/**
 *Submitted for verification at Etherscan.io on 2021-03-20
*/

// SPDX-License-Identifier: MIT
pragma solidity 0.7.5;

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;
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function percentageAmount( uint256 total_, uint8 percentage_ ) internal pure returns ( uint256 percentAmount_ ) {
        return div( mul( total_, percentage_ ), 1000 );
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function substractPercentage( uint256 total_, uint8 percentageToSub_ ) internal pure returns ( uint256 result_ ) {
        return sub( total_, div( mul( total_, percentageToSub_ ), 1000 ) );
    }

    function percentageOfTotal( uint256 part_, uint256 total_ ) internal pure returns ( uint256 percent_ ) {
        return div( mul(part_, 100) , total_ );
    }

    /**
     * Taken from Hypersonic https://github.com/M2629/HyperSonic/blob/main/Math.sol
     * @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);
    }

    function quadraticPricing( uint256 payment_, uint256 multiplier_ ) internal pure returns (uint256) {
        return sqrrt( mul( multiplier_, payment_ ) );
    }

  function bondingCurve( uint256 supply_, uint256 multiplier_ ) internal pure returns (uint256) {
      return mul( multiplier_, supply_ );
  }
}

interface IOwnable {

  function owner() external view returns (address);

  function renounceOwnership() external;
  
  function transferOwnership( address newOwner_ ) external;
}

contract Ownable is IOwnable {
    
  address internal _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**
   * @dev Initializes the contract setting the deployer as the initial owner.
   */
  constructor () {
    _owner = msg.sender;
    emit OwnershipTransferred( address(0), _owner );
  }

  /**
   * @dev Returns the address of the current owner.
   */
  function owner() public view override returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require( _owner == msg.sender, "Ownable: caller is not the owner" );
    _;
  }

  /**
   * @dev Leaves the contract without owner. It will not be possible to call
   * `onlyOwner` functions anymore. Can only be called by the current owner.
   *
   * NOTE: Renouncing ownership will leave the contract without an owner,
   * thereby removing any functionality that is only available to the owner.
   */
  function renounceOwnership() public virtual override onlyOwner() {
    emit OwnershipTransferred( _owner, address(0) );
    _owner = address(0);
  }

  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Can only be called by the current owner.
   */
  function transferOwnership( address newOwner_ ) public virtual override onlyOwner() {
    require( newOwner_ != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred( _owner, newOwner_ );
    _owner = newOwner_;
  }
}

interface IStaking {

    function initialize(
        address olyTokenAddress_,
        address sOLY_,
        address dai_
    ) external;

    //function stakeOLY(uint amountToStake_) external {
    function stakeOLYWithPermit (
        uint256 amountToStake_,
        uint256 deadline_,
        uint8 v_,
        bytes32 r_,
        bytes32 s_
    ) external;

    //function unstakeOLY( uint amountToWithdraw_) external {
    function unstakeOLYWithPermit (
        uint256 amountToWithdraw_,
        uint256 deadline_,
        uint8 v_,
        bytes32 r_,
        bytes32 s_
    ) external;

    function stakeOLY( uint amountToStake_ ) external returns ( bool );

    function unstakeOLY( uint amountToWithdraw_ ) external returns ( bool );

    function distributeOLYProfits() external;
}

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);
}

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 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);
    }

    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);
            }
        }
    }

  /**
     * @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 v3.3._
     */
    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 v3.3._
     */
    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);
            }
        }
    }

    function addressToString(address _address) internal pure returns(string memory) {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = "0123456789abcdef";
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for(uint256 i = 0; i < 20; i++) {
            _addr[2+i*2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3+i*2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);

    }
}

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");
        }
    }
}
interface ITreasury {

  function getBondingCalculator() external returns ( address );
  function payDebt( address depositor_ ) external returns ( bool );
  function getTimelockEndBlock() external returns ( uint );
  function getManagedToken() external returns ( address );
  function getDebtAmountDue() external returns ( uint );
  function incurDebt( address principleToken_, uint principieTokenAmountDeposited_ ) external returns ( bool );
}

interface IOHMandsOHM {
    function rebase(uint256 ohmProfit)
        external
        returns (uint256);

    function circulatingSupply() external view returns (uint256);

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

    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

contract OlympusStaking is Ownable {

  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  uint256 public epochLengthInBlocks;

  address public ohm;
  address public sOHM;
  uint256 public ohmToDistributeNextEpoch;

  uint256 nextEpochBlock;

  bool isInitialized;

  modifier notInitialized() {
    require( !isInitialized );
    _;
  }

  function initialize(
        address ohmTokenAddress_,
        address sOHM_,
        uint8 epochLengthInBlocks_
    ) external onlyOwner() notInitialized() {
        ohm = ohmTokenAddress_;
        sOHM = sOHM_;
        epochLengthInBlocks = epochLengthInBlocks_;
        isInitialized = true;
    }

  function setEpochLengthintBlock( uint256 newEpochLengthInBlocks_ ) external onlyOwner() {
    epochLengthInBlocks = newEpochLengthInBlocks_;
  }

  function _distributeOHMProfits() internal {
    if( nextEpochBlock <= block.number ) {
      IOHMandsOHM(sOHM).rebase(ohmToDistributeNextEpoch);
      uint256 _ohmBalance = IOHMandsOHM(ohm).balanceOf(address(this));
      uint256 _sohmSupply = IOHMandsOHM(sOHM).circulatingSupply();
      ohmToDistributeNextEpoch = _ohmBalance.sub(_sohmSupply);
      nextEpochBlock = nextEpochBlock.add( epochLengthInBlocks );
    }
  }

  function _stakeOHM( uint256 amountToStake_ ) internal {
    _distributeOHMProfits();
        
    IERC20(ohm).safeTransferFrom(
        msg.sender,
        address(this),
        amountToStake_
      );

    IERC20(sOHM).safeTransfer(msg.sender, amountToStake_);
  }

  function stakeOHMWithPermit (
        uint256 amountToStake_,
        uint256 deadline_,
        uint8 v_,
        bytes32 r_,
        bytes32 s_
    ) external {

        IOHMandsOHM(ohm).permit(
            msg.sender,
            address(this),
            amountToStake_,
            deadline_,
            v_,
            r_,
            s_
        );

        _stakeOHM( amountToStake_ );
    }

    function stakeOHM( uint amountToStake_ ) external returns ( bool ) {

      _stakeOHM( amountToStake_ );

      return true;

    }

    function _unstakeOHM( uint256 amountToUnstake_ ) internal {

      _distributeOHMProfits();

      IERC20(sOHM).safeTransferFrom(
            msg.sender,
            address(this),
            amountToUnstake_
        );

      IERC20(ohm).safeTransfer(msg.sender, amountToUnstake_);
    }

    function unstakeOHMWithPermit (
        uint256 amountToWithdraw_,
        uint256 deadline_,
        uint8 v_,
        bytes32 r_,
        bytes32 s_
    ) external {
        
        IOHMandsOHM(sOHM).permit(
            msg.sender,
            address(this),
            amountToWithdraw_,
            deadline_,
            v_,
            r_,
            s_
        );

        _unstakeOHM( amountToWithdraw_ );

    }

    function unstakeOHM( uint amountToWithdraw_ ) external returns ( bool ) {

        _unstakeOHM( amountToWithdraw_ );

        return true;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.7.5;


/**
 * @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;
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function percentageAmount( uint256 total_, uint8 percentage_ ) internal pure returns ( uint256 percentAmount_ ) {
        return div( mul( total_, percentage_ ), 1000 );
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function substractPercentage( uint256 total_, uint8 percentageToSub_ ) internal pure returns ( uint256 result_ ) {
        return sub( total_, div( mul( total_, percentageToSub_ ), 1000 ) );
    }

    function percentageOfTotal( uint256 part_, uint256 total_ ) internal pure returns ( uint256 percent_ ) {
        return div( mul(part_, 100) , total_ );
    }

    /**
     * Taken from Hypersonic https://github.com/M2629/HyperSonic/blob/main/Math.sol
     * @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);
    }

    function quadraticPricing( uint256 payment_, uint256 multiplier_ ) internal pure returns (uint256) {
        return sqrrt( mul( multiplier_, payment_ ) );
    }

  function bondingCurve( uint256 supply_, uint256 multiplier_ ) internal pure returns (uint256) {
      return mul( multiplier_, supply_ );
  }
}

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 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);
    }

    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);
            }
        }
    }

  /**
     * @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 v3.3._
     */
    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 v3.3._
     */
    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);
            }
        }
    }

    function addressToString(address _address) internal pure returns(string memory) {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = "0123456789abcdef";
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for(uint256 i = 0; i < 20; i++) {
            _addr[2+i*2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3+i*2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);

    }
}

interface IOwnable {

  function owner() external view returns (address);

  function renounceOwnership() external;
  
  function transferOwnership( address newOwner_ ) external;
}

contract Ownable is IOwnable {
    
  address internal _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**
   * @dev Initializes the contract setting the deployer as the initial owner.
   */
  constructor () {
    _owner = msg.sender;
    emit OwnershipTransferred( address(0), _owner );
  }

  /**
   * @dev Returns the address of the current owner.
   */
  function owner() public view override returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require( _owner == msg.sender, "Ownable: caller is not the owner" );
    _;
  }

  /**
   * @dev Leaves the contract without owner. It will not be possible to call
   * `onlyOwner` functions anymore. Can only be called by the current owner.
   *
   * NOTE: Renouncing ownership will leave the contract without an owner,
   * thereby removing any functionality that is only available to the owner.
   */
  function renounceOwnership() public virtual override onlyOwner() {
    emit OwnershipTransferred( _owner, address(0) );
    _owner = address(0);
  }

  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Can only be called by the current owner.
   */
  function transferOwnership( address newOwner_ ) public virtual override onlyOwner() {
    require( newOwner_ != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred( _owner, newOwner_ );
    _owner = newOwner_;
  }
}

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);
}

abstract contract ERC20
  is 
    IERC20
  {

  using SafeMath for uint256;

  // TODO comment actual hash value.
  bytes32 constant private ERC20TOKEN_ERC1820_INTERFACE_ID = keccak256( "ERC20Token" );
    
  // Present in ERC777
  mapping (address => uint256) internal _balances;

  // Present in ERC777
  mapping (address => mapping (address => uint256)) internal _allowances;

  // Present in ERC777
  uint256 internal _totalSupply;

  // Present in ERC777
  string internal _name;
    
  // Present in ERC777
  string internal _symbol;
    
  // Present in ERC777
  uint8 internal _decimals;

  /**
   * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
   * a default value of 18.
   *
   * To select a different value for {decimals}, use {_setupDecimals}.
   *
   * All three of these values are immutable: they can only be set once during
   * construction.
   */
  constructor (string memory name_, string memory symbol_, uint8 decimals_) {
    _name = name_;
    _symbol = symbol_;
    _decimals = decimals_;
  }

  /**
   * @dev Returns the name of the token.
   */
  // Present in ERC777
  function name() public view returns (string memory) {
    return _name;
  }

  /**
   * @dev Returns the symbol of the token, usually a shorter version of the
   * name.
   */
  // Present in ERC777
  function symbol() public view returns (string memory) {
    return _symbol;
  }

  /**
   * @dev Returns the number of decimals used to get its user representation.
   * For example, if `decimals` equals `2`, a balance of `505` tokens should
   * be displayed to a user as `5,05` (`505 / 10 ** 2`).
   *
   * Tokens usually opt for a value of 18, imitating the relationship between
   * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
   * called.
   *
   * NOTE: This information is only used for _display_ purposes: it in
   * no way affects any of the arithmetic of the contract, including
   * {IERC20-balanceOf} and {IERC20-transfer}.
   */
  // Present in ERC777
  function decimals() public view returns (uint8) {
    return _decimals;
  }

  /**
   * @dev See {IERC20-totalSupply}.
   */
  // Present in ERC777
  function totalSupply() public view override returns (uint256) {
    return _totalSupply;
  }

  /**
   * @dev See {IERC20-balanceOf}.
   */
  // Present in ERC777
  function balanceOf(address account) public view virtual override returns (uint256) {
    return _balances[account];
  }

  /**
   * @dev See {IERC20-transfer}.
   *
   * Requirements:
   *
   * - `recipient` cannot be the zero address.
   * - the caller must have a balance of at least `amount`.
   */
  // Overrideen in ERC777
  // Confirm that this behavior changes 
  function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
    _transfer(msg.sender, recipient, amount);
    return true;
  }

    /**
     * @dev See {IERC20-allowance}.
     */
    // Present in ERC777
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    // Present in ERC777
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    // Present in ERC777
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

  /**
   * @dev Moves tokens `amount` from `sender` to `recipient`.
   *
   * This is internal function is equivalent to {transfer}, and can be used to
   * e.g. implement automatic token fees, slashing mechanisms, etc.
   *
   * Emits a {Transfer} event.
   *
   * Requirements:
   *
   * - `sender` cannot be the zero address.
   * - `recipient` cannot be the zero address.
   * - `sender` must have a balance of at least `amount`.
   */
  function _transfer(address sender, address recipient, uint256 amount) internal virtual {
    require(sender != address(0), "ERC20: transfer from the zero address");
    require(recipient != address(0), "ERC20: transfer to the zero address");

    _beforeTokenTransfer(sender, recipient, amount);

    _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfer(sender, recipient, amount);
  }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    // Present in ERC777
    function _mint(address account_, uint256 ammount_) internal virtual {
        require(account_ != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address( this ), account_, ammount_);
        _totalSupply = _totalSupply.add(ammount_);
        _balances[account_] = _balances[account_].add(ammount_);
        emit Transfer(address( this ), account_, ammount_);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    // Present in ERC777
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    // Present in ERC777
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    // Considering deprication to reduce size of bytecode as changing _decimals to internal acheived the same functionality.
    // function _setupDecimals(uint8 decimals_) internal {
    //     _decimals = decimals_;
    // }

  /**
   * @dev Hook that is called before any transfer of tokens. This includes
   * minting and burning.
   *
   * Calling conditions:
   *
   * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
   * will be to transferred to `to`.
   * - when `from` is zero, `amount` tokens will be minted for `to`.
   * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
   * - `from` and `to` are never both zero.
   *
   * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
   */
  // Present in ERC777
  function _beforeTokenTransfer( address from_, address to_, uint256 amount_ ) internal virtual { }
}

library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // The {SafeMath} overflow check can be skipped here, see the comment at the top
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

interface IERC2612Permit {
    /**
     * @dev Sets `amount` as the allowance of `spender` over `owner`'s tokens,
     * given `owner`'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current ERC2612 nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);
}

abstract contract ERC20Permit is ERC20, IERC2612Permit {
    using Counters for Counters.Counter;

    mapping(address => Counters.Counter) private _nonces;

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    bytes32 public DOMAIN_SEPARATOR;

    constructor() {
        uint256 chainID;
        assembly {
            chainID := chainid()
        }

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(name())),
                keccak256(bytes("1")), // Version
                chainID,
                address(this)
            )
        );
    }

    /**
     * @dev See {IERC2612Permit-permit}.
     *
     */
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual override {
        require(block.timestamp <= deadline, "Permit: expired deadline");

        bytes32 hashStruct =
            keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, amount, _nonces[owner].current(), deadline));

        bytes32 _hash = keccak256(abi.encodePacked(uint16(0x1901), DOMAIN_SEPARATOR, hashStruct));

        address signer = ecrecover(_hash, v, r, s);
        require(signer != address(0) && signer == owner, "ZeroSwapPermit: Invalid signature");

        _nonces[owner].increment();
        _approve(owner, spender, amount);
    }

    /**
     * @dev See {IERC2612Permit-nonces}.
     */
    function nonces(address owner) public view override returns (uint256) {
        return _nonces[owner].current();
    }
}

contract sOlympus is ERC20Permit, Ownable {

    using SafeMath for uint256;

    event LogRebase(uint256 indexed epoch, uint256 totalSupply);
    event LogMonetaryPolicyUpdated(address monetaryPolicy);

    // Used for authentication
    address public monetaryPolicy;

    address public stakingContract;

    modifier onlyMonetaryPolicy() {
        require(msg.sender == monetaryPolicy);
        _;
    }

    modifier validRecipient(address to) {
        require(to != address(0x0));
        require(to != address(this));
        _;
    }

    uint256 private constant MAX_UINT256 = ~uint256(0);
    uint256 private constant INITIAL_FRAGMENTS_SUPPLY = 500000 * 10**9;

    // TOTAL_GONS is a multiple of INITIAL_FRAGMENTS_SUPPLY so that _gonsPerFragment is an integer.
    // Use the highest value that fits in a uint256 for max granularity.
    uint256 private constant TOTAL_GONS = MAX_UINT256 - (MAX_UINT256 % INITIAL_FRAGMENTS_SUPPLY);

    // MAX_SUPPLY = maximum integer < (sqrt(4*TOTAL_GONS + 1) - 1) / 2
    uint256 private constant MAX_SUPPLY = ~uint128(0);  // (2^128) - 1

    uint256 private _gonsPerFragment;
    mapping(address => uint256) private _gonBalances;

    // This is denominated in Fragments, because the gons-fragments conversion might change before
    // it's fully paid.
    mapping (address => mapping (address => uint256)) private _allowedFragments;

    constructor() ERC20("Staked Olympus", "sOHM", 9) {
       _totalSupply = INITIAL_FRAGMENTS_SUPPLY;
       _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        emit Transfer(address(0x0), msg.sender, _totalSupply);
    }

    function setStakingContract( address newStakingContract_ ) external onlyOwner() {
      stakingContract = newStakingContract_;
      _gonBalances[stakingContract] = TOTAL_GONS;
    }

    function setMonetaryPolicy(address monetaryPolicy_) external onlyOwner() {
        monetaryPolicy = monetaryPolicy_;
        emit LogMonetaryPolicyUpdated(monetaryPolicy_);
    }

    function rebase(uint256 olyProfit) public onlyMonetaryPolicy() returns (uint256) {
        uint256 _rebase;

        if (olyProfit == 0) {
            emit LogRebase(block.timestamp, _totalSupply);
            return _totalSupply;
        }

        if(circulatingSupply() > 0 ){
            _rebase = olyProfit.mul(_totalSupply).div(circulatingSupply());
        }

        else {
            _rebase = olyProfit;
        }

        _totalSupply = _totalSupply.add(_rebase);


        if (_totalSupply > MAX_SUPPLY) {
            _totalSupply = MAX_SUPPLY;
        }

        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        emit LogRebase(block.timestamp, _totalSupply);
        return _totalSupply;
    }

    function balanceOf(address who) public view override returns (uint256) {
        return _gonBalances[who].div(_gonsPerFragment);
    }

    function circulatingSupply() public view returns (uint) {
       return _totalSupply.sub(balanceOf(stakingContract));
    }

    function transfer(address to, uint256 value) public override validRecipient(to) returns (bool) {
        require(msg.sender == stakingContract, 'transfer not from staking contract');

        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[msg.sender] = _gonBalances[msg.sender].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(msg.sender, to, value);
        return true;
    }

    function allowance(address owner_, address spender) public view override returns (uint256) {
        return _allowedFragments[owner_][spender];
    }

    function transferFrom(address from, address to, uint256 value) public override validRecipient(to) returns (bool) {
        require(stakingContract == to, 'transfer from not to staking contract');

       _allowedFragments[from][msg.sender] = _allowedFragments[from][msg.sender].sub(value);

        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[from] = _gonBalances[from].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(from, to, value);

        return true;
    }

    function approve(address spender, uint256 value) public override returns (bool) {
         _allowedFragments[msg.sender][spender] = value;
         emit Approval(msg.sender, spender, value);
         return true;
    }

    // What gets called in a permit
    function _approve(address owner, address spender, uint256 value) internal override virtual {
        _allowedFragments[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    function increaseAllowance(address spender, uint256 addedValue) public override returns (bool) {
        _allowedFragments[msg.sender][spender] =
            _allowedFragments[msg.sender][spender].add(addedValue);
        emit Approval(msg.sender, spender, _allowedFragments[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public override returns (bool) {
        uint256 oldValue = _allowedFragments[msg.sender][spender];
        if (subtractedValue >= oldValue) {
            _allowedFragments[msg.sender][spender] = 0;
        } else {
            _allowedFragments[msg.sender][spender] = oldValue.sub(subtractedValue);
        }
        emit Approval(msg.sender, spender, _allowedFragments[msg.sender][spender]);
        return true;
    }
}

// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

/**
 * @dev Intended to update the TWAP for a token based on accepting an update call from that token.
 *  expectation is to have this happen in the _beforeTokenTransfer function of ERC20.
 *  Provides a method for a token to register its price sourve adaptor.
 *  Provides a function for a token to register its TWAP updater. Defaults to token itself.
 *  Provides a function a tokent to set its TWAP epoch.
 *  Implements automatic closeing and opening up a TWAP epoch when epoch ends.
 *  Provides a function to report the TWAP from the last epoch when passed a token address.
 */
interface ITWAPOracle {

  function uniV2CompPairAddressForLastEpochUpdateBlockTimstamp( address ) external returns ( uint32 );

  function priceTokenAddressForPricingTokenAddressForLastEpochUpdateBlockTimstamp( address tokenToPrice_, address tokenForPriceComparison_, uint epochPeriod_ ) external returns ( uint32 );

  function pricedTokenForPricingTokenForEpochPeriodForPrice( address, address, uint ) external returns ( uint );

  function pricedTokenForPricingTokenForEpochPeriodForLastEpochPrice( address, address, uint ) external returns ( uint );

  function updateTWAP( address uniV2CompatPairAddressToUpdate_, uint eopchPeriodToUpdate_ ) external returns ( bool );
}

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];
  }

  function _getValues( Set storage set_ ) private view returns ( bytes32[] storage ) {
    return set_._values;
  }

  // TODO needs insert function that maintains order.
  // TODO needs NatSpec documentation comment.
  /**
   * Inserts new value by moving existing value at provided index to end of array and setting provided value at provided index
   */
  function _insert(Set storage set_, uint256 index_, bytes32 valueToInsert_ ) private returns ( bool ) {
    require(  set_._values.length > index_ );
    require( !_contains( set_, valueToInsert_ ), "Remove value you wish to insert if you wish to reorder array." );
    bytes32 existingValue_ = _at( set_, index_ );
    set_._values[index_] = valueToInsert_;
    return _add( set_, existingValue_);
  } 

  struct Bytes4Set {
    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(Bytes4Set storage set, bytes4 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(Bytes4Set storage set, bytes4 value) internal returns (bool) {
    return _remove(set._inner, value);
  }

  /**
   * @dev Returns true if the value is in the set. O(1).
   */
  function contains(Bytes4Set storage set, bytes4 value) internal view returns (bool) {
    return _contains(set._inner, value);
  }

  /**
   * @dev Returns the number of values on the set. O(1).
   */
  function length(Bytes4Set 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(Bytes4Set storage set, uint256 index) internal view returns ( bytes4 ) {
    return bytes4( _at( set._inner, index ) );
  }

  function getValues( Bytes4Set storage set_ ) internal view returns ( bytes4[] memory ) {
    bytes4[] memory bytes4Array_;
    for( uint256 iteration_ = 0; _length( set_._inner ) > iteration_; iteration_++ ) {
      bytes4Array_[iteration_] = bytes4( _at( set_._inner, iteration_ ) );
    }
    return bytes4Array_;
  }

  function insert( Bytes4Set storage set_, uint256 index_, bytes4 valueToInsert_ ) internal returns ( bool ) {
    return _insert( set_._inner, index_, valueToInsert_ );
  }

    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 on 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);
    }

  function getValues( Bytes32Set storage set_ ) internal view returns ( bytes4[] memory ) {
    bytes4[] memory bytes4Array_;

      for( uint256 iteration_ = 0; _length( set_._inner ) >= iteration_; iteration_++ ){
        bytes4Array_[iteration_] = bytes4( at( set_, iteration_ ) );
      }

      return bytes4Array_;
  }

  function insert( Bytes32Set storage set_, uint256 index_, bytes32 valueToInsert_ ) internal returns ( bool ) {
    return _insert( set_._inner, index_, valueToInsert_ );
  }

  // 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)));
  }

  /**
   * TODO Might require explicit conversion of bytes32[] to address[].
   *  Might require iteration.
   */
  function getValues( AddressSet storage set_ ) internal view returns ( address[] memory ) {

    address[] memory addressArray;

    for( uint256 iteration_ = 0; _length(set_._inner) >= iteration_; iteration_++ ){
      addressArray[iteration_] = at( set_, iteration_ );
    }

    return addressArray;
  }

  function insert(AddressSet storage set_, uint256 index_, address valueToInsert_ ) internal returns ( bool ) {
    return _insert( set_._inner, index_, bytes32(uint256(valueToInsert_)) );
  }


    // 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));
    }

    struct UInt256Set {
        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(UInt256Set 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(UInt256Set 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(UInt256Set 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(UInt256Set 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(UInt256Set storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

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);
}

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;
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function percentageAmount( uint256 total_, uint8 percentage_ ) internal pure returns ( uint256 percentAmount_ ) {
        return div( mul( total_, percentage_ ), 1000 );
    }

    /*
     * Expects percentage to be trailed by 00,
    */
    function substractPercentage( uint256 total_, uint8 percentageToSub_ ) internal pure returns ( uint256 result_ ) {
        return sub( total_, div( mul( total_, percentageToSub_ ), 1000 ) );
    }

    function percentageOfTotal( uint256 part_, uint256 total_ ) internal pure returns ( uint256 percent_ ) {
        return div( mul(part_, 100) , total_ );
    }

    /**
     * Taken from Hypersonic https://github.com/M2629/HyperSonic/blob/main/Math.sol
     * @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);
    }

    function quadraticPricing( uint256 payment_, uint256 multiplier_ ) internal pure returns (uint256) {
        return sqrrt( mul( multiplier_, payment_ ) );
    }

  function bondingCurve( uint256 supply_, uint256 multiplier_ ) internal pure returns (uint256) {
      return mul( multiplier_, supply_ );
  }
}

abstract contract ERC20
  is 
    IERC20
  {

  using SafeMath for uint256;

  // TODO comment actual hash value.
  bytes32 constant private ERC20TOKEN_ERC1820_INTERFACE_ID = keccak256( "ERC20Token" );
    
  // Present in ERC777
  mapping (address => uint256) internal _balances;

  // Present in ERC777
  mapping (address => mapping (address => uint256)) internal _allowances;

  // Present in ERC777
  uint256 internal _totalSupply;

  // Present in ERC777
  string internal _name;
    
  // Present in ERC777
  string internal _symbol;
    
  // Present in ERC777
  uint8 internal _decimals;

  /**
   * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
   * a default value of 18.
   *
   * To select a different value for {decimals}, use {_setupDecimals}.
   *
   * All three of these values are immutable: they can only be set once during
   * construction.
   */
  constructor (string memory name_, string memory symbol_, uint8 decimals_) {
    _name = name_;
    _symbol = symbol_;
    _decimals = decimals_;
  }

  /**
   * @dev Returns the name of the token.
   */
  // Present in ERC777
  function name() public view returns (string memory) {
    return _name;
  }

  /**
   * @dev Returns the symbol of the token, usually a shorter version of the
   * name.
   */
  // Present in ERC777
  function symbol() public view returns (string memory) {
    return _symbol;
  }

  /**
   * @dev Returns the number of decimals used to get its user representation.
   * For example, if `decimals` equals `2`, a balance of `505` tokens should
   * be displayed to a user as `5,05` (`505 / 10 ** 2`).
   *
   * Tokens usually opt for a value of 18, imitating the relationship between
   * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
   * called.
   *
   * NOTE: This information is only used for _display_ purposes: it in
   * no way affects any of the arithmetic of the contract, including
   * {IERC20-balanceOf} and {IERC20-transfer}.
   */
  // Present in ERC777
  function decimals() public view returns (uint8) {
    return _decimals;
  }

  /**
   * @dev See {IERC20-totalSupply}.
   */
  // Present in ERC777
  function totalSupply() public view override returns (uint256) {
    return _totalSupply;
  }

  /**
   * @dev See {IERC20-balanceOf}.
   */
  // Present in ERC777
  function balanceOf(address account) public view virtual override returns (uint256) {
    return _balances[account];
  }

  /**
   * @dev See {IERC20-transfer}.
   *
   * Requirements:
   *
   * - `recipient` cannot be the zero address.
   * - the caller must have a balance of at least `amount`.
   */
  // Overrideen in ERC777
  // Confirm that this behavior changes 
  function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
    _transfer(msg.sender, recipient, amount);
    return true;
  }

    /**
     * @dev See {IERC20-allowance}.
     */
    // Present in ERC777
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    // Present in ERC777
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    // Present in ERC777
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

  /**
   * @dev Moves tokens `amount` from `sender` to `recipient`.
   *
   * This is internal function is equivalent to {transfer}, and can be used to
   * e.g. implement automatic token fees, slashing mechanisms, etc.
   *
   * Emits a {Transfer} event.
   *
   * Requirements:
   *
   * - `sender` cannot be the zero address.
   * - `recipient` cannot be the zero address.
   * - `sender` must have a balance of at least `amount`.
   */
  function _transfer(address sender, address recipient, uint256 amount) internal virtual {
    require(sender != address(0), "ERC20: transfer from the zero address");
    require(recipient != address(0), "ERC20: transfer to the zero address");

    _beforeTokenTransfer(sender, recipient, amount);

    _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfer(sender, recipient, amount);
  }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    // Present in ERC777
    function _mint(address account_, uint256 amount_) internal virtual {
        require(account_ != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address( this ), account_, amount_);
        _totalSupply = _totalSupply.add(amount_);
        _balances[account_] = _balances[account_].add(amount_);
        emit Transfer(address( this ), account_, amount_);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    // Present in ERC777
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    // Present in ERC777
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    // Considering deprication to reduce size of bytecode as changing _decimals to internal acheived the same functionality.
    // function _setupDecimals(uint8 decimals_) internal {
    //     _decimals = decimals_;
    // }

  /**
   * @dev Hook that is called before any transfer of tokens. This includes
   * minting and burning.
   *
   * Calling conditions:
   *
   * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
   * will be to transferred to `to`.
   * - when `from` is zero, `amount` tokens will be minted for `to`.
   * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
   * - `from` and `to` are never both zero.
   *
   * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
   */
  // Present in ERC777
  function _beforeTokenTransfer( address from_, address to_, uint256 amount_ ) internal virtual { }
}

library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // The {SafeMath} overflow check can be skipped here, see the comment at the top
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

interface IERC2612Permit {
    /**
     * @dev Sets `amount` as the allowance of `spender` over `owner`'s tokens,
     * given `owner`'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current ERC2612 nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);
}

abstract contract ERC20Permit is ERC20, IERC2612Permit {
    using Counters for Counters.Counter;

    mapping(address => Counters.Counter) private _nonces;

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    bytes32 public DOMAIN_SEPARATOR;

    constructor() {
        uint256 chainID;
        assembly {
            chainID := chainid()
        }

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(name())),
                keccak256(bytes("1")), // Version
                chainID,
                address(this)
            )
        );
    }

    /**
     * @dev See {IERC2612Permit-permit}.
     *
     */
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual override {
        require(block.timestamp <= deadline, "Permit: expired deadline");

        bytes32 hashStruct =
            keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, amount, _nonces[owner].current(), deadline));

        bytes32 _hash = keccak256(abi.encodePacked(uint16(0x1901), DOMAIN_SEPARATOR, hashStruct));

        address signer = ecrecover(_hash, v, r, s);
        require(signer != address(0) && signer == owner, "ZeroSwapPermit: Invalid signature");

        _nonces[owner].increment();
        _approve(owner, spender, amount);
    }

    /**
     * @dev See {IERC2612Permit-nonces}.
     */
    function nonces(address owner) public view override returns (uint256) {
        return _nonces[owner].current();
    }
}

interface IOwnable {

  function owner() external view returns (address);

  function renounceOwnership() external;
  
  function transferOwnership( address newOwner_ ) external;
}

contract Ownable is IOwnable {
    
  address internal _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**
   * @dev Initializes the contract setting the deployer as the initial owner.
   */
  constructor () {
    _owner = msg.sender;
    emit OwnershipTransferred( address(0), _owner );
  }

  /**
   * @dev Returns the address of the current owner.
   */
  function owner() public view override returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require( _owner == msg.sender, "Ownable: caller is not the owner" );
    _;
  }

  /**
   * @dev Leaves the contract without owner. It will not be possible to call
   * `onlyOwner` functions anymore. Can only be called by the current owner.
   *
   * NOTE: Renouncing ownership will leave the contract without an owner,
   * thereby removing any functionality that is only available to the owner.
   */
  function renounceOwnership() public virtual override onlyOwner() {
    emit OwnershipTransferred( _owner, address(0) );
    _owner = address(0);
  }

  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Can only be called by the current owner.
   */
  function transferOwnership( address newOwner_ ) public virtual override onlyOwner() {
    require( newOwner_ != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred( _owner, newOwner_ );
    _owner = newOwner_;
  }
}

contract VaultOwned is Ownable {
    
  address internal _vault;

  function setVault( address vault_ ) external onlyOwner() returns ( bool ) {
    _vault = vault_;

    return true;
  }

  /**
   * @dev Returns the address of the current vault.
   */
  function vault() public view returns (address) {
    return _vault;
  }

  /**
   * @dev Throws if called by any account other than the vault.
   */
  modifier onlyVault() {
    require( _vault == msg.sender, "VaultOwned: caller is not the Vault" );
    _;
  }

}

contract TWAPOracleUpdater is ERC20Permit, VaultOwned {

  using EnumerableSet for EnumerableSet.AddressSet;

  event TWAPOracleChanged( address indexed previousTWAPOracle, address indexed newTWAPOracle );
  event TWAPEpochChanged( uint previousTWAPEpochPeriod, uint newTWAPEpochPeriod );
  event TWAPSourceAdded( address indexed newTWAPSource );
  event TWAPSourceRemoved( address indexed removedTWAPSource );
    
  EnumerableSet.AddressSet private _dexPoolsTWAPSources;

  ITWAPOracle public twapOracle;

  uint public twapEpochPeriod;

  constructor(
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    ) ERC20(name_, symbol_, decimals_) {
    }

  function changeTWAPOracle( address newTWAPOracle_ ) external onlyOwner() {
    emit TWAPOracleChanged( address(twapOracle), newTWAPOracle_);
    twapOracle = ITWAPOracle( newTWAPOracle_ );
  }

  function changeTWAPEpochPeriod( uint newTWAPEpochPeriod_ ) external onlyOwner() {
    require( newTWAPEpochPeriod_ > 0, "TWAPOracleUpdater: TWAP Epoch period must be greater than 0." );
    emit TWAPEpochChanged( twapEpochPeriod, newTWAPEpochPeriod_ );
    twapEpochPeriod = newTWAPEpochPeriod_;
  }

  function addTWAPSource( address newTWAPSourceDexPool_ ) external onlyOwner() {
    require( _dexPoolsTWAPSources.add( newTWAPSourceDexPool_ ), "OlympusERC20TOken: TWAP Source already stored." );
    emit TWAPSourceAdded( newTWAPSourceDexPool_ );
  }

  function removeTWAPSource( address twapSourceToRemove_ ) external onlyOwner() {
    require( _dexPoolsTWAPSources.remove( twapSourceToRemove_ ), "OlympusERC20TOken: TWAP source not present." );
    emit TWAPSourceRemoved( twapSourceToRemove_ );
  }

  function _uodateTWAPOracle( address dexPoolToUpdateFrom_, uint twapEpochPeriodToUpdate_ ) internal {
    if ( _dexPoolsTWAPSources.contains( dexPoolToUpdateFrom_ )) {
      twapOracle.updateTWAP( dexPoolToUpdateFrom_, twapEpochPeriodToUpdate_ );
    }
  }

  function _beforeTokenTransfer( address from_, address to_, uint256 amount_ ) internal override virtual {
      if( _dexPoolsTWAPSources.contains( from_ ) ) {
        _uodateTWAPOracle( from_, twapEpochPeriod );
      } else {
        if ( _dexPoolsTWAPSources.contains( to_ ) ) {
          _uodateTWAPOracle( to_, twapEpochPeriod );
        }
      }
    }
}

contract Divine is TWAPOracleUpdater {
  constructor(
    string memory name_,
    string memory symbol_,
    uint8 decimals_
  ) TWAPOracleUpdater(name_, symbol_, decimals_) {
  }
}

contract OlympusERC20Token is Divine {

  using SafeMath for uint256;

    constructor() Divine("Olympus", "OHM", 9) {
    }

    function mint(address account_, uint256 amount_) external onlyVault() {
        _mint(account_, amount_);
    }

    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See {ERC20-_burn}.
     */
    function burn(uint256 amount) public virtual {
        _burn(msg.sender, amount);
    }

    // function _beforeTokenTransfer( address from_, address to_, uint256 amount_ ) internal override virtual {
    //   if( _dexPoolsTWAPSources.contains( from_ ) ) {
    //     _uodateTWAPOracle( from_, twapEpochPeriod );
    //   } else {
    //     if ( _dexPoolsTWAPSources.contains( to_ ) ) {
    //       _uodateTWAPOracle( to_, twapEpochPeriod );
    //     }
    //   }
    // }

    /*
     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
     * allowance.
     *
     * See {ERC20-_burn} and {ERC20-allowance}.
     *
     * Requirements:
     *
     * - the caller must have allowance for ``accounts``'s tokens of at least
     * `amount`.
     */
     
    function burnFrom(address account_, uint256 amount_) public virtual {
        _burnFrom(account_, amount_);
    }

    function _burnFrom(address account_, uint256 amount_) public virtual {
        uint256 decreasedAllowance_ =
            allowance(account_, msg.sender).sub(
                amount_,
                "ERC20: burn amount exceeds allowance"
            );

        _approve(account_, msg.sender, decreasedAllowance_);
        _burn(account_, amount_);
    }
}