverterFactory(addressOf(CONVERTER_FACTORY));
        IConverterAnchor anchor = IConverterAnchor(factory.createAnchor(_type, _name, _symbol, _decimals));
        IConverter converter = IConverter(factory.createConverter(_type, anchor, registry, _maxConversionFee));

        anchor.acceptOwnership();
        converter.acceptOwnership();

        for (uint256 i = 0; i < length; i++) converter.addReserve(_reserveTokens[i], _reserveWeights[i]);

        anchor.transferOwnership(address(converter));
        converter.acceptAnchorOwnership();
        converter.transferOwnership(msg.sender);

        addConverterInternal(converter);
        return converter;
    }

    /**
     * @dev adds an existing converter to the registry
     * can only be called by the owner
     *
     * @param _converter converter
     */
    function addConverter(IConverter _converter) public ownerOnly {
        require(isConverterValid(_converter), "ERR_INVALID_CONVERTER");
        addConverterInternal(_converter);
    }

    /**
     * @dev removes a converter from the registry
     * anyone can remove an existing converter from the registry, as long as the converter is invalid
     * note that the owner can also remove valid converters
     *
     * @param _converter converter
     */
    function removeConverter(IConverter _converter) public {
        require(msg.sender == owner || !isConverterValid(_converter), "ERR_ACCESS_DENIED");
        removeConverterInternal(_converter);
    }

    /**
     * @dev returns the number of converter anchors in the registry
     *
     * @return number of anchors
     */
    function getAnchorCount() public view override returns (uint256) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getSmartTokenCount();
    }

    /**
     * @dev returns the list of converter anchors in the registry
     *
     * @return list of anchors
     */
    function getAnchors() public view override returns (address[] memory) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getSmartTokens();
    }

    /**
     * @dev returns the converter anchor at a given index
     *
     * @param _index index
     * @return anchor at the given index
     */
    function getAnchor(uint256 _index) public view override returns (IConverterAnchor) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getSmartToken(_index);
    }

    /**
     * @dev checks whether or not a given value is a converter anchor
     *
     * @param _value value
     * @return true if the given value is an anchor, false if not
     */
    function isAnchor(address _value) public view override returns (bool) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).isSmartToken(_value);
    }

    /**
     * @dev returns the number of liquidity pools in the registry
     *
     * @return number of liquidity pools
     */
    function getLiquidityPoolCount() public view override returns (uint256) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getLiquidityPoolCount();
    }

    /**
     * @dev returns the list of liquidity pools in the registry
     *
     * @return list of liquidity pools
     */
    function getLiquidityPools() public view override returns (address[] memory) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getLiquidityPools();
    }

    /**
     * @dev returns the liquidity pool at a given index
     *
     * @param _index index
     * @return liquidity pool at the given index
     */
    function getLiquidityPool(uint256 _index) public view override returns (IConverterAnchor) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getLiquidityPool(_index);
    }

    /**
     * @dev checks whether or not a given value is a liquidity pool
     *
     * @param _value value
     * @return true if the given value is a liquidity pool, false if not
     */
    function isLiquidityPool(address _value) public view override returns (bool) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).isLiquidityPool(_value);
    }

    /**
     * @dev returns the number of convertible tokens in the registry
     *
     * @return number of convertible tokens
     */
    function getConvertibleTokenCount() public view override returns (uint256) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleTokenCount();
    }

    /**
     * @dev returns the list of convertible tokens in the registry
     *
     * @return list of convertible tokens
     */
    function getConvertibleTokens() public view override returns (address[] memory) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleTokens();
    }

    /**
     * @dev returns the convertible token at a given index
     *
     * @param _index index
     * @return convertible token at the given index
     */
    function getConvertibleToken(uint256 _index) public view override returns (IERC20Token) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleToken(_index);
    }

    /**
     * @dev checks whether or not a given value is a convertible token
     *
     * @param _value value
     * @return true if the given value is a convertible token, false if not
     */
    function isConvertibleToken(address _value) public view override returns (bool) {
        return IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).isConvertibleToken(_value);
    }

    /**
     * @dev returns the number of converter anchors associated with a given convertible token
     *
     * @param _convertibleToken convertible token
     * @return number of anchors associated with the given convertible token
     */
    function getConvertibleTokenAnchorCount(IERC20Token _convertibleToken) public view override returns (uint256) {
        return
            IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleTokenSmartTokenCount(
                _convertibleToken
            );
    }

    /**
     * @dev returns the list of aoncerter anchors associated with a given convertible token
     *
     * @param _convertibleToken convertible token
     * @return list of anchors associated with the given convertible token
     */
    function getConvertibleTokenAnchors(IERC20Token _convertibleToken) public view override returns (address[] memory) {
        return
            IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleTokenSmartTokens(
                _convertibleToken
            );
    }

    /**
     * @dev returns the converter anchor associated with a given convertible token at a given index
     *
     * @param _index index
     * @return anchor associated with the given convertible token at the given index
     */
    function getConvertibleTokenAnchor(IERC20Token _convertibleToken, uint256 _index)
        public
        view
        override
        returns (IConverterAnchor)
    {
        return
            IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).getConvertibleTokenSmartToken(
                _convertibleToken,
                _index
            );
    }

    /**
     * @dev checks whether or not a given value is a converter anchor of a given convertible token
     *
     * @param _convertibleToken convertible token
     * @param _value value
     * @return true if the given value is an anchor of the given convertible token, false if not
     */
    function isConvertibleTokenAnchor(IERC20Token _convertibleToken, address _value)
        public
        view
        override
        returns (bool)
    {
        return
            IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA)).isConvertibleTokenSmartToken(
                _convertibleToken,
                _value
            );
    }

    /**
     * @dev returns a list of converters for a given list of anchors
     * this is a utility function that can be used to reduce the number of calls to the contract
     *
     * @param _anchors list of converter anchors
     * @return list of converters
     */
    function getConvertersByAnchors(address[] memory _anchors) public view returns (IConverter[] memory) {
        IConverter[] memory converters = new IConverter[](_anchors.length);

        for (uint256 i = 0; i < _anchors.length; i++)
            converters[i] = IConverter(payable(IConverterAnchor(_anchors[i]).owner()));

        return converters;
    }

    /**
     * @dev checks whether or not a given converter is valid
     *
     * @param _converter converter
     * @return true if the given converter is valid, false if not
     */
    function isConverterValid(IConverter _converter) public view returns (bool) {
        // verify that the converter is active
        return _converter.token().owner() == address(_converter);
    }

    /**
     * @dev checks if a liquidity pool with given configuration is already registered
     *
     * @param _converter converter with specific configuration
     * @return if a liquidity pool with the same configuration is already registered
     */
    function isSimilarLiquidityPoolRegistered(IConverter _converter) public view returns (bool) {
        uint256 reserveTokenCount = _converter.connectorTokenCount();
        IERC20Token[] memory reserveTokens = new IERC20Token[](reserveTokenCount);
        uint32[] memory reserveWeights = new uint32[](reserveTokenCount);

        // get the reserve-configuration of the converter
        for (uint256 i = 0; i < reserveTokenCount; i++) {
            IERC20Token reserveToken = _converter.connectorTokens(i);
            reserveTokens[i] = reserveToken;
            reserveWeights[i] = getReserveWeight(_converter, reserveToken);
        }

        // return if a liquidity pool with the same configuration is already registered
        return
            getLiquidityPoolByConfig(getConverterType(_converter, reserveTokenCount), reserveTokens, reserveWeights) !=
            IConverterAnchor(0);
    }

    /**
     * @dev searches for a liquidity pool with specific configuration
     *
     * @param _type            converter type, see ConverterBase contract main doc
     * @param _reserveTokens   reserve tokens
     * @param _reserveWeights  reserve weights
     * @return the liquidity pool, or zero if no such liquidity pool exists
     */
    function getLiquidityPoolByConfig(
        uint16 _type,
        IERC20Token[] memory _reserveTokens,
        uint32[] memory _reserveWeights
    ) public view returns (IConverterAnchor) {
        // verify that the input parameters represent a valid liquidity pool
        if (_reserveTokens.length == _reserveWeights.length && _reserveTokens.length > 1) {
            // get the anchors of the least frequent token (optimization)
            address[] memory convertibleTokenAnchors = getLeastFrequentTokenAnchors(_reserveTokens);
            // search for a converter with the same configuration
            for (uint256 i = 0; i < convertibleTokenAnchors.length; i++) {
                IConverterAnchor anchor = IConverterAnchor(convertibleTokenAnchors[i]);
                IConverter converter = IConverter(payable(anchor.owner()));
                if (isConverterReserveConfigEqual(converter, _type, _reserveTokens, _reserveWeights)) return anchor;
            }
        }

        return IConverterAnchor(0);
    }

    /**
     * @dev adds a converter anchor to the registry
     *
     * @param _anchor converter anchor
     */
    function addAnchor(IConverterRegistryData _converterRegistryData, IConverterAnchor _anchor) internal {
        _converterRegistryData.addSmartToken(_anchor);
        emit ConverterAnchorAdded(_anchor);
        emit SmartTokenAdded(_anchor);
    }

    /**
     * @dev removes a converter anchor from the registry
     *
     * @param _anchor converter anchor
     */
    function removeAnchor(IConverterRegistryData _converterRegistryData, IConverterAnchor _anchor) internal {
        _converterRegistryData.removeSmartToken(_anchor);
        emit ConverterAnchorRemoved(_anchor);
        emit SmartTokenRemoved(_anchor);
    }

    /**
     * @dev adds a liquidity pool to the registry
     *
     * @param _liquidityPoolAnchor liquidity pool converter anchor
     */
    function addLiquidityPool(IConverterRegistryData _converterRegistryData, IConverterAnchor _liquidityPoolAnchor)
        internal
    {
        _converterRegistryData.addLiquidityPool(_liquidityPoolAnchor);
        emit LiquidityPoolAdded(_liquidityPoolAnchor);
    }

    /**
     * @dev removes a liquidity pool from the registry
     *
     * @param _liquidityPoolAnchor liquidity pool converter anchor
     */
    function removeLiquidityPool(IConverterRegistryData _converterRegistryData, IConverterAnchor _liquidityPoolAnchor)
        internal
    {
        _converterRegistryData.removeLiquidityPool(_liquidityPoolAnchor);
        emit LiquidityPoolRemoved(_liquidityPoolAnchor);
    }

    /**
     * @dev adds a convertible token to the registry
     *
     * @param _convertibleToken    convertible token
     * @param _anchor              associated converter anchor
     */
    function addConvertibleToken(
        IConverterRegistryData _converterRegistryData,
        IERC20Token _convertibleToken,
        IConverterAnchor _anchor
    ) internal {
        _converterRegistryData.addConvertibleToken(_convertibleToken, _anchor);
        emit ConvertibleTokenAdded(_convertibleToken, _anchor);
    }

    /**
     * @dev removes a convertible token from the registry
     *
     * @param _convertibleToken    convertible token
     * @param _anchor              associated converter anchor
     */
    function removeConvertibleToken(
        IConverterRegistryData _converterRegistryData,
        IERC20Token _convertibleToken,
        IConverterAnchor _anchor
    ) internal {
        _converterRegistryData.removeConvertibleToken(_convertibleToken, _anchor);
        emit ConvertibleTokenRemoved(_convertibleToken, _anchor);
    }

    /**
     * @dev checks whether or not a given configuration depicts a standard pool
     *
     * @param _reserveWeights  reserve weights
     *
     * @return true if the given configuration depicts a standard pool, false otherwise
     */
    function isStandardPool(uint32[] memory _reserveWeights) internal view virtual returns (bool) {
        this; // silent state mutability warning without generating additional bytecode
        return
            _reserveWeights.length == 2 &&
            _reserveWeights[0] == PPM_RESOLUTION / 2 &&
            _reserveWeights[1] == PPM_RESOLUTION / 2;
    }

    function addConverterInternal(IConverter _converter) private {
        IConverterRegistryData converterRegistryData = IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA));
        IConverterAnchor anchor = IConverter(_converter).token();
        uint256 reserveTokenCount = _converter.connectorTokenCount();

        // add the converter anchor
        addAnchor(converterRegistryData, anchor);
        if (reserveTokenCount > 1) addLiquidityPool(converterRegistryData, anchor);
        else addConvertibleToken(converterRegistryData, IDSToken(address(anchor)), anchor);

        // add all reserve tokens
        for (uint256 i = 0; i < reserveTokenCount; i++)
            addConvertibleToken(converterRegistryData, _converter.connectorTokens(i), anchor);
    }

    function removeConverterInternal(IConverter _converter) private {
        IConverterRegistryData converterRegistryData = IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA));
        IConverterAnchor anchor = IConverter(_converter).token();
        uint256 reserveTokenCount = _converter.connectorTokenCount();

        // remove the converter anchor
        removeAnchor(converterRegistryData, anchor);
        if (reserveTokenCount > 1) removeLiquidityPool(converterRegistryData, anchor);
        else removeConvertibleToken(converterRegistryData, IDSToken(address(anchor)), anchor);

        // remove all reserve tokens
        for (uint256 i = 0; i < reserveTokenCount; i++)
            removeConvertibleToken(converterRegistryData, _converter.connectorTokens(i), anchor);
    }

    function getLeastFrequentTokenAnchors(IERC20Token[] memory _reserveTokens) private view returns (address[] memory) {
        IConverterRegistryData converterRegistryData = IConverterRegistryData(addressOf(CONVERTER_REGISTRY_DATA));
        uint256 minAnchorCount = converterRegistryData.getConvertibleTokenSmartTokenCount(_reserveTokens[0]);
        uint256 index = 0;

        // find the reserve token which has the smallest number of converter anchors
        for (uint256 i = 1; i < _reserveTokens.length; i++) {
            uint256 convertibleTokenAnchorCount = converterRegistryData.getConvertibleTokenSmartTokenCount(
                _reserveTokens[i]
            );
            if (minAnchorCount > convertibleTokenAnchorCount) {
                minAnchorCount = convertibleTokenAnchorCount;
                index = i;
            }
        }

        return converterRegistryData.getConvertibleTokenSmartTokens(_reserveTokens[index]);
    }

    function isConverterReserveConfigEqual(
        IConverter _converter,
        uint16 _type,
        IERC20Token[] memory _reserveTokens,
        uint32[] memory _reserveWeights
    ) private view returns (bool) {
        uint256 reserveTokenCount = _converter.connectorTokenCount();

        if (_type != getConverterType(_converter, reserveTokenCount)) return false;

        if (_reserveTokens.length != reserveTokenCount) return false;

        for (uint256 i = 0; i < _reserveTokens.length; i++) {
            if (_reserveWeights[i] != getReserveWeight(_converter, _reserveTokens[i])) return false;
        }

        return true;
    }

    // utility to get the reserve weight (including from older converters that don't support the new getReserveWeight function)
    function getReserveWeight(IConverter _converter, IERC20Token _reserveToken) private view returns (uint32) {
        (, uint32 weight, , , ) = _converter.connectors(_reserveToken);
        return weight;
    }

    bytes4 private constant CONVERTER_TYPE_FUNC_SELECTOR = bytes4(keccak256("converterType()"));

    // utility to get the converter type (including from older converters that don't support the new converterType function)
    function getConverterType(IConverter _converter, uint256 _reserveTokenCount) private view returns (uint16) {
        (bool success, bytes memory returnData) = address(_converter).staticcall(
            abi.encodeWithSelector(CONVERTER_TYPE_FUNC_SELECTOR)
        );
        if (success && returnData.length == 32) return abi.decode(returnData, (uint16));
        return _reserveTokenCount > 1 ? 1 : 0;
    }

    /**
     * @dev deprecated, backward compatibility, use `getAnchorCount`
     */
    function getSmartTokenCount() public view returns (uint256) {
        return getAnchorCount();
    }

    /**
     * @dev deprecated, backward compatibility, use `getAnchors`
     */
    function getSmartTokens() public view returns (address[] memory) {
        return getAnchors();
    }

    /**
     * @dev deprecated, backward compatibility, use `getAnchor`
     */
    function getSmartToken(uint256 _index) public view returns (IConverterAnchor) {
        return getAnchor(_index);
    }

    /**
     * @dev deprecated, backward compatibility, use `isAnchor`
     */
    function isSmartToken(address _value) public view returns (bool) {
        return isAnchor(_value);
    }

    /**
     * @dev deprecated, backward compatibility, use `getConvertibleTokenAnchorCount`
     */
    function getConvertibleTokenSmartTokenCount(IERC20Token _convertibleToken) public view returns (uint256) {
        return getConvertibleTokenAnchorCount(_convertibleToken);
    }

    /**
     * @dev deprecated, backward compatibility, use `getConvertibleTokenAnchors`
     */
    function getConvertibleTokenSmartTokens(IERC20Token _convertibleToken) public view returns (address[] memory) {
        return getConvertibleTokenAnchors(_convertibleToken);
    }

    /**
     * @dev deprecated, backward compatibility, use `getConvertibleTokenAnchor`
     */
    function getConvertibleTokenSmartToken(IERC20Token _convertibleToken, uint256 _index)
        public
        view
        returns (IConverterAnchor)
    {
        return getConvertibleTokenAnchor(_convertibleToken, _index);
    }

    /**
     * @dev deprecated, backward compatibility, use `isConvertibleTokenAnchor`
     */
    function isConvertibleTokenSmartToken(IERC20Token _convertibleToken, address _value) public view returns (bool) {
        return isConvertibleTokenAnchor(_convertibleToken, _value);
    }

    /**
     * @dev deprecated, backward compatibility, use `getConvertersByAnchors`
     */
    function getConvertersBySmartTokens(address[] memory _smartTokens) public view returns (IConverter[] memory) {
        return getConvertersByAnchors(_smartTokens);
    }

    /**
     * @dev deprecated, backward compatibility, use `getLiquidityPoolByConfig`
     */
    function getLiquidityPoolByReserveConfig(IERC20Token[] memory _reserveTokens, uint32[] memory _reserveWeights)
        public
        view
        returns (IConverterAnchor)
    {
        return getLiquidityPoolByConfig(_reserveTokens.length > 1 ? 1 : 0, _reserveTokens, _reserveWeights);
    }
}

// File: contracts/utility/interfaces/IOwned.sol

pragma solidity 0.4.26;

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {this;}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

pragma solidity 0.4.26;


/**
  * @dev Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    /**
      * @dev triggered when the owner is updated
      * 
      * @param _prevOwner previous owner
      * @param _newOwner  new owner
    */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
      * @dev initializes a new Owned instance
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
      * @dev allows transferring the contract ownership
      * the new owner still needs to accept the transfer
      * can only be called by the contract owner
      * 
      * @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
      * @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Utils.sol

pragma solidity 0.4.26;

/**
  * @dev Utilities & Common Modifiers
*/
contract Utils {
    /**
      * constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

}

// File: contracts/utility/interfaces/IContractRegistry.sol

pragma solidity 0.4.26;

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/utility/ContractRegistryClient.sol

pragma solidity 0.4.26;




/**
  * @dev Base contract for ContractRegistry clients
*/
contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant NON_STANDARD_TOKEN_REGISTRY = "NonStandardTokenRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant BANCOR_FORMULA = "BancorFormula";
    bytes32 internal constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 internal constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";
    bytes32 internal constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant BANCOR_CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant BANCOR_CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";

    IContractRegistry public registry;      // address of the current contract-registry
    IContractRegistry public prevRegistry;  // address of the previous contract-registry
    bool public adminOnly;                  // only an administrator can update the contract-registry

    /**
      * @dev verifies that the caller is mapped to the given contract name
      * 
      * @param _contractName    contract name
    */
    modifier only(bytes32 _contractName) {
        require(msg.sender == addressOf(_contractName));
        _;
    }

    /**
      * @dev initializes a new ContractRegistryClient instance
      * 
      * @param  _registry   address of a contract-registry contract
    */
    constructor(IContractRegistry _registry) internal validAddress(_registry) {
        registry = IContractRegistry(_registry);
        prevRegistry = IContractRegistry(_registry);
    }

    /**
      * @dev updates to the new contract-registry
     */
    function updateRegistry() public {
        // verify that this function is permitted
        require(!adminOnly || isAdmin());

        // get the new contract-registry
        address newRegistry = addressOf(CONTRACT_REGISTRY);

        // verify that the new contract-registry is different and not zero
        require(newRegistry != address(registry) && newRegistry != address(0));

        // verify that the new contract-registry is pointing to a non-zero contract-registry
        require(IContractRegistry(newRegistry).addressOf(CONTRACT_REGISTRY) != address(0));

        // save a backup of the current contract-registry before replacing it
        prevRegistry = registry;

        // replace the current contract-registry with the new contract-registry
        registry = IContractRegistry(newRegistry);
    }

    /**
      * @dev restores the previous contract-registry
    */
    function restoreRegistry() public {
        // verify that this function is permitted
        require(isAdmin());

        // restore the previous contract-registry
        registry = prevRegistry;
    }

    /**
      * @dev restricts the permission to update the contract-registry
      * 
      * @param _adminOnly    indicates whether or not permission is restricted to administrator only
    */
    function restrictRegistryUpdate(bool _adminOnly) public {
        // verify that this function is permitted
        require(adminOnly != _adminOnly && isAdmin());

        // change the permission to update the contract-registry
        adminOnly = _adminOnly;
    }

    /**
      * @dev returns whether or not the caller is an administrator
     */
    function isAdmin() internal view returns (bool) {
        return msg.sender == owner;
    }

    /**
      * @dev returns the address associated with the given contract name
      * 
      * @param _contractName    contract name
      * 
      * @return contract address
    */
    function addressOf(bytes32 _contractName) internal view returns (address) {
        return registry.addressOf(_contractName);
    }
}

// File: contracts/converter/interfaces/IBancorConverterRegistryData.sol

pragma solidity 0.4.26;

interface IBancorConverterRegistryData {
    function addSmartToken(address _smartToken) external;
    function removeSmartToken(address _smartToken) external;
    function addLiquidityPool(address _liquidityPool) external;
    function removeLiquidityPool(address _liquidityPool) external;
    function addConvertibleToken(address _convertibleToken, address _smartToken) external;
    function removeConvertibleToken(address _convertibleToken, address _smartToken) external;
    function getSmartTokenCount() external view returns (uint);
    function getSmartTokens() external view returns (address[]);
    function getSmartToken(uint _index) external view returns (address);
    function isSmartToken(address _value) external view returns (bool);
    function getLiquidityPoolCount() external view returns (uint);
    function getLiquidityPools() external view returns (address[]);
    function getLiquidityPool(uint _index) external view returns (address);
    function isLiquidityPool(address _value) external view returns (bool);
    function getConvertibleTokenCount() external view returns (uint);
    function getConvertibleTokens() external view returns (address[]);
    function getConvertibleToken(uint _index) external view returns (address);
    function isConvertibleToken(address _value) external view returns (bool);
    function getConvertibleTokenSmartTokenCount(address _convertibleToken) external view returns (uint);
    function getConvertibleTokenSmartTokens(address _convertibleToken) external view returns (address[]);
    function getConvertibleTokenSmartToken(address _convertibleToken, uint _index) external view returns (address);
    function isConvertibleTokenSmartToken(address _convertibleToken, address _value) external view returns (bool);
}

// File: contracts/converter/BancorConverterRegistryData.sol

pragma solidity 0.4.26;



/*
 *  The BancorConverterRegistryData contract is an integral part of the Bancor converter registry
 *  as it serves as the database contract that holds all registry data.
 *
 *  The registry is separated into two different contracts for upgradability - the data contract
 *  is harder to upgrade as it requires migrating all registry data into a new contract, while
 *  the registry contract itself can be easily upgraded.
 *
 *  For that same reason, the data contract is simple and contains no logic beyond the basic data
 *  access utilities that it exposes.
*/
contract BancorConverterRegistryData is IBancorConverterRegistryData, ContractRegistryClient {
    struct Item {
        bool valid;
        uint index;
    }

    struct Items {
        address[] array;
        mapping(address => Item) table;
    }

    struct List {
        uint index;
        Items items;
    }

    struct Lists {
        address[] array;
        mapping(address => List) table;
    }

    Items smartTokens;
    Items liquidityPools;
    Lists convertibleTokens;

    /**
      * @dev initializes a new BancorConverterRegistryData instance
      * 
      * @param _registry address of a contract registry contract
    */
    constructor(IContractRegistry _registry) ContractRegistryClient(_registry) public {
    }

    /**
      * @dev adds a smart token
      * 
      * @param _smartToken smart token
    */
    function addSmartToken(address _smartToken) external only(BANCOR_CONVERTER_REGISTRY) {
        addItem(smartTokens, _smartToken);
    }

    /**
      * @dev removes a smart token
      * 
      * @param _smartToken smart token
    */
    function removeSmartToken(address _smartToken) external only(BANCOR_CONVERTER_REGISTRY) {
        removeItem(smartTokens, _smartToken);
    }

    /**
      * @dev adds a liquidity pool
      * 
      * @param _liquidityPool liquidity pool
    */
    function addLiquidityPool(address _liquidityPool) external only(BANCOR_CONVERTER_REGISTRY) {
        addItem(liquidityPools, _liquidityPool);
    }

    /**
      * @dev removes a liquidity pool
      * 
      * @param _liquidityPool liquidity pool
    */
    function removeLiquidityPool(address _liquidityPool) external only(BANCOR_CONVERTER_REGISTRY) {
        removeItem(liquidityPools, _liquidityPool);
    }

    /**
      * @dev adds a convertible token
      * 
      * @param _convertibleToken convertible token
      * @param _smartToken associated smart token
    */
    function addConvertibleToken(address _convertibleToken, address _smartToken) external only(BANCOR_CONVERTER_REGISTRY) {
        List storage list = convertibleTokens.table[_convertibleToken];
        if (list.items.array.length == 0) {
            list.index = convertibleTokens.array.push(_convertibleToken) - 1;
        }
        addItem(list.items, _smartToken);
    }

    /**
      * @dev removes a convertible token
      * 
      * @param _convertibleToken convertible token
      * @param _smartToken associated smart token
    */
    function removeConvertibleToken(address _convertibleToken, address _smartToken) external only(BANCOR_CONVERTER_REGISTRY) {
        List storage list = convertibleTokens.table[_convertibleToken];
        removeItem(list.items, _smartToken);
        if (list.items.array.length == 0) {
            address lastConvertibleToken = convertibleTokens.array[convertibleTokens.array.length - 1];
            convertibleTokens.table[lastConvertibleToken].index = list.index;
            convertibleTokens.array[list.index] = lastConvertibleToken;
            convertibleTokens.array.length--;
            delete convertibleTokens.table[_convertibleToken];
        }
    }

    /**
      * @dev returns the number of smart tokens
      * 
      * @return number of smart tokens
    */
    function getSmartTokenCount() external view returns (uint) {
        return smartTokens.array.length;
    }

    /**
      * @dev returns the list of smart tokens
      * 
      * @return list of smart tokens
    */
    function getSmartTokens() external view returns (address[]) {
        return smartTokens.array;
    }

    /**
      * @dev returns the smart token at a given index
      * 
      * @param _index index
      * @return smart token at the given index
    */
    function getSmartToken(uint _index) external view returns (address) {
        return smartTokens.array[_index];
    }

    /**
      * @dev checks whether or not a given value is a smart token
      * 
      * @param _value value
      * @return true if the given value is a smart token, false if not
    */
    function isSmartToken(address _value) external view returns (bool) {
        return smartTokens.table[_value].valid;
    }

    /**
      * @dev returns the number of liquidity pools
      * 
      * @return number of liquidity pools
    */
    function getLiquidityPoolCount() external view returns (uint) {
        return liquidityPools.array.length;
    }

    /**
      * @dev returns the list of liquidity pools
      * 
      * @return list of liquidity pools
    */
    function getLiquidityPools() external view returns (address[]) {
        return liquidityPools.array;
    }

    /**
      * @dev returns the liquidity pool at a given index
      * 
      * @param _index index
      * @return liquidity pool at the given index
    */
    function getLiquidityPool(uint _index) external view returns (address) {
        return liquidityPools.array[_index];
    }

    /**
      * @dev checks whether or not a given value is a liquidity pool
      * 
      * @param _value value
      * @return true if the given value is a liquidity pool, false if not
    */
    function isLiquidityPool(address _value) external view returns (bool) {
        return liquidityPools.table[_value].valid;
    }

    /**
      * @dev returns the number of convertible tokens
      * 
      * @return number of convertible tokens
    */
    function getConvertibleTokenCount() external view returns (uint) {
        return convertibleTokens.array.length;
    }

    /**
      * @dev returns the list of convertible tokens
      * 
      * @return list of convertible tokens
    */
    function getConvertibleTokens() external view returns (address[]) {
        return convertibleTokens.array;
    }

    /**
      * @dev returns the convertible token at a given index
      * 
      * @param _index index
      * @return convertible token at the given index
    */
    function getConvertibleToken(uint _index) external view returns (address) {
        return convertibleTokens.array[_index];
    }

    /**
      * @dev checks whether or not a given value is a convertible token
      * 
      * @param _value value
      * @return true if the given value is a convertible token, false if not
    */
    function isConvertibleToken(address _value) external view returns (bool) {
        return convertibleTokens.table[_value].items.array.length > 0;
    }

    /**
      * @dev returns the number of smart tokens associated with a given convertible token
      * 
      * @param _convertibleToken convertible token
      * @return number of smart tokens associated with the given convertible token
    */
    function getConvertibleTokenSmartTokenCount(address _convertibleToken) external view returns (uint) {
        return convertibleTokens.table[_convertibleToken].items.array.length;
    }

    /**
      * @dev returns the list of smart tokens associated with a given convertible token
      * 
      * @param _convertibleToken convertible token
      * @return list of smart tokens associated with the given convertible token
    */
    function getConvertibleTokenSmartTokens(address _convertibleToken) external view returns (address[]) {
        return convertibleTokens.table[_convertibleToken].items.array;
    }

    /**
      * @dev returns the smart token associated with a given convertible token at a given index
      * 
      * @param _index index
      * @return smart token associated with the given convertible token at the given index
    */
    function getConvertibleTokenSmartToken(address _convertibleToken, uint _index) external view returns (address) {
        return convertibleTokens.table[_convertibleToken].items.array[_index];
    }

    /**
      * @dev checks whether or not a given value is a smart token of a given convertible token
      * 
      * @param _convertibleToken convertible token
      * @param _value value
      * @return true if the given value is a smart token of the given convertible token, false it not
    */
    function isConvertibleTokenSmartToken(address _convertibleToken, address _value) external view returns (bool) {
        return convertibleTokens.table[_convertibleToken].items.table[_value].valid;
    }

    /**
      * @dev adds an item to a list of items
      * 
      * @param _items list of items
      * @param _value item's value
    */
    function addItem(Items storage _items, address _value) internal {
        Item storage item = _items.table[_value];
        require(item.valid == false);

        item.index = _items.array.push(_value) - 1;
        item.valid = true;
    }

    /**
      * @dev removes an item from a list of items
      * 
      * @param _items list of items
      * @param _value item's value
    */
    function removeItem(Items storage _items, address _value) internal {
        Item storage item = _items.table[_value];
        require(item.valid == true);

        address lastValue = _items.array[_items.array.length - 1];
        _items.table[lastValue].index = item.index;
        _items.array[item.index] = lastValue;
        _items.array.length--;
        delete _items.table[_value];
    }
}

pragma solidity ^0.4.24;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

// File: contracts/token/ERC20Token.sol

/**
    ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, Utils {
    string public standard = 'Token 0.1';
    string public name = '';
    string public symbol = '';
    uint8 public decimals = 0;
    uint256 public totalSupply = 0;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
        @dev constructor

        @param _name        token name
        @param _symbol      token symbol
        @param _decimals    decimal points, for display purposes
    */
    constructor(string _name, string _symbol, uint8 _decimals) public {
        require(bytes(_name).length > 0 && bytes(_symbol).length > 0); // validate input

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        validAddress(_to)
        returns (bool success)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        validAddress(_from)
        validAddress(_to)
        returns (bool success)
    {
        allowance[_from][msg.sender] = safeSub(allowance[_from][msg.sender], _value);
        balanceOf[_from] = safeSub(balanceOf[_from], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
        @dev allow another account/contract to spend some tokens on your behalf
        throws on any error rather then return a false flag to minimize user errors

        also, to minimize the risk of the approve/transferFrom attack vector
        (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), approve has to be called twice
        in 2 separate transactions - once to change the allowance to 0 and secondly to change it to the new allowance value

        @param _spender approved address
        @param _value   allowance amount

        @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        validAddress(_spender)
        returns (bool success)
    {
        // if the allowance isn't 0, it can only be updated to 0 to prevent an allowance change immediately after withdrawal
        require(_value == 0 || allowance[msg.sender][_spender] == 0);

        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/utility/TokenHolder.sol

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    constructor() public {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

// File: contracts/token/SmartToken.sol

/*
    Smart Token v0.3

    'Owned' is specified here for readability reasons
*/
contract SmartToken is ISmartToken, Owned, ERC20Token, TokenHolder {
    string public version = '0.3';

    bool public transfersEnabled = true;    // true if transfer/transferFrom are enabled, false if not

    // triggered when a smart token is deployed - the _token address is defined for forward compatibility, in case we want to trigger the event from a factory
    event NewSmartToken(address _token);
    // triggered when the total supply is increased
    event Issuance(uint256 _amount);
    // triggered when the total supply is decreased
    event Destruction(uint256 _amount);

    /**
        @dev constructor

        @param _name       token name
        @param _symbol     token short symbol, minimum 1 character
        @param _decimals   for display purposes only
    */
    constructor(string _name, string _symbol, uint8 _decimals)
        public
        ERC20Token(_name, _symbol, _decimals)
    {
        emit NewSmartToken(address(this));
    }

    // allows execution only when transfers aren't disabled
    modifier transfersAllowed {
        assert(transfersEnabled);
        _;
    }

    /**
        @dev disables/enables transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTransfers(bool _disable) public ownerOnly {
        transfersEnabled = !_disable;
    }

    /**
        @dev increases the token supply and sends the new tokens to an account
        can only be called by the contract owner

        @param _to         account to receive the new amount
        @param _amount     amount to increase the supply by
    */
    function issue(address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        totalSupply = safeAdd(totalSupply, _amount);
        balanceOf[_to] = safeAdd(balanceOf[_to], _amount);

        emit Issuance(_amount);
        emit Transfer(this, _to, _amount);
    }

    /**
        @dev removes tokens from an account and decreases the token supply
        can be called by the contract owner to destroy tokens from any account or by any holder to destroy tokens from his/her own account

        @param _from       account to remove the amount from
        @param _amount     amount to decrease the supply by
    */
    function destroy(address _from, uint256 _amount) public {
        require(msg.sender == _from || msg.sender == owner); // validate input

        balanceOf[_from] = safeSub(balanceOf[_from], _amount);
        totalSupply = safeSub(totalSupply, _amount);

        emit Transfer(_from, this, _amount);
        emit Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra functionality

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors
        in addition to the standard checks, the function throws if transfers are disabled

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transfer(_to, _value));
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors
        in addition to the standard checks, the function throws if transfers are disabled

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transferFrom(_from, _to, _value));
        return true;
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



pragma solidity >=0.6.0 <0.8.0;




/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: solidity/contracts/converter/ConverterVersion.sol


pragma solidity 0.6.12;

contract ConverterVersion {
    uint16 public constant version = 46;
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/converter/interfaces/IConverter.sol


pragma solidity 0.6.12;




/*
    Converter interface
*/
interface IConverter is IOwned {
    function converterType() external pure returns (uint16);

    function anchor() external view returns (IConverterAnchor);

    function isActive() external view returns (bool);

    function targetAmountAndFee(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount
    ) external view returns (uint256, uint256);

    function convert(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) external payable returns (uint256);

    function conversionFee() external view returns (uint32);

    function maxConversionFee() external view returns (uint32);

    function reserveBalance(IERC20 _reserveToken) external view returns (uint256);

    receive() external payable;

    function transferAnchorOwnership(address _newOwner) external;

    function acceptAnchorOwnership() external;

    function setConversionFee(uint32 _conversionFee) external;

    function addReserve(IERC20 _token, uint32 _weight) external;

    function transferReservesOnUpgrade(address _newConverter) external;

    function onUpgradeComplete() external;

    // deprecated, backward compatibility
    function token() external view returns (IConverterAnchor);

    function transferTokenOwnership(address _newOwner) external;

    function acceptTokenOwnership() external;

    function connectors(IERC20 _address)
        external
        view
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        );

    function getConnectorBalance(IERC20 _connectorToken) external view returns (uint256);

    function connectorTokens(uint256 _index) external view returns (IERC20);

    function connectorTokenCount() external view returns (uint16);

    /**
     * @dev triggered when the converter is activated
     *
     * @param _type        converter type
     * @param _anchor      converter anchor
     * @param _activated   true if the converter was activated, false if it was deactivated
     */
    event Activation(uint16 indexed _type, IConverterAnchor indexed _anchor, bool indexed _activated);

    /**
     * @dev triggered when a conversion between two tokens occurs
     *
     * @param _fromToken       source ERC20 token
     * @param _toToken         target ERC20 token
     * @param _trader          wallet that initiated the trade
     * @param _amount          input amount in units of the source token
     * @param _return          output amount minus conversion fee in units of the target token
     * @param _conversionFee   conversion fee in units of the target token
     */
    event Conversion(
        IERC20 indexed _fromToken,
        IERC20 indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );

    /**
     * @dev triggered when the rate between two tokens in the converter changes
     * note that the event might be dispatched for rate updates between any two tokens in the converter
     *
     * @param  _token1 address of the first token
     * @param  _token2 address of the second token
     * @param  _rateN  rate of 1 unit of `_token1` in `_token2` (numerator)
     * @param  _rateD  rate of 1 unit of `_token1` in `_token2` (denominator)
     */
    event TokenRateUpdate(IERC20 indexed _token1, IERC20 indexed _token2, uint256 _rateN, uint256 _rateD);

    /**
     * @dev triggered when the conversion fee is updated
     *
     * @param  _prevFee    previous fee percentage, represented in ppm
     * @param  _newFee     new fee percentage, represented in ppm
     */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);
}

// File: solidity/contracts/converter/interfaces/IConverterUpgrader.sol


pragma solidity 0.6.12;

/*
    Converter Upgrader interface
*/
interface IConverterUpgrader {
    function upgrade(bytes32 _version) external;

    function upgrade(uint16 _version) external;
}

// File: solidity/contracts/utility/interfaces/ITokenHolder.sol


pragma solidity 0.6.12;



/*
    Token Holder interface
*/
interface ITokenHolder is IOwned {
    receive() external payable;

    function withdrawTokens(
        IERC20 token,
        address payable to,
        uint256 amount
    ) external;

    function withdrawTokensMultiple(
        IERC20[] calldata tokens,
        address payable to,
        uint256[] calldata amounts
    ) external;
}

// File: solidity/contracts/INetworkSettings.sol


pragma solidity 0.6.12;


interface INetworkSettings {
    function networkFeeParams() external view returns (ITokenHolder, uint32);

    function networkFeeWallet() external view returns (ITokenHolder);

    function networkFee() external view returns (uint32);
}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20 {
    function issue(address _to, uint256 _amount) external;

    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/utility/MathEx.sol


pragma solidity 0.6.12;

/**
 * @dev This library provides a set of complex math operations.
 */
library MathEx {
    uint256 private constant MAX_EXP_BIT_LEN = 4;
    uint256 private constant MAX_EXP = 2**MAX_EXP_BIT_LEN - 1;
    uint256 private constant MAX_UINT128 = 2**128 - 1;

    /**
     * @dev returns the largest integer smaller than or equal to the square root of a positive integer
     *
     * @param _num a positive integer
     *
     * @return the largest integer smaller than or equal to the square root of the positive integer
     */
    function floorSqrt(uint256 _num) internal pure returns (uint256) {
        uint256 x = _num / 2 + 1;
        uint256 y = (x + _num / x) / 2;
        while (x > y) {
            x = y;
            y = (x + _num / x) / 2;
        }
        return x;
    }

    /**
     * @dev returns the smallest integer larger than or equal to the square root of a positive integer
     *
     * @param _num a positive integer
     *
     * @return the smallest integer larger than or equal to the square root of the positive integer
     */
    function ceilSqrt(uint256 _num) internal pure returns (uint256) {
        uint256 x = floorSqrt(_num);
        return x * x == _num ? x : x + 1;
    }

    /**
     * @dev computes a powered ratio
     *
     * @param _n   ratio numerator
     * @param _d   ratio denominator
     * @param _exp ratio exponent
     *
     * @return powered ratio's numerator and denominator
     */
    function poweredRatio(
        uint256 _n,
        uint256 _d,
        uint256 _exp
    ) internal pure returns (uint256, uint256) {
        require(_exp <= MAX_EXP, "ERR_EXP_TOO_LARGE");

        uint256[MAX_EXP_BIT_LEN] memory ns;
        uint256[MAX_EXP_BIT_LEN] memory ds;

        (ns[0], ds[0]) = reducedRatio(_n, _d, MAX_UINT128);
        for (uint256 i = 0; (_exp >> i) > 1; i++) {
            (ns[i + 1], ds[i + 1]) = reducedRatio(ns[i] ** 2, ds[i] ** 2, MAX_UINT128);
        }

        uint256 n = 1;
        uint256 d = 1;

        for (uint256 i = 0; (_exp >> i) > 0; i++) {
            if (((_exp >> i) & 1) > 0) {
                (n, d) = reducedRatio(n * ns[i], d * ds[i], MAX_UINT128);
            }
        }

        return (n, d);
    }

    /**
     * @dev computes a reduced-scalar ratio
     *
     * @param _n   ratio numerator
     * @param _d   ratio denominator
     * @param _max maximum desired scalar
     *
     * @return ratio's numerator and denominator
     */
    function reducedRatio(
        uint256 _n,
        uint256 _d,
        uint256 _max
    ) internal pure returns (uint256, uint256) {
        (uint256 n, uint256 d) = (_n, _d);
        if (n > _max || d > _max) {
            (n, d) = normalizedRatio(n, d, _max);
        }
        if (n != d) {
            return (n, d);
        }
        return (1, 1);
    }

    /**
     * @dev computes "scale * a / (a + b)" and "scale * b / (a + b)".
     */
    function normalizedRatio(
        uint256 _a,
        uint256 _b,
        uint256 _scale
    ) internal pure returns (uint256, uint256) {
        if (_a <= _b) {
            return accurateRatio(_a, _b, _scale);
        }
        (uint256 y, uint256 x) = accurateRatio(_b, _a, _scale);
        return (x, y);
    }

    /**
     * @dev computes "scale * a / (a + b)" and "scale * b / (a + b)", assuming that "a <= b".
     */
    function accurateRatio(
        uint256 _a,
        uint256 _b,
        uint256 _scale
    ) internal pure returns (uint256, uint256) {
        uint256 maxVal = uint256(-1) / _scale;
        if (_a > maxVal) {
            uint256 c = _a / (maxVal + 1) + 1;
            _a /= c; // we can now safely compute `_a * _scale`
            _b /= c;
        }
        if (_a != _b) {
            uint256 n = _a * _scale;
            uint256 d = _a + _b; // can overflow
            if (d >= _a) {
                // no overflow in `_a + _b`
                uint256 x = roundDiv(n, d); // we can now safely compute `_scale - x`
                uint256 y = _scale - x;
                return (x, y);
            }
            if (n < _b - (_b - _a) / 2) {
                return (0, _scale); // `_a * _scale < (_a + _b) / 2 < MAX_UINT256 < _a + _b`
            }
            return (1, _scale - 1); // `(_a + _b) / 2 < _a * _scale < MAX_UINT256 < _a + _b`
        }
        return (_scale / 2, _scale / 2); // allow reduction to `(1, 1)` in the calling function
    }

    /**
     * @dev computes the nearest integer to a given quotient without overflowing or underflowing.
     */
    function roundDiv(uint256 _n, uint256 _d) internal pure returns (uint256) {
        return _n / _d + (_n % _d) / (_d - _d / 2);
    }

    /**
     * @dev returns the average number of decimal digits in a given list of positive integers
     *
     * @param _values  list of positive integers
     *
     * @return the average number of decimal digits in the given list of positive integers
     */
    function geometricMean(uint256[] memory _values) internal pure returns (uint256) {
        uint256 numOfDigits = 0;
        uint256 length = _values.length;
        for (uint256 i = 0; i < length; i++) {
            numOfDigits += decimalLength(_values[i]);
        }
        return uint256(10)**(roundDivUnsafe(numOfDigits, length) - 1);
    }

    /**
     * @dev returns the number of decimal digits in a given positive integer
     *
     * @param _x   positive integer
     *
     * @return the number of decimal digits in the given positive integer
     */
    function decimalLength(uint256 _x) internal pure returns (uint256) {
        uint256 y = 0;
        for (uint256 x = _x; x > 0; x /= 10) {
            y++;
        }
        return y;
    }

    /**
     * @dev returns the nearest integer to a given quotient
     * the computation is overflow-safe assuming that the input is sufficiently small
     *
     * @param _n   quotient numerator
     * @param _d   quotient denominator
     *
     * @return the nearest integer to the given quotient
     */
    function roundDivUnsafe(uint256 _n, uint256 _d) internal pure returns (uint256) {
        return (_n + _d / 2) / _d;
    }

    /**
     * @dev returns the larger of two values
     *
     * @param _val1 the first value
     * @param _val2 the second value
     */
    function max(uint256 _val1, uint256 _val2) internal pure returns (uint256) {
        return _val1 > _val2 ? _val1 : _val2;
    }
}

// File: solidity/contracts/utility/Owned.sol


pragma solidity 0.6.12;


/**
 * @dev This contract provides support and utilities for contract ownership.
 */
contract Owned is IOwned {
    address public override owner;
    address public newOwner;

    /**
     * @dev triggered when the owner is updated
     *
     * @param _prevOwner previous owner
     * @param _newOwner  new owner
     */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
     * @dev initializes a new Owned instance
     */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }

    // error message binary size optimization
    function _ownerOnly() internal view {
        require(msg.sender == owner, "ERR_ACCESS_DENIED");
    }

    /**
     * @dev allows transferring the contract ownership
     * the new owner still needs to accept the transfer
     * can only be called by the contract owner
     *
     * @param _newOwner    new contract owner
     */
    function transferOwnership(address _newOwner) public override ownerOnly {
        require(_newOwner != owner, "ERR_SAME_OWNER");
        newOwner = _newOwner;
    }

    /**
     * @dev used by a new owner to accept an ownership transfer
     */
    function acceptOwnership() public override {
        require(msg.sender == newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: solidity/contracts/utility/Utils.sol


pragma solidity 0.6.12;


/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    uint32 internal constant PPM_RESOLUTION = 1000000;
    IERC20 internal constant NATIVE_TOKEN_ADDRESS = IERC20(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);

    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }

    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }

    // ensures that the portion is valid
    modifier validPortion(uint32 _portion) {
        _validPortion(_portion);
        _;
    }

    // error message binary size optimization
    function _validPortion(uint32 _portion) internal pure {
        require(_portion > 0 && _portion <= PPM_RESOLUTION, "ERR_INVALID_PORTION");
    }

    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address _address) {
        _validExternalAddress(_address);
        _;
    }

    // error message binary size optimization
    function _validExternalAddress(address _address) internal view {
        require(_address != address(0) && _address != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }

    // ensures that the fee is valid
    modifier validFee(uint32 fee) {
        _validFee(fee);
        _;
    }

    // error message binary size optimization
    function _validFee(uint32 fee) internal pure {
        require(fee <= PPM_RESOLUTION, "ERR_INVALID_FEE");
    }
}

// File: solidity/contracts/utility/interfaces/IContractRegistry.sol


pragma solidity 0.6.12;

/*
    Contract Registry interface
*/
interface IContractRegistry {
    function addressOf(bytes32 _contractName) external view returns (address);
}

// File: solidity/contracts/utility/ContractRegistryClient.sol


pragma solidity 0.6.12;




/**
 * @dev This is the base contract for ContractRegistry clients.
 */
contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant BANCOR_FORMULA = "BancorFormula";
    bytes32 internal constant CONVERTER_FACTORY = "ConverterFactory";
    bytes32 internal constant CONVERSION_PATH_FINDER = "ConversionPathFinder";
    bytes32 internal constant CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";
    bytes32 internal constant LIQUIDITY_PROTECTION = "LiquidityProtection";
    bytes32 internal constant NETWORK_SETTINGS = "NetworkSettings";

    IContractRegistry public registry; // address of the current contract-registry
    IContractRegistry public prevRegistry; // address of the previous contract-registry
    bool public onlyOwnerCanUpdateRegistry; // only an owner can update the contract-registry

    /**
     * @dev verifies that the caller is mapped to the given contract name
     *
     * @param _contractName    contract name
     */
    modifier only(bytes32 _contractName) {
        _only(_contractName);
        _;
    }

    // error message binary size optimization
    function _only(bytes32 _contractName) internal view {
        require(msg.sender == addressOf(_contractName), "ERR_ACCESS_DENIED");
    }

    /**
     * @dev initializes a new ContractRegistryClient instance
     *
     * @param  _registry   address of a contract-registry contract
     */
    constructor(IContractRegistry _registry) internal validAddress(address(_registry)) {
        registry = IContractRegistry(_registry);
        prevRegistry = IContractRegistry(_registry);
    }

    /**
     * @dev updates to the new contract-registry
     */
    function updateRegistry() public {
        // verify that this function is permitted
        require(msg.sender == owner || !onlyOwnerCanUpdateRegistry, "ERR_ACCESS_DENIED");

        // get the new contract-registry
        IContractRegistry newRegistry = IContractRegistry(addressOf(CONTRACT_REGISTRY));

        // verify that the new contract-registry is different and not zero
        require(newRegistry != registry && address(newRegistry) != address(0), "ERR_INVALID_REGISTRY");

        // verify that the new contract-registry is pointing to a non-zero contract-registry
        require(newRegistry.addressOf(CONTRACT_REGISTRY) != address(0), "ERR_INVALID_REGISTRY");

        // save a backup of the current contract-registry before replacing it
        prevRegistry = registry;

        // replace the current contract-registry with the new contract-registry
        registry = newRegistry;
    }

    /**
     * @dev restores the previous contract-registry
     */
    function restoreRegistry() public ownerOnly {
        // restore the previous contract-registry
        registry = prevRegistry;
    }

    /**
     * @dev restricts the permission to update the contract-registry
     *
     * @param _onlyOwnerCanUpdateRegistry  indicates whether or not permission is restricted to owner only
     */
    function restrictRegistryUpdate(bool _onlyOwnerCanUpdateRegistry) public ownerOnly {
        // change the permission to update the contract-registry
        onlyOwnerCanUpdateRegistry = _onlyOwnerCanUpdateRegistry;
    }

    /**
     * @dev returns the address associated with the given contract name
     *
     * @param _contractName    contract name
     *
     * @return contract address
     */
    function addressOf(bytes32 _contractName) internal view returns (address) {
        return registry.addressOf(_contractName);
    }
}

// File: solidity/contracts/utility/ReentrancyGuard.sol


pragma solidity 0.6.12;

/**
 * @dev This contract provides protection against calling a function
 * (directly or indirectly) from within itself.
 */
contract ReentrancyGuard {
    uint256 private constant UNLOCKED = 1;
    uint256 private constant LOCKED = 2;

    // LOCKED while protected code is being executed, UNLOCKED otherwise
    uint256 private state = UNLOCKED;

    /**
     * @dev ensures instantiation only by sub-contracts
     */
    constructor() internal {}

    // protects a function against reentrancy attacks
    modifier protected() {
        _protected();
        state = LOCKED;
        _;
        state = UNLOCKED;
    }

    // error message binary size optimization
    function _protected() internal view {
        require(state == UNLOCKED, "ERR_REENTRANCY");
    }
}

// File: solidity/contracts/utility/Time.sol


pragma solidity 0.6.12;

/*
    Time implementing contract
*/
contract Time {
    /**
     * @dev returns the current time
     */
    function time() internal view virtual returns (uint256) {
        return block.timestamp;
    }
}

// File: solidity/contracts/converter/types/standard-pool/StandardPoolConverter.sol


pragma solidity 0.6.12;













/**
 * @dev This contract is a specialized version of the converter, which is
 * optimized for a liquidity pool that has 2 reserves with 50%/50% weights.
 */
contract StandardPoolConverter is ConverterVersion, IConverter, ContractRegistryClient, ReentrancyGuard, Time {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    using MathEx for *;

    uint256 private constant MAX_UINT128 = 2**128 - 1;
    uint256 private constant MAX_UINT112 = 2**112 - 1;
    uint256 private constant MAX_UINT32 = 2**32 - 1;
    uint256 private constant AVERAGE_RATE_PERIOD = 10 minutes;

    uint256 private __reserveBalances;
    uint256 private _reserveBalancesProduct;
    IERC20[] private __reserveTokens;
    mapping(IERC20 => uint256) private __reserveIds;

    IConverterAnchor public override anchor; // converter anchor contract
    uint32 public override maxConversionFee; // maximum conversion fee, represented in ppm, 0...1000000
    uint32 public override conversionFee; // current conversion fee, represented in ppm, 0...maxConversionFee

    // average rate details:
    // bits 0...111 represent the numerator of the rate between reserve token 0 and reserve token 1
    // bits 111...223 represent the denominator of the rate between reserve token 0 and reserve token 1
    // bits 224...255 represent the update-time of the rate between reserve token 0 and reserve token 1
    // where `numerator / denominator` gives the worth of one reserve token 0 in units of reserve token 1
    uint256 public averageRateInfo;

    /**
     * @dev triggered after liquidity is added
     *
     * @param  _provider       liquidity provider
     * @param  _reserveToken   reserve token address
     * @param  _amount         reserve token amount
     * @param  _newBalance     reserve token new balance
     * @param  _newSupply      pool token new supply
     */
    event LiquidityAdded(
        address indexed _provider,
        IERC20 indexed _reserveToken,
        uint256 _amount,
        uint256 _newBalance,
        uint256 _newSupply
    );

    /**
     * @dev triggered after liquidity is removed
     *
     * @param  _provider       liquidity provider
     * @param  _reserveToken   reserve token address
     * @param  _amount         reserve token amount
     * @param  _newBalance     reserve token new balance
     * @param  _newSupply      pool token new supply
     */
    event LiquidityRemoved(
        address indexed _provider,
        IERC20 indexed _reserveToken,
        uint256 _amount,
        uint256 _newBalance,
        uint256 _newSupply
    );

    /**
     * @dev initializes a new StandardPoolConverter instance
     *
     * @param  _anchor             anchor governed by the converter
     * @param  _registry           address of a contract registry contract
     * @param  _maxConversionFee   maximum conversion fee, represented in ppm
     */
    constructor(
        IConverterAnchor _anchor,
        IContractRegistry _registry,
        uint32 _maxConversionFee
    ) public ContractRegistryClient(_registry) validAddress(address(_anchor)) validConversionFee(_maxConversionFee) {
        anchor = _anchor;
        maxConversionFee = _maxConversionFee;
    }

    // ensures that the converter is active
    modifier active() {
        _active();
        _;
    }

    // error message binary size optimization
    function _active() internal view {
        require(isActive(), "ERR_INACTIVE");
    }

    // ensures that the converter is not active
    modifier inactive() {
        _inactive();
        _;
    }

    // error message binary size optimization
    function _inactive() internal view {
        require(!isActive(), "ERR_ACTIVE");
    }

    // validates a reserve token address - verifies that the address belongs to one of the reserve tokens
    modifier validReserve(IERC20 _address) {
        _validReserve(_address);
        _;
    }

    // error message binary size optimization
    function _validReserve(IERC20 _address) internal view {
        require(__reserveIds[_address] != 0, "ERR_INVALID_RESERVE");
    }

    // validates conversion fee
    modifier validConversionFee(uint32 _conversionFee) {
        _validConversionFee(_conversionFee);
        _;
    }

    // error message binary size optimization
    function _validConversionFee(uint32 _conversionFee) internal pure {
        require(_conversionFee <= PPM_RESOLUTION, "ERR_INVALID_CONVERSION_FEE");
    }

    // validates reserve weight
    modifier validReserveWeight(uint32 _weight) {
        _validReserveWeight(_weight);
        _;
    }

    // error message binary size optimization
    function _validReserveWeight(uint32 _weight) internal pure {
        require(_weight == PPM_RESOLUTION / 2, "ERR_INVALID_RESERVE_WEIGHT");
    }

    /**
     * @dev returns the converter type
     *
     * @return see the converter types in the the main contract doc
     */
    function converterType() public pure virtual override returns (uint16) {
        return 3;
    }

    /**
     * @dev deposits ether
     * can only be called if the converter has an ETH reserve
     */
    receive() external payable override(IConverter) validReserve(NATIVE_TOKEN_ADDRESS) {}

    /**
     * @dev checks whether or not the converter version is 28 or higher
     *
     * @return true, since the converter version is 28 or higher
     */
    function isV28OrHigher() public pure returns (bool) {
        return true;
    }

    /**
     * @dev returns true if the converter is active, false otherwise
     *
     * @return true if the converter is active, false otherwise
     */
    function isActive() public view virtual override returns (bool) {
        return anchor.owner() == address(this);
    }

    /**
     * @dev transfers the anchor ownership
     * the new owner needs to accept the transfer
     * can only be called by the converter upgrader while the upgrader is the owner
     * note that prior to version 28, you should use 'transferAnchorOwnership' instead
     *
     * @param _newOwner    new token owner
     */
    function transferAnchorOwnership(address _newOwner) public override ownerOnly only(CONVERTER_UPGRADER) {
        anchor.transferOwnership(_newOwner);
    }

    /**
     * @dev accepts ownership of the anchor after an ownership transfer
     * most converters are also activated as soon as they accept the anchor ownership
     * can only be called by the contract owner
     * note that prior to version 28, you should use 'acceptTokenOwnership' instead
     */
    function acceptAnchorOwnership() public virtual override ownerOnly {
        // verify the the converter has exactly two reserves
        require(reserveTokenCount() == 2, "ERR_INVALID_RESERVE_COUNT");
        anchor.acceptOwnership();
        syncReserveBalances(0);
        emit Activation(converterType(), anchor, true);
    }

    /**
     * @dev updates the current conversion fee
     * can only be called by the contract owner
     *
     * @param _conversionFee new conversion fee, represented in ppm
     */
    function setConversionFee(uint32 _conversionFee) public override ownerOnly {
        require(_conversionFee <= maxConversionFee, "ERR_INVALID_CONVERSION_FEE");
        emit ConversionFeeUpdate(conversionFee, _conversionFee);
        conversionFee = _conversionFee;
    }

    /**
     * @dev transfers reserve balances to a new converter during an upgrade
     * can only be called by the converter upgraded which should be set at its owner
     *
     * @param _newConverter address of the converter to receive the new amount
     */
    function transferReservesOnUpgrade(address _newConverter)
        external
        override
        protected
        ownerOnly
        only(CONVERTER_UPGRADER)
    {
        uint256 reserveCount = __reserveTokens.length;
        for (uint256 i = 0; i < reserveCount; ++i) {
            IERC20 reserveToken = __reserveTokens[i];

            uint256 amount;
            if (reserveToken == NATIVE_TOKEN_ADDRESS) {
                amount = address(this).balance;
            } else {
                amount = reserveToken.balanceOf(address(this));
            }

            safeTransfer(reserveToken, _newConverter, amount);

            syncReserveBalance(reserveToken);
        }
    }

    /**
     * @dev upgrades the converter to the latest version
     * can only be called by the owner
     * note that the owner needs to call acceptOwnership on the new converter after the upgrade
     */
    function upgrade() public ownerOnly {
        IConverterUpgrader converterUpgrader = IConverterUpgrader(addressOf(CONVERTER_UPGRADER));

        // trigger de-activation event
        emit Activation(converterType(), anchor, false);

        transferOwnership(address(converterUpgrader));
        converterUpgrader.upgrade(version);
        acceptOwnership();
    }

    /**
     * @dev executed by the upgrader at the end of the upgrade process to handle custom pool logic
     */
    function onUpgradeComplete()
        external
        override
        protected
        ownerOnly
        only(CONVERTER_UPGRADER)
    {
        (uint256 reserveBalance0, uint256 reserveBalance1) = reserveBalances(1, 2);
        _reserveBalancesProduct = reserveBalance0 * reserveBalance1;
    }

    /**
     * @dev returns the number of reserve tokens
     * note that prior to version 17, you should use 'connectorTokenCount' instead
     *
     * @return number of reserve tokens
     */
    function reserveTokenCount() public view returns (uint16) {
        return uint16(__reserveTokens.length);
    }

    /**
     * @dev returns the array of reserve tokens
     *
     * @return array of reserve tokens
     */
    function reserveTokens() public view returns (IERC20[] memory) {
        return __reserveTokens;
    }

    /**
     * @dev defines a new reserve token for the converter
     * can only be called by the owner while the converter is inactive
     *
     * @param _token   address of the reserve token
     * @param _weight  reserve weight, represented in ppm, 1-1000000
     */
    function addReserve(IERC20 _token, uint32 _weight)
        public
        virtual
        override
        ownerOnly
        inactive
        validExternalAddress(address(_token))
        validReserveWeight(_weight)
    {
        // validate input
        require(address(_token) != address(anchor) && __reserveIds[_token] == 0, "ERR_INVALID_RESERVE");
        require(reserveTokenCount() < 2, "ERR_INVALID_RESERVE_COUNT");

        __reserveTokens.push(_token);
        __reserveIds[_token] = __reserveTokens.length;
    }

    /**
     * @dev returns the reserve's weight
     * added in version 28
     *
     * @param _reserveToken    reserve token contract address
     *
     * @return reserve weight
     */
    function reserveWeight(IERC20 _reserveToken) public view validReserve(_reserveToken) returns (uint32) {
        return PPM_RESOLUTION / 2;
    }

    /**
     * @dev returns the balance of a given reserve token
     *
     * @param _reserveToken    reserve token contract address
     *
     * @return the balance of the given reserve token
     */
    function reserveBalance(IERC20 _reserveToken) public view override returns (uint256) {
        uint256 reserveId = __reserveIds[_reserveToken];
        require(reserveId != 0, "ERR_INVALID_RESERVE");
        return reserveBalance(reserveId);
    }

    /**
     * @dev returns the balances of both reserve tokens
     *
     * @return the balances of both reserve tokens
     */
    function reserveBalances() public view returns (uint256, uint256) {
        return reserveBalances(1, 2);
    }

    /**
     * @dev syncs all stored reserve balances
     */
    function syncReserveBalances() external {
        syncReserveBalances(0);
    }

    /**
     * @dev calculates the accumulated network fee and transfers it to the network fee wallet
     */
    function processNetworkFees() external protected {
        (uint256 reserveBalance0, uint256 reserveBalance1) = processNetworkFees(0);
        _reserveBalancesProduct = reserveBalance0 * reserveBalance1;
    }

    /**
     * @dev calculates the accumulated network fee and transfers it to the network fee wallet
     *
     * @param _value amount of ether to exclude from the ether reserve balance (if relevant)
     *
     * @return new reserve balances
     */
    function processNetworkFees(uint256 _value) internal returns (uint256, uint256) {
        syncReserveBalances(_value);
        (uint256 reserveBalance0, uint256 reserveBalance1) = reserveBalances(1, 2);
        (ITokenHolder wallet, uint256 fee0, uint256 fee1) = networkWalletAndFees(reserveBalance0, reserveBalance1);
        reserveBalance0 -= fee0;
        reserveBalance1 -= fee1;
        setReserveBalances(1, 2, reserveBalance0, reserveBalance1);
        safeTransfer(__reserveTokens[0], address(wallet), fee0);
        safeTransfer(__reserveTokens[1], address(wallet), fee1);
        return (reserveBalance0, reserveBalance1);
    }

    /**
     * @dev returns the reserve balances of the given reserve tokens minus their corresponding fees
     *
     * @param _reserveTokens reserve tokens
     *
     * @return reserve balances minus their corresponding fees
     */
    function baseReserveBalances(IERC20[] memory _reserveTokens) internal view returns (uint256[2] memory) {
        uint256 reserveId0 = __reserveIds[_reserveTokens[0]];
        uint256 reserveId1 = __reserveIds[_reserveTokens[1]];
        (uint256 reserveBalance0, uint256 reserveBalance1) = reserveBalances(reserveId0, reserveId1);
        (, uint256 fee0, uint256 fee1) = networkWalletAndFees(reserveBalance0, reserveBalance1);
        return [reserveBalance0 - fee0, reserveBalance1 - fee1];
    }

    /**
     * @dev converts a specific amount of source tokens to target tokens
     * can only be called by the bancor network contract
     *
     * @param _sourceToken source ERC20 token
     * @param _targetToken target ERC20 token
     * @param _amount      amount of tokens to convert (in units of the source token)
     * @param _trader      address of the caller who executed the conversion
     * @param _beneficiary wallet to receive the conversion result
     *
     * @return amount of tokens received (in units of the target token)
     */
    function convert(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) public payable override protected only(BANCOR_NETWORK) returns (uint256) {
        // validate input
        require(_sourceToken != _targetToken, "ERR_SAME_SOURCE_TARGET");

        return doConvert(_sourceToken, _targetToken, _amount, _trader, _beneficiary);
    }

    /**
     * @dev returns the conversion fee for a given target amount
     *
     * @param _targetAmount  target amount
     *
     * @return conversion fee
     */
    function calculateFee(uint256 _targetAmount) internal view returns (uint256) {
        return _targetAmount.mul(conversionFee) / PPM_RESOLUTION;
    }

    /**
     * @dev returns the conversion fee taken from a given target amount
     *
     * @param _targetAmount  target amount
     *
     * @return conversion fee
     */
    function calculateFeeInv(uint256 _targetAmount) internal view returns (uint256) {
        return _targetAmount.mul(conversionFee).div(PPM_RESOLUTION - conversionFee);
    }

    /**
     * @dev loads the stored reserve balance for a given reserve id
     *
     * @param _reserveId   reserve id
     */
    function reserveBalance(uint256 _reserveId) internal view returns (uint256) {
        return decodeReserveBalance(__reserveBalances, _reserveId);
    }

    /**
     * @dev loads the stored reserve balances
     *
     * @param _sourceId    source reserve id
     * @param _targetId    target reserve id
     */
    function reserveBalances(uint256 _sourceId, uint256 _targetId) internal view returns (uint256, uint256) {
        require((_sourceId == 1 && _targetId == 2) || (_sourceId == 2 && _targetId == 1), "ERR_INVALID_RESERVES");
        return decodeReserveBalances(__reserveBalances, _sourceId, _targetId);
    }

    /**
     * @dev stores the stored reserve balance for a given reserve id
     *
     * @param _reserveId       reserve id
     * @param _reserveBalance  reserve balance
     */
    function setReserveBalance(uint256 _reserveId, uint256 _reserveBalance) internal {
        require(_reserveBalance <= MAX_UINT128, "ERR_RESERVE_BALANCE_OVERFLOW");
        uint256 otherBalance = decodeReserveBalance(__reserveBalances, 3 - _reserveId);
        __reserveBalances = encodeReserveBalances(_reserveBalance, _reserveId, otherBalance, 3 - _reserveId);
    }

    /**
     * @dev stores the stored reserve balances
     *
     * @param _sourceId        source reserve id
     * @param _targetId        target reserve id
     * @param _sourceBalance   source reserve balance
     * @param _targetBalance   target reserve balance
     */
    function setReserveBalances(
        uint256 _sourceId,
        uint256 _targetId,
        uint256 _sourceBalance,
        uint256 _targetBalance
    ) internal {
        require(_sourceBalance <= MAX_UINT128 && _targetBalance <= MAX_UINT128, "ERR_RESERVE_BALANCE_OVERFLOW");
        __reserveBalances = encodeReserveBalances(_sourceBalance, _sourceId, _targetBalance, _targetId);
    }

    /**
     * @dev syncs the stored reserve balance for a given reserve with the real reserve balance
     *
     * @param _reserveToken    address of the reserve token
     */
    function syncReserveBalance(IERC20 _reserveToken) internal {
        uint256 reserveId = __reserveIds[_reserveToken];
        uint256 balance =
            _reserveToken == NATIVE_TOKEN_ADDRESS ? address(this).balance : _reserveToken.balanceOf(address(this));
        setReserveBalance(reserveId, balance);
    }

    /**
     * @dev syncs all stored reserve balances, excluding a given amount of ether from the ether reserve balance (if relevant)
     *
     * @param _value   amount of ether to exclude from the ether reserve balance (if relevant)
     */
    function syncReserveBalances(uint256 _value) internal {
        IERC20 _reserveToken0 = __reserveTokens[0];
        IERC20 _reserveToken1 = __reserveTokens[1];
        uint256 balance0 =
            _reserveToken0 == NATIVE_TOKEN_ADDRESS
                ? address(this).balance - _value
                : _reserveToken0.balanceOf(address(this));
        uint256 balance1 =
            _reserveToken1 == NATIVE_TOKEN_ADDRESS
                ? address(this).balance - _value
                : _reserveToken1.balanceOf(address(this));
        setReserveBalances(1, 2, balance0, balance1);
    }

    /**
     * @dev helper, dispatches the Conversion event
     *
     * @param _sourceToken     source ERC20 token
     * @param _targetToken     target ERC20 token
     * @param _trader          address of the caller who executed the conversion
     * @param _amount          amount purchased/sold (in the source token)
     * @param _returnAmount    amount returned (in the target token)
     */
    function dispatchConversionEvent(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        address _trader,
        uint256 _amount,
        uint256 _returnAmount,
        uint256 _feeAmount
    ) internal {
        emit Conversion(_sourceToken, _targetToken, _trader, _amount, _returnAmount, int256(_feeAmount));
    }

    /**
     * @dev returns the expected amount and expected fee for converting one reserve to another
     *
     * @param _sourceToken address of the source reserve token contract
     * @param _targetToken address of the target reserve token contract
     * @param _amount      amount of source reserve tokens converted
     *
     * @return expected amount in units of the target reserve token
     * @return expected fee in units of the target reserve token
     */
    function targetAmountAndFee(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount
    ) public view virtual override active returns (uint256, uint256) {
        uint256 sourceId = __reserveIds[_sourceToken];
        uint256 targetId = __reserveIds[_targetToken];

        (uint256 sourceBalance, uint256 targetBalance) = reserveBalances(sourceId, targetId);

        return targetAmountAndFee(_sourceToken, _targetToken, sourceBalance, targetBalance, _amount);
    }

    /**
     * @dev returns the expected amount and expected fee for converting one reserve to another
     *
     * @param _sourceBalance    balance in the source reserve token contract
     * @param _targetBalance    balance in the target reserve token contract
     * @param _amount           amount of source reserve tokens converted
     *
     * @return expected amount in units of the target reserve token
     * @return expected fee in units of the target reserve token
     */
    function targetAmountAndFee(
        IERC20, /* _sourceToken */
        IERC20, /* _targetToken */
        uint256 _sourceBalance,
        uint256 _targetBalance,
        uint256 _amount
    ) internal view virtual returns (uint256, uint256) {
        uint256 amount = crossReserveTargetAmount(_sourceBalance, _targetBalance, _amount);

        uint256 fee = calculateFee(amount);

        return (amount - fee, fee);
    }

    /**
     * @dev returns the required amount and expected fee for converting one reserve to another
     *
     * @param _sourceToken address of the source reserve token contract
     * @param _targetToken address of the target reserve token contract
     * @param _amount      amount of target reserve tokens desired
     *
     * @return required amount in units of the source reserve token
     * @return expected fee in units of the target reserve token
     */
    function sourceAmountAndFee(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount
    ) public view virtual active returns (uint256, uint256) {
        uint256 sourceId = __reserveIds[_sourceToken];
        uint256 targetId = __reserveIds[_targetToken];

        (uint256 sourceBalance, uint256 targetBalance) = reserveBalances(sourceId, targetId);

        uint256 fee = calculateFeeInv(_amount);

        uint256 amount = crossReserveSourceAmount(sourceBalance, targetBalance, _amount.add(fee));

        return (amount, fee);
    }

    /**
     * @dev converts a specific amount of source tokens to target tokens
     *
     * @param _sourceToken source ERC20 token
     * @param _targetToken target ERC20 token
     * @param _amount      amount of tokens to convert (in units of the source token)
     * @param _trader      address of the caller who executed the conversion
     * @param _beneficiary wallet to receive the conversion result
     *
     * @return amount of tokens received (in units of the target token)
     */
    function doConvert(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) internal returns (uint256) {
        // update the recent average rate
        updateRecentAverageRate();

        uint256 sourceId = __reserveIds[_sourceToken];
        uint256 targetId = __reserveIds[_targetToken];

        (uint256 sourceBalance, uint256 targetBalance) = reserveBalances(sourceId, targetId);

        // get the target amount minus the conversion fee and the conversion fee
        (uint256 amount, uint256 fee) =
            targetAmountAndFee(_sourceToken, _targetToken, sourceBalance, targetBalance, _amount);

        // ensure that the trade gives something in return
        require(amount != 0, "ERR_ZERO_TARGET_AMOUNT");

        // ensure that the trade won't deplete the reserve balance
        assert(amount < targetBalance);

        // ensure that the input amount was already deposited
        uint256 actualSourceBalance;
        if (_sourceToken == NATIVE_TOKEN_ADDRESS) {
            actualSourceBalance = address(this).balance;
            require(msg.value == _amount, "ERR_ETH_AMOUNT_MISMATCH");
        } else {
            actualSourceBalance = _sourceToken.balanceOf(address(this));
            require(msg.value == 0 && actualSourceBalance.sub(sourceBalance) >= _amount, "ERR_INVALID_AMOUNT");
        }

        // sync the reserve balances
        setReserveBalances(sourceId, targetId, actualSourceBalance, targetBalance - amount);

        // transfer funds to the beneficiary in the to reserve token
        safeTransfer(_targetToken, _beneficiary, amount);

        // dispatch the conversion event
        dispatchConversionEvent(_sourceToken, _targetToken, _trader, _amount, amount, fee);

        // dispatch rate updates
        dispatchTokenRateUpdateEvents(_sourceToken, _targetToken, actualSourceBalance, targetBalance - amount);

        return amount;
    }

    /**
     * @dev returns the recent average rate of 1 `_token` in the other reserve token units
     *
     * @param _token   token to get the rate for
     *
     * @return recent average rate between the reserves (numerator)
     * @return recent average rate between the reserves (denominator)
     */
    function recentAverageRate(IERC20 _token) external view validReserve(_token) returns (uint256, uint256) {
        // get the recent average rate of reserve 0
        uint256 rate = calcRecentAverageRate(averageRateInfo);

        uint256 rateN = decodeAverageRateN(rate);
        uint256 rateD = decodeAverageRateD(rate);

        if (_token == __reserveTokens[0]) {
            return (rateN, rateD);
        }

        return (rateD, rateN);
    }

    /**
     * @dev updates the recent average rate if needed
     */
    function updateRecentAverageRate() internal {
        uint256 averageRateInfo1 = averageRateInfo;
        uint256 averageRateInfo2 = calcRecentAverageRate(averageRateInfo1);
        if (averageRateInfo1 != averageRateInfo2) {
            averageRateInfo = averageRateInfo2;
        }
    }

    /**
     * @dev returns the recent average rate of 1 reserve token 0 in reserve token 1 units
     *
     * @param _averageRateInfo a local copy of the `averageRateInfo` state-variable
     *
     * @return recent average rate between the reserves
     */
    function calcRecentAverageRate(uint256 _averageRateInfo) internal view returns (uint256) {
        // get the previous average rate and its update-time
        uint256 prevAverageRateT = decodeAverageRateT(_averageRateInfo);
        uint256 prevAverageRateN = decodeAverageRateN(_averageRateInfo);
        uint256 prevAverageRateD = decodeAverageRateD(_averageRateInfo);

        // get the elapsed time since the previous average rate was calculated
        uint256 currentTime = time();
        uint256 timeElapsed = currentTime - prevAverageRateT;

        // if the previous average rate was calculated in the current block, the average rate remains unchanged
        if (timeElapsed == 0) {
            return _averageRateInfo;
        }

        // get the current rate between the reserves
        (uint256 currentRateD, uint256 currentRateN) = reserveBalances();

        // if the previous average rate was calculated a while ago or never, the average rate is equal to the current rate
        if (timeElapsed >= AVERAGE_RATE_PERIOD || prevAverageRateT == 0) {
            (currentRateN, currentRateD) = MathEx.reducedRatio(currentRateN, currentRateD, MAX_UINT112);
            return encodeAverageRateInfo(currentTime, currentRateN, currentRateD);
        }

        uint256 x = prevAverageRateD.mul(currentRateN);
        uint256 y = prevAverageRateN.mul(currentRateD);

        // since we know that timeElapsed < AVERAGE_RATE_PERIOD, we can avoid using SafeMath:
        uint256 newRateN = y.mul(AVERAGE_RATE_PERIOD - timeElapsed).add(x.mul(timeElapsed));
        uint256 newRateD = prevAverageRateD.mul(currentRateD).mul(AVERAGE_RATE_PERIOD);

        (newRateN, newRateD) = MathEx.reducedRatio(newRateN, newRateD, MAX_UINT112);
        return encodeAverageRateInfo(currentTime, newRateN, newRateD);
    }

    /**
     * @dev increases the pool's liquidity and mints new shares in the pool to the caller
     *
     * @param _reserveTokens   address of each reserve token
     * @param _reserveAmounts  amount of each reserve token
     * @param _minReturn       token minimum return-amount
     *
     * @return amount of pool tokens issued
     */
    function addLiquidity(
        IERC20[] memory _reserveTokens,
        uint256[] memory _reserveAmounts,
        uint256 _minReturn
    ) public payable protected active returns (uint256) {
        // verify the user input
        verifyLiquidityInput(_reserveTokens, _reserveAmounts, _minReturn);

        // if one of the reserves is ETH, then verify that the input amount of ETH is equal to the input value of ETH
        for (uint256 i = 0; i < 2; i++) {
            if (_reserveTokens[i] == NATIVE_TOKEN_ADDRESS) {
                require(_reserveAmounts[i] == msg.value, "ERR_ETH_AMOUNT_MISMATCH");
            }
        }

        // if the input value of ETH is larger than zero, then verify that one of the reserves is ETH
        if (msg.value > 0) {
            require(__reserveIds[NATIVE_TOKEN_ADDRESS] != 0, "ERR_NO_ETH_RESERVE");
        }

        // save a local copy of the pool token
        IDSToken poolToken = IDSToken(address(anchor));

        // get the total supply
        uint256 totalSupply = poolToken.totalSupply();

        uint256[2] memory prevReserveBalances;
        uint256[2] memory newReserveBalances;

        // process the network fees and get the reserve balances
        (prevReserveBalances[0], prevReserveBalances[1]) = processNetworkFees(msg.value);

        uint256 amount;
        uint256[2] memory reserveAmounts;

        // calculate the amount of pool tokens to mint for the caller
        // and the amount of reserve tokens to transfer from the caller
        if (totalSupply == 0) {
            amount = MathEx.geometricMean(_reserveAmounts);
            reserveAmounts[0] = _reserveAmounts[0];
            reserveAmounts[1] = _reserveAmounts[1];
        } else {
            (amount, reserveAmounts) = addLiquidityAmounts(
                _reserveTokens,
                _reserveAmounts,
                prevReserveBalances,
                totalSupply
            );
        }

        uint256 newPoolTokenSupply = totalSupply.add(amount);
        for (uint256 i = 0; i < 2; i++) {
            IERC20 reserveToken = _reserveTokens[i];
            uint256 reserveAmount = reserveAmounts[i];
            require(reserveAmount > 0, "ERR_ZERO_TARGET_AMOUNT");
            assert(reserveAmount <= _reserveAmounts[i]);

            // transfer each one of the reserve amounts from the user to the pool
            if (reserveToken != NATIVE_TOKEN_ADDRESS) {
                // ETH has already been transferred as part of the transaction
                reserveToken.safeTransferFrom(msg.sender, address(this), reserveAmount);
            } else if (_reserveAmounts[i] > reserveAmount) {
                // transfer the extra amount of ETH back to the user
                msg.sender.transfer(_reserveAmounts[i] - reserveAmount);
            }

            // save the new reserve balance
            newReserveBalances[i] = prevReserveBalances[i].add(reserveAmount);

            emit LiquidityAdded(msg.sender, reserveToken, reserveAmount, newReserveBalances[i], newPoolTokenSupply);

            // dispatch the `TokenRateUpdate` event for the pool token
            emit TokenRateUpdate(poolToken, reserveToken, newReserveBalances[i], newPoolTokenSupply);
        }

        // set the reserve balances
        setReserveBalances(1, 2, newReserveBalances[0], newReserveBalances[1]);

        // set the reserve balances product
        _reserveBalancesProduct = newReserveBalances[0] * newReserveBalances[1];

        // verify that the equivalent amount of tokens is equal to or larger than the user's expectation
        require(amount >= _minReturn, "ERR_RETURN_TOO_LOW");

        // issue the tokens to the user
        poolToken.issue(msg.sender, amount);

        // return the amount of pool tokens issued
        return amount;
    }

    /**
     * @dev get the amount of pool tokens to mint for the caller
     * and the amount of reserve tokens to transfer from the caller
     *
     * @param _reserveAmounts   amount of each reserve token
     * @param _reserveBalances  balance of each reserve token
     * @param _totalSupply      total supply of pool tokens
     *
     * @return amount of pool tokens to mint for the caller
     * @return amount of reserve tokens to transfer from the caller
     */
    function addLiquidityAmounts(
        IERC20[] memory, /* _reserveTokens */
        uint256[] memory _reserveAmounts,
        uint256[2] memory _reserveBalances,
        uint256 _totalSupply
    ) internal view virtual returns (uint256, uint256[2] memory) {
        this;

        uint256 index =
            _reserveAmounts[0].mul(_reserveBalances[1]) < _reserveAmounts[1].mul(_reserveBalances[0]) ? 0 : 1;
        uint256 amount = fundSupplyAmount(_totalSupply, _reserveBalances[index], _reserveAmounts[index]);

        uint256[2] memory reserveAmounts =
            [fundCost(_totalSupply, _reserveBalances[0], amount), fundCost(_totalSupply, _reserveBalances[1], amount)];

        return (amount, reserveAmounts);
    }

    /**
     * @dev decreases the pool's liquidity and burns the caller's shares in the pool
     *
     * @param _amount                  token amount
     * @param _reserveTokens           address of each reserve token
     * @param _reserveMinReturnAmounts minimum return-amount of each reserve token
     *
     * @return the amount of each reserve token granted for the given amount of pool tokens
     */
    function removeLiquidity(
        uint256 _amount,
        IERC20[] memory _reserveTokens,
        uint256[] memory _reserveMinReturnAmounts
    ) public protected active returns (uint256[] memory) {
        // verify the user input
        bool inputRearranged = verifyLiquidityInput(_reserveTokens, _reserveMinReturnAmounts, _amount);

        // save a local copy of the pool token
        IDSToken poolToken = IDSToken(address(anchor));

        // get the total supply BEFORE destroying the user tokens
        uint256 totalSupply = poolToken.totalSupply();

        // destroy the user tokens
        poolToken.destroy(msg.sender, _amount);

        uint256 newPoolTokenSupply = totalSupply.sub(_amount);

        uint256[2] memory prevReserveBalances;
        uint256[2] memory newReserveBalances;

        // process the network fees and get the reserve balances
        (prevReserveBalances[0], prevReserveBalances[1]) = processNetworkFees(0);

        uint256[] memory reserveAmounts = removeLiquidityReserveAmounts(_amount, totalSupply, prevReserveBalances);

        for (uint256 i = 0; i < 2; i++) {
            IERC20 reserveToken = _reserveTokens[i];
            uint256 reserveAmount = reserveAmounts[i];
            require(reserveAmount >= _reserveMinReturnAmounts[i], "ERR_ZERO_TARGET_AMOUNT");

            // save the new reserve balance
            newReserveBalances[i] = prevReserveBalances[i].sub(reserveAmount);

            // transfer each one of the reserve amounts from the pool to the user
            safeTransfer(reserveToken, msg.sender, reserveAmount);

            emit LiquidityRemoved(msg.sender, reserveToken, reserveAmount, newReserveBalances[i], newPoolTokenSupply);

            // dispatch the `TokenRateUpdate` event for the pool token
            emit TokenRateUpdate(poolToken, reserveToken, newReserveBalances[i], newPoolTokenSupply);
        }

        // set the reserve balances
        setReserveBalances(1, 2, newReserveBalances[0], newReserveBalances[1]);

        // set the reserve balances product
        _reserveBalancesProduct = newReserveBalances[0] * newReserveBalances[1];

        if (inputRearranged) {
            uint256 tempReserveAmount = reserveAmounts[0];
            reserveAmounts[0] = reserveAmounts[1];
            reserveAmounts[1] = tempReserveAmount;
        }

        // return the amount of each reserve token granted for the given amount of pool tokens
        return reserveAmounts;
    }

    /**
     * @dev given the amount of one of the reserve tokens to add liquidity of,
     * returns the required amount of each one of the other reserve tokens
     * since an empty pool can be funded with any list of non-zero input amounts,
     * this function assumes that the pool is not empty (has already been funded)
     *
     * @param _reserveTokens       address of each reserve token
     * @param _reserveTokenIndex   index of the relevant reserve token
     * @param _reserveAmount       amount of the relevant reserve token
     *
     * @return the required amount of each one of the reserve tokens
     */
    function addLiquidityCost(
        IERC20[] memory _reserveTokens,
        uint256 _reserveTokenIndex,
        uint256 _reserveAmount
    ) public view returns (uint256[] memory) {
        uint256 totalSupply = IDSToken(address(anchor)).totalSupply();
        uint256[2] memory baseBalances = baseReserveBalances(_reserveTokens);
        uint256 amount = fundSupplyAmount(totalSupply, baseBalances[_reserveTokenIndex], _reserveAmount);

        uint256[] memory reserveAmounts = new uint256[](2);
        reserveAmounts[0] = fundCost(totalSupply, baseBalances[0], amount);
        reserveAmounts[1] = fundCost(totalSupply, baseBalances[1], amount);
        return reserveAmounts;
    }

    /**
     * @dev returns the amount of pool tokens entitled for given amounts of reserve tokens
     * since an empty pool can be funded with any list of non-zero input amounts,
     * this function assumes that the pool is not empty (has already been funded)
     *
     * @param _reserveTokens   address of each reserve token
     * @param _reserveAmounts  amount of each reserve token
     *
     * @return the amount of pool tokens entitled for the given amounts of reserve tokens
     */
    function addLiquidityReturn(IERC20[] memory _reserveTokens, uint256[] memory _reserveAmounts)
        public
        view
        returns (uint256)
    {
        uint256 totalSupply = IDSToken(address(anchor)).totalSupply();
        uint256[2] memory baseBalances = baseReserveBalances(_reserveTokens);
        (uint256 amount, ) = addLiquidityAmounts(_reserveTokens, _reserveAmounts, baseBalances, totalSupply);
        return amount;
    }

    /**
     * @dev returns the amount of each reserve token entitled for a given amount of pool tokens
     *
     * @param _amount          amount of pool tokens
     * @param _reserveTokens   address of each reserve token
     *
     * @return the amount of each reserve token entitled for the given amount of pool tokens
     */
    function removeLiquidityReturn(uint256 _amount, IERC20[] memory _reserveTokens)
        public
        view
        returns (uint256[] memory)
    {
        uint256 totalSupply = IDSToken(address(anchor)).totalSupply();
        uint256[2] memory baseBalances = baseReserveBalances(_reserveTokens);
        return removeLiquidityReserveAmounts(_amount, totalSupply, baseBalances);
    }

    /**
     * @dev verifies that a given array of tokens is identical to the converter's array of reserve tokens
     * we take this input in order to allow specifying the corresponding reserve amounts in any order
     * this function rearranges the input arrays according to the converter's array of reserve tokens
     *
     * @param _reserveTokens   array of reserve tokens
     * @param _reserveAmounts  array of reserve amounts
     * @param _amount          token amount
     *
     * @return true if the function has rearranged the input arrays; false otherwise
     */
    function verifyLiquidityInput(
        IERC20[] memory _reserveTokens,
        uint256[] memory _reserveAmounts,
        uint256 _amount
    ) private view returns (bool) {
        require(validReserveAmounts(_reserveAmounts) && _amount > 0, "ERR_ZERO_AMOUNT");

        uint256 reserve0Id = __reserveIds[_reserveTokens[0]];
        uint256 reserve1Id = __reserveIds[_reserveTokens[1]];

        if (reserve0Id == 2 && reserve1Id == 1) {
            IERC20 tempReserveToken = _reserveTokens[0];
            _reserveTokens[0] = _reserveTokens[1];
            _reserveTokens[1] = tempReserveToken;
            uint256 tempReserveAmount = _reserveAmounts[0];
            _reserveAmounts[0] = _reserveAmounts[1];
            _reserveAmounts[1] = tempReserveAmount;
            return true;
        }

        require(reserve0Id == 1 && reserve1Id == 2, "ERR_INVALID_RESERVE");
        return false;
    }

    /**
     * @dev checks whether or not both reserve amounts are larger than zero
     *
     * @param _reserveAmounts  array of reserve amounts
     *
     * @return true if both reserve amounts are larger than zero; false otherwise
     */
    function validReserveAmounts(uint256[] memory _reserveAmounts) internal pure virtual returns (bool) {
        return _reserveAmounts[0] > 0 && _reserveAmounts[1] > 0;
    }

    /**
     * @dev returns the amount of each reserve token entitled for a given amount of pool tokens
     *
     * @param _amount          amount of pool tokens
     * @param _totalSupply     total supply of pool tokens
     * @param _reserveBalances balance of each reserve token
     *
     * @return the amount of each reserve token entitled for the given amount of pool tokens
     */
    function removeLiquidityReserveAmounts(
        uint256 _amount,
        uint256 _totalSupply,
        uint256[2] memory _reserveBalances
    ) private pure returns (uint256[] memory) {
        uint256[] memory reserveAmounts = new uint256[](2);
        reserveAmounts[0] = liquidateReserveAmount(_totalSupply, _reserveBalances[0], _amount);
        reserveAmounts[1] = liquidateReserveAmount(_totalSupply, _reserveBalances[1], _amount);
        return reserveAmounts;
    }

    /**
     * @dev dispatches token rate update events for the reserve tokens and the pool token
     *
     * @param _sourceToken     address of the source reserve token
     * @param _targetToken     address of the target reserve token
     * @param _sourceBalance   balance of the source reserve token
     * @param _targetBalance   balance of the target reserve token
     */
    function dispatchTokenRateUpdateEvents(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _sourceBalance,
        uint256 _targetBalance
    ) private {
        // save a local copy of the pool token
        IDSToken poolToken = IDSToken(address(anchor));

        // get the total supply of pool tokens
        uint256 poolTokenSupply = poolToken.totalSupply();

        // dispatch token rate update event for the reserve tokens
        emit TokenRateUpdate(_sourceToken, _targetToken, _targetBalance, _sourceBalance);

        // dispatch token rate update events for the pool token
        emit TokenRateUpdate(poolToken, _sourceToken, _sourceBalance, poolTokenSupply);
        emit TokenRateUpdate(poolToken, _targetToken, _targetBalance, poolTokenSupply);
    }

    function encodeReserveBalance(uint256 _balance, uint256 _id) private pure returns (uint256) {
        assert(_balance <= MAX_UINT128 && (_id == 1 || _id == 2));
        return _balance << ((_id - 1) * 128);
    }

    function decodeReserveBalance(uint256 _balances, uint256 _id) private pure returns (uint256) {
        assert(_id == 1 || _id == 2);
        return (_balances >> ((_id - 1) * 128)) & MAX_UINT128;
    }

    function encodeReserveBalances(
        uint256 _balance0,
        uint256 _id0,
        uint256 _balance1,
        uint256 _id1
    ) private pure returns (uint256) {
        return encodeReserveBalance(_balance0, _id0) | encodeReserveBalance(_balance1, _id1);
    }

    function decodeReserveBalances(
        uint256 _balances,
        uint256 _id0,
        uint256 _id1
    ) private pure returns (uint256, uint256) {
        return (decodeReserveBalance(_balances, _id0), decodeReserveBalance(_balances, _id1));
    }

    function encodeAverageRateInfo(
        uint256 _averageRateT,
        uint256 _averageRateN,
        uint256 _averageRateD
    ) private pure returns (uint256) {
        assert(_averageRateT <= MAX_UINT32 && _averageRateN <= MAX_UINT112 && _averageRateD <= MAX_UINT112);
        return (_averageRateT << 224) | (_averageRateN << 112) | _averageRateD;
    }

    function decodeAverageRateT(uint256 _averageRateInfo) private pure returns (uint256) {
        return _averageRateInfo >> 224;
    }

    function decodeAverageRateN(uint256 _averageRateInfo) private pure returns (uint256) {
        return (_averageRateInfo >> 112) & MAX_UINT112;
    }

    function decodeAverageRateD(uint256 _averageRateInfo) private pure returns (uint256) {
        return _averageRateInfo & MAX_UINT112;
    }

    /**
     * @dev returns the largest integer smaller than or equal to the square root of a given value
     *
     * @param x the given value
     *
     * @return the largest integer smaller than or equal to the square root of the given value
     */
    function floorSqrt(uint256 x) private pure returns (uint256) {
        return x > 0 ? MathEx.floorSqrt(x) : 0;
    }

    function crossReserveTargetAmount(
        uint256 _sourceReserveBalance,
        uint256 _targetReserveBalance,
        uint256 _amount
    ) private pure returns (uint256) {
        // validate input
        require(_sourceReserveBalance > 0 && _targetReserveBalance > 0, "ERR_INVALID_RESERVE_BALANCE");

        return _targetReserveBalance.mul(_amount) / _sourceReserveBalance.add(_amount);
    }

    function crossReserveSourceAmount(
        uint256 _sourceReserveBalance,
        uint256 _targetReserveBalance,
        uint256 _amount
    ) private pure returns (uint256) {
        // validate input
        require(_sourceReserveBalance > 0, "ERR_INVALID_RESERVE_BALANCE");
        require(_amount < _targetReserveBalance, "ERR_INVALID_AMOUNT");

        if (_amount == 0) {
            return 0;
        }

        return (_sourceReserveBalance.mul(_amount) - 1) / (_targetReserveBalance - _amount) + 1;
    }

    function fundCost(
        uint256 _supply,
        uint256 _reserveBalance,
        uint256 _amount
    ) private pure returns (uint256) {
        // validate input
        require(_supply > 0, "ERR_INVALID_SUPPLY");
        require(_reserveBalance > 0, "ERR_INVALID_RESERVE_BALANCE");

        // special case for 0 amount
        if (_amount == 0) {
            return 0;
        }

        return (_amount.mul(_reserveBalance) - 1) / _supply + 1;
    }

    function fundSupplyAmount(
        uint256 _supply,
        uint256 _reserveBalance,
        uint256 _amount
    ) private pure returns (uint256) {
        // validate input
        require(_supply > 0, "ERR_INVALID_SUPPLY");
        require(_reserveBalance > 0, "ERR_INVALID_RESERVE_BALANCE");

        // special case for 0 amount
        if (_amount == 0) {
            return 0;
        }

        return _amount.mul(_supply) / _reserveBalance;
    }

    function liquidateReserveAmount(
        uint256 _supply,
        uint256 _reserveBalance,
        uint256 _amount
    ) private pure returns (uint256) {
        // validate input
        require(_supply > 0, "ERR_INVALID_SUPPLY");
        require(_reserveBalance > 0, "ERR_INVALID_RESERVE_BALANCE");
        require(_amount <= _supply, "ERR_INVALID_AMOUNT");

        // special case for 0 amount
        if (_amount == 0) {
            return 0;
        }

        // special case for liquidating the entire supply
        if (_amount == _supply) {
            return _reserveBalance;
        }

        return _amount.mul(_reserveBalance) / _supply;
    }

    /**
     * @dev returns the network wallet and fees
     *
     * @param reserveBalance0 1st reserve balance
     * @param reserveBalance1 2nd reserve balance
     *
     * @return the network wallet
     * @return the network fee on the 1st reserve
     * @return the network fee on the 2nd reserve
     */
    function networkWalletAndFees(uint256 reserveBalance0, uint256 reserveBalance1)
        private
        view
        returns (
            ITokenHolder,
            uint256,
            uint256
        )
    {
        uint256 prevPoint = floorSqrt(_reserveBalancesProduct);
        uint256 currPoint = floorSqrt(reserveBalance0 * reserveBalance1);

        if (prevPoint >= currPoint) {
            return (ITokenHolder(address(0)), 0, 0);
        }

        (ITokenHolder networkFeeWallet, uint32 networkFee) =
            INetworkSettings(addressOf(NETWORK_SETTINGS)).networkFeeParams();
        uint256 n = (currPoint - prevPoint) * networkFee;
        uint256 d = currPoint * PPM_RESOLUTION;
        return (networkFeeWallet, reserveBalance0.mul(n).div(d), reserveBalance1.mul(n).div(d));
    }

    /**
     * @dev transfers funds held by the contract and sends them to an account
     *
     * @param token ERC20 token contract address
     * @param to account to receive the new amount
     * @param amount amount to withdraw
     */
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 amount
    ) private {
        if (amount == 0) {
            return;
        }

        if (token == NATIVE_TOKEN_ADDRESS) {
            payable(to).transfer(amount);
        } else {
            token.safeTransfer(to, amount);
        }
    }

    /**
     * @dev deprecated since version 28, backward compatibility - use only for earlier versions
     */
    function token() public view override returns (IConverterAnchor) {
        return anchor;
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function transferTokenOwnership(address _newOwner) public override ownerOnly {
        transferAnchorOwnership(_newOwner);
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function acceptTokenOwnership() public override ownerOnly {
        acceptAnchorOwnership();
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function connectors(IERC20 _address)
        public
        view
        override
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        )
    {
        uint256 reserveId = __reserveIds[_address];
        if (reserveId != 0) {
            return (reserveBalance(reserveId), PPM_RESOLUTION / 2, false, false, true);
        }
        return (0, 0, false, false, false);
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function connectorTokens(uint256 _index) public view override returns (IERC20) {
        return __reserveTokens[_index];
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function connectorTokenCount() public view override returns (uint16) {
        return reserveTokenCount();
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function getConnectorBalance(IERC20 _connectorToken) public view override returns (uint256) {
        return reserveBalance(_connectorToken);
    }

    /**
     * @dev deprecated, backward compatibility
     */
    function getReturn(
        IERC20 _sourceToken,
        IERC20 _targetToken,
        uint256 _amount
    ) public view returns (uint256, uint256) {
        return targetAmountAndFee(_sourceToken, _targetToken, _amount);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@bancor/token-governance/contracts/ITokenGovernance.sol";
import "../utility/ContractRegistryClient.sol";
import "../utility/Utils.sol";
import "../utility/Time.sol";
import "../utility/interfaces/ICheckpointStore.sol";
import "../token/ReserveToken.sol";
import "../liquidity-protection/interfaces/ILiquidityProtection.sol";
import "./interfaces/IStakingRewards.sol";
/**
 * @dev This contract manages the distribution of the staking rewards
 */
contract StakingRewards is IStakingRewards, AccessControl, Time, Utils, ContractRegistryClient {
    using SafeMath for uint256;
    using ReserveToken for IReserveToken;
    using SafeERC20 for IERC20;
    using SafeERC20Ex for IERC20;
    // the role is used to globally govern the contract and its governing roles.
    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    // the roles is used to restrict who is allowed to publish liquidity protection events.
    bytes32 public constant ROLE_PUBLISHER = keccak256("ROLE_PUBLISHER");
    // the roles is used to restrict who is allowed to update/cache provider rewards.
    bytes32 public constant ROLE_UPDATER = keccak256("ROLE_UPDATER");
    // the weekly 25% increase of the rewards multiplier (in units of PPM).
    uint32 private constant MULTIPLIER_INCREMENT = PPM_RESOLUTION / 4;
    // the maximum weekly 200% rewards multiplier (in units of PPM).
    uint32 private constant MAX_MULTIPLIER = PPM_RESOLUTION + MULTIPLIER_INCREMENT * 4;
    // the rewards halving factor we need to take into account during the sanity verification process.
    uint8 private constant REWARDS_HALVING_FACTOR = 4;
    // since we will be dividing by the total amount of protected tokens in units of wei, we can encounter cases
    // where the total amount in the denominator is higher than the product of the rewards rate and staking duration. In
    // order to avoid this imprecision, we will amplify the reward rate by the units amount.
    uint256 private constant REWARD_RATE_FACTOR = 1e18;
    uint256 private constant MAX_UINT256 = uint256(-1);
    // the staking rewards settings.
    IStakingRewardsStore private immutable _store;
    // the permissioned wrapper around the network token which should allow this contract to mint staking rewards.
    ITokenGovernance private immutable _networkTokenGovernance;
    // the address of the network token.
    IERC20 private immutable _networkToken;
    // the checkpoint store recording last protected position removal times.
    ICheckpointStore private immutable _lastRemoveTimes;
    /**
     * @dev initializes a new StakingRewards contract
     */
    constructor(
        IStakingRewardsStore store,
        ITokenGovernance networkTokenGovernance,
        ICheckpointStore lastRemoveTimes,
        IContractRegistry registry
    )
        public
        validAddress(address(store))
        validAddress(address(networkTokenGovernance))
        validAddress(address(lastRemoveTimes))
        ContractRegistryClient(registry)
    {
        _store = store;
        _networkTokenGovernance = networkTokenGovernance;
        _networkToken = networkTokenGovernance.token();
        _lastRemoveTimes = lastRemoveTimes;
        // set up administrative roles.
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_PUBLISHER, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_UPDATER, ROLE_SUPERVISOR);
        // allow the deployer to initially govern the contract.
        _setupRole(ROLE_SUPERVISOR, _msgSender());
    }
    modifier onlyPublisher() {
        _onlyPublisher();
        _;
    }
    function _onlyPublisher() internal view {
        require(hasRole(ROLE_PUBLISHER, msg.sender), "ERR_ACCESS_DENIED");
    }
    modifier onlyUpdater() {
        _onlyUpdater();
        _;
    }
    function _onlyUpdater() internal view {
        require(hasRole(ROLE_UPDATER, msg.sender), "ERR_ACCESS_DENIED");
    }
    /**
     * @dev liquidity provision notification callback. The callback should be called *before* the liquidity is added in
     * the LP contract
     *
     * Requirements:
     *
     * - the caller must have the ROLE_PUBLISHER role
     */
    function onAddingLiquidity(
        address provider,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256, /* poolAmount */
        uint256 /* reserveAmount */
    ) external override onlyPublisher validExternalAddress(provider) {
        IDSToken poolToken = IDSToken(address(poolAnchor));
        PoolProgram memory program = _poolProgram(poolToken);
        if (program.startTime == 0) {
            return;
        }
        _updateRewards(provider, poolToken, reserveToken, program, _liquidityProtectionStats());
    }
    /**
     * @dev liquidity removal callback. The callback must be called *before* the liquidity is removed in the LP
     * contract
     *
     * Requirements:
     *
     * - the caller must have the ROLE_PUBLISHER role
     */
    function onRemovingLiquidity(
        uint256, /* id */
        address provider,
        IConverterAnchor, /* poolAnchor */
        IReserveToken, /* reserveToken */
        uint256, /* poolAmount */
        uint256 /* reserveAmount */
    ) external override onlyPublisher validExternalAddress(provider) {
        ILiquidityProtectionStats lpStats = _liquidityProtectionStats();
        // make sure that all pending rewards are properly stored for future claims, with retroactive rewards
        // multipliers.
        _storeRewards(provider, lpStats.providerPools(provider), lpStats);
    }
    /**
     * @dev returns the staking rewards store
     */
    function store() external view override returns (IStakingRewardsStore) {
        return _store;
    }
    /**
     * @dev returns specific provider's pending rewards for all participating pools
     */
    function pendingRewards(address provider) external view override returns (uint256) {
        return _pendingRewards(provider, _liquidityProtectionStats());
    }
    /**
     * @dev returns specific provider's pending rewards for a specific participating pool
     */
    function pendingPoolRewards(address provider, IDSToken poolToken) external view override returns (uint256) {
        return _pendingRewards(provider, poolToken, _liquidityProtectionStats());
    }
    /**
     * @dev returns specific provider's pending rewards for a specific participating pool/reserve
     */
    function pendingReserveRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view override returns (uint256) {
        PoolProgram memory program = _poolProgram(poolToken);
        return _pendingRewards(provider, poolToken, reserveToken, program, _liquidityProtectionStats());
    }
    /**
     * @dev returns the current rewards multiplier for a provider in a given pool
     */
    function rewardsMultiplier(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view override returns (uint32) {
        ProviderRewards memory providerRewards = _providerRewards(provider, poolToken, reserveToken);
        PoolProgram memory program = _poolProgram(poolToken);
        return _rewardsMultiplier(provider, providerRewards.effectiveStakingTime, program);
    }
    /**
     * @dev returns specific provider's total claimed rewards from all participating pools
     */
    function totalClaimedRewards(address provider) external view override returns (uint256) {
        uint256 totalRewards = 0;
        ILiquidityProtectionStats lpStats = _liquidityProtectionStats();
        IDSToken[] memory poolTokens = lpStats.providerPools(provider);
        for (uint256 i = 0; i < poolTokens.length; ++i) {
            IDSToken poolToken = poolTokens[i];
            PoolProgram memory program = _poolProgram(poolToken);
            for (uint256 j = 0; j < program.reserveTokens.length; ++j) {
                IReserveToken reserveToken = program.reserveTokens[j];
                ProviderRewards memory providerRewards = _providerRewards(provider, poolToken, reserveToken);
                totalRewards = totalRewards.add(providerRewards.totalClaimedRewards);
            }
        }
        return totalRewards;
    }
    /**
     * @dev claims pending rewards from all participating pools
     */
    function claimRewards() external override returns (uint256) {
        return _claimPendingRewards(msg.sender, _liquidityProtectionStats());
    }
    /**
     * @dev stakes specific pending rewards from all participating pools
     */
    function stakeRewards(uint256 maxAmount, IDSToken poolToken) external override returns (uint256, uint256) {
        return _stakeRewards(msg.sender, maxAmount, poolToken, _liquidityProtectionStats());
    }
    /**
     * @dev store pending rewards for a list of providers in a specific pool for future claims
     *
     * Requirements:
     *
     * - the caller must have the ROLE_UPDATER role
     */
    function storePoolRewards(address[] calldata providers, IDSToken poolToken) external override onlyUpdater {
        ILiquidityProtectionStats lpStats = _liquidityProtectionStats();
        PoolProgram memory program = _poolProgram(poolToken);
        for (uint256 i = 0; i < providers.length; ++i) {
            for (uint256 j = 0; j < program.reserveTokens.length; ++j) {
                _storeRewards(providers[i], poolToken, program.reserveTokens[j], program, lpStats, false);
            }
        }
    }
    /**
     * @dev returns specific provider's pending rewards for all participating pools
     */
    function _pendingRewards(address provider, ILiquidityProtectionStats lpStats) private view returns (uint256) {
        return _pendingRewards(provider, lpStats.providerPools(provider), lpStats);
    }
    /**
     * @dev returns specific provider's pending rewards for a specific list of participating pools
     */
    function _pendingRewards(
        address provider,
        IDSToken[] memory poolTokens,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256) {
        uint256 reward = 0;
        uint256 length = poolTokens.length;
        for (uint256 i = 0; i < length; ++i) {
            uint256 poolReward = _pendingRewards(provider, poolTokens[i], lpStats);
            reward = reward.add(poolReward);
        }
        return reward;
    }
    /**
     * @dev returns specific provider's pending rewards for a specific pool
     */
    function _pendingRewards(
        address provider,
        IDSToken poolToken,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256) {
        uint256 reward = 0;
        PoolProgram memory program = _poolProgram(poolToken);
        for (uint256 i = 0; i < program.reserveTokens.length; ++i) {
            uint256 reserveReward = _pendingRewards(provider, poolToken, program.reserveTokens[i], program, lpStats);
            reward = reward.add(reserveReward);
        }
        return reward;
    }
    /**
     * @dev returns specific provider's pending rewards for a specific pool/reserve
     */
    function _pendingRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256) {
        if (!_isProgramValid(reserveToken, program)) {
            return 0;
        }
        // calculate the new reward rate per-token
        PoolRewards memory poolRewardsData = _poolRewards(poolToken, reserveToken);
        // rewardPerToken must be calculated with the previous value of lastUpdateTime
        poolRewardsData.rewardPerToken = _rewardPerToken(poolToken, reserveToken, poolRewardsData, program, lpStats);
        poolRewardsData.lastUpdateTime = Math.min(_time(), program.endTime);
        // update provider's rewards with the newly claimable base rewards and the new reward rate per-token
        ProviderRewards memory providerRewards = _providerRewards(provider, poolToken, reserveToken);
        // if this is the first liquidity provision - set the effective staking time to the current time
        if (
            providerRewards.effectiveStakingTime == 0 &&
            lpStats.totalProviderAmount(provider, poolToken, reserveToken) == 0
        ) {
            providerRewards.effectiveStakingTime = _time();
        }
        // pendingBaseRewards must be calculated with the previous value of providerRewards.rewardPerToken
        providerRewards.pendingBaseRewards = providerRewards.pendingBaseRewards.add(
            _baseRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats)
        );
        providerRewards.rewardPerToken = poolRewardsData.rewardPerToken;
        // get full rewards and the respective rewards multiplier
        (uint256 fullReward, ) =
            _fullRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats);
        return fullReward;
    }
    /**
     * @dev claims specific provider's pending rewards for a specific list of participating pools
     */
    function _claimPendingRewards(
        address provider,
        IDSToken[] memory poolTokens,
        uint256 maxAmount,
        ILiquidityProtectionStats lpStats,
        bool resetStakingTime
    ) private returns (uint256) {
        uint256 reward = 0;
        uint256 length = poolTokens.length;
        for (uint256 i = 0; i < length && maxAmount > 0; ++i) {
            uint256 poolReward = _claimPendingRewards(provider, poolTokens[i], maxAmount, lpStats, resetStakingTime);
            reward = reward.add(poolReward);
            if (maxAmount != MAX_UINT256) {
                maxAmount = maxAmount.sub(poolReward);
            }
        }
        return reward;
    }
    /**
     * @dev claims specific provider's pending rewards for a specific pool
     */
    function _claimPendingRewards(
        address provider,
        IDSToken poolToken,
        uint256 maxAmount,
        ILiquidityProtectionStats lpStats,
        bool resetStakingTime
    ) private returns (uint256) {
        uint256 reward = 0;
        PoolProgram memory program = _poolProgram(poolToken);
        for (uint256 i = 0; i < program.reserveTokens.length && maxAmount > 0; ++i) {
            uint256 reserveReward =
                _claimPendingRewards(
                    provider,
                    poolToken,
                    program.reserveTokens[i],
                    program,
                    maxAmount,
                    lpStats,
                    resetStakingTime
                );
            reward = reward.add(reserveReward);
            if (maxAmount != MAX_UINT256) {
                maxAmount = maxAmount.sub(reserveReward);
            }
        }
        return reward;
    }
    /**
     * @dev claims specific provider's pending rewards for a specific pool/reserve
     */
    function _claimPendingRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolProgram memory program,
        uint256 maxAmount,
        ILiquidityProtectionStats lpStats,
        bool resetStakingTime
    ) private returns (uint256) {
        // update all provider's pending rewards, in order to apply retroactive reward multipliers
        (PoolRewards memory poolRewardsData, ProviderRewards memory providerRewards) =
            _updateRewards(provider, poolToken, reserveToken, program, lpStats);
        // get full rewards and the respective rewards multiplier
        (uint256 fullReward, uint32 multiplier) =
            _fullRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats);
        // mark any debt as repaid.
        providerRewards.baseRewardsDebt = 0;
        providerRewards.baseRewardsDebtMultiplier = 0;
        if (maxAmount != MAX_UINT256 && fullReward > maxAmount) {
            // get the amount of the actual base rewards that were claimed
            providerRewards.baseRewardsDebt = _removeMultiplier(fullReward.sub(maxAmount), multiplier);
            // store the current multiplier for future retroactive rewards correction
            providerRewards.baseRewardsDebtMultiplier = multiplier;
            // grant only maxAmount rewards
            fullReward = maxAmount;
        }
        // update pool rewards data total claimed rewards
        _store.updatePoolRewardsData(
            poolToken,
            reserveToken,
            poolRewardsData.lastUpdateTime,
            poolRewardsData.rewardPerToken,
            poolRewardsData.totalClaimedRewards.add(fullReward)
        );
        // update provider rewards data with the remaining pending rewards and if needed, set the effective
        // staking time to the timestamp of the current block
        _store.updateProviderRewardsData(
            provider,
            poolToken,
            reserveToken,
            providerRewards.rewardPerToken,
            0,
            providerRewards.totalClaimedRewards.add(fullReward),
            resetStakingTime ? _time() : providerRewards.effectiveStakingTime,
            providerRewards.baseRewardsDebt,
            providerRewards.baseRewardsDebtMultiplier
        );
        return fullReward;
    }
    /**
     * @dev claims specific provider's pending rewards from all participating pools
     */
    function _claimPendingRewards(address provider, ILiquidityProtectionStats lpStats) private returns (uint256) {
        return _claimPendingRewards(provider, lpStats.providerPools(provider), MAX_UINT256, lpStats);
    }
    /**
     * @dev claims specific provider's pending rewards for a specific list of participating pools
     */
    function _claimPendingRewards(
        address provider,
        IDSToken[] memory poolTokens,
        uint256 maxAmount,
        ILiquidityProtectionStats lpStats
    ) private returns (uint256) {
        uint256 amount = _claimPendingRewards(provider, poolTokens, maxAmount, lpStats, true);
        if (amount == 0) {
            return amount;
        }
        // make sure to update the last claim time so that it'll be taken into effect when calculating the next rewards
        // multiplier
        _store.updateProviderLastClaimTime(provider);
        // mint the reward tokens directly to the provider
        _networkTokenGovernance.mint(provider, amount);
        emit RewardsClaimed(provider, amount);
        return amount;
    }
    /**
     * @dev stakes specific provider's pending rewards from all participating pools
     */
    function _stakeRewards(
        address provider,
        uint256 maxAmount,
        IDSToken poolToken,
        ILiquidityProtectionStats lpStats
    ) private returns (uint256, uint256) {
        return _stakeRewards(provider, lpStats.providerPools(provider), maxAmount, poolToken, lpStats);
    }
    /**
     * @dev claims and stakes specific provider's pending rewards for a specific list of participating pools
     */
    function _stakeRewards(
        address provider,
        IDSToken[] memory poolTokens,
        uint256 maxAmount,
        IDSToken newPoolToken,
        ILiquidityProtectionStats lpStats
    ) private returns (uint256, uint256) {
        uint256 amount = _claimPendingRewards(provider, poolTokens, maxAmount, lpStats, false);
        if (amount == 0) {
            return (amount, 0);
        }
        // approve the LiquidityProtection contract to pull the rewards
        ILiquidityProtection liquidityProtection = _liquidityProtection();
        address liquidityProtectionAddress = address(liquidityProtection);
        _networkToken.ensureApprove(liquidityProtectionAddress, amount);
        // mint the reward tokens directly to the staking contract, so that the LiquidityProtection could pull the
        // rewards and attribute them to the provider
        _networkTokenGovernance.mint(address(this), amount);
        uint256 newId =
            liquidityProtection.addLiquidityFor(provider, newPoolToken, IReserveToken(address(_networkToken)), amount);
        // please note, that in order to incentivize staking, we won't be updating the time of the last claim, thus
        // preserving the rewards bonus multiplier
        emit RewardsStaked(provider, newPoolToken, amount, newId);
        return (amount, newId);
    }
    /**
     * @dev store specific provider's pending rewards for future claims
     */
    function _storeRewards(
        address provider,
        IDSToken[] memory poolTokens,
        ILiquidityProtectionStats lpStats
    ) private {
        for (uint256 i = 0; i < poolTokens.length; ++i) {
            IDSToken poolToken = poolTokens[i];
            PoolProgram memory program = _poolProgram(poolToken);
            for (uint256 j = 0; j < program.reserveTokens.length; ++j) {
                _storeRewards(provider, poolToken, program.reserveTokens[j], program, lpStats, true);
            }
        }
    }
    /**
     * @dev store specific provider's pending rewards for future claims
     */
    function _storeRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats,
        bool resetStakingTime
    ) private {
        if (!_isProgramValid(reserveToken, program)) {
            return;
        }
        // update all provider's pending rewards, in order to apply retroactive reward multipliers
        (PoolRewards memory poolRewardsData, ProviderRewards memory providerRewards) =
            _updateRewards(provider, poolToken, reserveToken, program, lpStats);
        // get full rewards and the respective rewards multiplier
        (uint256 fullReward, uint32 multiplier) =
            _fullRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats);
        // get the amount of the actual base rewards that were claimed
        providerRewards.baseRewardsDebt = _removeMultiplier(fullReward, multiplier);
        // update store data with the store pending rewards and set the last update time to the timestamp of the
        // current block. if we're resetting the effective staking time, then we'd have to store the rewards multiplier in order to
        // account for it in the future. Otherwise, we must store base rewards without any rewards multiplier
        _store.updateProviderRewardsData(
            provider,
            poolToken,
            reserveToken,
            providerRewards.rewardPerToken,
            0,
            providerRewards.totalClaimedRewards,
            resetStakingTime ? _time() : providerRewards.effectiveStakingTime,
            providerRewards.baseRewardsDebt,
            resetStakingTime ? multiplier : PPM_RESOLUTION
        );
    }
    /**
     * @dev updates pool rewards
     */
    function _updateReserveRewards(
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private returns (PoolRewards memory) {
        // calculate the new reward rate per-token and update it in the store
        PoolRewards memory poolRewardsData = _poolRewards(poolToken, reserveToken);
        bool update = false;
        // rewardPerToken must be calculated with the previous value of lastUpdateTime
        uint256 newRewardPerToken = _rewardPerToken(poolToken, reserveToken, poolRewardsData, program, lpStats);
        if (poolRewardsData.rewardPerToken != newRewardPerToken) {
            poolRewardsData.rewardPerToken = newRewardPerToken;
            update = true;
        }
        uint256 newLastUpdateTime = Math.min(_time(), program.endTime);
        if (poolRewardsData.lastUpdateTime != newLastUpdateTime) {
            poolRewardsData.lastUpdateTime = newLastUpdateTime;
            update = true;
        }
        if (update) {
            _store.updatePoolRewardsData(
                poolToken,
                reserveToken,
                poolRewardsData.lastUpdateTime,
                poolRewardsData.rewardPerToken,
                poolRewardsData.totalClaimedRewards
            );
        }
        return poolRewardsData;
    }
    /**
     * @dev updates provider rewards. this function is called during every liquidity changes
     */
    function _updateProviderRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolRewards memory poolRewardsData,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private returns (ProviderRewards memory) {
        // update provider's rewards with the newly claimable base rewards and the new reward rate per-token
        ProviderRewards memory providerRewards = _providerRewards(provider, poolToken, reserveToken);
        bool update = false;
        // if this is the first liquidity provision - set the effective staking time to the current time
        if (
            providerRewards.effectiveStakingTime == 0 &&
            lpStats.totalProviderAmount(provider, poolToken, reserveToken) == 0
        ) {
            providerRewards.effectiveStakingTime = _time();
            update = true;
        }
        // pendingBaseRewards must be calculated with the previous value of providerRewards.rewardPerToken
        uint256 rewards =
            _baseRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats);
        if (rewards != 0) {
            providerRewards.pendingBaseRewards = providerRewards.pendingBaseRewards.add(rewards);
            update = true;
        }
        if (providerRewards.rewardPerToken != poolRewardsData.rewardPerToken) {
            providerRewards.rewardPerToken = poolRewardsData.rewardPerToken;
            update = true;
        }
        if (update) {
            _store.updateProviderRewardsData(
                provider,
                poolToken,
                reserveToken,
                providerRewards.rewardPerToken,
                providerRewards.pendingBaseRewards,
                providerRewards.totalClaimedRewards,
                providerRewards.effectiveStakingTime,
                providerRewards.baseRewardsDebt,
                providerRewards.baseRewardsDebtMultiplier
            );
        }
        return providerRewards;
    }
    /**
     * @dev updates pool and provider rewards. this function is called during every liquidity changes
     */
    function _updateRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private returns (PoolRewards memory, ProviderRewards memory) {
        PoolRewards memory poolRewardsData = _updateReserveRewards(poolToken, reserveToken, program, lpStats);
        ProviderRewards memory providerRewards =
            _updateProviderRewards(provider, poolToken, reserveToken, poolRewardsData, program, lpStats);
        return (poolRewardsData, providerRewards);
    }
    /**
     * @dev returns the aggregated reward rate per-token
     */
    function _rewardPerToken(
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolRewards memory poolRewardsData,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256) {
        // if there is no longer any liquidity in this reserve, return the historic rate (i.e., rewards won't accrue)
        uint256 totalReserveAmount = lpStats.totalReserveAmount(poolToken, reserveToken);
        if (totalReserveAmount == 0) {
            return poolRewardsData.rewardPerToken;
        }
        // don't grant any rewards before the starting time of the program
        uint256 currentTime = _time();
        if (currentTime < program.startTime) {
            return 0;
        }
        uint256 stakingEndTime = Math.min(currentTime, program.endTime);
        uint256 stakingStartTime = Math.max(program.startTime, poolRewardsData.lastUpdateTime);
        if (stakingStartTime == stakingEndTime) {
            return poolRewardsData.rewardPerToken;
        }
        // since we will be dividing by the total amount of protected tokens in units of wei, we can encounter cases
        // where the total amount in the denominator is higher than the product of the rewards rate and staking duration.
        // in order to avoid this imprecision, we will amplify the reward rate by the units amount
        return
            poolRewardsData.rewardPerToken.add( // the aggregated reward rate
                stakingEndTime
                    .sub(stakingStartTime) // the duration of the staking
                    .mul(program.rewardRate) // multiplied by the rate
                    .mul(REWARD_RATE_FACTOR) // and factored to increase precision
                    .mul(_rewardShare(reserveToken, program)) // and applied the specific token share of the whole reward
                    .div(totalReserveAmount.mul(PPM_RESOLUTION)) // and divided by the total protected tokens amount in the pool
            );
    }
    /**
     * @dev returns the base rewards since the last claim
     */
    function _baseRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolRewards memory poolRewardsData,
        ProviderRewards memory providerRewards,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256) {
        uint256 totalProviderAmount = lpStats.totalProviderAmount(provider, poolToken, reserveToken);
        uint256 newRewardPerToken = _rewardPerToken(poolToken, reserveToken, poolRewardsData, program, lpStats);
        return
            totalProviderAmount // the protected tokens amount held by the provider
                .mul(newRewardPerToken.sub(providerRewards.rewardPerToken)) // multiplied by the difference between the previous and the current rate
                .div(REWARD_RATE_FACTOR); // and factored back
    }
    /**
     * @dev returns the full rewards since the last claim
     */
    function _fullRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        PoolRewards memory poolRewardsData,
        ProviderRewards memory providerRewards,
        PoolProgram memory program,
        ILiquidityProtectionStats lpStats
    ) private view returns (uint256, uint32) {
        // calculate the claimable base rewards (since the last claim)
        uint256 newBaseRewards =
            _baseRewards(provider, poolToken, reserveToken, poolRewardsData, providerRewards, program, lpStats);
        // make sure that we aren't exceeding the reward rate for any reason
        _verifyBaseReward(newBaseRewards, providerRewards.effectiveStakingTime, reserveToken, program);
        // calculate pending rewards and apply the rewards multiplier
        uint32 multiplier = _rewardsMultiplier(provider, providerRewards.effectiveStakingTime, program);
        uint256 fullReward = _applyMultiplier(providerRewards.pendingBaseRewards.add(newBaseRewards), multiplier);
        // add any debt, while applying the best retroactive multiplier
        fullReward = fullReward.add(
            _applyHigherMultiplier(
                providerRewards.baseRewardsDebt,
                multiplier,
                providerRewards.baseRewardsDebtMultiplier
            )
        );
        // make sure that we aren't exceeding the full reward rate for any reason
        _verifyFullReward(fullReward, reserveToken, poolRewardsData, program);
        return (fullReward, multiplier);
    }
    /**
     * @dev returns the specific reserve token's share of all rewards
     */
    function _rewardShare(IReserveToken reserveToken, PoolProgram memory program) private pure returns (uint32) {
        if (reserveToken == program.reserveTokens[0]) {
            return program.rewardShares[0];
        }
        return program.rewardShares[1];
    }
    /**
     * @dev returns the rewards multiplier for the specific provider
     */
    function _rewardsMultiplier(
        address provider,
        uint256 stakingStartTime,
        PoolProgram memory program
    ) private view returns (uint32) {
        uint256 effectiveStakingEndTime = Math.min(_time(), program.endTime);
        uint256 effectiveStakingStartTime =
            Math.max( // take the latest of actual staking start time and the latest multiplier reset
                Math.max(stakingStartTime, program.startTime), // don't count staking before the start of the program
                Math.max(_lastRemoveTimes.checkpoint(provider), _store.providerLastClaimTime(provider)) // get the latest multiplier reset timestamp
            );
        // check that the staking range is valid. for example, it can be invalid when calculating the multiplier when
        // the staking has started before the start of the program, in which case the effective staking start time will
        // be in the future, compared to the effective staking end time (which will be the time of the current block)
        if (effectiveStakingStartTime >= effectiveStakingEndTime) {
            return PPM_RESOLUTION;
        }
        uint256 effectiveStakingDuration = effectiveStakingEndTime.sub(effectiveStakingStartTime);
        // given x representing the staking duration (in seconds), the resulting multiplier (in PPM) is:
        // * for 0 <= x <= 1 weeks: 100% PPM
        // * for 1 <= x <= 2 weeks: 125% PPM
        // * for 2 <= x <= 3 weeks: 150% PPM
        // * for 3 <= x <= 4 weeks: 175% PPM
        // * for x > 4 weeks: 200% PPM
        return PPM_RESOLUTION + MULTIPLIER_INCREMENT * uint32(Math.min(effectiveStakingDuration.div(1 weeks), 4));
    }
    /**
     * @dev returns the pool program for a specific pool
     */
    function _poolProgram(IDSToken poolToken) private view returns (PoolProgram memory) {
        PoolProgram memory program;
        (program.startTime, program.endTime, program.rewardRate, program.reserveTokens, program.rewardShares) = _store
            .poolProgram(poolToken);
        return program;
    }
    /**
     * @dev returns pool rewards for a specific pool and reserve
     */
    function _poolRewards(IDSToken poolToken, IReserveToken reserveToken) private view returns (PoolRewards memory) {
        PoolRewards memory data;
        (data.lastUpdateTime, data.rewardPerToken, data.totalClaimedRewards) = _store.poolRewards(
            poolToken,
            reserveToken
        );
        return data;
    }
    /**
     * @dev returns provider rewards for a specific pool and reserve
     */
    function _providerRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) private view returns (ProviderRewards memory) {
        ProviderRewards memory data;
        (
            data.rewardPerToken,
            data.pendingBaseRewards,
            data.totalClaimedRewards,
            data.effectiveStakingTime,
            data.baseRewardsDebt,
            data.baseRewardsDebtMultiplier
        ) = _store.providerRewards(provider, poolToken, reserveToken);
        return data;
    }
    /**
     * @dev applies the multiplier on the provided amount
     */
    function _applyMultiplier(uint256 amount, uint32 multiplier) private pure returns (uint256) {
        if (multiplier == PPM_RESOLUTION) {
            return amount;
        }
        return amount.mul(multiplier).div(PPM_RESOLUTION);
    }
    /**
     * @dev removes the multiplier on the provided amount
     */
    function _removeMultiplier(uint256 amount, uint32 multiplier) private pure returns (uint256) {
        if (multiplier == PPM_RESOLUTION) {
            return amount;
        }
        return amount.mul(PPM_RESOLUTION).div(multiplier);
    }
    /**
     * @dev applies the best of two rewards multipliers on the provided amount
     */
    function _applyHigherMultiplier(
        uint256 amount,
        uint32 multiplier1,
        uint32 multiplier2
    ) private pure returns (uint256) {
        return _applyMultiplier(amount, multiplier1 > multiplier2 ? multiplier1 : multiplier2);
    }
    /**
     * @dev performs a sanity check on the newly claimable base rewards
     */
    function _verifyBaseReward(
        uint256 baseReward,
        uint256 stakingStartTime,
        IReserveToken reserveToken,
        PoolProgram memory program
    ) private view {
        // don't grant any rewards before the starting time of the program or for stakes after the end of the program
        uint256 currentTime = _time();
        if (currentTime < program.startTime || stakingStartTime >= program.endTime) {
            require(baseReward == 0, "ERR_BASE_REWARD_TOO_HIGH");
            return;
        }
        uint256 effectiveStakingStartTime = Math.max(stakingStartTime, program.startTime);
        uint256 effectiveStakingEndTime = Math.min(currentTime, program.endTime);
        // make sure that we aren't exceeding the base reward rate for any reason
        require(
            baseReward <=
                (program.rewardRate * REWARDS_HALVING_FACTOR)
                    .mul(effectiveStakingEndTime.sub(effectiveStakingStartTime))
                    .mul(_rewardShare(reserveToken, program))
                    .div(PPM_RESOLUTION),
            "ERR_BASE_REWARD_RATE_TOO_HIGH"
        );
    }
    /**
     * @dev performs a sanity check on the newly claimable full rewards
     */
    function _verifyFullReward(
        uint256 fullReward,
        IReserveToken reserveToken,
        PoolRewards memory poolRewardsData,
        PoolProgram memory program
    ) private pure {
        uint256 maxClaimableReward =
            (
                (program.rewardRate * REWARDS_HALVING_FACTOR)
                    .mul(program.endTime.sub(program.startTime))
                    .mul(_rewardShare(reserveToken, program))
                    .mul(MAX_MULTIPLIER)
                    .div(PPM_RESOLUTION)
                    .div(PPM_RESOLUTION)
            )
                .sub(poolRewardsData.totalClaimedRewards);
        // make sure that we aren't exceeding the full reward rate for any reason
        require(fullReward <= maxClaimableReward, "ERR_REWARD_RATE_TOO_HIGH");
    }
    /**
     * @dev returns the liquidity protection stats data contract
     */
    function _liquidityProtectionStats() private view returns (ILiquidityProtectionStats) {
        return _liquidityProtection().stats();
    }
    /**
     * @dev returns the liquidity protection contract
     */
    function _liquidityProtection() private view returns (ILiquidityProtection) {
        return ILiquidityProtection(_addressOf(LIQUIDITY_PROTECTION));
    }
    /**
     * @dev returns if the program is valid
     */
    function _isProgramValid(IReserveToken reserveToken, PoolProgram memory program) private pure returns (bool) {
        return
            address(reserveToken) != address(0) &&
            (program.reserveTokens[0] == reserveToken || program.reserveTokens[1] == reserveToken);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../utils/Context.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }
    mapping (bytes32 => RoleData) private _roles;
    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
        _grantRole(role, account);
    }
    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
        _revokeRole(role, account);
    }
    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");
        _revokeRole(role, account);
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }
    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";
/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }
    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.
        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "./IMintableToken.sol";
/// @title The interface for mintable/burnable token governance.
interface ITokenGovernance {
    // The address of the mintable ERC20 token.
    function token() external view returns (IMintableToken);
    /// @dev Mints new tokens.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external;
    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "./Owned.sol";
import "./Utils.sol";
import "./interfaces/IContractRegistry.sol";
/**
 * @dev This is the base contract for ContractRegistry clients.
 */
contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant CONVERTER_FACTORY = "ConverterFactory";
    bytes32 internal constant CONVERSION_PATH_FINDER = "ConversionPathFinder";
    bytes32 internal constant CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";
    bytes32 internal constant LIQUIDITY_PROTECTION = "LiquidityProtection";
    bytes32 internal constant NETWORK_SETTINGS = "NetworkSettings";
    // address of the current contract registry
    IContractRegistry private _registry;
    // address of the previous contract registry
    IContractRegistry private _prevRegistry;
    // only the owner can update the contract registry
    bool private _onlyOwnerCanUpdateRegistry;
    /**
     * @dev verifies that the caller is mapped to the given contract name
     */
    modifier only(bytes32 contractName) {
        _only(contractName);
        _;
    }
    // error message binary size optimization
    function _only(bytes32 contractName) internal view {
        require(msg.sender == _addressOf(contractName), "ERR_ACCESS_DENIED");
    }
    /**
     * @dev initializes a new ContractRegistryClient instance
     */
    constructor(IContractRegistry initialRegistry) internal validAddress(address(initialRegistry)) {
        _registry = IContractRegistry(initialRegistry);
        _prevRegistry = IContractRegistry(initialRegistry);
    }
    /**
     * @dev updates to the new contract registry
     */
    function updateRegistry() external {
        // verify that this function is permitted
        require(msg.sender == owner() || !_onlyOwnerCanUpdateRegistry, "ERR_ACCESS_DENIED");
        // get the new contract registry
        IContractRegistry newRegistry = IContractRegistry(_addressOf(CONTRACT_REGISTRY));
        // verify that the new contract registry is different and not zero
        require(newRegistry != _registry && address(newRegistry) != address(0), "ERR_INVALID_REGISTRY");
        // verify that the new contract registry is pointing to a non-zero contract registry
        require(newRegistry.addressOf(CONTRACT_REGISTRY) != address(0), "ERR_INVALID_REGISTRY");
        // save a backup of the current contract registry before replacing it
        _prevRegistry = _registry;
        // replace the current contract registry with the new contract registry
        _registry = newRegistry;
    }
    /**
     * @dev restores the previous contract registry
     */
    function restoreRegistry() external ownerOnly {
        // restore the previous contract registry
        _registry = _prevRegistry;
    }
    /**
     * @dev restricts the permission to update the contract registry
     */
    function restrictRegistryUpdate(bool restrictOwnerOnly) public ownerOnly {
        // change the permission to update the contract registry
        _onlyOwnerCanUpdateRegistry = restrictOwnerOnly;
    }
    /**
     * @dev returns the address of the current contract registry
     */
    function registry() public view returns (IContractRegistry) {
        return _registry;
    }
    /**
     * @dev returns the address of the previous contract registry
     */
    function prevRegistry() external view returns (IContractRegistry) {
        return _prevRegistry;
    }
    /**
     * @dev returns whether only the owner can update the contract registry
     */
    function onlyOwnerCanUpdateRegistry() external view returns (bool) {
        return _onlyOwnerCanUpdateRegistry;
    }
    /**
     * @dev returns the address associated with the given contract name
     */
    function _addressOf(bytes32 contractName) internal view returns (address) {
        return _registry.addressOf(contractName);
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    uint32 internal constant PPM_RESOLUTION = 1000000;
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 value) {
        _greaterThanZero(value);
        _;
    }
    // error message binary size optimization
    function _greaterThanZero(uint256 value) internal pure {
        require(value > 0, "ERR_ZERO_VALUE");
    }
    // validates an address - currently only checks that it isn't null
    modifier validAddress(address addr) {
        _validAddress(addr);
        _;
    }
    // error message binary size optimization
    function _validAddress(address addr) internal pure {
        require(addr != address(0), "ERR_INVALID_ADDRESS");
    }
    // ensures that the portion is valid
    modifier validPortion(uint32 _portion) {
        _validPortion(_portion);
        _;
    }
    // error message binary size optimization
    function _validPortion(uint32 _portion) internal pure {
        require(_portion > 0 && _portion <= PPM_RESOLUTION, "ERR_INVALID_PORTION");
    }
    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address addr) {
        _validExternalAddress(addr);
        _;
    }
    // error message binary size optimization
    function _validExternalAddress(address addr) internal view {
        require(addr != address(0) && addr != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }
    // ensures that the fee is valid
    modifier validFee(uint32 fee) {
        _validFee(fee);
        _;
    }
    // error message binary size optimization
    function _validFee(uint32 fee) internal pure {
        require(fee <= PPM_RESOLUTION, "ERR_INVALID_FEE");
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/*
    Time implementing contract
*/
contract Time {
    /**
     * @dev returns the current time
     */
    function _time() internal view virtual returns (uint256) {
        return block.timestamp;
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev Checkpoint store contract interface
 */
interface ICheckpointStore {
    function addCheckpoint(address target) external;
    function addPastCheckpoint(address target, uint256 timestamp) external;
    function addPastCheckpoints(address[] calldata targets, uint256[] calldata timestamps) external;
    function checkpoint(address target) external view returns (uint256);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "@openzeppelin/contracts/math/SafeMath.sol";
import "./interfaces/IReserveToken.sol";
import "./SafeERC20Ex.sol";
/**
 * @dev This library implements ERC20 and SafeERC20 utilities for reserve tokens, which can be either ERC20 tokens or ETH
 */
library ReserveToken {
    using SafeERC20 for IERC20;
    using SafeERC20Ex for IERC20;
    // the address that represents an ETH reserve
    IReserveToken public constant NATIVE_TOKEN_ADDRESS = IReserveToken(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);
    /**
     * @dev returns whether the provided token represents an ERC20 or ETH reserve
     */
    function isNativeToken(IReserveToken reserveToken) internal pure returns (bool) {
        return reserveToken == NATIVE_TOKEN_ADDRESS;
    }
    /**
     * @dev returns the balance of the reserve token
     */
    function balanceOf(IReserveToken reserveToken, address account) internal view returns (uint256) {
        if (isNativeToken(reserveToken)) {
            return account.balance;
        }
        return toIERC20(reserveToken).balanceOf(account);
    }
    /**
     * @dev transfers a specific amount of the reserve token
     */
    function safeTransfer(
        IReserveToken reserveToken,
        address to,
        uint256 amount
    ) internal {
        if (amount == 0) {
            return;
        }
        if (isNativeToken(reserveToken)) {
            payable(to).transfer(amount);
        } else {
            toIERC20(reserveToken).safeTransfer(to, amount);
        }
    }
    /**
     * @dev transfers a specific amount of the reserve token from a specific holder using the allowance mechanism
     *
     * note that the function ignores a reserve token which represents an ETH reserve
     */
    function safeTransferFrom(
        IReserveToken reserveToken,
        address from,
        address to,
        uint256 amount
    ) internal {
        if (amount == 0 || isNativeToken(reserveToken)) {
            return;
        }
        toIERC20(reserveToken).safeTransferFrom(from, to, amount);
    }
    /**
     * @dev ensures that the spender has sufficient allowance
     *
     * note that this function ignores a reserve token which represents an ETH reserve
     */
    function ensureApprove(
        IReserveToken reserveToken,
        address spender,
        uint256 amount
    ) internal {
        if (isNativeToken(reserveToken)) {
            return;
        }
        toIERC20(reserveToken).ensureApprove(spender, amount);
    }
    /**
     * @dev utility function that converts an IReserveToken to an IERC20
     */
    function toIERC20(IReserveToken reserveToken) private pure returns (IERC20) {
        return IERC20(address(reserveToken));
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "./ILiquidityProtectionStore.sol";
import "./ILiquidityProtectionStats.sol";
import "./ILiquidityProtectionSettings.sol";
import "./ILiquidityProtectionSystemStore.sol";
import "./ITransferPositionCallback.sol";
import "../../utility/interfaces/ITokenHolder.sol";
import "../../token/interfaces/IReserveToken.sol";
import "../../converter/interfaces/IConverterAnchor.sol";
/**
 * @dev Liquidity Protection interface
 */
interface ILiquidityProtection {
    function store() external view returns (ILiquidityProtectionStore);
    function stats() external view returns (ILiquidityProtectionStats);
    function settings() external view returns (ILiquidityProtectionSettings);
    function systemStore() external view returns (ILiquidityProtectionSystemStore);
    function wallet() external view returns (ITokenHolder);
    function addLiquidityFor(
        address owner,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    ) external payable returns (uint256);
    function addLiquidity(
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 amount
    ) external payable returns (uint256);
    function removeLiquidity(uint256 id, uint32 portion) external;
    function transferPosition(uint256 id, address newProvider) external returns (uint256);
    function transferPositionAndNotify(
        uint256 id,
        address newProvider,
        ITransferPositionCallback callback,
        bytes calldata data
    ) external returns (uint256);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "../../liquidity-protection/interfaces/ILiquidityProvisionEventsSubscriber.sol";
import "./IStakingRewardsStore.sol";
interface IStakingRewards is ILiquidityProvisionEventsSubscriber {
    /**
     * @dev triggered when pending rewards are being claimed
     */
    event RewardsClaimed(address indexed provider, uint256 amount);
    /**
     * @dev triggered when pending rewards are being staked in a pool
     */
    event RewardsStaked(address indexed provider, IDSToken indexed poolToken, uint256 amount, uint256 indexed newId);
    function store() external view returns (IStakingRewardsStore);
    function pendingRewards(address provider) external view returns (uint256);
    function pendingPoolRewards(address provider, IDSToken poolToken) external view returns (uint256);
    function pendingReserveRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view returns (uint256);
    function rewardsMultiplier(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view returns (uint32);
    function totalClaimedRewards(address provider) external view returns (uint256);
    function claimRewards() external returns (uint256);
    function stakeRewards(uint256 maxAmount, IDSToken poolToken) external returns (uint256, uint256);
    function storePoolRewards(address[] calldata providers, IDSToken poolToken) external;
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // Bytes32Set
    struct Bytes32Set {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <0.8.0;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./IClaimable.sol";
/// @title Mintable Token interface
interface IMintableToken is IERC20, IClaimable {
    function issue(address to, uint256 amount) external;
    function destroy(address from, uint256 amount) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
/// @title Claimable contract interface
interface IClaimable {
    function owner() external view returns (address);
    function transferOwnership(address newOwner) external;
    function acceptOwnership() external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "./interfaces/IOwned.sol";
/**
 * @dev This contract provides support and utilities for contract ownership.
 */
contract Owned is IOwned {
    address private _owner;
    address private _newOwner;
    /**
     * @dev triggered when the owner is updated
     */
    event OwnerUpdate(address indexed prevOwner, address indexed newOwner);
    /**
     * @dev initializes a new Owned instance
     */
    constructor() public {
        _owner = msg.sender;
    }
    // allows execution by the owner only
    modifier ownerOnly {
        _ownerOnly();
        _;
    }
    // error message binary size optimization
    function _ownerOnly() private view {
        require(msg.sender == _owner, "ERR_ACCESS_DENIED");
    }
    /**
     * @dev allows transferring the contract ownership
     *
     * Requirements:
     *
     * - the caller must be the owner of the contract
     *
     * note the new owner still needs to accept the transfer
     */
    function transferOwnership(address newOwner) public override ownerOnly {
        require(newOwner != _owner, "ERR_SAME_OWNER");
        _newOwner = newOwner;
    }
    /**
     * @dev used by a new owner to accept an ownership transfer
     */
    function acceptOwnership() public override {
        require(msg.sender == _newOwner, "ERR_ACCESS_DENIED");
        emit OwnerUpdate(_owner, _newOwner);
        _owner = _newOwner;
        _newOwner = address(0);
    }
    /**
     * @dev returns the address of the current owner
     */
    function owner() public view override returns (address) {
        return _owner;
    }
    /**
     * @dev returns the address of the new owner candidate
     */
    function newOwner() external view returns (address) {
        return _newOwner;
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev Contract Registry interface
 */
interface IContractRegistry {
    function addressOf(bytes32 contractName) external view returns (address);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev Owned interface
 */
interface IOwned {
    function owner() external view returns (address);
    function transferOwnership(address newOwner) external;
    function acceptOwnership() external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev This contract is used to represent reserve tokens, which are tokens that can either be regular ERC20 tokens or
 * native ETH (represented by the NATIVE_TOKEN_ADDRESS address)
 *
 * Please note that this interface is intentionally doesn't inherit from IERC20, so that it'd be possible to effectively
 * override its balanceOf() function in the ReserveToken library
 */
interface IReserveToken {
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
/**
 * @dev Extends the SafeERC20 library with additional operations
 */
library SafeERC20Ex {
    using SafeERC20 for IERC20;
    /**
     * @dev ensures that the spender has sufficient allowance
     */
    function ensureApprove(
        IERC20 token,
        address spender,
        uint256 amount
    ) internal {
        if (amount == 0) {
            return;
        }
        uint256 allowance = token.allowance(address(this), spender);
        if (allowance >= amount) {
            return;
        }
        if (allowance > 0) {
            token.safeApprove(spender, 0);
        }
        token.safeApprove(spender, amount);
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../token/interfaces/IDSToken.sol";
import "../../token/interfaces/IReserveToken.sol";
import "../../utility/interfaces/IOwned.sol";
/**
 * @dev Liquidity Protection Store interface
 */
interface ILiquidityProtectionStore is IOwned {
    function withdrawTokens(
        IReserveToken token,
        address recipient,
        uint256 amount
    ) external;
    function protectedLiquidity(uint256 id)
        external
        view
        returns (
            address,
            IDSToken,
            IReserveToken,
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        );
    function addProtectedLiquidity(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount,
        uint256 reserveRateN,
        uint256 reserveRateD,
        uint256 timestamp
    ) external returns (uint256);
    function updateProtectedLiquidityAmounts(
        uint256 id,
        uint256 poolNewAmount,
        uint256 reserveNewAmount
    ) external;
    function removeProtectedLiquidity(uint256 id) external;
    function lockedBalance(address provider, uint256 index) external view returns (uint256, uint256);
    function lockedBalanceRange(
        address provider,
        uint256 startIndex,
        uint256 endIndex
    ) external view returns (uint256[] memory, uint256[] memory);
    function addLockedBalance(
        address provider,
        uint256 reserveAmount,
        uint256 expirationTime
    ) external returns (uint256);
    function removeLockedBalance(address provider, uint256 index) external;
    function systemBalance(IReserveToken poolToken) external view returns (uint256);
    function incSystemBalance(IReserveToken poolToken, uint256 poolAmount) external;
    function decSystemBalance(IReserveToken poolToken, uint256 poolAmount) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../token/interfaces/IDSToken.sol";
import "../../token/interfaces/IReserveToken.sol";
/**
 * @dev Liquidity Protection Stats interface
 */
interface ILiquidityProtectionStats {
    function increaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
    function decreaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
    function addProviderPool(address provider, IDSToken poolToken) external returns (bool);
    function removeProviderPool(address provider, IDSToken poolToken) external returns (bool);
    function totalPoolAmount(IDSToken poolToken) external view returns (uint256);
    function totalReserveAmount(IDSToken poolToken, IReserveToken reserveToken) external view returns (uint256);
    function totalProviderAmount(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    ) external view returns (uint256);
    function providerPools(address provider) external view returns (IDSToken[] memory);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../token/interfaces/IReserveToken.sol";
import "./ILiquidityProvisionEventsSubscriber.sol";
/**
 * @dev Liquidity Protection Settings interface
 */
interface ILiquidityProtectionSettings {
    function isPoolWhitelisted(IConverterAnchor poolAnchor) external view returns (bool);
    function poolWhitelist() external view returns (address[] memory);
    function subscribers() external view returns (address[] memory);
    function isPoolSupported(IConverterAnchor poolAnchor) external view returns (bool);
    function minNetworkTokenLiquidityForMinting() external view returns (uint256);
    function defaultNetworkTokenMintingLimit() external view returns (uint256);
    function networkTokenMintingLimits(IConverterAnchor poolAnchor) external view returns (uint256);
    function addLiquidityDisabled(IConverterAnchor poolAnchor, IReserveToken reserveToken) external view returns (bool);
    function minProtectionDelay() external view returns (uint256);
    function maxProtectionDelay() external view returns (uint256);
    function minNetworkCompensation() external view returns (uint256);
    function lockDuration() external view returns (uint256);
    function averageRateMaxDeviation() external view returns (uint32);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "../../converter/interfaces/IConverterAnchor.sol";
/**
 * @dev Liquidity Protection System Store interface
 */
interface ILiquidityProtectionSystemStore {
    function systemBalance(IERC20 poolToken) external view returns (uint256);
    function incSystemBalance(IERC20 poolToken, uint256 poolAmount) external;
    function decSystemBalance(IERC20 poolToken, uint256 poolAmount) external;
    function networkTokensMinted(IConverterAnchor poolAnchor) external view returns (uint256);
    function incNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;
    function decNetworkTokensMinted(IConverterAnchor poolAnchor, uint256 amount) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev Transfer position event callback interface
 */
interface ITransferPositionCallback {
    function onTransferPosition(
        uint256 newId,
        address provider,
        bytes calldata data
    ) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../token/interfaces/IReserveToken.sol";
import "./IOwned.sol";
/**
 * @dev Token Holder interface
 */
interface ITokenHolder is IOwned {
    receive() external payable;
    function withdrawTokens(
        IReserveToken reserveToken,
        address payable to,
        uint256 amount
    ) external;
    function withdrawTokensMultiple(
        IReserveToken[] calldata reserveTokens,
        address payable to,
        uint256[] calldata amounts
    ) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../utility/interfaces/IOwned.sol";
/**
 * @dev Converter Anchor interface
 */
interface IConverterAnchor is IOwned {
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../utility/interfaces/IOwned.sol";
/**
 * @dev DSToken interface
 */
interface IDSToken is IConverterAnchor, IERC20 {
    function issue(address recipient, uint256 amount) external;
    function destroy(address recipient, uint256 amount) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../token/interfaces/IReserveToken.sol";
/**
 * @dev Liquidity provision events subscriber interface
 */
interface ILiquidityProvisionEventsSubscriber {
    function onAddingLiquidity(
        address provider,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
    function onRemovingLiquidity(
        uint256 id,
        address provider,
        IConverterAnchor poolAnchor,
        IReserveToken reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "../../token/interfaces/IReserveToken.sol";
import "../../token/interfaces/IDSToken.sol";
struct PoolProgram {
    uint256 startTime;
    uint256 endTime;
    uint256 rewardRate;
    IReserveToken[2] reserveTokens;
    uint32[2] rewardShares;
}
struct PoolRewards {
    uint256 lastUpdateTime;
    uint256 rewardPerToken;
    uint256 totalClaimedRewards;
}
struct ProviderRewards {
    uint256 rewardPerToken;
    uint256 pendingBaseRewards;
    uint256 totalClaimedRewards;
    uint256 effectiveStakingTime;
    uint256 baseRewardsDebt;
    uint32 baseRewardsDebtMultiplier;
}
interface IStakingRewardsStore {
    function isPoolParticipating(IDSToken poolToken) external view returns (bool);
    function isReserveParticipating(IDSToken poolToken, IReserveToken reserveToken) external view returns (bool);
    function addPoolProgram(
        IDSToken poolToken,
        IReserveToken[2] calldata reserveTokens,
        uint32[2] calldata rewardShares,
        uint256 endTime,
        uint256 rewardRate
    ) external;
    function removePoolProgram(IDSToken poolToken) external;
    function setPoolProgramEndTime(IDSToken poolToken, uint256 newEndTime) external;
    function poolProgram(IDSToken poolToken)
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            IReserveToken[2] memory,
            uint32[2] memory
        );
    function poolPrograms()
        external
        view
        returns (
            IDSToken[] memory,
            uint256[] memory,
            uint256[] memory,
            uint256[] memory,
            IReserveToken[2][] memory,
            uint32[2][] memory
        );
    function poolRewards(IDSToken poolToken, IReserveToken reserveToken)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );
    function updatePoolRewardsData(
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 lastUpdateTime,
        uint256 rewardPerToken,
        uint256 totalClaimedRewards
    ) external;
    function providerRewards(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken
    )
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint32
        );
    function updateProviderRewardsData(
        address provider,
        IDSToken poolToken,
        IReserveToken reserveToken,
        uint256 rewardPerToken,
        uint256 pendingBaseRewards,
        uint256 totalClaimedRewards,
        uint256 effectiveStakingTime,
        uint256 baseRewardsDebt,
        uint32 baseRewardsDebtMultiplier
    ) external;
    function updateProviderLastClaimTime(address provider) external;
    function providerLastClaimTime(address provider) external view returns (uint256);
}

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@bancor/contracts/solidity/contracts/token/interfaces/IDSToken.sol";
import "@bancor/contracts/solidity/contracts/token/interfaces/IERC20Token.sol";
struct PoolProgram {
    uint256 startTime;
    uint256 endTime;
    uint256 rewardRate;
    IERC20Token[2] reserveTokens;
    uint32[2] rewardShares;
}
struct PoolRewards {
    uint256 lastUpdateTime;
    uint256 rewardPerToken;
    uint256 totalClaimedRewards;
}
struct ProviderRewards {
    uint256 rewardPerToken;
    uint256 pendingBaseRewards;
    uint256 totalClaimedRewards;
    uint256 effectiveStakingTime;
    uint256 baseRewardsDebt;
    uint32 baseRewardsDebtMultiplier;
}
interface IStakingRewardsStore {
    function isPoolParticipating(IDSToken poolToken) external view returns (bool);
    function isReserveParticipating(IDSToken poolToken, IERC20Token reserveToken) external view returns (bool);
    function addPoolProgram(
        IDSToken poolToken,
        IERC20Token[2] calldata reserveTokens,
        uint32[2] calldata rewardShares,
        uint256 endTime,
        uint256 rewardRate
    ) external;
    function removePoolProgram(IDSToken poolToken) external;
    function setPoolProgramEndTime(IDSToken poolToken, uint256 newEndTime) external;
    function poolProgram(IDSToken poolToken)
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            IERC20Token[2] memory,
            uint32[2] memory
        );
    function poolPrograms()
        external
        view
        returns (
            IDSToken[] memory,
            uint256[] memory,
            uint256[] memory,
            uint256[] memory,
            IERC20Token[2][] memory,
            uint32[2][] memory
        );
    function poolRewards(IDSToken poolToken, IERC20Token reserveToken)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );
    function updatePoolRewardsData(
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 lastUpdateTime,
        uint256 rewardPerToken,
        uint256 totalClaimedRewards
    ) external;
    function providerRewards(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken
    )
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint32
        );
    function updateProviderRewardsData(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 rewardPerToken,
        uint256 pendingBaseRewards,
        uint256 totalClaimedRewards,
        uint256 effectiveStakingTime,
        uint256 baseRewardsDebt,
        uint32 baseRewardsDebtMultiplier
    ) external;
    function updateProviderLastClaimTime(address provider) external;
    function providerLastClaimTime(address provider) external view returns (uint256);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/utils/EnumerableSet.sol";
import "@bancor/contracts/solidity/contracts/utility/Utils.sol";
import "@bancor/contracts/solidity/contracts/utility/Time.sol";
import "@bancor/contracts/solidity/contracts/utility/interfaces/IOwned.sol";
import "@bancor/contracts/solidity/contracts/converter/interfaces/IConverter.sol";
import "@bancor/contracts/solidity/contracts/token/interfaces/IDSToken.sol";
import "@bancor/contracts/solidity/contracts/token/interfaces/IERC20Token.sol";
import "./IStakingRewardsStore.sol";
/**
 * @dev This contract stores staking rewards liquidity and pool specific data
 */
contract StakingRewardsStore is IStakingRewardsStore, AccessControl, Utils, Time {
    using SafeMath for uint32;
    using SafeMath for uint256;
    using EnumerableSet for EnumerableSet.AddressSet;
    // the supervisor role is used to globally govern the contract and its governing roles.
    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    // the owner role is used to set the values in the store.
    bytes32 public constant ROLE_OWNER = keccak256("ROLE_OWNER");
    // the manager role is used to manage the programs in the store.
    bytes32 public constant ROLE_MANAGER = keccak256("ROLE_MANAGER");
    // the seeder roles is used to seed the store with past values.
    bytes32 public constant ROLE_SEEDER = keccak256("ROLE_SEEDER");
    uint32 private constant PPM_RESOLUTION = 1000000;
    // the mapping between pool tokens and their respective rewards program information.
    mapping(IDSToken => PoolProgram) private _programs;
    // the set of participating pools.
    EnumerableSet.AddressSet private _pools;
    // the mapping between pools, reserve tokens, and their rewards.
    mapping(IDSToken => mapping(IERC20Token => PoolRewards)) internal _poolRewards;
    // the mapping between pools, reserve tokens, and provider specific rewards.
    mapping(address => mapping(IDSToken => mapping(IERC20Token => ProviderRewards))) internal _providerRewards;
    // the mapping between providers and their respective last claim times.
    mapping(address => uint256) private _providerLastClaimTimes;
    /**
     * @dev triggered when a program is being added
     *
     * @param poolToken the pool token representing the rewards pool
     * @param startTime the starting time of the program
     * @param endTime the ending time of the program
     * @param rewardRate the program's rewards rate per-second
     */
    event PoolProgramAdded(IDSToken indexed poolToken, uint256 startTime, uint256 endTime, uint256 rewardRate);
    /**
     * @dev triggered when a program is being removed
     *
     * @param poolToken the pool token representing the rewards pool
     */
    event PoolProgramRemoved(IDSToken indexed poolToken);
    /**
     * @dev triggered when provider's last claim time is being updated
     *
     * @param provider the owner of the liquidity
     * @param claimTime the time of the last claim
     */
    event ProviderLastClaimTimeUpdated(address indexed provider, uint256 claimTime);
    /**
     * @dev initializes a new StakingRewardsStore contract
     */
    constructor() public {
        // set up administrative roles.
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_OWNER, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_MANAGER, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_SEEDER, ROLE_SUPERVISOR);
        // allow the deployer to initially govern the contract.
        _setupRole(ROLE_SUPERVISOR, _msgSender());
    }
    // allows execution only by an owner
    modifier onlyOwner {
        _hasRole(ROLE_OWNER);
        _;
    }
    // allows execution only by an manager
    modifier onlyManager {
        _hasRole(ROLE_MANAGER);
        _;
    }
    // allows execution only by a seeder
    modifier onlySeeder {
        _hasRole(ROLE_SEEDER);
        _;
    }
    // error message binary size optimization
    function _hasRole(bytes32 role) internal view {
        require(hasRole(role, msg.sender), "ERR_ACCESS_DENIED");
    }
    /**
     * @dev returns whether the specified pool is participating in the rewards program
     *
     * @param poolToken the pool token representing the rewards pool
     *
     * @return whether the specified pool is participating in the rewards program
     */
    function isPoolParticipating(IDSToken poolToken) public view override returns (bool) {
        PoolProgram memory program = _programs[poolToken];
        return program.endTime > time();
    }
    /**
     * @dev returns whether the specified reserve is participating in the rewards program
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token of the added liquidity
     *
     * @return whether the specified reserve is participating in the rewards program
     */
    function isReserveParticipating(IDSToken poolToken, IERC20Token reserveToken) public view override returns (bool) {
        if (!isPoolParticipating(poolToken)) {
            return false;
        }
        PoolProgram memory program = _programs[poolToken];
        return program.reserveTokens[0] == reserveToken || program.reserveTokens[1] == reserveToken;
    }
    /**
     * @dev adds a program
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveTokens the reserve tokens representing the liquidity in the pool
     * @param rewardShares reserve reward shares
     * @param endTime the ending time of the program
     * @param rewardRate the program's rewards rate per-second
     */
    function addPoolProgram(
        IDSToken poolToken,
        IERC20Token[2] calldata reserveTokens,
        uint32[2] calldata rewardShares,
        uint256 endTime,
        uint256 rewardRate
    ) external override onlyManager validAddress(address(poolToken)) {
        uint256 currentTime = time();
        addPoolProgram(poolToken, reserveTokens, rewardShares, currentTime, endTime, rewardRate);
        emit PoolProgramAdded(poolToken, currentTime, endTime, rewardRate);
    }
    /**
     * @dev adds past programs
     *
     * @param poolTokens pool tokens representing the rewards pool
     * @param reserveTokens reserve tokens representing the liquidity in the pool
     * @param rewardShares reserve reward shares
     * @param startTime starting times of the program
     * @param endTimes ending times of the program
     * @param rewardRates program's rewards rate per-second
     */
    function addPastPoolPrograms(
        IDSToken[] calldata poolTokens,
        IERC20Token[2][] calldata reserveTokens,
        uint32[2][] calldata rewardShares,
        uint256[] calldata startTime,
        uint256[] calldata endTimes,
        uint256[] calldata rewardRates
    ) external onlySeeder {
        uint256 length = poolTokens.length;
        require(
            length == reserveTokens.length &&
                length == rewardShares.length &&
                length == startTime.length &&
                length == endTimes.length &&
                length == rewardRates.length,
            "ERR_INVALID_LENGTH"
        );
        for (uint256 i = 0; i < length; ++i) {
            addPastPoolProgram(
                poolTokens[i],
                reserveTokens[i],
                rewardShares[i],
                startTime[i],
                endTimes[i],
                rewardRates[i]
            );
        }
    }
    /**
     * @dev adds a past program
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveTokens the reserve tokens representing the liquidity in the pool
     * @param rewardShares reserve reward shares
     * @param startTime the starting time of the program
     * @param endTime the ending time of the program
     * @param rewardRate the program's rewards rate per-second
     */
    function addPastPoolProgram(
        IDSToken poolToken,
        IERC20Token[2] calldata reserveTokens,
        uint32[2] calldata rewardShares,
        uint256 startTime,
        uint256 endTime,
        uint256 rewardRate
    ) private validAddress(address(poolToken)) {
        require(startTime < time(), "ERR_INVALID_TIME");
        addPoolProgram(poolToken, reserveTokens, rewardShares, startTime, endTime, rewardRate);
    }
    /**
     * @dev adds a program
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveTokens the reserve tokens representing the liquidity in the pool
     * @param rewardShares reserve reward shares
     * @param endTime the ending time of the program
     * @param rewardRate the program's rewards rate per-second
     */
    function addPoolProgram(
        IDSToken poolToken,
        IERC20Token[2] calldata reserveTokens,
        uint32[2] calldata rewardShares,
        uint256 startTime,
        uint256 endTime,
        uint256 rewardRate
    ) private {
        require(startTime < endTime && endTime > time(), "ERR_INVALID_DURATION");
        require(rewardRate > 0, "ERR_ZERO_VALUE");
        require(rewardShares[0].add(rewardShares[1]) == PPM_RESOLUTION, "ERR_INVALID_REWARD_SHARES");
        require(_pools.add(address(poolToken)), "ERR_ALREADY_PARTICIPATING");
        PoolProgram storage program = _programs[poolToken];
        program.startTime = startTime;
        program.endTime = endTime;
        program.rewardRate = rewardRate;
        program.rewardShares = rewardShares;
        // verify that reserve tokens correspond to the pool.
        IConverter converter = IConverter(payable(IConverterAnchor(poolToken).owner()));
        uint256 length = converter.connectorTokenCount();
        require(length == 2, "ERR_POOL_NOT_SUPPORTED");
        require(
            (address(converter.connectorTokens(0)) == address(reserveTokens[0]) &&
                address(converter.connectorTokens(1)) == address(reserveTokens[1])) ||
                (address(converter.connectorTokens(0)) == address(reserveTokens[1]) &&
                    address(converter.connectorTokens(1)) == address(reserveTokens[0])),
            "ERR_INVALID_RESERVE_TOKENS"
        );
        program.reserveTokens = reserveTokens;
    }
    /**
     * @dev removes a program
     *
     * @param poolToken the pool token representing the rewards pool
     */
    function removePoolProgram(IDSToken poolToken) external override onlyManager {
        require(_pools.remove(address(poolToken)), "ERR_POOL_NOT_PARTICIPATING");
        delete _programs[poolToken];
        emit PoolProgramRemoved(poolToken);
    }
    /**
     * @dev updates the ending time of a program
     * note that the new ending time must be in the future
     *
     * @param poolToken the pool token representing the rewards pool
     * @param newEndTime the new ending time of the program
     */
    function setPoolProgramEndTime(IDSToken poolToken, uint256 newEndTime) external override onlyManager {
        require(isPoolParticipating(poolToken), "ERR_POOL_NOT_PARTICIPATING");
        PoolProgram storage program = _programs[poolToken];
        require(newEndTime > time(), "ERR_INVALID_DURATION");
        program.endTime = newEndTime;
    }
    /**
     * @dev returns a program
     *
     * @return the program's starting and ending times
     */
    function poolProgram(IDSToken poolToken)
        external
        view
        override
        returns (
            uint256,
            uint256,
            uint256,
            IERC20Token[2] memory,
            uint32[2] memory
        )
    {
        PoolProgram memory program = _programs[poolToken];
        return (program.startTime, program.endTime, program.rewardRate, program.reserveTokens, program.rewardShares);
    }
    /**
     * @dev returns all programs
     *
     * @return all programs
     */
    function poolPrograms()
        external
        view
        override
        returns (
            IDSToken[] memory,
            uint256[] memory,
            uint256[] memory,
            uint256[] memory,
            IERC20Token[2][] memory,
            uint32[2][] memory
        )
    {
        uint256 length = _pools.length();
        IDSToken[] memory poolTokens = new IDSToken[](length);
        uint256[] memory startTimes = new uint256[](length);
        uint256[] memory endTimes = new uint256[](length);
        uint256[] memory rewardRates = new uint256[](length);
        IERC20Token[2][] memory reserveTokens = new IERC20Token[2][](length);
        uint32[2][] memory rewardShares = new uint32[2][](length);
        for (uint256 i = 0; i < length; ++i) {
            IDSToken poolToken = IDSToken(_pools.at(i));
            PoolProgram memory program = _programs[poolToken];
            poolTokens[i] = poolToken;
            startTimes[i] = program.startTime;
            endTimes[i] = program.endTime;
            rewardRates[i] = program.rewardRate;
            reserveTokens[i] = program.reserveTokens;
            rewardShares[i] = program.rewardShares;
        }
        return (poolTokens, startTimes, endTimes, rewardRates, reserveTokens, rewardShares);
    }
    /**
     * @dev returns the rewards data of a specific reserve in a specific pool
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token in the rewards pool
     *
     * @return rewards data
     */
    function poolRewards(IDSToken poolToken, IERC20Token reserveToken)
        external
        view
        override
        returns (
            uint256,
            uint256,
            uint256
        )
    {
        PoolRewards memory data = _poolRewards[poolToken][reserveToken];
        return (data.lastUpdateTime, data.rewardPerToken, data.totalClaimedRewards);
    }
    /**
     * @dev updates the reward data of a specific reserve in a specific pool
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token in the rewards pool
     * @param lastUpdateTime the last update time
     * @param rewardPerToken the new reward rate per-token
     * @param totalClaimedRewards the total claimed rewards up until now
     */
    function updatePoolRewardsData(
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 lastUpdateTime,
        uint256 rewardPerToken,
        uint256 totalClaimedRewards
    ) external override onlyOwner {
        PoolRewards storage data = _poolRewards[poolToken][reserveToken];
        data.lastUpdateTime = lastUpdateTime;
        data.rewardPerToken = rewardPerToken;
        data.totalClaimedRewards = totalClaimedRewards;
    }
    /**
     * @dev seeds pool rewards data for multiple pools
     *
     * @param poolTokens pool tokens representing the rewards pool
     * @param reserveTokens reserve tokens representing the liquidity in the pool
     * @param lastUpdateTimes last update times (for both the network and reserve tokens)
     * @param rewardsPerToken reward rates per-token (for both the network and reserve tokens)
     * @param totalClaimedRewards total claimed rewards up until now (for both the network and reserve tokens)
     */
    function setPoolsRewardData(
        IDSToken[] calldata poolTokens,
        IERC20Token[] calldata reserveTokens,
        uint256[] calldata lastUpdateTimes,
        uint256[] calldata rewardsPerToken,
        uint256[] calldata totalClaimedRewards
    ) external onlySeeder {
        uint256 length = poolTokens.length;
        require(
            length == reserveTokens.length && length == lastUpdateTimes.length && length == rewardsPerToken.length,
            "ERR_INVALID_LENGTH"
        );
        for (uint256 i = 0; i < length; ++i) {
            IDSToken poolToken = poolTokens[i];
            _validAddress(address(poolToken));
            IERC20Token reserveToken = reserveTokens[i];
            _validAddress(address(reserveToken));
            PoolRewards storage data = _poolRewards[poolToken][reserveToken];
            data.lastUpdateTime = lastUpdateTimes[i];
            data.rewardPerToken = rewardsPerToken[i];
            data.totalClaimedRewards = totalClaimedRewards[i];
        }
    }
    /**
     * @dev returns rewards data of a specific provider
     *
     * @param provider the owner of the liquidity
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token in the rewards pool
     *
     * @return rewards data
     */
    function providerRewards(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken
    )
        external
        view
        override
        returns (
            uint256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint32
        )
    {
        ProviderRewards memory data = _providerRewards[provider][poolToken][reserveToken];
        return (
            data.rewardPerToken,
            data.pendingBaseRewards,
            data.totalClaimedRewards,
            data.effectiveStakingTime,
            data.baseRewardsDebt,
            data.baseRewardsDebtMultiplier
        );
    }
    /**
     * @dev updates provider rewards data
     *
     * @param provider the owner of the liquidity
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token in the rewards pool
     * @param rewardPerToken the new reward rate per-token
     * @param pendingBaseRewards the updated pending base rewards
     * @param totalClaimedRewards the total claimed rewards up until now
     * @param effectiveStakingTime the new effective staking time
     * @param baseRewardsDebt the updated base rewards debt
     * @param baseRewardsDebtMultiplier the updated base rewards debt multiplier
     */
    function updateProviderRewardsData(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 rewardPerToken,
        uint256 pendingBaseRewards,
        uint256 totalClaimedRewards,
        uint256 effectiveStakingTime,
        uint256 baseRewardsDebt,
        uint32 baseRewardsDebtMultiplier
    ) external override onlyOwner {
        ProviderRewards storage data = _providerRewards[provider][poolToken][reserveToken];
        data.rewardPerToken = rewardPerToken;
        data.pendingBaseRewards = pendingBaseRewards;
        data.totalClaimedRewards = totalClaimedRewards;
        data.effectiveStakingTime = effectiveStakingTime;
        data.baseRewardsDebt = baseRewardsDebt;
        data.baseRewardsDebtMultiplier = baseRewardsDebtMultiplier;
    }
    /**
     * @dev seeds specific provider's reward data for multiple providers
     *
     * @param poolToken the pool token representing the rewards pool
     * @param reserveToken the reserve token in the rewards pool
     * @param providers owners of the liquidity
     * @param rewardsPerToken new reward rates per-token
     * @param pendingBaseRewards updated pending base rewards
     * @param totalClaimedRewards total claimed rewards up until now
     * @param effectiveStakingTimes new effective staking times
     * @param baseRewardsDebts updated base rewards debts
     * @param baseRewardsDebtMultipliers updated base rewards debt multipliers
     */
    function setProviderRewardData(
        IDSToken poolToken,
        IERC20Token reserveToken,
        address[] memory providers,
        uint256[] memory rewardsPerToken,
        uint256[] memory pendingBaseRewards,
        uint256[] memory totalClaimedRewards,
        uint256[] memory effectiveStakingTimes,
        uint256[] memory baseRewardsDebts,
        uint32[] memory baseRewardsDebtMultipliers
    ) external onlySeeder validAddress(address(poolToken)) validAddress(address(reserveToken)) {
        uint256 length = providers.length;
        require(
            length == rewardsPerToken.length &&
                length == pendingBaseRewards.length &&
                length == totalClaimedRewards.length &&
                length == effectiveStakingTimes.length &&
                length == baseRewardsDebts.length &&
                length == baseRewardsDebtMultipliers.length,
            "ERR_INVALID_LENGTH"
        );
        for (uint256 i = 0; i < length; ++i) {
            ProviderRewards storage data = _providerRewards[providers[i]][poolToken][reserveToken];
            uint256 baseRewardsDebt = baseRewardsDebts[i];
            uint32 baseRewardsDebtMultiplier = baseRewardsDebtMultipliers[i];
            require(
                baseRewardsDebt == 0 ||
                    (baseRewardsDebtMultiplier >= PPM_RESOLUTION && baseRewardsDebtMultiplier <= 2 * PPM_RESOLUTION),
                "ERR_INVALID_MULTIPLIER"
            );
            data.rewardPerToken = rewardsPerToken[i];
            data.pendingBaseRewards = pendingBaseRewards[i];
            data.totalClaimedRewards = totalClaimedRewards[i];
            data.effectiveStakingTime = effectiveStakingTimes[i];
            data.baseRewardsDebt = baseRewardsDebts[i];
            data.baseRewardsDebtMultiplier = baseRewardsDebtMultiplier;
        }
    }
    /**
     * @dev updates provider's last claim time
     *
     * @param provider the owner of the liquidity
     */
    function updateProviderLastClaimTime(address provider) external override onlyOwner {
        uint256 time = time();
        _providerLastClaimTimes[provider] = time;
        emit ProviderLastClaimTimeUpdated(provider, time);
    }
    /**
     * @dev returns provider's last claim time
     *
     * @param provider the owner of the liquidity
     *
     * @return provider's last claim time
     */
    function providerLastClaimTime(address provider) external view override returns (uint256) {
        return _providerLastClaimTimes[provider];
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "./IConverterAnchor.sol";
import "../../token/interfaces/IERC20Token.sol";
import "../../utility/interfaces/IOwned.sol";
/*
    Converter interface
*/
interface IConverter is IOwned {
    function converterType() external pure returns (uint16);
    function anchor() external view returns (IConverterAnchor);
    function isActive() external view returns (bool);
    function targetAmountAndFee(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount
    ) external view returns (uint256, uint256);
    function convert(
        IERC20Token _sourceToken,
        IERC20Token _targetToken,
        uint256 _amount,
        address _trader,
        address payable _beneficiary
    ) external payable returns (uint256);
    function conversionFee() external view returns (uint32);
    function maxConversionFee() external view returns (uint32);
    function reserveBalance(IERC20Token _reserveToken) external view returns (uint256);
    receive() external payable;
    function transferAnchorOwnership(address _newOwner) external;
    function acceptAnchorOwnership() external;
    function setConversionFee(uint32 _conversionFee) external;
    function withdrawTokens(
        IERC20Token _token,
        address _to,
        uint256 _amount
    ) external;
    function withdrawETH(address payable _to) external;
    function addReserve(IERC20Token _token, uint32 _ratio) external;
    // deprecated, backward compatibility
    function token() external view returns (IConverterAnchor);
    function transferTokenOwnership(address _newOwner) external;
    function acceptTokenOwnership() external;
    function connectors(IERC20Token _address)
        external
        view
        returns (
            uint256,
            uint32,
            bool,
            bool,
            bool
        );
    function getConnectorBalance(IERC20Token _connectorToken) external view returns (uint256);
    function connectorTokens(uint256 _index) external view returns (IERC20Token);
    function connectorTokenCount() external view returns (uint16);
    /**
     * @dev triggered when the converter is activated
     *
     * @param _type        converter type
     * @param _anchor      converter anchor
     * @param _activated   true if the converter was activated, false if it was deactivated
     */
    event Activation(uint16 indexed _type, IConverterAnchor indexed _anchor, bool indexed _activated);
    /**
     * @dev triggered when a conversion between two tokens occurs
     *
     * @param _fromToken       source ERC20 token
     * @param _toToken         target ERC20 token
     * @param _trader          wallet that initiated the trade
     * @param _amount          input amount in units of the source token
     * @param _return          output amount minus conversion fee in units of the target token
     * @param _conversionFee   conversion fee in units of the target token
     */
    event Conversion(
        IERC20Token indexed _fromToken,
        IERC20Token indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );
    /**
     * @dev triggered when the rate between two tokens in the converter changes
     * note that the event might be dispatched for rate updates between any two tokens in the converter
     *
     * @param  _token1 address of the first token
     * @param  _token2 address of the second token
     * @param  _rateN  rate of 1 unit of `_token1` in `_token2` (numerator)
     * @param  _rateD  rate of 1 unit of `_token1` in `_token2` (denominator)
     */
    event TokenRateUpdate(IERC20Token indexed _token1, IERC20Token indexed _token2, uint256 _rateN, uint256 _rateD);
    /**
     * @dev triggered when the conversion fee is updated
     *
     * @param  _prevFee    previous fee percentage, represented in ppm
     * @param  _newFee     new fee percentage, represented in ppm
     */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "../../utility/interfaces/IOwned.sol";
/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
import "./IERC20Token.sol";
import "../../converter/interfaces/IConverterAnchor.sol";
import "../../utility/interfaces/IOwned.sol";
/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20Token {
    function issue(address _to, uint256 _amount) external;
    function destroy(address _from, uint256 _amount) external;
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address _owner) external view returns (uint256);
    function allowance(address _owner, address _spender) external view returns (uint256);
    function transfer(address _to, uint256 _value) external returns (bool);
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool);
    function approve(address _spender, uint256 _value) external returns (bool);
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/*
    Time implementing contract
*/
contract Time {
    /**
     * @dev returns the current time
     */
    function time() internal view virtual returns (uint256) {
        return block.timestamp;
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/**
 * @dev Utilities & Common Modifiers
 */
contract Utils {
    // verifies that a value is greater than zero
    modifier greaterThanZero(uint256 _value) {
        _greaterThanZero(_value);
        _;
    }
    // error message binary size optimization
    function _greaterThanZero(uint256 _value) internal pure {
        require(_value > 0, "ERR_ZERO_VALUE");
    }
    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        _validAddress(_address);
        _;
    }
    // error message binary size optimization
    function _validAddress(address _address) internal pure {
        require(_address != address(0), "ERR_INVALID_ADDRESS");
    }
    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        _notThis(_address);
        _;
    }
    // error message binary size optimization
    function _notThis(address _address) internal view {
        require(_address != address(this), "ERR_ADDRESS_IS_SELF");
    }
    // validates an external address - currently only checks that it isn't null or this
    modifier validExternalAddress(address _address) {
        _validExternalAddress(_address);
        _;
    }
    // error message binary size optimization
    function _validExternalAddress(address _address) internal view {
        require(_address != address(0) && _address != address(this), "ERR_INVALID_EXTERNAL_ADDRESS");
    }
}
// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.6.12;
/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);
    function transferOwnership(address _newOwner) external;
    function acceptOwnership() external;
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../GSN/Context.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }
    mapping (bytes32 => RoleData) private _roles;
    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
        _grantRole(role, account);
    }
    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
        _revokeRole(role, account);
    }
    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");
        _revokeRole(role, account);
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }
    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }
    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <0.8.0;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // Bytes32Set
    struct Bytes32Set {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.6.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/AccessControl.sol



pragma solidity ^0.6.0;




/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;

    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }

    mapping (bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");

        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");

        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }

    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }

    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



pragma solidity ^0.6.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: solidity/contracts/utility/interfaces/IOwned.sol


pragma solidity 0.6.12;

/*
    Owned contract interface
*/
interface IOwned {
    // this function isn't since the compiler emits automatically generated getter functions as external
    function owner() external view returns (address);

    function transferOwnership(address _newOwner) external;

    function acceptOwnership() external;
}

// File: solidity/contracts/converter/interfaces/IConverterAnchor.sol


pragma solidity 0.6.12;


/*
    Converter Anchor interface
*/
interface IConverterAnchor is IOwned {

}

// File: solidity/contracts/token/interfaces/IERC20Token.sol


pragma solidity 0.6.12;

/*
    ERC20 Standard Token interface
*/
interface IERC20Token {
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address _owner) external view returns (uint256);

    function allowance(address _owner, address _spender) external view returns (uint256);

    function transfer(address _to, uint256 _value) external returns (bool);

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool);

    function approve(address _spender, uint256 _value) external returns (bool);
}

// File: solidity/contracts/token/interfaces/IDSToken.sol


pragma solidity 0.6.12;




/*
    DSToken interface
*/
interface IDSToken is IConverterAnchor, IERC20Token {
    function issue(address _to, uint256 _amount) external;

    function destroy(address _from, uint256 _amount) external;
}

// File: solidity/contracts/liquidity-protection/interfaces/ILiquidityProtectionStats.sol


pragma solidity 0.6.12;




/*
    Liquidity Protection Stats interface
*/
interface ILiquidityProtectionStats {
    function increaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function decreaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external;

    function addProviderPool(address provider, IDSToken poolToken) external returns (bool);

    function removeProviderPool(address provider, IDSToken poolToken) external returns (bool);

    function totalPoolAmount(IDSToken poolToken) external view returns (uint256);

    function totalReserveAmount(IDSToken poolToken, IERC20Token reserveToken) external view returns (uint256);

    function totalProviderAmount(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken
    ) external view returns (uint256);

    function providerPools(address provider) external view returns (IDSToken[] memory);
}

// File: solidity/contracts/liquidity-protection/LiquidityProtectionStats.sol


pragma solidity 0.6.12;







/**
 * @dev This contract aggregates the statistics of the liquidity protection mechanism.
 */
contract LiquidityProtectionStats is ILiquidityProtectionStats, AccessControl {
    using EnumerableSet for EnumerableSet.AddressSet;
    using SafeMath for uint256;

    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    bytes32 public constant ROLE_SEEDER = keccak256("ROLE_SEEDER");
    bytes32 public constant ROLE_OWNER = keccak256("ROLE_OWNER");

    mapping(IDSToken => uint256) private _totalPoolAmounts;
    mapping(IDSToken => mapping(IERC20Token => uint256)) private _totalReserveAmounts;
    mapping(address => mapping(IDSToken => mapping(IERC20Token => uint256))) private _totalProviderAmounts;

    mapping(address => EnumerableSet.AddressSet) private _providerPools;

    // allows execution only by an owner
    modifier ownerOnly {
        _hasRole(ROLE_OWNER);
        _;
    }

    // allows execution only by a seeder
    modifier seederOnly {
        _hasRole(ROLE_SEEDER);
        _;
    }

    // error message binary size optimization
    function _hasRole(bytes32 role) internal view {
        require(hasRole(role, msg.sender), "ERR_ACCESS_DENIED");
    }

    constructor() public {
        // set up administrative roles
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_SEEDER, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_OWNER, ROLE_SUPERVISOR);

        // allow the deployer to initially govern the contract
        _setupRole(ROLE_SUPERVISOR, msg.sender);
    }

    /**
     * @dev increases the total amounts
     * can only be executed only by an owner
     *
     * @param provider          liquidity provider address
     * @param poolToken         pool token address
     * @param reserveToken      reserve token address
     * @param poolAmount        pool token amount
     * @param reserveAmount     reserve token amount
     */
    function increaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external override ownerOnly {
        _totalPoolAmounts[poolToken] = _totalPoolAmounts[poolToken].add(poolAmount);
        _totalReserveAmounts[poolToken][reserveToken] = _totalReserveAmounts[poolToken][reserveToken].add(
            reserveAmount
        );
        _totalProviderAmounts[provider][poolToken][reserveToken] = _totalProviderAmounts[provider][poolToken][
            reserveToken
        ]
            .add(reserveAmount);
    }

    /**
     * @dev decreases the total amounts
     * can only be executed only by an owner
     *
     * @param provider          liquidity provider address
     * @param poolToken         pool token address
     * @param reserveToken      reserve token address
     * @param poolAmount        pool token amount
     * @param reserveAmount     reserve token amount
     */
    function decreaseTotalAmounts(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken,
        uint256 poolAmount,
        uint256 reserveAmount
    ) external override ownerOnly {
        _totalPoolAmounts[poolToken] = _totalPoolAmounts[poolToken].sub(poolAmount);
        _totalReserveAmounts[poolToken][reserveToken] = _totalReserveAmounts[poolToken][reserveToken].sub(
            reserveAmount
        );
        _totalProviderAmounts[provider][poolToken][reserveToken] = _totalProviderAmounts[provider][poolToken][
            reserveToken
        ]
            .sub(reserveAmount);
    }

    /**
     * @dev adds a pool to the list of pools of a liquidity provider
     * can only be executed only by an owner
     *
     * @param provider  liquidity provider address
     * @param poolToken pool token address
     */
    function addProviderPool(address provider, IDSToken poolToken) external override ownerOnly returns (bool) {
        return _providerPools[provider].add(address(poolToken));
    }

    /**
     * @dev removes a pool from the list of pools of a liquidity provider
     * can only be executed only by an owner
     *
     * @param provider  liquidity provider address
     * @param poolToken pool token address
     */
    function removeProviderPool(address provider, IDSToken poolToken) external override ownerOnly returns (bool) {
        return _providerPools[provider].remove(address(poolToken));
    }

    /**
     * @dev returns the total amount of protected pool tokens
     *
     * @param poolToken pool token address
     * @return total amount of protected pool tokens
     */
    function totalPoolAmount(IDSToken poolToken) external view override returns (uint256) {
        return _totalPoolAmounts[poolToken];
    }

    /**
     * @dev returns the total amount of protected reserve tokens
     *
     * @param poolToken     pool token address
     * @param reserveToken  reserve token address
     * @return total amount of protected reserve tokens
     */
    function totalReserveAmount(IDSToken poolToken, IERC20Token reserveToken) external view override returns (uint256) {
        return _totalReserveAmounts[poolToken][reserveToken];
    }

    /**
     * @dev returns the total amount of a liquidity provider's protected reserve tokens
     *
     * @param provider      liquidity provider address
     * @param poolToken     pool token address
     * @param reserveToken  reserve token address
     * @return total amount of the liquidity provider's protected reserve tokens
     */
    function totalProviderAmount(
        address provider,
        IDSToken poolToken,
        IERC20Token reserveToken
    ) external view override returns (uint256) {
        return _totalProviderAmounts[provider][poolToken][reserveToken];
    }

    /**
     * @dev returns the list of pools of a liquidity provider
     *
     * @param provider  liquidity provider address
     * @return pool tokens
     */
    function providerPools(address provider) external view override returns (IDSToken[] memory) {
        EnumerableSet.AddressSet storage set = _providerPools[provider];
        uint256 length = set.length();
        IDSToken[] memory arr = new IDSToken[](length);
        for (uint256 i = 0; i < length; i++) {
            arr[i] = IDSToken(set.at(i));
        }
        return arr;
    }

    /**
     * @dev seeds the total amount of protected pool tokens
     * can only be executed only by a seeder
     *
     * @param poolTokens    pool token addresses
     * @param poolAmounts   pool token amounts
     */
    function seedPoolAmounts(IDSToken[] calldata poolTokens, uint256[] calldata poolAmounts) external seederOnly {
        uint256 length = poolTokens.length;
        for (uint256 i = 0; i < length; i++) {
            _totalPoolAmounts[poolTokens[i]] = poolAmounts[i];
        }
    }

    /**
     * @dev seeds the total amount of protected reserve tokens
     * can only be executed only by a seeder
     *
     * @param poolTokens        pool token addresses
     * @param reserveTokens     reserve token addresses
     * @param reserveAmounts    reserve token amounts
     */
    function seedReserveAmounts(
        IDSToken[] calldata poolTokens,
        IERC20Token[] calldata reserveTokens,
        uint256[] calldata reserveAmounts
    ) external seederOnly {
        uint256 length = poolTokens.length;
        for (uint256 i = 0; i < length; i++) {
            _totalReserveAmounts[poolTokens[i]][reserveTokens[i]] = reserveAmounts[i];
        }
    }

    /**
     * @dev seeds the total amount of protected reserve tokens per liquidity provider
     * can only be executed only by a seeder
     *
     * @param providers         liquidity provider addresses
     * @param poolTokens        pool token addresses
     * @param reserveTokens     reserve token addresses
     * @param reserveAmounts    reserve token amounts
     */
    function seedProviderAmounts(
        address[] calldata providers,
        IDSToken[] calldata poolTokens,
        IERC20Token[] calldata reserveTokens,
        uint256[] calldata reserveAmounts
    ) external seederOnly {
        uint256 length = providers.length;
        for (uint256 i = 0; i < length; i++) {
            _totalProviderAmounts[providers[i]][poolTokens[i]][reserveTokens[i]] = reserveAmounts[i];
        }
    }

    /**
     * @dev seeds the list of pools per liquidity provider
     * can only be executed only by a seeder
     *
     * @param providers     liquidity provider addresses
     * @param poolTokens    pool token addresses
     */
    function seedProviderPools(address[] calldata providers, IDSToken[] calldata poolTokens) external seederOnly {
        uint256 length = providers.length;
        for (uint256 i = 0; i < length; i++) {
            _providerPools[providers[i]].add(address(poolTokens[i]));
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
/// @title Claimable contract interface
interface IClaimable {
    function owner() external view returns (address);
    function transferOwnership(address newOwner) external;
    function acceptOwnership() external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./IClaimable.sol";
/// @title Mintable Token interface
interface IMintableToken is IERC20, IClaimable {
    function issue(address to, uint256 amount) external;
    function destroy(address from, uint256 amount) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "./IMintableToken.sol";
/// @title The interface for mintable/burnable token governance.
interface ITokenGovernance {
    // The address of the mintable ERC20 token.
    function token() external view returns (IMintableToken);
    /// @dev Mints new tokens.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external;
    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/access/AccessControl.sol";
import "./ITokenGovernance.sol";
/// @title The Token Governance contract is used to govern a mintable ERC20 token by restricting its launch-time initial
/// administrative privileges.
contract TokenGovernance is ITokenGovernance, AccessControl {
    // The supervisor role is used to globally govern the contract and its governing roles.
    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    // The governor role is used to govern the minter role.
    bytes32 public constant ROLE_GOVERNOR = keccak256("ROLE_GOVERNOR");
    // The minter role is used to control who can request the mintable ERC20 token to mint additional tokens.
    bytes32 public constant ROLE_MINTER = keccak256("ROLE_MINTER");
    // The address of the mintable ERC20 token.
    IMintableToken public immutable override token;
    /// @dev Initializes the contract.
    ///
    /// @param mintableToken The address of the mintable ERC20 token.
    constructor(IMintableToken mintableToken) public {
        require(address(mintableToken) != address(0), "ERR_INVALID_ADDRESS");
        token = mintableToken;
        // Set up administrative roles.
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_GOVERNOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_MINTER, ROLE_GOVERNOR);
        // Allow the deployer to initially govern the contract.
        _setupRole(ROLE_SUPERVISOR, _msgSender());
    }
    /// @dev Accepts the ownership of the token. Only allowed by the SUPERVISOR role.
    function acceptTokenOwnership() external {
        require(hasRole(ROLE_SUPERVISOR, _msgSender()), "ERR_ACCESS_DENIED");
        token.acceptOwnership();
    }
    /// @dev Mints new tokens. Only allowed by the MINTER role.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external override {
        require(hasRole(ROLE_MINTER, _msgSender()), "ERR_ACCESS_DENIED");
        token.issue(to, amount);
    }
    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external override {
        token.destroy(_msgSender(), amount);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../GSN/Context.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }
    mapping (bytes32 => RoleData) private _roles;
    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
        _grantRole(role, account);
    }
    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
        _revokeRole(role, account);
    }
    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");
        _revokeRole(role, account);
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }
    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.2;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }
    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
/// @title Claimable contract interface
interface IClaimable {
    function owner() external view returns (address);
    function transferOwnership(address newOwner) external;
    function acceptOwnership() external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./IClaimable.sol";
/// @title Mintable Token interface
interface IMintableToken is IERC20, IClaimable {
    function issue(address to, uint256 amount) external;
    function destroy(address from, uint256 amount) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "./IMintableToken.sol";
/// @title The interface for mintable/burnable token governance.
interface ITokenGovernance {
    // The address of the mintable ERC20 token.
    function token() external view returns (IMintableToken);
    /// @dev Mints new tokens.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external;
    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external;
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "@openzeppelin/contracts/access/AccessControl.sol";
import "./ITokenGovernance.sol";
/// @title The Token Governance contract is used to govern a mintable ERC20 token by restricting its launch-time initial
/// administrative privileges.
contract TokenGovernance is ITokenGovernance, AccessControl {
    // The supervisor role is used to globally govern the contract and its governing roles.
    bytes32 public constant ROLE_SUPERVISOR = keccak256("ROLE_SUPERVISOR");
    // The governor role is used to govern the minter role.
    bytes32 public constant ROLE_GOVERNOR = keccak256("ROLE_GOVERNOR");
    // The minter role is used to control who can request the mintable ERC20 token to mint additional tokens.
    bytes32 public constant ROLE_MINTER = keccak256("ROLE_MINTER");
    // The address of the mintable ERC20 token.
    IMintableToken public immutable override token;
    /// @dev Initializes the contract.
    ///
    /// @param mintableToken The address of the mintable ERC20 token.
    constructor(IMintableToken mintableToken) public {
        require(address(mintableToken) != address(0), "ERR_INVALID_ADDRESS");
        token = mintableToken;
        // Set up administrative roles.
        _setRoleAdmin(ROLE_SUPERVISOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_GOVERNOR, ROLE_SUPERVISOR);
        _setRoleAdmin(ROLE_MINTER, ROLE_GOVERNOR);
        // Allow the deployer to initially govern the contract.
        _setupRole(ROLE_SUPERVISOR, _msgSender());
    }
    /// @dev Accepts the ownership of the token. Only allowed by the SUPERVISOR role.
    function acceptTokenOwnership() external {
        require(hasRole(ROLE_SUPERVISOR, _msgSender()), "ERR_ACCESS_DENIED");
        token.acceptOwnership();
    }
    /// @dev Mints new tokens. Only allowed by the MINTER role.
    ///
    /// @param to Account to receive the new amount.
    /// @param amount Amount to increase the supply by.
    ///
    function mint(address to, uint256 amount) external override {
        require(hasRole(ROLE_MINTER, _msgSender()), "ERR_ACCESS_DENIED");
        token.issue(to, amount);
    }
    /// @dev Burns tokens from the caller.
    ///
    /// @param amount Amount to decrease the supply by.
    ///
    function burn(uint256 amount) external override {
        token.destroy(_msgSender(), amount);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../GSN/Context.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }
    mapping (bytes32 => RoleData) private _roles;
    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view returns (bytes32) {
        return _roles[role].adminRole;
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
        _grantRole(role, account);
    }
    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
        _revokeRole(role, account);
    }
    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");
        _revokeRole(role, account);
    }
    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }
    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.2;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }
    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}