/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: SynthRedeemer.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/SynthRedeemer.sol
* Docs: https://docs.synthetix.io/contracts/SynthRedeemer
*
* Contract Dependencies: 
*	- IAddressResolver
*	- ISynthRedeemer
*	- MixinResolver
*	- Owned
* Libraries: 
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2021 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    // Restricted: used internally to Synthetix
    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external;

    function liquidateDelinquentAccount(
        address account,
        uint susdAmount,
        address liquidator
    ) external returns (uint totalRedeemed, uint amountToLiquidate);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination =
                resolver.requireAndGetAddress(name, string(abi.encodePacked("Resolver missing target: ", name)));
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


interface ISynthRedeemer {
    // Rate of redemption - 0 for none
    function redemptions(address synthProxy) external view returns (uint redeemRate);

    // sUSD balance of deprecated token holder
    function balanceOf(IERC20 synthProxy, address account) external view returns (uint balanceOfInsUSD);

    // Full sUSD supply of token
    function totalSupply(IERC20 synthProxy) external view returns (uint totalSupplyInsUSD);

    function redeem(IERC20 synthProxy) external;

    function redeemAll(IERC20[] calldata synthProxies) external;

    function redeemPartial(IERC20 synthProxy, uint amountOfSynth) external;

    // Restricted to Issuer
    function deprecate(IERC20 synthProxy, uint rateToRedeem) external;
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }
}


// Inheritence


// Libraries


// Internal references


contract SynthRedeemer is ISynthRedeemer, MixinResolver {
    using SafeDecimalMath for uint;

    bytes32 public constant CONTRACT_NAME = "SynthRedeemer";

    mapping(address => uint) public redemptions;

    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_SYNTHSUSD = "SynthsUSD";

    constructor(address _resolver) public MixinResolver(_resolver) {}

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](2);
        addresses[0] = CONTRACT_ISSUER;
        addresses[1] = CONTRACT_SYNTHSUSD;
    }

    function issuer() internal view returns (IIssuer) {
        return IIssuer(requireAndGetAddress(CONTRACT_ISSUER));
    }

    function sUSD() internal view returns (IERC20) {
        return IERC20(requireAndGetAddress(CONTRACT_SYNTHSUSD));
    }

    function totalSupply(IERC20 synthProxy) public view returns (uint supplyInsUSD) {
        supplyInsUSD = synthProxy.totalSupply().multiplyDecimal(redemptions[address(synthProxy)]);
    }

    function balanceOf(IERC20 synthProxy, address account) external view returns (uint balanceInsUSD) {
        balanceInsUSD = synthProxy.balanceOf(account).multiplyDecimal(redemptions[address(synthProxy)]);
    }

    function redeemAll(IERC20[] calldata synthProxies) external {
        for (uint i = 0; i < synthProxies.length; i++) {
            _redeem(synthProxies[i], synthProxies[i].balanceOf(msg.sender));
        }
    }

    function redeem(IERC20 synthProxy) external {
        _redeem(synthProxy, synthProxy.balanceOf(msg.sender));
    }

    function redeemPartial(IERC20 synthProxy, uint amountOfSynth) external {
        // technically this check isn't necessary - Synth.burn would fail due to safe sub,
        // but this is a useful error message to the user
        require(synthProxy.balanceOf(msg.sender) >= amountOfSynth, "Insufficient balance");
        _redeem(synthProxy, amountOfSynth);
    }

    function _redeem(IERC20 synthProxy, uint amountOfSynth) internal {
        uint rateToRedeem = redemptions[address(synthProxy)];
        require(rateToRedeem > 0, "Synth not redeemable");
        require(amountOfSynth > 0, "No balance of synth to redeem");
        issuer().burnForRedemption(address(synthProxy), msg.sender, amountOfSynth);
        uint amountInsUSD = amountOfSynth.multiplyDecimal(rateToRedeem);
        sUSD().transfer(msg.sender, amountInsUSD);
        emit SynthRedeemed(address(synthProxy), msg.sender, amountOfSynth, amountInsUSD);
    }

    function deprecate(IERC20 synthProxy, uint rateToRedeem) external onlyIssuer {
        address synthProxyAddress = address(synthProxy);
        require(redemptions[synthProxyAddress] == 0, "Synth is already deprecated");
        require(rateToRedeem > 0, "No rate for synth to redeem");
        uint totalSynthSupply = synthProxy.totalSupply();
        uint supplyInsUSD = totalSynthSupply.multiplyDecimal(rateToRedeem);
        require(sUSD().balanceOf(address(this)) >= supplyInsUSD, "sUSD must first be supplied");
        redemptions[synthProxyAddress] = rateToRedeem;
        emit SynthDeprecated(address(synthProxy), rateToRedeem, totalSynthSupply, supplyInsUSD);
    }

    function requireOnlyIssuer() internal view {
        require(msg.sender == address(issuer()), "Restricted to Issuer contract");
    }

    modifier onlyIssuer() {
        requireOnlyIssuer();
        _;
    }

    event SynthRedeemed(address synth, address account, uint amountOfSynth, uint amountInsUSD);
    event SynthDeprecated(address synth, uint rateToRedeem, uint totalSynthSupply, uint supplyInsUSD);
}

    

/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski

date:       2018-2-26

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).

-----------------------------------------------------------------
*/

pragma solidity 0.4.25;

/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;

    /**
     * @dev Owned Constructor
     */
    constructor(address _owner)
        public
    {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner
    {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxy.sol
version:    1.3
author:     Anton Jurisevic

date:       2018-05-29

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that, if it does not recognise the function
being called on it, passes all value and call data to an
underlying target contract.

This proxy has the capacity to toggle between DELEGATECALL
and CALL style proxy functionality.

The former executes in the proxy's context, and so will preserve 
msg.sender and store data at the proxy address. The latter will not.
Therefore, any contract the proxy wraps in the CALL style must
implement the Proxyable interface, in order that it can pass msg.sender
into the underlying contract as the state parameter, messageSender.

-----------------------------------------------------------------
*/


contract Proxy is Owned {

    Proxyable public target;
    bool public useDELEGATECALL;

    constructor(address _owner)
        Owned(_owner)
        public
    {}

    function setTarget(Proxyable _target)
        external
        onlyOwner
    {
        target = _target;
        emit TargetUpdated(_target);
    }

    function setUseDELEGATECALL(bool value) 
        external
        onlyOwner
    {
        useDELEGATECALL = value;
    }

    function _emit(bytes callData, uint numTopics, bytes32 topic1, bytes32 topic2, bytes32 topic3, bytes32 topic4)
        external
        onlyTarget
    {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi). 
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
            case 0 {
                log0(add(_callData, 32), size)
            } 
            case 1 {
                log1(add(_callData, 32), size, topic1)
            }
            case 2 {
                log2(add(_callData, 32), size, topic1, topic2)
            }
            case 3 {
                log3(add(_callData, 32), size, topic1, topic2, topic3)
            }
            case 4 {
                log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
            }
        }
    }

    function()
        external
        payable
    {
        if (useDELEGATECALL) {
            assembly {
                /* Copy call data into free memory region. */
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* Forward all gas and call data to the target contract. */
                let result := delegatecall(gas, sload(target_slot), free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                /* Revert if the call failed, otherwise return the result. */
                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        } else {
            /* Here we are as above, but must send the messageSender explicitly 
             * since we are using CALL rather than DELEGATECALL. */
            target.setMessageSender(msg.sender);
            assembly {
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* We must explicitly forward ether to the underlying contract as well. */
                let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxyable.sol
version:    1.1
author:     Anton Jurisevic

date:       2018-05-15

checked:    Mike Spain
approved:   Samuel Brooks

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxyable contract that works hand in hand with the Proxy contract
to allow for anyone to interact with the underlying contract both
directly and through the proxy.

-----------------------------------------------------------------
*/


// This contract should be treated like an abstract contract
contract Proxyable is Owned {
    /* The proxy this contract exists behind. */
    Proxy public proxy;
    Proxy public integrationProxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address messageSender;

    constructor(address _proxy, address _owner)
        Owned(_owner)
        public
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address _proxy)
        external
        onlyOwner
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setIntegrationProxy(address _integrationProxy)
        external
        onlyOwner
    {
        integrationProxy = Proxy(_integrationProxy);
    }

    function setMessageSender(address sender)
        external
        onlyProxy
    {
        messageSender = sender;
    }

    modifier onlyProxy {
        require(Proxy(msg.sender) == proxy || Proxy(msg.sender) == integrationProxy, "Only the proxy can call");
        _;
    }

    modifier optionalProxy
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        _;
    }

    modifier optionalProxy_onlyOwner
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
        _;
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract IERC20 {
    function totalSupply() public view returns (uint);

    function balanceOf(address owner) public view returns (uint);

    function allowance(address owner, address spender) public view returns (uint);

    function transfer(address to, uint value) public returns (bool);

    function approve(address spender, uint value) public returns (bool);

    function transferFrom(address from, address to, uint value) public returns (bool);

    // ERC20 Optional
    function name() public view returns (string);
    function symbol() public view returns (string);
    function decimals() public view returns (uint8);

    event Transfer(
      address indexed from,
      address indexed to,
      uint value
    );

    event Approval(
      address indexed owner,
      address indexed spender,
      uint value
    );
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       ProxyERC20.sol
version:    1.0
author:     Jackson Chan, Clinton Ennis

date:       2019-06-19

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that is ERC20 compliant for the Synthetix Network.

If it does not recognise a function being called on it, passes all
value and call data to an underlying target contract.

The ERC20 standard has been explicitly implemented to ensure
contract to contract calls are compatable on MAINNET

-----------------------------------------------------------------
*/


contract ProxyERC20 is Proxy, IERC20 {

    constructor(address _owner)
        Proxy(_owner)
        public
    {}

    // ------------- ERC20 Details ------------- //

    function name() public view returns (string){
        // Immutable static call from target contract
        return IERC20(target).name();
    }

    function symbol() public view returns (string){
         // Immutable static call from target contract
        return IERC20(target).symbol();
    }

    function decimals() public view returns (uint8){
         // Immutable static call from target contract
        return IERC20(target).decimals();
    }

    // ------------- ERC20 Interface ------------- //

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).totalSupply();
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).balanceOf(owner);
    }

    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param owner address The address which owns the funds.
    * @param spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(
        address owner,
        address spender
    )
        public
        view
        returns (uint256)
    {
        // Immutable static call from target contract
        return IERC20(target).allowance(owner, spender);
    }

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transfer(to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * 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
    * @param spender The address which will spend the funds.
    * @param value The amount of tokens to be spent.
    */
    function approve(address spender, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).approve(spender, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param from address The address which you want to send tokens from
    * @param to address The address which you want to transfer to
    * @param value uint256 the amount of tokens to be transferred
    */
    function transferFrom(
        address from,
        address to,
        uint256 value
    )
        public
        returns (bool)
    {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transferFrom(from, to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }
}

/**
 *Submitted for verification at Etherscan.io on 2019-08-08
*/

/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski

date:       2018-2-26

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).

-----------------------------------------------------------------
*/

pragma solidity 0.4.25;

/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;

    /**
     * @dev Owned Constructor
     */
    constructor(address _owner)
        public
    {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner
    {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxy.sol
version:    1.3
author:     Anton Jurisevic

date:       2018-05-29

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that, if it does not recognise the function
being called on it, passes all value and call data to an
underlying target contract.

This proxy has the capacity to toggle between DELEGATECALL
and CALL style proxy functionality.

The former executes in the proxy's context, and so will preserve 
msg.sender and store data at the proxy address. The latter will not.
Therefore, any contract the proxy wraps in the CALL style must
implement the Proxyable interface, in order that it can pass msg.sender
into the underlying contract as the state parameter, messageSender.

-----------------------------------------------------------------
*/


contract Proxy is Owned {

    Proxyable public target;
    bool public useDELEGATECALL;

    constructor(address _owner)
        Owned(_owner)
        public
    {}

    function setTarget(Proxyable _target)
        external
        onlyOwner
    {
        target = _target;
        emit TargetUpdated(_target);
    }

    function setUseDELEGATECALL(bool value) 
        external
        onlyOwner
    {
        useDELEGATECALL = value;
    }

    function _emit(bytes callData, uint numTopics, bytes32 topic1, bytes32 topic2, bytes32 topic3, bytes32 topic4)
        external
        onlyTarget
    {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi). 
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
            case 0 {
                log0(add(_callData, 32), size)
            } 
            case 1 {
                log1(add(_callData, 32), size, topic1)
            }
            case 2 {
                log2(add(_callData, 32), size, topic1, topic2)
            }
            case 3 {
                log3(add(_callData, 32), size, topic1, topic2, topic3)
            }
            case 4 {
                log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
            }
        }
    }

    function()
        external
        payable
    {
        if (useDELEGATECALL) {
            assembly {
                /* Copy call data into free memory region. */
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* Forward all gas and call data to the target contract. */
                let result := delegatecall(gas, sload(target_slot), free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                /* Revert if the call failed, otherwise return the result. */
                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        } else {
            /* Here we are as above, but must send the messageSender explicitly 
             * since we are using CALL rather than DELEGATECALL. */
            target.setMessageSender(msg.sender);
            assembly {
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* We must explicitly forward ether to the underlying contract as well. */
                let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxyable.sol
version:    1.1
author:     Anton Jurisevic

date:       2018-05-15

checked:    Mike Spain
approved:   Samuel Brooks

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxyable contract that works hand in hand with the Proxy contract
to allow for anyone to interact with the underlying contract both
directly and through the proxy.

-----------------------------------------------------------------
*/


// This contract should be treated like an abstract contract
contract Proxyable is Owned {
    /* The proxy this contract exists behind. */
    Proxy public proxy;
    Proxy public integrationProxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address messageSender;

    constructor(address _proxy, address _owner)
        Owned(_owner)
        public
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address _proxy)
        external
        onlyOwner
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setIntegrationProxy(address _integrationProxy)
        external
        onlyOwner
    {
        integrationProxy = Proxy(_integrationProxy);
    }

    function setMessageSender(address sender)
        external
        onlyProxy
    {
        messageSender = sender;
    }

    modifier onlyProxy {
        require(Proxy(msg.sender) == proxy || Proxy(msg.sender) == integrationProxy, "Only the proxy can call");
        _;
    }

    modifier optionalProxy
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        _;
    }

    modifier optionalProxy_onlyOwner
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
        _;
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract IERC20 {
    function totalSupply() public view returns (uint);

    function balanceOf(address owner) public view returns (uint);

    function allowance(address owner, address spender) public view returns (uint);

    function transfer(address to, uint value) public returns (bool);

    function approve(address spender, uint value) public returns (bool);

    function transferFrom(address from, address to, uint value) public returns (bool);

    // ERC20 Optional
    function name() public view returns (string);
    function symbol() public view returns (string);
    function decimals() public view returns (uint8);

    event Transfer(
      address indexed from,
      address indexed to,
      uint value
    );

    event Approval(
      address indexed owner,
      address indexed spender,
      uint value
    );
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       ProxyERC20.sol
version:    1.0
author:     Jackson Chan, Clinton Ennis

date:       2019-06-19

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that is ERC20 compliant for the Synthetix Network.

If it does not recognise a function being called on it, passes all
value and call data to an underlying target contract.

The ERC20 standard has been explicitly implemented to ensure
contract to contract calls are compatable on MAINNET

-----------------------------------------------------------------
*/


contract ProxyERC20 is Proxy, IERC20 {

    constructor(address _owner)
        Proxy(_owner)
        public
    {}

    // ------------- ERC20 Details ------------- //

    function name() public view returns (string){
        // Immutable static call from target contract
        return IERC20(target).name();
    }

    function symbol() public view returns (string){
         // Immutable static call from target contract
        return IERC20(target).symbol();
    }

    function decimals() public view returns (uint8){
         // Immutable static call from target contract
        return IERC20(target).decimals();
    }

    // ------------- ERC20 Interface ------------- //

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).totalSupply();
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).balanceOf(owner);
    }

    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param owner address The address which owns the funds.
    * @param spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(
        address owner,
        address spender
    )
        public
        view
        returns (uint256)
    {
        // Immutable static call from target contract
        return IERC20(target).allowance(owner, spender);
    }

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transfer(to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * 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
    * @param spender The address which will spend the funds.
    * @param value The amount of tokens to be spent.
    */
    function approve(address spender, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).approve(spender, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param from address The address which you want to send tokens from
    * @param to address The address which you want to transfer to
    * @param value uint256 the amount of tokens to be transferred
    */
    function transferFrom(
        address from,
        address to,
        uint256 value
    )
        public
        returns (bool)
    {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transferFrom(from, to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }
}

/*

⚠⚠⚠ WARNING WARNING WARNING ⚠⚠⚠

This is a TARGET contract - DO NOT CONNECT TO IT DIRECTLY IN YOUR CONTRACTS or DAPPS!

This contract has an associated PROXY that MUST be used for all integrations - this TARGET will be REPLACED in an upcoming Synthetix release!
The proxy can be found by looking up the PROXY property on this contract.

*//*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: PurgeableSynth.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/PurgeableSynth.sol
* Docs: https://docs.synthetix.io/contracts/PurgeableSynth
*
* Contract Dependencies: 
*	- ExternStateToken
*	- IAddressResolver
*	- IERC20
*	- ISynth
*	- MixinResolver
*	- Owned
*	- Proxyable
*	- State
*	- Synth
* Libraries: 
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;


// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxy
contract Proxy is Owned {
    Proxyable public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(Proxyable _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(_target);
    }

    function _emit(
        bytes calldata callData,
        uint numTopics,
        bytes32 topic1,
        bytes32 topic2,
        bytes32 topic3,
        bytes32 topic4
    ) external onlyTarget {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi).
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
                case 0 {
                    log0(add(_callData, 32), size)
                }
                case 1 {
                    log1(add(_callData, 32), size, topic1)
                }
                case 2 {
                    log2(add(_callData, 32), size, topic1, topic2)
                }
                case 3 {
                    log3(add(_callData, 32), size, topic1, topic2, topic3)
                }
                case 4 {
                    log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
                }
        }
    }

    // solhint-disable no-complex-fallback
    function() external payable {
        // Mutable call setting Proxyable.messageSender as this is using call not delegatecall
        target.setMessageSender(msg.sender);

        assembly {
            let free_ptr := mload(0x40)
            calldatacopy(free_ptr, 0, calldatasize)

            /* We must explicitly forward ether to the underlying contract as well. */
            let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
            returndatacopy(free_ptr, 0, returndatasize)

            if iszero(result) {
                revert(free_ptr, returndatasize)
            }
            return(free_ptr, returndatasize)
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxyable
contract Proxyable is Owned {
    // This contract should be treated like an abstract contract

    /* The proxy this contract exists behind. */
    Proxy public proxy;
    Proxy public integrationProxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address public messageSender;

    constructor(address payable _proxy) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address payable _proxy) external onlyOwner {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setIntegrationProxy(address payable _integrationProxy) external onlyOwner {
        integrationProxy = Proxy(_integrationProxy);
    }

    function setMessageSender(address sender) external onlyProxy {
        messageSender = sender;
    }

    modifier onlyProxy {
        _onlyProxy();
        _;
    }

    function _onlyProxy() private view {
        require(Proxy(msg.sender) == proxy || Proxy(msg.sender) == integrationProxy, "Only the proxy can call");
    }

    modifier optionalProxy {
        _optionalProxy();
        _;
    }

    function _optionalProxy() private {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
    }

    modifier optionalProxy_onlyOwner {
        _optionalProxy_onlyOwner();
        _;
    }

    // solhint-disable-next-line func-name-mixedcase
    function _optionalProxy_onlyOwner() private {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/state
contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;

    constructor(address _associatedContract) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract) external onlyOwner {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract {
        require(msg.sender == associatedContract, "Only the associated contract can perform this action");
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address associatedContract);
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/tokenstate
contract TokenState is Owned, State {
    /* ERC20 fields. */
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    constructor(address _owner, address _associatedContract) public Owned(_owner) State(_associatedContract) {}

    /* ========== SETTERS ========== */

    /**
     * @notice Set ERC20 allowance.
     * @dev Only the associated contract may call this.
     * @param tokenOwner The authorising party.
     * @param spender The authorised party.
     * @param value The total value the authorised party may spend on the
     * authorising party's behalf.
     */
    function setAllowance(
        address tokenOwner,
        address spender,
        uint value
    ) external onlyAssociatedContract {
        allowance[tokenOwner][spender] = value;
    }

    /**
     * @notice Set the balance in a given account
     * @dev Only the associated contract may call this.
     * @param account The account whose value to set.
     * @param value The new balance of the given account.
     */
    function setBalanceOf(address account, uint value) external onlyAssociatedContract {
        balanceOf[account] = value;
    }
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/externstatetoken
contract ExternStateToken is Owned, Proxyable {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /* ========== STATE VARIABLES ========== */

    /* Stores balances and allowances. */
    TokenState public tokenState;

    /* Other ERC20 fields. */
    string public name;
    string public symbol;
    uint public totalSupply;
    uint8 public decimals;

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _name,
        string memory _symbol,
        uint _totalSupply,
        uint8 _decimals,
        address _owner
    ) public Owned(_owner) Proxyable(_proxy) {
        tokenState = _tokenState;

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

    /* ========== VIEWS ========== */

    /**
     * @notice Returns the ERC20 allowance of one party to spend on behalf of another.
     * @param owner The party authorising spending of their funds.
     * @param spender The party spending tokenOwner's funds.
     */
    function allowance(address owner, address spender) public view returns (uint) {
        return tokenState.allowance(owner, spender);
    }

    /**
     * @notice Returns the ERC20 token balance of a given account.
     */
    function balanceOf(address account) external view returns (uint) {
        return tokenState.balanceOf(account);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    /**
     * @notice Set the address of the TokenState contract.
     * @dev This can be used to "pause" transfer functionality, by pointing the tokenState at 0x000..
     * as balances would be unreachable.
     */
    function setTokenState(TokenState _tokenState) external optionalProxy_onlyOwner {
        tokenState = _tokenState;
        emitTokenStateUpdated(address(_tokenState));
    }

    function _internalTransfer(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Disallow transfers to irretrievable-addresses. */
        require(to != address(0) && to != address(this) && to != address(proxy), "Cannot transfer to this address");

        // Insufficient balance will be handled by the safe subtraction.
        tokenState.setBalanceOf(from, tokenState.balanceOf(from).sub(value));
        tokenState.setBalanceOf(to, tokenState.balanceOf(to).add(value));

        // Emit a standard ERC20 transfer event
        emitTransfer(from, to, value);

        return true;
    }

    /**
     * @dev Perform an ERC20 token transfer. Designed to be called by transfer functions possessing
     * the onlyProxy or optionalProxy modifiers.
     */
    function _transferByProxy(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        return _internalTransfer(from, to, value);
    }

    /*
     * @dev Perform an ERC20 token transferFrom. Designed to be called by transferFrom functions
     * possessing the optionalProxy or optionalProxy modifiers.
     */
    function _transferFromByProxy(
        address sender,
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Insufficient allowance will be handled by the safe subtraction. */
        tokenState.setAllowance(from, sender, tokenState.allowance(from, sender).sub(value));
        return _internalTransfer(from, to, value);
    }

    /**
     * @notice Approves spender to transfer on the message sender's behalf.
     */
    function approve(address spender, uint value) public optionalProxy returns (bool) {
        address sender = messageSender;

        tokenState.setAllowance(sender, spender, value);
        emitApproval(sender, spender, value);
        return true;
    }

    /* ========== EVENTS ========== */
    function addressToBytes32(address input) internal pure returns (bytes32) {
        return bytes32(uint256(uint160(input)));
    }

    event Transfer(address indexed from, address indexed to, uint value);
    bytes32 internal constant TRANSFER_SIG = keccak256("Transfer(address,address,uint256)");

    function emitTransfer(
        address from,
        address to,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, TRANSFER_SIG, addressToBytes32(from), addressToBytes32(to), 0);
    }

    event Approval(address indexed owner, address indexed spender, uint value);
    bytes32 internal constant APPROVAL_SIG = keccak256("Approval(address,address,uint256)");

    function emitApproval(
        address owner,
        address spender,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, APPROVAL_SIG, addressToBytes32(owner), addressToBytes32(spender), 0);
    }

    event TokenStateUpdated(address newTokenState);
    bytes32 internal constant TOKENSTATEUPDATED_SIG = keccak256("TokenStateUpdated(address)");

    function emitTokenStateUpdated(address newTokenState) internal {
        proxy._emit(abi.encode(newTokenState), 1, TOKENSTATEUPDATED_SIG, 0, 0, 0);
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeEtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    // Restricted: used internally to Synthetix
    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function liquidateDelinquentAccount(
        address account,
        uint susdAmount,
        address liquidator
    ) external returns (uint totalRedeemed, uint amountToLiquidate);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}


// solhint-disable payable-fallback

// https://docs.synthetix.io/contracts/source/contracts/readproxy
contract ReadProxy is Owned {
    address public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(address _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(target);
    }

    function() external {
        // The basics of a proxy read call
        // Note that msg.sender in the underlying will always be the address of this contract.
        assembly {
            calldatacopy(0, 0, calldatasize)

            // Use of staticcall - this will revert if the underlying function mutates state
            let result := staticcall(gas, sload(target_slot), 0, calldatasize, 0, 0)
            returndatacopy(0, 0, returndatasize)

            if iszero(result) {
                revert(0, returndatasize)
            }
            return(0, returndatasize)
        }
    }

    event TargetUpdated(address newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination = resolver.requireAndGetAddress(
                name,
                string(abi.encodePacked("Resolver missing target: ", name))
            );
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


// https://docs.synthetix.io/contracts/source/interfaces/isystemstatus
interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    // Restricted functions
    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/ifeepool
interface IFeePool {
    // Views

    // solhint-disable-next-line func-name-mixedcase
    function FEE_ADDRESS() external view returns (address);

    function feesAvailable(address account) external view returns (uint, uint);

    function feePeriodDuration() external view returns (uint);

    function isFeesClaimable(address account) external view returns (bool);

    function targetThreshold() external view returns (uint);

    function totalFeesAvailable() external view returns (uint);

    function totalRewardsAvailable() external view returns (uint);

    // Mutative Functions
    function claimFees() external returns (bool);

    function claimOnBehalf(address claimingForAddress) external returns (bool);

    function closeCurrentFeePeriod() external;

    // Restricted: used internally to Synthetix
    function appendAccountIssuanceRecord(
        address account,
        uint lockedAmount,
        uint debtEntryIndex
    ) external;

    function recordFeePaid(uint sUSDAmount) external;

    function setRewardsToDistribute(uint amount) external;
}


interface IVirtualSynth {
    // Views
    function balanceOfUnderlying(address account) external view returns (uint);

    function rate() external view returns (uint);

    function readyToSettle() external view returns (bool);

    function secsLeftInWaitingPeriod() external view returns (uint);

    function settled() external view returns (bool);

    function synth() external view returns (ISynth);

    // Mutative functions
    function settle(address account) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchanger
interface IExchanger {
    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint exchangeFeeRate);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    // Mutative functions
    function exchange(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress
    ) external returns (uint amountReceived);

    function exchangeOnBehalf(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeWithTracking(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeWithVirtual(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    function setLastExchangeRateForSynth(bytes32 currencyKey, uint rate) external;

    function suspendSynthWithInvalidRate(bytes32 currencyKey) external;
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/synth
contract Synth is Owned, IERC20, ExternStateToken, MixinResolver, ISynth {
    /* ========== STATE VARIABLES ========== */

    // Currency key which identifies this Synth to the Synthetix system
    bytes32 public currencyKey;

    uint8 public constant DECIMALS = 18;

    // Where fees are pooled in sUSD
    address public constant FEE_ADDRESS = 0xfeEFEEfeefEeFeefEEFEEfEeFeefEEFeeFEEFEeF;

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 private constant CONTRACT_EXCHANGER = "Exchanger";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _tokenName,
        string memory _tokenSymbol,
        address _owner,
        bytes32 _currencyKey,
        uint _totalSupply,
        address _resolver
    )
        public
        ExternStateToken(_proxy, _tokenState, _tokenName, _tokenSymbol, _totalSupply, DECIMALS, _owner)
        MixinResolver(_resolver)
    {
        require(_proxy != address(0), "_proxy cannot be 0");
        require(_owner != address(0), "_owner cannot be 0");

        currencyKey = _currencyKey;
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function transfer(address to, uint value) public optionalProxy returns (bool) {
        _ensureCanTransfer(messageSender, value);

        // transfers to FEE_ADDRESS will be exchanged into sUSD and recorded as fee
        if (to == FEE_ADDRESS) {
            return _transferToFeeAddress(to, value);
        }

        // transfers to 0x address will be burned
        if (to == address(0)) {
            return _internalBurn(messageSender, value);
        }

        return super._internalTransfer(messageSender, to, value);
    }

    function transferAndSettle(address to, uint value) public optionalProxy returns (bool) {
        // Exchanger.settle ensures synth is active
        (, , uint numEntriesSettled) = exchanger().settle(messageSender, currencyKey);

        // Save gas instead of calling transferableSynths
        uint balanceAfter = value;

        if (numEntriesSettled > 0) {
            balanceAfter = tokenState.balanceOf(messageSender);
        }

        // Reduce the value to transfer if balance is insufficient after reclaimed
        value = value > balanceAfter ? balanceAfter : value;

        return super._internalTransfer(messageSender, to, value);
    }

    function transferFrom(
        address from,
        address to,
        uint value
    ) public optionalProxy returns (bool) {
        _ensureCanTransfer(from, value);

        return _internalTransferFrom(from, to, value);
    }

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) public optionalProxy returns (bool) {
        // Exchanger.settle() ensures synth is active
        (, , uint numEntriesSettled) = exchanger().settle(from, currencyKey);

        // Save gas instead of calling transferableSynths
        uint balanceAfter = value;

        if (numEntriesSettled > 0) {
            balanceAfter = tokenState.balanceOf(from);
        }

        // Reduce the value to transfer if balance is insufficient after reclaimed
        value = value >= balanceAfter ? balanceAfter : value;

        return _internalTransferFrom(from, to, value);
    }

    /**
     * @notice _transferToFeeAddress function
     * non-sUSD synths are exchanged into sUSD via synthInitiatedExchange
     * notify feePool to record amount as fee paid to feePool */
    function _transferToFeeAddress(address to, uint value) internal returns (bool) {
        uint amountInUSD;

        // sUSD can be transferred to FEE_ADDRESS directly
        if (currencyKey == "sUSD") {
            amountInUSD = value;
            super._internalTransfer(messageSender, to, value);
        } else {
            // else exchange synth into sUSD and send to FEE_ADDRESS
            amountInUSD = exchanger().exchange(messageSender, currencyKey, value, "sUSD", FEE_ADDRESS);
        }

        // Notify feePool to record sUSD to distribute as fees
        feePool().recordFeePaid(amountInUSD);

        return true;
    }

    function issue(address account, uint amount) external onlyInternalContracts {
        _internalIssue(account, amount);
    }

    function burn(address account, uint amount) external onlyInternalContracts {
        _internalBurn(account, amount);
    }

    function _internalIssue(address account, uint amount) internal {
        tokenState.setBalanceOf(account, tokenState.balanceOf(account).add(amount));
        totalSupply = totalSupply.add(amount);
        emitTransfer(address(0), account, amount);
        emitIssued(account, amount);
    }

    function _internalBurn(address account, uint amount) internal returns (bool) {
        tokenState.setBalanceOf(account, tokenState.balanceOf(account).sub(amount));
        totalSupply = totalSupply.sub(amount);
        emitTransfer(account, address(0), amount);
        emitBurned(account, amount);

        return true;
    }

    // Allow owner to set the total supply on import.
    function setTotalSupply(uint amount) external optionalProxy_onlyOwner {
        totalSupply = amount;
    }

    /* ========== VIEWS ========== */

    // Note: use public visibility so that it can be invoked in a subclass
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](4);
        addresses[0] = CONTRACT_SYSTEMSTATUS;
        addresses[1] = CONTRACT_EXCHANGER;
        addresses[2] = CONTRACT_ISSUER;
        addresses[3] = CONTRACT_FEEPOOL;
    }

    function systemStatus() internal view returns (ISystemStatus) {
        return ISystemStatus(requireAndGetAddress(CONTRACT_SYSTEMSTATUS));
    }

    function feePool() internal view returns (IFeePool) {
        return IFeePool(requireAndGetAddress(CONTRACT_FEEPOOL));
    }

    function exchanger() internal view returns (IExchanger) {
        return IExchanger(requireAndGetAddress(CONTRACT_EXCHANGER));
    }

    function issuer() internal view returns (IIssuer) {
        return IIssuer(requireAndGetAddress(CONTRACT_ISSUER));
    }

    function _ensureCanTransfer(address from, uint value) internal view {
        require(exchanger().maxSecsLeftInWaitingPeriod(from, currencyKey) == 0, "Cannot transfer during waiting period");
        require(transferableSynths(from) >= value, "Insufficient balance after any settlement owing");
        systemStatus().requireSynthActive(currencyKey);
    }

    function transferableSynths(address account) public view returns (uint) {
        (uint reclaimAmount, , ) = exchanger().settlementOwing(account, currencyKey);

        // Note: ignoring rebate amount here because a settle() is required in order to
        // allow the transfer to actually work

        uint balance = tokenState.balanceOf(account);

        if (reclaimAmount > balance) {
            return 0;
        } else {
            return balance.sub(reclaimAmount);
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _internalTransferFrom(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        // Skip allowance update in case of infinite allowance
        if (tokenState.allowance(from, messageSender) != uint(-1)) {
            // Reduce the allowance by the amount we're transferring.
            // The safeSub call will handle an insufficient allowance.
            tokenState.setAllowance(from, messageSender, tokenState.allowance(from, messageSender).sub(value));
        }

        return super._internalTransfer(from, to, value);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyInternalContracts() {
        bool isFeePool = msg.sender == address(feePool());
        bool isExchanger = msg.sender == address(exchanger());
        bool isIssuer = msg.sender == address(issuer());

        require(isFeePool || isExchanger || isIssuer, "Only FeePool, Exchanger or Issuer contracts allowed");
        _;
    }

    /* ========== EVENTS ========== */
    event Issued(address indexed account, uint value);
    bytes32 private constant ISSUED_SIG = keccak256("Issued(address,uint256)");

    function emitIssued(address account, uint value) internal {
        proxy._emit(abi.encode(value), 2, ISSUED_SIG, addressToBytes32(account), 0, 0);
    }

    event Burned(address indexed account, uint value);
    bytes32 private constant BURNED_SIG = keccak256("Burned(address,uint256)");

    function emitBurned(address account, uint value) internal {
        proxy._emit(abi.encode(value), 2, BURNED_SIG, addressToBytes32(account), 0, 0);
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangerates
interface IExchangeRates {
    // Structs
    struct RateAndUpdatedTime {
        uint216 rate;
        uint40 time;
    }

    struct InversePricing {
        uint entryPoint;
        uint upperLimit;
        uint lowerLimit;
        bool frozenAtUpperLimit;
        bool frozenAtLowerLimit;
    }

    // Views
    function aggregators(bytes32 currencyKey) external view returns (address);

    function aggregatorWarningFlags() external view returns (address);

    function anyRateIsInvalid(bytes32[] calldata currencyKeys) external view returns (bool);

    function canFreezeRate(bytes32 currencyKey) external view returns (bool);

    function currentRoundForRate(bytes32 currencyKey) external view returns (uint);

    function currenciesUsingAggregator(address aggregator) external view returns (bytes32[] memory);

    function effectiveValue(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external view returns (uint value);

    function effectiveValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveValueAtRound(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        uint roundIdForSrc,
        uint roundIdForDest
    ) external view returns (uint value);

    function getCurrentRoundId(bytes32 currencyKey) external view returns (uint);

    function getLastRoundIdBeforeElapsedSecs(
        bytes32 currencyKey,
        uint startingRoundId,
        uint startingTimestamp,
        uint timediff
    ) external view returns (uint);

    function inversePricing(bytes32 currencyKey)
        external
        view
        returns (
            uint entryPoint,
            uint upperLimit,
            uint lowerLimit,
            bool frozenAtUpperLimit,
            bool frozenAtLowerLimit
        );

    function lastRateUpdateTimes(bytes32 currencyKey) external view returns (uint256);

    function oracle() external view returns (address);

    function rateAndTimestampAtRound(bytes32 currencyKey, uint roundId) external view returns (uint rate, uint time);

    function rateAndUpdatedTime(bytes32 currencyKey) external view returns (uint rate, uint time);

    function rateAndInvalid(bytes32 currencyKey) external view returns (uint rate, bool isInvalid);

    function rateForCurrency(bytes32 currencyKey) external view returns (uint);

    function rateIsFlagged(bytes32 currencyKey) external view returns (bool);

    function rateIsFrozen(bytes32 currencyKey) external view returns (bool);

    function rateIsInvalid(bytes32 currencyKey) external view returns (bool);

    function rateIsStale(bytes32 currencyKey) external view returns (bool);

    function rateStalePeriod() external view returns (uint);

    function ratesAndUpdatedTimeForCurrencyLastNRounds(bytes32 currencyKey, uint numRounds)
        external
        view
        returns (uint[] memory rates, uint[] memory times);

    function ratesAndInvalidForCurrencies(bytes32[] calldata currencyKeys)
        external
        view
        returns (uint[] memory rates, bool anyRateInvalid);

    function ratesForCurrencies(bytes32[] calldata currencyKeys) external view returns (uint[] memory);

    // Mutative functions
    function freezeRate(bytes32 currencyKey) external;
}


// Inheritance


// Libraries


// Internal References


// https://docs.synthetix.io/contracts/source/contracts/purgeablesynth
contract PurgeableSynth is Synth {
    using SafeDecimalMath for uint;

    // The maximum allowed amount of tokenSupply in equivalent sUSD value for this synth to permit purging
    uint public maxSupplyToPurgeInUSD = 100000 * SafeDecimalMath.unit(); // 100,000

    bytes32 private constant CONTRACT_EXRATES = "ExchangeRates";

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _tokenName,
        string memory _tokenSymbol,
        address payable _owner,
        bytes32 _currencyKey,
        uint _totalSupply,
        address _resolver
    ) public Synth(_proxy, _tokenState, _tokenName, _tokenSymbol, _owner, _currencyKey, _totalSupply, _resolver) {}

    /* ========== VIEWS ========== */
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = Synth.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](1);
        newAddresses[0] = CONTRACT_EXRATES;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    function exchangeRates() internal view returns (IExchangeRates) {
        return IExchangeRates(requireAndGetAddress(CONTRACT_EXRATES));
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function purge(address[] calldata addresses) external optionalProxy_onlyOwner {
        IExchangeRates exRates = exchangeRates();

        uint maxSupplyToPurge = exRates.effectiveValue("sUSD", maxSupplyToPurgeInUSD, currencyKey);

        // Only allow purge when total supply is lte the max or the rate is frozen in ExchangeRates
        require(
            totalSupply <= maxSupplyToPurge || exRates.rateIsFrozen(currencyKey),
            "Cannot purge as total supply is above threshold and rate is not frozen."
        );

        for (uint i = 0; i < addresses.length; i++) {
            address holder = addresses[i];

            uint amountHeld = tokenState.balanceOf(holder);

            if (amountHeld > 0) {
                exchanger().exchange(holder, currencyKey, amountHeld, "sUSD", holder);
                emitPurged(holder, amountHeld);
            }
        }
    }

    /* ========== EVENTS ========== */
    event Purged(address indexed account, uint value);
    bytes32 private constant PURGED_SIG = keccak256("Purged(address,uint256)");

    function emitPurged(address account, uint value) internal {
        proxy._emit(abi.encode(value), 2, PURGED_SIG, addressToBytes32(account), 0, 0);
    }
}

    

/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski

date:       2018-2-26

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).

-----------------------------------------------------------------
*/

pragma solidity 0.4.25;

/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;

    /**
     * @dev Owned Constructor
     */
    constructor(address _owner)
        public
    {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner
    {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}

/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       State.sol
version:    1.1
author:     Dominic Romanowski
            Anton Jurisevic

date:       2018-05-15

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

This contract is used side by side with external state token
contracts, such as Synthetix and Synth.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.

The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.

-----------------------------------------------------------------
*/


contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;


    constructor(address _owner, address _associatedContract)
        Owned(_owner)
        public
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract)
        external
        onlyOwner
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract
    {
        require(msg.sender == associatedContract, "Only the associated contract can perform this action");
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address associatedContract);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       TokenState.sol
version:    1.1
author:     Dominic Romanowski
            Anton Jurisevic

date:       2018-05-15

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A contract that holds the state of an ERC20 compliant token.

This contract is used side by side with external state token
contracts, such as Synthetix and Synth.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.

The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.

-----------------------------------------------------------------
*/


/**
 * @title ERC20 Token State
 * @notice Stores balance information of an ERC20 token contract.
 */
contract TokenState is State {

    /* ERC20 fields. */
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    /**
     * @dev Constructor
     * @param _owner The address which controls this contract.
     * @param _associatedContract The ERC20 contract whose state this composes.
     */
    constructor(address _owner, address _associatedContract)
        State(_owner, _associatedContract)
        public
    {}

    /* ========== SETTERS ========== */

    /**
     * @notice Set ERC20 allowance.
     * @dev Only the associated contract may call this.
     * @param tokenOwner The authorising party.
     * @param spender The authorised party.
     * @param value The total value the authorised party may spend on the
     * authorising party's behalf.
     */
    function setAllowance(address tokenOwner, address spender, uint value)
        external
        onlyAssociatedContract
    {
        allowance[tokenOwner][spender] = value;
    }

    /**
     * @notice Set the balance in a given account
     * @dev Only the associated contract may call this.
     * @param account The account whose value to set.
     * @param value The new balance of the given account.
     */
    function setBalanceOf(address account, uint value)
        external
        onlyAssociatedContract
    {
        balanceOf[account] = value;
    }
}

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: Issuer.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/Issuer.sol
* Docs: https://docs.synthetix.io/contracts/Issuer
*
* Contract Dependencies: 
*	- IAddressResolver
*	- IIssuer
*	- MixinResolver
*	- MixinSystemSettings
*	- Owned
* Libraries: 
*	- SafeCast
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2023 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views

    function allNetworksDebtInfo()
        external
        view
        returns (
            uint256 debt,
            uint256 sharesSupply,
            bool isStale
        );

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    function liquidationAmounts(address account, bool isSelfLiquidation)
        external
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint initialDebtBalance
        );

    // Restricted: used internally to Synthetix
    function addSynths(ISynth[] calldata synthsToAdd) external;

    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external;

    function setCurrentPeriodId(uint128 periodId) external;

    function liquidateAccount(address account, bool isSelfLiquidation)
        external
        returns (
            uint totalRedeemed,
            uint debtRemoved,
            uint escrowToLiquidate
        );

    function issueSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);

    function burnSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);

    function modifyDebtSharesForMigration(address account, uint amount) external;
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination =
                resolver.requireAndGetAddress(name, string(abi.encodePacked("Resolver missing target: ", name)));
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// https://docs.synthetix.io/contracts/source/interfaces/iflexiblestorage
interface IFlexibleStorage {
    // Views
    function getUIntValue(bytes32 contractName, bytes32 record) external view returns (uint);

    function getUIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (uint[] memory);

    function getIntValue(bytes32 contractName, bytes32 record) external view returns (int);

    function getIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (int[] memory);

    function getAddressValue(bytes32 contractName, bytes32 record) external view returns (address);

    function getAddressValues(bytes32 contractName, bytes32[] calldata records) external view returns (address[] memory);

    function getBoolValue(bytes32 contractName, bytes32 record) external view returns (bool);

    function getBoolValues(bytes32 contractName, bytes32[] calldata records) external view returns (bool[] memory);

    function getBytes32Value(bytes32 contractName, bytes32 record) external view returns (bytes32);

    function getBytes32Values(bytes32 contractName, bytes32[] calldata records) external view returns (bytes32[] memory);

    // Mutative functions
    function deleteUIntValue(bytes32 contractName, bytes32 record) external;

    function deleteIntValue(bytes32 contractName, bytes32 record) external;

    function deleteAddressValue(bytes32 contractName, bytes32 record) external;

    function deleteBoolValue(bytes32 contractName, bytes32 record) external;

    function deleteBytes32Value(bytes32 contractName, bytes32 record) external;

    function setUIntValue(
        bytes32 contractName,
        bytes32 record,
        uint value
    ) external;

    function setUIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        uint[] calldata values
    ) external;

    function setIntValue(
        bytes32 contractName,
        bytes32 record,
        int value
    ) external;

    function setIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        int[] calldata values
    ) external;

    function setAddressValue(
        bytes32 contractName,
        bytes32 record,
        address value
    ) external;

    function setAddressValues(
        bytes32 contractName,
        bytes32[] calldata records,
        address[] calldata values
    ) external;

    function setBoolValue(
        bytes32 contractName,
        bytes32 record,
        bool value
    ) external;

    function setBoolValues(
        bytes32 contractName,
        bytes32[] calldata records,
        bool[] calldata values
    ) external;

    function setBytes32Value(
        bytes32 contractName,
        bytes32 record,
        bytes32 value
    ) external;

    function setBytes32Values(
        bytes32 contractName,
        bytes32[] calldata records,
        bytes32[] calldata values
    ) external;
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinsystemsettings
contract MixinSystemSettings is MixinResolver {
    // must match the one defined SystemSettingsLib, defined in both places due to sol v0.5 limitations
    bytes32 internal constant SETTING_CONTRACT_NAME = "SystemSettings";

    bytes32 internal constant SETTING_WAITING_PERIOD_SECS = "waitingPeriodSecs";
    bytes32 internal constant SETTING_PRICE_DEVIATION_THRESHOLD_FACTOR = "priceDeviationThresholdFactor";
    bytes32 internal constant SETTING_ISSUANCE_RATIO = "issuanceRatio";
    bytes32 internal constant SETTING_FEE_PERIOD_DURATION = "feePeriodDuration";
    bytes32 internal constant SETTING_TARGET_THRESHOLD = "targetThreshold";
    bytes32 internal constant SETTING_LIQUIDATION_DELAY = "liquidationDelay";
    bytes32 internal constant SETTING_LIQUIDATION_RATIO = "liquidationRatio";
    bytes32 internal constant SETTING_LIQUIDATION_ESCROW_DURATION = "liquidationEscrowDuration";
    bytes32 internal constant SETTING_LIQUIDATION_PENALTY = "liquidationPenalty";
    bytes32 internal constant SETTING_SNX_LIQUIDATION_PENALTY = "snxLiquidationPenalty";
    bytes32 internal constant SETTING_SELF_LIQUIDATION_PENALTY = "selfLiquidationPenalty";
    bytes32 internal constant SETTING_FLAG_REWARD = "flagReward";
    bytes32 internal constant SETTING_LIQUIDATE_REWARD = "liquidateReward";
    bytes32 internal constant SETTING_RATE_STALE_PERIOD = "rateStalePeriod";
    /* ========== Exchange Fees Related ========== */
    bytes32 internal constant SETTING_EXCHANGE_FEE_RATE = "exchangeFeeRate";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD = "exchangeDynamicFeeThreshold";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY = "exchangeDynamicFeeWeightDecay";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS = "exchangeDynamicFeeRounds";
    bytes32 internal constant SETTING_EXCHANGE_MAX_DYNAMIC_FEE = "exchangeMaxDynamicFee";
    /* ========== End Exchange Fees Related ========== */
    bytes32 internal constant SETTING_MINIMUM_STAKE_TIME = "minimumStakeTime";
    bytes32 internal constant SETTING_AGGREGATOR_WARNING_FLAGS = "aggregatorWarningFlags";
    bytes32 internal constant SETTING_TRADING_REWARDS_ENABLED = "tradingRewardsEnabled";
    bytes32 internal constant SETTING_DEBT_SNAPSHOT_STALE_TIME = "debtSnapshotStaleTime";
    bytes32 internal constant SETTING_CROSS_DOMAIN_DEPOSIT_GAS_LIMIT = "crossDomainDepositGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_ESCROW_GAS_LIMIT = "crossDomainEscrowGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_REWARD_GAS_LIMIT = "crossDomainRewardGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_WITHDRAWAL_GAS_LIMIT = "crossDomainWithdrawalGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_FEE_PERIOD_CLOSE_GAS_LIMIT = "crossDomainCloseGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_RELAY_GAS_LIMIT = "crossDomainRelayGasLimit";
    bytes32 internal constant SETTING_ETHER_WRAPPER_MAX_ETH = "etherWrapperMaxETH";
    bytes32 internal constant SETTING_ETHER_WRAPPER_MINT_FEE_RATE = "etherWrapperMintFeeRate";
    bytes32 internal constant SETTING_ETHER_WRAPPER_BURN_FEE_RATE = "etherWrapperBurnFeeRate";
    bytes32 internal constant SETTING_WRAPPER_MAX_TOKEN_AMOUNT = "wrapperMaxTokens";
    bytes32 internal constant SETTING_WRAPPER_MINT_FEE_RATE = "wrapperMintFeeRate";
    bytes32 internal constant SETTING_WRAPPER_BURN_FEE_RATE = "wrapperBurnFeeRate";
    bytes32 internal constant SETTING_INTERACTION_DELAY = "interactionDelay";
    bytes32 internal constant SETTING_COLLAPSE_FEE_RATE = "collapseFeeRate";
    bytes32 internal constant SETTING_ATOMIC_MAX_VOLUME_PER_BLOCK = "atomicMaxVolumePerBlock";
    bytes32 internal constant SETTING_ATOMIC_TWAP_WINDOW = "atomicTwapWindow";
    bytes32 internal constant SETTING_ATOMIC_EQUIVALENT_FOR_DEX_PRICING = "atomicEquivalentForDexPricing";
    bytes32 internal constant SETTING_ATOMIC_EXCHANGE_FEE_RATE = "atomicExchangeFeeRate";
    bytes32 internal constant SETTING_ATOMIC_VOLATILITY_CONSIDERATION_WINDOW = "atomicVolConsiderationWindow";
    bytes32 internal constant SETTING_ATOMIC_VOLATILITY_UPDATE_THRESHOLD = "atomicVolUpdateThreshold";
    bytes32 internal constant SETTING_PURE_CHAINLINK_PRICE_FOR_ATOMIC_SWAPS_ENABLED = "pureChainlinkForAtomicsEnabled";
    bytes32 internal constant SETTING_CROSS_SYNTH_TRANSFER_ENABLED = "crossChainSynthTransferEnabled";

    bytes32 internal constant CONTRACT_FLEXIBLESTORAGE = "FlexibleStorage";

    enum CrossDomainMessageGasLimits {Deposit, Escrow, Reward, Withdrawal, CloseFeePeriod, Relay}

    struct DynamicFeeConfig {
        uint threshold;
        uint weightDecay;
        uint rounds;
        uint maxFee;
    }

    constructor(address _resolver) internal MixinResolver(_resolver) {}

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](1);
        addresses[0] = CONTRACT_FLEXIBLESTORAGE;
    }

    function flexibleStorage() internal view returns (IFlexibleStorage) {
        return IFlexibleStorage(requireAndGetAddress(CONTRACT_FLEXIBLESTORAGE));
    }

    function _getGasLimitSetting(CrossDomainMessageGasLimits gasLimitType) internal pure returns (bytes32) {
        if (gasLimitType == CrossDomainMessageGasLimits.Deposit) {
            return SETTING_CROSS_DOMAIN_DEPOSIT_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Escrow) {
            return SETTING_CROSS_DOMAIN_ESCROW_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Reward) {
            return SETTING_CROSS_DOMAIN_REWARD_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Withdrawal) {
            return SETTING_CROSS_DOMAIN_WITHDRAWAL_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Relay) {
            return SETTING_CROSS_DOMAIN_RELAY_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.CloseFeePeriod) {
            return SETTING_CROSS_DOMAIN_FEE_PERIOD_CLOSE_GAS_LIMIT;
        } else {
            revert("Unknown gas limit type");
        }
    }

    function getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits gasLimitType) internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, _getGasLimitSetting(gasLimitType));
    }

    function getTradingRewardsEnabled() internal view returns (bool) {
        return flexibleStorage().getBoolValue(SETTING_CONTRACT_NAME, SETTING_TRADING_REWARDS_ENABLED);
    }

    function getWaitingPeriodSecs() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_WAITING_PERIOD_SECS);
    }

    function getPriceDeviationThresholdFactor() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_PRICE_DEVIATION_THRESHOLD_FACTOR);
    }

    function getIssuanceRatio() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ISSUANCE_RATIO);
    }

    function getFeePeriodDuration() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_FEE_PERIOD_DURATION);
    }

    function getTargetThreshold() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_TARGET_THRESHOLD);
    }

    function getLiquidationDelay() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_DELAY);
    }

    function getLiquidationRatio() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_RATIO);
    }

    function getLiquidationEscrowDuration() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_ESCROW_DURATION);
    }

    function getLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_PENALTY);
    }

    function getSnxLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_SNX_LIQUIDATION_PENALTY);
    }

    function getSelfLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_SELF_LIQUIDATION_PENALTY);
    }

    function getFlagReward() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_FLAG_REWARD);
    }

    function getLiquidateReward() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATE_REWARD);
    }

    function getRateStalePeriod() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_RATE_STALE_PERIOD);
    }

    /* ========== Exchange Related Fees ========== */
    function getExchangeFeeRate(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_EXCHANGE_FEE_RATE, currencyKey))
            );
    }

    /// @notice Get exchange dynamic fee related keys
    /// @return threshold, weight decay, rounds, and max fee
    function getExchangeDynamicFeeConfig() internal view returns (DynamicFeeConfig memory) {
        bytes32[] memory keys = new bytes32[](4);
        keys[0] = SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD;
        keys[1] = SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY;
        keys[2] = SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS;
        keys[3] = SETTING_EXCHANGE_MAX_DYNAMIC_FEE;
        uint[] memory values = flexibleStorage().getUIntValues(SETTING_CONTRACT_NAME, keys);
        return DynamicFeeConfig({threshold: values[0], weightDecay: values[1], rounds: values[2], maxFee: values[3]});
    }

    /* ========== End Exchange Related Fees ========== */

    function getMinimumStakeTime() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_MINIMUM_STAKE_TIME);
    }

    function getAggregatorWarningFlags() internal view returns (address) {
        return flexibleStorage().getAddressValue(SETTING_CONTRACT_NAME, SETTING_AGGREGATOR_WARNING_FLAGS);
    }

    function getDebtSnapshotStaleTime() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_DEBT_SNAPSHOT_STALE_TIME);
    }

    function getEtherWrapperMaxETH() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_MAX_ETH);
    }

    function getEtherWrapperMintFeeRate() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_MINT_FEE_RATE);
    }

    function getEtherWrapperBurnFeeRate() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_BURN_FEE_RATE);
    }

    function getWrapperMaxTokenAmount(address wrapper) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_MAX_TOKEN_AMOUNT, wrapper))
            );
    }

    function getWrapperMintFeeRate(address wrapper) internal view returns (int) {
        return
            flexibleStorage().getIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_MINT_FEE_RATE, wrapper))
            );
    }

    function getWrapperBurnFeeRate(address wrapper) internal view returns (int) {
        return
            flexibleStorage().getIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_BURN_FEE_RATE, wrapper))
            );
    }

    function getInteractionDelay(address collateral) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_INTERACTION_DELAY, collateral))
            );
    }

    function getCollapseFeeRate(address collateral) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_COLLAPSE_FEE_RATE, collateral))
            );
    }

    function getAtomicMaxVolumePerBlock() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ATOMIC_MAX_VOLUME_PER_BLOCK);
    }

    function getAtomicTwapWindow() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ATOMIC_TWAP_WINDOW);
    }

    function getAtomicEquivalentForDexPricing(bytes32 currencyKey) internal view returns (address) {
        return
            flexibleStorage().getAddressValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_EQUIVALENT_FOR_DEX_PRICING, currencyKey))
            );
    }

    function getAtomicExchangeFeeRate(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_EXCHANGE_FEE_RATE, currencyKey))
            );
    }

    function getAtomicVolatilityConsiderationWindow(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_VOLATILITY_CONSIDERATION_WINDOW, currencyKey))
            );
    }

    function getAtomicVolatilityUpdateThreshold(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_VOLATILITY_UPDATE_THRESHOLD, currencyKey))
            );
    }

    function getPureChainlinkPriceForAtomicSwapsEnabled(bytes32 currencyKey) internal view returns (bool) {
        return
            flexibleStorage().getBoolValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_PURE_CHAINLINK_PRICE_FOR_ATOMIC_SWAPS_ENABLED, currencyKey))
            );
    }

    function getCrossChainSynthTransferEnabled(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_CROSS_SYNTH_TRANSFER_ENABLED, currencyKey))
            );
    }

    function getExchangeMaxDynamicFee() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_MAX_DYNAMIC_FEE);
    }

    function getExchangeDynamicFeeRounds() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS);
    }

    function getExchangeDynamicFeeThreshold() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD);
    }

    function getExchangeDynamicFeeWeightDecay() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY);
    }
}


// SPDX-License-Identifier: MIT


/**
 * @dev Wrappers over Solidity's uintXX casting operators with added overflow
 * checks.
 *
 * Downcasting from uint256 in Solidity does not revert on overflow. This can
 * easily result in undesired exploitation or bugs, since developers usually
 * assume that overflows raise errors. `SafeCast` restores this intuition by
 * reverting the transaction when such 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.
 *
 * Can be combined with {SafeMath} to extend it to smaller types, by performing
 * all math on `uint256` and then downcasting.
 */
library SafeCast {
    /**
     * @dev Returns the downcasted uint128 from uint256, reverting on
     * overflow (when the input is greater than largest uint128).
     *
     * Counterpart to Solidity's `uint128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     */
    function toUint128(uint256 value) internal pure returns (uint128) {
        require(value < 2**128, "SafeCast: value doesn't fit in 128 bits");
        return uint128(value);
    }

    /**
     * @dev Returns the downcasted uint64 from uint256, reverting on
     * overflow (when the input is greater than largest uint64).
     *
     * Counterpart to Solidity's `uint64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     */
    function toUint64(uint256 value) internal pure returns (uint64) {
        require(value < 2**64, "SafeCast: value doesn't fit in 64 bits");
        return uint64(value);
    }

    /**
     * @dev Returns the downcasted uint32 from uint256, reverting on
     * overflow (when the input is greater than largest uint32).
     *
     * Counterpart to Solidity's `uint32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     */
    function toUint32(uint256 value) internal pure returns (uint32) {
        require(value < 2**32, "SafeCast: value doesn't fit in 32 bits");
        return uint32(value);
    }

    /**
     * @dev Returns the downcasted uint16 from uint256, reverting on
     * overflow (when the input is greater than largest uint16).
     *
     * Counterpart to Solidity's `uint16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     */
    function toUint16(uint256 value) internal pure returns (uint16) {
        require(value < 2**16, "SafeCast: value doesn't fit in 16 bits");
        return uint16(value);
    }

    /**
     * @dev Returns the downcasted uint8 from uint256, reverting on
     * overflow (when the input is greater than largest uint8).
     *
     * Counterpart to Solidity's `uint8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     */
    function toUint8(uint256 value) internal pure returns (uint8) {
        require(value < 2**8, "SafeCast: value doesn't fit in 8 bits");
        return uint8(value);
    }

    /**
     * @dev Converts a signed int256 into an unsigned uint256.
     *
     * Requirements:
     *
     * - input must be greater than or equal to 0.
     */
    function toUint256(int256 value) internal pure returns (uint256) {
        require(value >= 0, "SafeCast: value must be positive");
        return uint256(value);
    }

    /**
     * @dev Converts an unsigned uint256 into a signed int256.
     *
     * Requirements:
     *
     * - input must be less than or equal to maxInt256.
     */
    function toInt256(uint256 value) internal pure returns (int256) {
        require(value < 2**255, "SafeCast: value doesn't fit in an int256");
        return int256(value);
    }
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }

    /* ---------- Utilities ---------- */
    /*
     * Absolute value of the input, returned as a signed number.
     */
    function signedAbs(int x) internal pure returns (int) {
        return x < 0 ? -x : x;
    }

    /*
     * Absolute value of the input, returned as an unsigned number.
     */
    function abs(int x) internal pure returns (uint) {
        return uint(signedAbs(x));
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/isynthetixdebtshare
interface ISynthetixDebtShare {
    // Views

    function currentPeriodId() external view returns (uint128);

    function allowance(address account, address spender) external view returns (uint);

    function balanceOf(address account) external view returns (uint);

    function balanceOfOnPeriod(address account, uint periodId) external view returns (uint);

    function totalSupply() external view returns (uint);

    function sharePercent(address account) external view returns (uint);

    function sharePercentOnPeriod(address account, uint periodId) external view returns (uint);

    // Mutative functions

    function takeSnapshot(uint128 id) external;

    function mintShare(address account, uint256 amount) external;

    function burnShare(address account, uint256 amount) external;

    function approve(address, uint256) external pure returns (bool);

    function transfer(address to, uint256 amount) external pure returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);

    function addAuthorizedBroker(address target) external;

    function removeAuthorizedBroker(address target) external;

    function addAuthorizedToSnapshot(address target) external;

    function removeAuthorizedToSnapshot(address target) external;
}


interface IVirtualSynth {
    // Views
    function balanceOfUnderlying(address account) external view returns (uint);

    function rate() external view returns (uint);

    function readyToSettle() external view returns (bool);

    function secsLeftInWaitingPeriod() external view returns (uint);

    function settled() external view returns (bool);

    function synth() external view returns (ISynth);

    // Mutative functions
    function settle(address account) external;
}


pragma experimental ABIEncoderV2;


// https://docs.synthetix.io/contracts/source/interfaces/iexchanger
interface IExchanger {
    struct ExchangeEntrySettlement {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint reclaim;
        uint rebate;
        uint srcRoundIdAtPeriodEnd;
        uint destRoundIdAtPeriodEnd;
        uint timestamp;
    }

    struct ExchangeEntry {
        uint sourceRate;
        uint destinationRate;
        uint destinationAmount;
        uint exchangeFeeRate;
        uint exchangeDynamicFeeRate;
        uint roundIdForSrc;
        uint roundIdForDest;
        uint sourceAmountAfterSettlement;
    }

    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view returns (uint);

    function dynamicFeeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint feeRate, bool tooVolatile);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    function lastExchangeRate(bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function exchange(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );
}

// Used to have strongly-typed access to internal mutative functions in Synthetix
interface ISynthetixInternal {
    function emitExchangeTracking(
        bytes32 trackingCode,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        uint256 fee
    ) external;

    function emitSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitAtomicSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitExchangeReclaim(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;

    function emitExchangeRebate(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;
}

interface IExchangerInternalDebtCache {
    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateCachedSynthDebts(bytes32[] calldata currencyKeys) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/idelegateapprovals
interface IDelegateApprovals {
    // Views
    function canBurnFor(address authoriser, address delegate) external view returns (bool);

    function canIssueFor(address authoriser, address delegate) external view returns (bool);

    function canClaimFor(address authoriser, address delegate) external view returns (bool);

    function canExchangeFor(address authoriser, address delegate) external view returns (bool);

    // Mutative
    function approveAllDelegatePowers(address delegate) external;

    function removeAllDelegatePowers(address delegate) external;

    function approveBurnOnBehalf(address delegate) external;

    function removeBurnOnBehalf(address delegate) external;

    function approveIssueOnBehalf(address delegate) external;

    function removeIssueOnBehalf(address delegate) external;

    function approveClaimOnBehalf(address delegate) external;

    function removeClaimOnBehalf(address delegate) external;

    function approveExchangeOnBehalf(address delegate) external;

    function removeExchangeOnBehalf(address delegate) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/IDirectIntegration
interface IDirectIntegrationManager {
    struct ParameterIntegrationSettings {
        bytes32 currencyKey;
        address dexPriceAggregator;
        address atomicEquivalentForDexPricing;
        uint atomicExchangeFeeRate;
        uint atomicTwapWindow;
        uint atomicMaxVolumePerBlock;
        uint atomicVolatilityConsiderationWindow;
        uint atomicVolatilityUpdateThreshold;
        uint exchangeFeeRate;
        uint exchangeMaxDynamicFee;
        uint exchangeDynamicFeeRounds;
        uint exchangeDynamicFeeThreshold;
        uint exchangeDynamicFeeWeightDecay;
    }

    function getExchangeParameters(address integration, bytes32 key)
        external
        view
        returns (ParameterIntegrationSettings memory settings);

    function setExchangeParameters(
        address integration,
        bytes32[] calldata currencyKeys,
        ParameterIntegrationSettings calldata params
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangerates
interface IExchangeRates {
    // Structs
    struct RateAndUpdatedTime {
        uint216 rate;
        uint40 time;
    }

    // Views
    function aggregators(bytes32 currencyKey) external view returns (address);

    function aggregatorWarningFlags() external view returns (address);

    function anyRateIsInvalid(bytes32[] calldata currencyKeys) external view returns (bool);

    function anyRateIsInvalidAtRound(bytes32[] calldata currencyKeys, uint[] calldata roundIds) external view returns (bool);

    function currenciesUsingAggregator(address aggregator) external view returns (bytes32[] memory);

    function effectiveValue(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external view returns (uint value);

    function effectiveValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveValueAndRatesAtRound(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        uint roundIdForSrc,
        uint roundIdForDest
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveAtomicValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function effectiveAtomicValueAndRates(
        IDirectIntegrationManager.ParameterIntegrationSettings calldata sourceSettings,
        uint sourceAmount,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata destinationSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata usdSettings
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function getCurrentRoundId(bytes32 currencyKey) external view returns (uint);

    function getLastRoundIdBeforeElapsedSecs(
        bytes32 currencyKey,
        uint startingRoundId,
        uint startingTimestamp,
        uint timediff
    ) external view returns (uint);

    function lastRateUpdateTimes(bytes32 currencyKey) external view returns (uint256);

    function rateAndTimestampAtRound(bytes32 currencyKey, uint roundId) external view returns (uint rate, uint time);

    function rateAndUpdatedTime(bytes32 currencyKey) external view returns (uint rate, uint time);

    function rateAndInvalid(bytes32 currencyKey) external view returns (uint rate, bool isInvalid);

    function rateForCurrency(bytes32 currencyKey) external view returns (uint);

    function rateIsFlagged(bytes32 currencyKey) external view returns (bool);

    function rateIsInvalid(bytes32 currencyKey) external view returns (bool);

    function rateIsStale(bytes32 currencyKey) external view returns (bool);

    function rateStalePeriod() external view returns (uint);

    function ratesAndUpdatedTimeForCurrencyLastNRounds(
        bytes32 currencyKey,
        uint numRounds,
        uint roundId
    ) external view returns (uint[] memory rates, uint[] memory times);

    function ratesAndInvalidForCurrencies(bytes32[] calldata currencyKeys)
        external
        view
        returns (uint[] memory rates, bool anyRateInvalid);

    function ratesForCurrencies(bytes32[] calldata currencyKeys) external view returns (uint[] memory);

    function synthTooVolatileForAtomicExchange(bytes32 currencyKey) external view returns (bool);

    function synthTooVolatileForAtomicExchange(IDirectIntegrationManager.ParameterIntegrationSettings calldata settings)
        external
        view
        returns (bool);

    function rateWithSafetyChecks(bytes32 currencyKey)
        external
        returns (
            uint rate,
            bool broken,
            bool invalid
        );
}


// https://docs.synthetix.io/contracts/source/interfaces/ICircuitBreaker
interface ICircuitBreaker {
    // Views
    function isInvalid(address oracleAddress, uint value) external view returns (bool);

    function priceDeviationThresholdFactor() external view returns (uint);

    function isDeviationAboveThreshold(uint base, uint comparison) external view returns (bool);

    function lastValue(address oracleAddress) external view returns (uint);

    function circuitBroken(address oracleAddress) external view returns (bool);

    // Mutative functions
    function resetLastValue(address[] calldata oracleAddresses, uint[] calldata values) external;

    function probeCircuitBreaker(address oracleAddress, uint value) external returns (bool circuitBroken);
}


// https://docs.synthetix.io/contracts/source/interfaces/ihasbalance
interface IHasBalance {
    // Views
    function balanceOf(address account) external view returns (uint);
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


interface ILiquidator {
    // Views
    function issuanceRatio() external view returns (uint);

    function liquidationDelay() external view returns (uint);

    function liquidationRatio() external view returns (uint);

    function liquidationEscrowDuration() external view returns (uint);

    function liquidationPenalty() external view returns (uint);

    function selfLiquidationPenalty() external view returns (uint);

    function liquidateReward() external view returns (uint);

    function flagReward() external view returns (uint);

    function liquidationCollateralRatio() external view returns (uint);

    function getLiquidationDeadlineForAccount(address account) external view returns (uint);

    function getLiquidationCallerForAccount(address account) external view returns (address);

    function isLiquidationOpen(address account, bool isSelfLiquidation) external view returns (bool);

    function isLiquidationDeadlinePassed(address account) external view returns (bool);

    function calculateAmountToFixCollateral(
        uint debtBalance,
        uint collateral,
        uint penalty
    ) external view returns (uint);

    function liquidationAmounts(address account, bool isSelfLiquidation)
        external
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint initialDebtBalance
        );

    // Mutative Functions
    function flagAccountForLiquidation(address account) external;

    // Restricted: used internally to Synthetix contracts
    function removeAccountInLiquidation(address account) external;

    function checkAndRemoveAccountInLiquidation(address account) external;
}


interface ILiquidatorRewards {
    // Views

    function earned(address account) external view returns (uint256);

    // Mutative

    function getReward(address account) external;

    function notifyRewardAmount(uint256 reward) external;

    function updateEntry(address account) external;
}


interface ISynthRedeemer {
    // Rate of redemption - 0 for none
    function redemptions(address synthProxy) external view returns (uint redeemRate);

    // sUSD balance of deprecated token holder
    function balanceOf(IERC20 synthProxy, address account) external view returns (uint balanceOfInsUSD);

    // Full sUSD supply of token
    function totalSupply(IERC20 synthProxy) external view returns (uint totalSupplyInsUSD);

    function redeem(IERC20 synthProxy) external;

    function redeemAll(IERC20[] calldata synthProxies) external;

    function redeemPartial(IERC20 synthProxy, uint amountOfSynth) external;

    // Restricted to Issuer
    function deprecate(IERC20 synthProxy, uint rateToRedeem) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/isystemstatus
interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function systemSuspended() external view returns (bool);

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireFuturesActive() external view;

    function requireFuturesMarketActive(bytes32 marketKey) external view;

    function requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function synthSuspended(bytes32 currencyKey) external view returns (bool);

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function systemSuspension() external view returns (bool suspended, uint248 reason);

    function issuanceSuspension() external view returns (bool suspended, uint248 reason);

    function exchangeSuspension() external view returns (bool suspended, uint248 reason);

    function futuresSuspension() external view returns (bool suspended, uint248 reason);

    function synthExchangeSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function futuresMarketSuspension(bytes32 marketKey) external view returns (bool suspended, uint248 reason);

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons);

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    // Restricted functions
    function suspendIssuance(uint256 reason) external;

    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxy
contract Proxy is Owned {
    Proxyable public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(Proxyable _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(_target);
    }

    function _emit(
        bytes calldata callData,
        uint numTopics,
        bytes32 topic1,
        bytes32 topic2,
        bytes32 topic3,
        bytes32 topic4
    ) external onlyTarget {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi).
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
                case 0 {
                    log0(add(_callData, 32), size)
                }
                case 1 {
                    log1(add(_callData, 32), size, topic1)
                }
                case 2 {
                    log2(add(_callData, 32), size, topic1, topic2)
                }
                case 3 {
                    log3(add(_callData, 32), size, topic1, topic2, topic3)
                }
                case 4 {
                    log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
                }
        }
    }

    // solhint-disable no-complex-fallback
    function() external payable {
        // Mutable call setting Proxyable.messageSender as this is using call not delegatecall
        target.setMessageSender(msg.sender);

        assembly {
            let free_ptr := mload(0x40)
            calldatacopy(free_ptr, 0, calldatasize)

            /* We must explicitly forward ether to the underlying contract as well. */
            let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
            returndatacopy(free_ptr, 0, returndatasize)

            if iszero(result) {
                revert(free_ptr, returndatasize)
            }
            return(free_ptr, returndatasize)
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxyable
contract Proxyable is Owned {
    // This contract should be treated like an abstract contract

    /* The proxy this contract exists behind. */
    Proxy public proxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address public messageSender;

    constructor(address payable _proxy) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address payable _proxy) external onlyOwner {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setMessageSender(address sender) external onlyProxy {
        messageSender = sender;
    }

    modifier onlyProxy {
        _onlyProxy();
        _;
    }

    function _onlyProxy() private view {
        require(Proxy(msg.sender) == proxy, "Only the proxy can call");
    }

    modifier optionalProxy {
        _optionalProxy();
        _;
    }

    function _optionalProxy() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
    }

    modifier optionalProxy_onlyOwner {
        _optionalProxy_onlyOwner();
        _;
    }

    // solhint-disable-next-line func-name-mixedcase
    function _optionalProxy_onlyOwner() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
    }

    event ProxyUpdated(address proxyAddress);
}


interface AggregatorInterface {
  function latestAnswer() external view returns (int256);
  function latestTimestamp() external view returns (uint256);
  function latestRound() external view returns (uint256);
  function getAnswer(uint256 roundId) external view returns (int256);
  function getTimestamp(uint256 roundId) external view returns (uint256);

  event AnswerUpdated(int256 indexed current, uint256 indexed roundId, uint256 timestamp);
  event NewRound(uint256 indexed roundId, address indexed startedBy, uint256 startedAt);
}


interface AggregatorV3Interface {

  function decimals() external view returns (uint8);
  function description() external view returns (string memory);
  function version() external view returns (uint256);

  // getRoundData and latestRoundData should both raise "No data present"
  // if they do not have data to report, instead of returning unset values
  // which could be misinterpreted as actual reported values.
  function getRoundData(uint80 _roundId)
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );
  function latestRoundData()
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

}


/**
 * @title The V2 & V3 Aggregator Interface
 * @notice Solidity V0.5 does not allow interfaces to inherit from other
 * interfaces so this contract is a combination of v0.5 AggregatorInterface.sol
 * and v0.5 AggregatorV3Interface.sol.
 */
interface AggregatorV2V3Interface {
  //
  // V2 Interface:
  //
  function latestAnswer() external view returns (int256);
  function latestTimestamp() external view returns (uint256);
  function latestRound() external view returns (uint256);
  function getAnswer(uint256 roundId) external view returns (int256);
  function getTimestamp(uint256 roundId) external view returns (uint256);

  event AnswerUpdated(int256 indexed current, uint256 indexed roundId, uint256 timestamp);
  event NewRound(uint256 indexed roundId, address indexed startedBy, uint256 startedAt);

  //
  // V3 Interface:
  //
  function decimals() external view returns (uint8);
  function description() external view returns (string memory);
  function version() external view returns (uint256);

  // getRoundData and latestRoundData should both raise "No data present"
  // if they do not have data to report, instead of returning unset values
  // which could be misinterpreted as actual reported values.
  function getRoundData(uint80 _roundId)
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );
  function latestRoundData()
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

}


// Inheritance


// Libraries


// Internal references


interface IProxy {
    function target() external view returns (address);
}

interface IIssuerInternalDebtCache {
    function updateCachedSynthDebtWithRate(bytes32 currencyKey, uint currencyRate) external;

    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateDebtCacheValidity(bool currentlyInvalid) external;

    function totalNonSnxBackedDebt() external view returns (uint excludedDebt, bool isInvalid);

    function cacheInfo()
        external
        view
        returns (
            uint cachedDebt,
            uint timestamp,
            bool isInvalid,
            bool isStale
        );

    function updateCachedsUSDDebt(int amount) external;
}

// https://docs.synthetix.io/contracts/source/contracts/issuer
contract Issuer is Owned, MixinSystemSettings, IIssuer {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    bytes32 public constant CONTRACT_NAME = "Issuer";

    // Available Synths which can be used with the system
    ISynth[] public availableSynths;
    mapping(bytes32 => ISynth) public synths;
    mapping(address => bytes32) public synthsByAddress;

    /* ========== ENCODED NAMES ========== */

    bytes32 internal constant sUSD = "sUSD";
    bytes32 internal constant SNX = "SNX";

    // Flexible storage names

    bytes32 internal constant LAST_ISSUE_EVENT = "lastIssueEvent";

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_SYNTHETIX = "Synthetix";
    bytes32 private constant CONTRACT_EXCHANGER = "Exchanger";
    bytes32 private constant CONTRACT_EXRATES = "ExchangeRates";
    bytes32 private constant CONTRACT_CIRCUIT_BREAKER = "CircuitBreaker";
    bytes32 private constant CONTRACT_SYNTHETIXDEBTSHARE = "SynthetixDebtShare";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";
    bytes32 private constant CONTRACT_DELEGATEAPPROVALS = "DelegateApprovals";
    bytes32 private constant CONTRACT_REWARDESCROW_V2 = "RewardEscrowV2";
    bytes32 private constant CONTRACT_LIQUIDATOR = "Liquidator";
    bytes32 private constant CONTRACT_LIQUIDATOR_REWARDS = "LiquidatorRewards";
    bytes32 private constant CONTRACT_DEBTCACHE = "DebtCache";
    bytes32 private constant CONTRACT_SYNTHREDEEMER = "SynthRedeemer";
    bytes32 private constant CONTRACT_SYNTHETIXBRIDGETOOPTIMISM = "SynthetixBridgeToOptimism";
    bytes32 private constant CONTRACT_SYNTHETIXBRIDGETOBASE = "SynthetixBridgeToBase";
    bytes32 private constant CONTRACT_DEBT_MIGRATOR_ON_ETHEREUM = "DebtMigratorOnEthereum";
    bytes32 private constant CONTRACT_DEBT_MIGRATOR_ON_OPTIMISM = "DebtMigratorOnOptimism";

    bytes32 private constant CONTRACT_EXT_AGGREGATOR_ISSUED_SYNTHS = "ext:AggregatorIssuedSynths";
    bytes32 private constant CONTRACT_EXT_AGGREGATOR_DEBT_RATIO = "ext:AggregatorDebtRatio";

    constructor(address _owner, address _resolver) public Owned(_owner) MixinSystemSettings(_resolver) {}

    /* ========== VIEWS ========== */
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = MixinSystemSettings.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](14);
        newAddresses[0] = CONTRACT_SYNTHETIX;
        newAddresses[1] = CONTRACT_EXCHANGER;
        newAddresses[2] = CONTRACT_EXRATES;
        newAddresses[3] = CONTRACT_CIRCUIT_BREAKER;
        newAddresses[4] = CONTRACT_SYNTHETIXDEBTSHARE;
        newAddresses[5] = CONTRACT_FEEPOOL;
        newAddresses[6] = CONTRACT_DELEGATEAPPROVALS;
        newAddresses[7] = CONTRACT_REWARDESCROW_V2;
        newAddresses[8] = CONTRACT_LIQUIDATOR;
        newAddresses[9] = CONTRACT_LIQUIDATOR_REWARDS;
        newAddresses[10] = CONTRACT_DEBTCACHE;
        newAddresses[11] = CONTRACT_SYNTHREDEEMER;
        newAddresses[12] = CONTRACT_EXT_AGGREGATOR_ISSUED_SYNTHS;
        newAddresses[13] = CONTRACT_EXT_AGGREGATOR_DEBT_RATIO;
        return combineArrays(existingAddresses, newAddresses);
    }

    function synthetixERC20() internal view returns (IERC20) {
        return IERC20(requireAndGetAddress(CONTRACT_SYNTHETIX));
    }

    function exchanger() internal view returns (IExchanger) {
        return IExchanger(requireAndGetAddress(CONTRACT_EXCHANGER));
    }

    function exchangeRates() internal view returns (IExchangeRates) {
        return IExchangeRates(requireAndGetAddress(CONTRACT_EXRATES));
    }

    function circuitBreaker() internal view returns (ICircuitBreaker) {
        return ICircuitBreaker(requireAndGetAddress(CONTRACT_CIRCUIT_BREAKER));
    }

    function synthetixDebtShare() internal view returns (ISynthetixDebtShare) {
        return ISynthetixDebtShare(requireAndGetAddress(CONTRACT_SYNTHETIXDEBTSHARE));
    }

    function liquidator() internal view returns (ILiquidator) {
        return ILiquidator(requireAndGetAddress(CONTRACT_LIQUIDATOR));
    }

    function liquidatorRewards() internal view returns (ILiquidatorRewards) {
        return ILiquidatorRewards(requireAndGetAddress(CONTRACT_LIQUIDATOR_REWARDS));
    }

    function delegateApprovals() internal view returns (IDelegateApprovals) {
        return IDelegateApprovals(requireAndGetAddress(CONTRACT_DELEGATEAPPROVALS));
    }

    function rewardEscrowV2() internal view returns (IHasBalance) {
        return IHasBalance(requireAndGetAddress(CONTRACT_REWARDESCROW_V2));
    }

    function debtCache() internal view returns (IIssuerInternalDebtCache) {
        return IIssuerInternalDebtCache(requireAndGetAddress(CONTRACT_DEBTCACHE));
    }

    function synthRedeemer() internal view returns (ISynthRedeemer) {
        return ISynthRedeemer(requireAndGetAddress(CONTRACT_SYNTHREDEEMER));
    }

    function allNetworksDebtInfo()
        public
        view
        returns (
            uint256 debt,
            uint256 sharesSupply,
            bool isStale
        )
    {
        (, int256 rawIssuedSynths, , uint issuedSynthsUpdatedAt, ) =
            _latestRoundData(requireAndGetAddress(CONTRACT_EXT_AGGREGATOR_ISSUED_SYNTHS));

        (uint rawRatio, uint ratioUpdatedAt) = _rawDebtRatioAndUpdatedAt();

        debt = uint(rawIssuedSynths);
        sharesSupply = rawRatio == 0 ? 0 : debt.divideDecimalRoundPrecise(uint(rawRatio));

        uint stalePeriod = getRateStalePeriod();

        isStale =
            stalePeriod < block.timestamp &&
            (block.timestamp - stalePeriod > issuedSynthsUpdatedAt || block.timestamp - stalePeriod > ratioUpdatedAt);
    }

    function issuanceRatio() external view returns (uint) {
        return getIssuanceRatio();
    }

    function _rateAndInvalid(bytes32 currencyKey) internal view returns (uint, bool) {
        return exchangeRates().rateAndInvalid(currencyKey);
    }

    function _latestRoundData(address aggregator)
        internal
        view
        returns (
            uint80,
            int256,
            uint256,
            uint256,
            uint80
        )
    {
        return AggregatorV2V3Interface(aggregator).latestRoundData();
    }

    function _rawDebtRatioAndUpdatedAt() internal view returns (uint, uint) {
        (, int256 rawRatioInt, , uint ratioUpdatedAt, ) =
            _latestRoundData(requireAndGetAddress(CONTRACT_EXT_AGGREGATOR_DEBT_RATIO));
        return (uint(rawRatioInt), ratioUpdatedAt);
    }

    function _sharesForDebt(uint debtAmount) internal view returns (uint) {
        (uint rawRatio, ) = _rawDebtRatioAndUpdatedAt();
        return rawRatio == 0 ? 0 : debtAmount.divideDecimalRoundPrecise(rawRatio);
    }

    function _debtForShares(uint sharesAmount) internal view returns (uint) {
        (uint rawRatio, ) = _rawDebtRatioAndUpdatedAt();
        return sharesAmount.multiplyDecimalRoundPrecise(rawRatio);
    }

    function _debtShareBalanceOf(address account) internal view returns (uint) {
        return synthetixDebtShare().balanceOf(account);
    }

    function _snxBalanceOf(address account) internal view returns (uint) {
        return synthetixERC20().balanceOf(account);
    }

    function _rewardEscrowBalanceOf(address account) internal view returns (uint) {
        return rewardEscrowV2().balanceOf(account);
    }

    function _availableCurrencyKeysWithOptionalSNX(bool withSNX) internal view returns (bytes32[] memory) {
        bytes32[] memory currencyKeys = new bytes32[](availableSynths.length + (withSNX ? 1 : 0));

        for (uint i = 0; i < availableSynths.length; i++) {
            currencyKeys[i] = synthsByAddress[address(availableSynths[i])];
        }

        if (withSNX) {
            currencyKeys[availableSynths.length] = SNX;
        }

        return currencyKeys;
    }

    // Returns the total value of the debt pool in currency specified by `currencyKey`.
    // To return only the SNX-backed debt, set `excludeCollateral` to true.
    function _totalIssuedSynths(bytes32 currencyKey, bool excludeCollateral)
        internal
        view
        returns (uint totalIssued, bool anyRateIsInvalid)
    {
        (uint debt, , bool cacheIsInvalid, bool cacheIsStale) = debtCache().cacheInfo();
        anyRateIsInvalid = cacheIsInvalid || cacheIsStale;

        // Add total issued synths from non snx collateral back into the total if not excluded
        if (!excludeCollateral) {
            (uint nonSnxDebt, bool invalid) = debtCache().totalNonSnxBackedDebt();
            debt = debt.add(nonSnxDebt);
            anyRateIsInvalid = anyRateIsInvalid || invalid;
        }

        if (currencyKey == sUSD) {
            return (debt, anyRateIsInvalid);
        }

        (uint currencyRate, bool currencyRateInvalid) = _rateAndInvalid(currencyKey);
        return (debt.divideDecimalRound(currencyRate), anyRateIsInvalid || currencyRateInvalid);
    }

    function _debtBalanceOfAndTotalDebt(uint debtShareBalance, bytes32 currencyKey)
        internal
        view
        returns (
            uint debtBalance,
            uint totalSystemValue,
            bool anyRateIsInvalid
        )
    {
        // What's the total value of the system excluding ETH backed synths in their requested currency?
        (uint snxBackedAmount, , bool debtInfoStale) = allNetworksDebtInfo();

        if (debtShareBalance == 0) {
            return (0, snxBackedAmount, debtInfoStale);
        }

        // existing functionality requires for us to convert into the exchange rate specified by `currencyKey`
        (uint currencyRate, bool currencyRateInvalid) = _rateAndInvalid(currencyKey);

        debtBalance = _debtForShares(debtShareBalance).divideDecimalRound(currencyRate);
        totalSystemValue = snxBackedAmount;

        anyRateIsInvalid = currencyRateInvalid || debtInfoStale;
    }

    function _canBurnSynths(address account) internal view returns (bool) {
        return now >= _lastIssueEvent(account).add(getMinimumStakeTime());
    }

    function _lastIssueEvent(address account) internal view returns (uint) {
        //  Get the timestamp of the last issue this account made
        return flexibleStorage().getUIntValue(CONTRACT_NAME, keccak256(abi.encodePacked(LAST_ISSUE_EVENT, account)));
    }

    function _remainingIssuableSynths(address _issuer)
        internal
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt,
            bool anyRateIsInvalid
        )
    {
        (alreadyIssued, totalSystemDebt, anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(_debtShareBalanceOf(_issuer), sUSD);
        (uint issuable, bool isInvalid) = _maxIssuableSynths(_issuer);
        maxIssuable = issuable;
        anyRateIsInvalid = anyRateIsInvalid || isInvalid;

        if (alreadyIssued >= maxIssuable) {
            maxIssuable = 0;
        } else {
            maxIssuable = maxIssuable.sub(alreadyIssued);
        }
    }

    function _snxToUSD(uint amount, uint snxRate) internal pure returns (uint) {
        return amount.multiplyDecimalRound(snxRate);
    }

    function _usdToSnx(uint amount, uint snxRate) internal pure returns (uint) {
        return amount.divideDecimalRound(snxRate);
    }

    function _maxIssuableSynths(address _issuer) internal view returns (uint, bool) {
        // What is the value of their SNX balance in sUSD
        (uint snxRate, bool isInvalid) = _rateAndInvalid(SNX);
        uint destinationValue = _snxToUSD(_collateral(_issuer), snxRate);

        // They're allowed to issue up to issuanceRatio of that value
        return (destinationValue.multiplyDecimal(getIssuanceRatio()), isInvalid);
    }

    function _collateralisationRatio(address _issuer) internal view returns (uint, bool) {
        uint totalOwnedSynthetix = _collateral(_issuer);

        (uint debtBalance, , bool anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(_debtShareBalanceOf(_issuer), SNX);

        // it's more gas intensive to put this check here if they have 0 SNX, but it complies with the interface
        if (totalOwnedSynthetix == 0) return (0, anyRateIsInvalid);

        return (debtBalance.divideDecimalRound(totalOwnedSynthetix), anyRateIsInvalid);
    }

    function _collateral(address account) internal view returns (uint) {
        return _snxBalanceOf(account).add(_rewardEscrowBalanceOf(account)).add(liquidatorRewards().earned(account));
    }

    function minimumStakeTime() external view returns (uint) {
        return getMinimumStakeTime();
    }

    function canBurnSynths(address account) external view returns (bool) {
        return _canBurnSynths(account);
    }

    function availableCurrencyKeys() external view returns (bytes32[] memory) {
        return _availableCurrencyKeysWithOptionalSNX(false);
    }

    function availableSynthCount() external view returns (uint) {
        return availableSynths.length;
    }

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid) {
        (, anyRateInvalid) = exchangeRates().ratesAndInvalidForCurrencies(_availableCurrencyKeysWithOptionalSNX(true));
    }

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint totalIssued) {
        (totalIssued, ) = _totalIssuedSynths(currencyKey, excludeOtherCollateral);
    }

    function lastIssueEvent(address account) external view returns (uint) {
        return _lastIssueEvent(account);
    }

    function collateralisationRatio(address _issuer) external view returns (uint cratio) {
        (cratio, ) = _collateralisationRatio(_issuer);
    }

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid)
    {
        return _collateralisationRatio(_issuer);
    }

    function collateral(address account) external view returns (uint) {
        return _collateral(account);
    }

    function debtBalanceOf(address _issuer, bytes32 currencyKey) external view returns (uint debtBalance) {
        // What was their initial debt ownership?
        uint debtShareBalance = _debtShareBalanceOf(_issuer);

        // If it's zero, they haven't issued, and they have no debt.
        if (debtShareBalance == 0) return 0;

        (debtBalance, , ) = _debtBalanceOfAndTotalDebt(debtShareBalance, currencyKey);
    }

    function remainingIssuableSynths(address _issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        )
    {
        (maxIssuable, alreadyIssued, totalSystemDebt, ) = _remainingIssuableSynths(_issuer);
    }

    function maxIssuableSynths(address _issuer) external view returns (uint) {
        (uint maxIssuable, ) = _maxIssuableSynths(_issuer);
        return maxIssuable;
    }

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid)
    {
        // How many SNX do they have, excluding escrow?
        // Note: We're excluding escrow here because we're interested in their transferable amount
        // and escrowed SNX are not transferable.

        // How many of those will be locked by the amount they've issued?
        // Assuming issuance ratio is 20%, then issuing 20 SNX of value would require
        // 100 SNX to be locked in their wallet to maintain their collateralisation ratio
        // The locked synthetix value can exceed their balance.
        uint debtBalance;
        (debtBalance, , anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(_debtShareBalanceOf(account), SNX);
        uint lockedSynthetixValue = debtBalance.divideDecimalRound(getIssuanceRatio());

        // If we exceed the balance, no SNX are transferable, otherwise the difference is.
        if (lockedSynthetixValue >= balance) {
            transferable = 0;
        } else {
            transferable = balance.sub(lockedSynthetixValue);
        }
    }

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory) {
        uint numKeys = currencyKeys.length;
        ISynth[] memory addresses = new ISynth[](numKeys);

        for (uint i = 0; i < numKeys; i++) {
            addresses[i] = synths[currencyKeys[i]];
        }

        return addresses;
    }

    /// @notice Provide the results that would be returned by the mutative liquidateAccount() method (that's reserved to Synthetix)
    /// @param account The account to be liquidated
    /// @param isSelfLiquidation boolean to determine if this is a forced or self-invoked liquidation
    /// @return totalRedeemed the total amount of collateral (SNX) to redeem (liquid and escrow)
    /// @return debtToRemove the amount of debt (sUSD) to burn in order to fix the account's c-ratio
    /// @return escrowToLiquidate the amount of escrow SNX that will be revoked during liquidation
    /// @return initialDebtBalance the amount of initial (sUSD) debt the account has
    function liquidationAmounts(address account, bool isSelfLiquidation)
        external
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint initialDebtBalance
        )
    {
        return _liquidationAmounts(account, isSelfLiquidation);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function _addSynth(ISynth synth) internal {
        bytes32 currencyKey = synth.currencyKey();
        require(synths[currencyKey] == ISynth(0), "Synth exists");
        require(synthsByAddress[address(synth)] == bytes32(0), "Synth address already exists");

        availableSynths.push(synth);
        synths[currencyKey] = synth;
        synthsByAddress[address(synth)] = currencyKey;

        emit SynthAdded(currencyKey, address(synth));
    }

    function addSynth(ISynth synth) external onlyOwner {
        _addSynth(synth);
        // Invalidate the cache to force a snapshot to be recomputed. If a synth were to be added
        // back to the system and it still somehow had cached debt, this would force the value to be
        // updated.
        debtCache().updateDebtCacheValidity(true);
    }

    function addSynths(ISynth[] calldata synthsToAdd) external onlyOwner {
        uint numSynths = synthsToAdd.length;
        for (uint i = 0; i < numSynths; i++) {
            _addSynth(synthsToAdd[i]);
        }

        // Invalidate the cache to force a snapshot to be recomputed.
        debtCache().updateDebtCacheValidity(true);
    }

    function _removeSynth(bytes32 currencyKey) internal {
        address synthToRemove = address(synths[currencyKey]);
        require(synthToRemove != address(0), "Synth does not exist");
        require(currencyKey != sUSD, "Cannot remove synth");

        uint synthSupply = IERC20(synthToRemove).totalSupply();

        if (synthSupply > 0) {
            (uint amountOfsUSD, uint rateToRedeem, ) =
                exchangeRates().effectiveValueAndRates(currencyKey, synthSupply, "sUSD");
            require(rateToRedeem > 0, "Cannot remove without rate");
            ISynthRedeemer _synthRedeemer = synthRedeemer();
            synths[sUSD].issue(address(_synthRedeemer), amountOfsUSD);
            // ensure the debt cache is aware of the new sUSD issued
            debtCache().updateCachedsUSDDebt(SafeCast.toInt256(amountOfsUSD));
            _synthRedeemer.deprecate(IERC20(address(Proxyable(synthToRemove).proxy())), rateToRedeem);
        }

        // Remove the synth from the availableSynths array.
        for (uint i = 0; i < availableSynths.length; i++) {
            if (address(availableSynths[i]) == synthToRemove) {
                delete availableSynths[i];

                // Copy the last synth into the place of the one we just deleted
                // If there's only one synth, this is synths[0] = synths[0].
                // If we're deleting the last one, it's also a NOOP in the same way.
                availableSynths[i] = availableSynths[availableSynths.length - 1];

                // Decrease the size of the array by one.
                availableSynths.length--;

                break;
            }
        }

        // And remove it from the synths mapping
        delete synthsByAddress[synthToRemove];
        delete synths[currencyKey];

        emit SynthRemoved(currencyKey, synthToRemove);
    }

    function removeSynth(bytes32 currencyKey) external onlyOwner {
        // Remove its contribution from the debt pool snapshot, and
        // invalidate the cache to force a new snapshot.
        IIssuerInternalDebtCache cache = debtCache();
        cache.updateCachedSynthDebtWithRate(currencyKey, 0);
        cache.updateDebtCacheValidity(true);

        _removeSynth(currencyKey);
    }

    function removeSynths(bytes32[] calldata currencyKeys) external onlyOwner {
        uint numKeys = currencyKeys.length;

        // Remove their contributions from the debt pool snapshot, and
        // invalidate the cache to force a new snapshot.
        IIssuerInternalDebtCache cache = debtCache();
        uint[] memory zeroRates = new uint[](numKeys);
        cache.updateCachedSynthDebtsWithRates(currencyKeys, zeroRates);
        cache.updateDebtCacheValidity(true);

        for (uint i = 0; i < numKeys; i++) {
            _removeSynth(currencyKeys[i]);
        }
    }

    function issueSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external onlyTrustedMinters returns (bool rateInvalid) {
        require(address(synths[currencyKey]) != address(0), "synth doesn't exist");
        require(amount > 0, "cannot issue 0 synths");

        // record issue timestamp
        _setLastIssueEvent(to);

        // Create their synths
        synths[currencyKey].issue(to, amount);

        // Account for the issued debt in the cache
        (uint rate, bool rateInvalid) = _rateAndInvalid(currencyKey);
        debtCache().updateCachedsUSDDebt(SafeCast.toInt256(amount.multiplyDecimal(rate)));

        // returned so that the caller can decide what to do if the rate is invalid
        return rateInvalid;
    }

    function burnSynthsWithoutDebt(
        bytes32 currencyKey,
        address from,
        uint amount
    ) external onlyTrustedMinters returns (bool rateInvalid) {
        require(address(synths[currencyKey]) != address(0), "synth doesn't exist");
        require(amount > 0, "cannot issue 0 synths");

        exchanger().settle(from, currencyKey);

        // Burn some synths
        synths[currencyKey].burn(from, amount);

        // Account for the burnt debt in the cache. If rate is invalid, the user won't be able to exchange
        (uint rate, bool rateInvalid) = _rateAndInvalid(currencyKey);
        debtCache().updateCachedsUSDDebt(-SafeCast.toInt256(amount.multiplyDecimal(rate)));

        // returned so that the caller can decide what to do if the rate is invalid
        return rateInvalid;
    }

    /**
     * SIP-237: Debt Migration
     * Function used for the one-way migration of all debt and liquid + escrowed SNX from L1 -> L2
     * @param account The address of the account that is being migrated
     * @param amount The amount of debt shares moving across layers
     */
    function modifyDebtSharesForMigration(address account, uint amount) external onlyTrustedMigrators {
        ISynthetixDebtShare sds = synthetixDebtShare();

        if (msg.sender == resolver.getAddress(CONTRACT_DEBT_MIGRATOR_ON_ETHEREUM)) {
            sds.burnShare(account, amount);
        } else if (msg.sender == resolver.getAddress(CONTRACT_DEBT_MIGRATOR_ON_OPTIMISM)) {
            sds.mintShare(account, amount);
        }
    }

    /**
     * Function used to migrate balances from the CollateralShort contract
     * @param short The address of the CollateralShort contract to be upgraded
     * @param amount The amount of sUSD collateral to be burnt
     */
    function upgradeCollateralShort(address short, uint amount) external onlyOwner {
        require(short == resolver.getAddress("CollateralShortLegacy"), "wrong address");
        require(amount > 0, "cannot burn 0 synths");

        exchanger().settle(short, sUSD);

        synths[sUSD].burn(short, amount);
    }

    function issueSynths(address from, uint amount) external onlySynthetix {
        require(amount > 0, "cannot issue 0 synths");

        _issueSynths(from, amount, false);
    }

    function issueMaxSynths(address from) external onlySynthetix {
        _issueSynths(from, 0, true);
    }

    function issueSynthsOnBehalf(
        address issueForAddress,
        address from,
        uint amount
    ) external onlySynthetix {
        _requireCanIssueOnBehalf(issueForAddress, from);
        _issueSynths(issueForAddress, amount, false);
    }

    function issueMaxSynthsOnBehalf(address issueForAddress, address from) external onlySynthetix {
        _requireCanIssueOnBehalf(issueForAddress, from);
        _issueSynths(issueForAddress, 0, true);
    }

    function burnSynths(address from, uint amount) external onlySynthetix {
        _voluntaryBurnSynths(from, amount, false);
    }

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external onlySynthetix {
        _requireCanBurnOnBehalf(burnForAddress, from);
        _voluntaryBurnSynths(burnForAddress, amount, false);
    }

    function burnSynthsToTarget(address from) external onlySynthetix {
        _voluntaryBurnSynths(from, 0, true);
    }

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external onlySynthetix {
        _requireCanBurnOnBehalf(burnForAddress, from);
        _voluntaryBurnSynths(burnForAddress, 0, true);
    }

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external onlySynthRedeemer {
        ISynth(IProxy(deprecatedSynthProxy).target()).burn(account, balance);
    }

    // SIP-148: Upgraded Liquidation Mechanism
    /// @notice This is where the core internal liquidation logic resides. This function can only be invoked by Synthetix.
    /// Reverts if liquidator().isLiquidationOpen() returns false (e.g. c-ratio is too high, delay hasn't passed,
    ///     account wasn't flagged etc)
    /// @param account The account to be liquidated
    /// @param isSelfLiquidation boolean to determine if this is a forced or self-invoked liquidation
    /// @return totalRedeemed the total amount of collateral (SNX) to redeem (liquid and escrow)
    /// @return debtRemoved the amount of debt (sUSD) to burn in order to fix the account's c-ratio
    /// @return escrowToLiquidate the amount of escrow SNX that will be revoked during liquidation
    function liquidateAccount(address account, bool isSelfLiquidation)
        external
        onlySynthetix
        returns (
            uint totalRedeemed,
            uint debtRemoved,
            uint escrowToLiquidate
        )
    {
        require(liquidator().isLiquidationOpen(account, isSelfLiquidation), "Not open for liquidation");

        // liquidationAmounts checks isLiquidationOpen for the account
        uint initialDebtBalance;
        (totalRedeemed, debtRemoved, escrowToLiquidate, initialDebtBalance) = _liquidationAmounts(
            account,
            isSelfLiquidation
        );

        // Reduce debt shares by amount to liquidate.
        _removeFromDebtRegister(account, debtRemoved, initialDebtBalance);

        if (!isSelfLiquidation) {
            // In case of forced liquidation only, remove the liquidation flag.
            liquidator().removeAccountInLiquidation(account);
        }
        // Note: To remove the flag after self liquidation, burn to target and then call Liquidator.checkAndRemoveAccountInLiquidation(account).
    }

    function _liquidationAmounts(address account, bool isSelfLiquidation)
        internal
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint debtBalance
        )
    {
        // Get the account's debt balance
        bool anyRateIsInvalid;
        (debtBalance, , anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(_debtShareBalanceOf(account), sUSD);

        // Get the SNX rate
        (uint snxRate, bool snxRateInvalid) = _rateAndInvalid(SNX);
        _requireRatesNotInvalid(anyRateIsInvalid || snxRateInvalid);

        uint penalty;
        if (isSelfLiquidation) {
            // Get self liquidation penalty
            penalty = getSelfLiquidationPenalty();

            // Calculate the amount of debt to remove and SNX to redeem for a self liquidation
            debtToRemove = liquidator().calculateAmountToFixCollateral(
                debtBalance,
                _snxToUSD(_collateral(account), snxRate),
                penalty
            );

            // Get the minimum values for both totalRedeemed and debtToRemove
            totalRedeemed = _getMinValue(
                _usdToSnx(debtToRemove, snxRate).multiplyDecimal(SafeDecimalMath.unit().add(penalty)),
                _snxBalanceOf(account)
            );
            debtToRemove = _getMinValue(
                _snxToUSD(totalRedeemed, snxRate).divideDecimal(SafeDecimalMath.unit().add(penalty)),
                debtToRemove
            );

            // Return escrow as zero since it cannot be self liquidated
            return (totalRedeemed, debtToRemove, 0, debtBalance);
        } else {
            // In the case of forced Liquidation
            // Get the forced liquidation penalty and sum of the flag and liquidate rewards.
            penalty = getSnxLiquidationPenalty();
            uint rewardsSum = getLiquidateReward().add(getFlagReward());

            // Get the total USD value of their SNX collateral (including escrow and rewards minus the flag and liquidate rewards)
            uint collateralForAccountUSD = _snxToUSD(_collateral(account).sub(rewardsSum), snxRate);

            // Calculate the amount of debt to remove and the sUSD value of the SNX required to liquidate.
            debtToRemove = liquidator().calculateAmountToFixCollateral(debtBalance, collateralForAccountUSD, penalty);
            uint redeemTarget = _usdToSnx(debtToRemove, snxRate).multiplyDecimal(SafeDecimalMath.unit().add(penalty));

            if (redeemTarget.add(rewardsSum) >= _collateral(account)) {
                // need to wipe out the account
                debtToRemove = debtBalance;
                totalRedeemed = _collateral(account).sub(rewardsSum);
                escrowToLiquidate = _rewardEscrowBalanceOf(account);
                return (totalRedeemed, debtToRemove, escrowToLiquidate, debtBalance);
            } else {
                // normal forced liquidation
                (totalRedeemed, escrowToLiquidate) = _redeemableCollateralForTarget(account, redeemTarget, rewardsSum);
                return (totalRedeemed, debtToRemove, escrowToLiquidate, debtBalance);
            }
        }
    }

    // SIP-252
    // calculates the amount of SNX that can be force liquidated (redeemed)
    // for the various cases of transferrable & escrowed collateral
    function _redeemableCollateralForTarget(
        address account,
        uint redeemTarget,
        uint rewardsSum
    ) internal view returns (uint totalRedeemed, uint escrowToLiquidate) {
        // The balanceOf here can be considered "transferable" since it's not escrowed,
        // and it is the only SNX that can potentially be transfered if unstaked.
        uint transferable = _snxBalanceOf(account);
        if (redeemTarget.add(rewardsSum) <= transferable) {
            // transferable is enough
            return (redeemTarget, 0);
        } else {
            // if transferable is not enough
            // need only part of the escrow, add the needed part to redeemed
            escrowToLiquidate = redeemTarget.add(rewardsSum).sub(transferable);
            return (redeemTarget, escrowToLiquidate);
        }
    }

    function _getMinValue(uint x, uint y) internal pure returns (uint) {
        return x < y ? x : y;
    }

    function setCurrentPeriodId(uint128 periodId) external {
        require(msg.sender == requireAndGetAddress(CONTRACT_FEEPOOL), "Must be fee pool");

        ISynthetixDebtShare sds = synthetixDebtShare();

        if (sds.currentPeriodId() < periodId) {
            sds.takeSnapshot(periodId);
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _requireRatesNotInvalid(bool anyRateIsInvalid) internal pure {
        require(!anyRateIsInvalid, "A synth or SNX rate is invalid");
    }

    function _requireCanIssueOnBehalf(address issueForAddress, address from) internal view {
        require(delegateApprovals().canIssueFor(issueForAddress, from), "Not approved to act on behalf");
    }

    function _requireCanBurnOnBehalf(address burnForAddress, address from) internal view {
        require(delegateApprovals().canBurnFor(burnForAddress, from), "Not approved to act on behalf");
    }

    function _issueSynths(
        address from,
        uint amount,
        bool issueMax
    ) internal {
        if (_verifyCircuitBreakers()) {
            return;
        }

        (uint maxIssuable, , , bool anyRateIsInvalid) = _remainingIssuableSynths(from);
        _requireRatesNotInvalid(anyRateIsInvalid);

        if (!issueMax) {
            require(amount <= maxIssuable, "Amount too large");
        } else {
            amount = maxIssuable;
        }

        // Keep track of the debt they're about to create
        _addToDebtRegister(from, amount);

        // record issue timestamp
        _setLastIssueEvent(from);

        // Create their synths
        synths[sUSD].issue(from, amount);

        // Account for the issued debt in the cache
        debtCache().updateCachedsUSDDebt(SafeCast.toInt256(amount));
    }

    function _burnSynths(
        address debtAccount,
        address burnAccount,
        uint amount,
        uint existingDebt
    ) internal returns (uint amountBurnt) {
        if (_verifyCircuitBreakers()) {
            return 0;
        }

        // liquidation requires sUSD to be already settled / not in waiting period

        // If they're trying to burn more debt than they actually owe, rather than fail the transaction, let's just
        // clear their debt and leave them be.
        amountBurnt = existingDebt < amount ? existingDebt : amount;

        // Remove liquidated debt from the ledger
        _removeFromDebtRegister(debtAccount, amountBurnt, existingDebt);

        // synth.burn does a safe subtraction on balance (so it will revert if there are not enough synths).
        synths[sUSD].burn(burnAccount, amountBurnt);

        // Account for the burnt debt in the cache.
        debtCache().updateCachedsUSDDebt(-SafeCast.toInt256(amountBurnt));
    }

    // If burning to target, `amount` is ignored, and the correct quantity of sUSD is burnt to reach the target
    // c-ratio, allowing fees to be claimed. In this case, pending settlements will be skipped as the user
    // will still have debt remaining after reaching their target.
    function _voluntaryBurnSynths(
        address from,
        uint amount,
        bool burnToTarget
    ) internal {
        if (_verifyCircuitBreakers()) {
            return;
        }

        if (!burnToTarget) {
            // If not burning to target, then burning requires that the minimum stake time has elapsed.
            require(_canBurnSynths(from), "Minimum stake time not reached");
            // First settle anything pending into sUSD as burning or issuing impacts the size of the debt pool
            (, uint refunded, uint numEntriesSettled) = exchanger().settle(from, sUSD);
            if (numEntriesSettled > 0) {
                amount = exchanger().calculateAmountAfterSettlement(from, sUSD, amount, refunded);
            }
        }

        (uint existingDebt, , bool anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(_debtShareBalanceOf(from), sUSD);
        (uint maxIssuableSynthsForAccount, bool snxRateInvalid) = _maxIssuableSynths(from);
        _requireRatesNotInvalid(anyRateIsInvalid || snxRateInvalid);
        require(existingDebt > 0, "No debt to forgive");

        if (burnToTarget) {
            amount = existingDebt.sub(maxIssuableSynthsForAccount);
        }

        uint amountBurnt = _burnSynths(from, from, amount, existingDebt);

        // Check and remove liquidation if existingDebt after burning is <= maxIssuableSynths
        // Issuance ratio is fixed so should remove any liquidations
        if (existingDebt.sub(amountBurnt) <= maxIssuableSynthsForAccount) {
            liquidator().removeAccountInLiquidation(from);
        }
    }

    function _setLastIssueEvent(address account) internal {
        // Set the timestamp of the last issueSynths
        flexibleStorage().setUIntValue(
            CONTRACT_NAME,
            keccak256(abi.encodePacked(LAST_ISSUE_EVENT, account)),
            block.timestamp
        );
    }

    function _addToDebtRegister(address from, uint amount) internal {
        // important: this has to happen before any updates to user's debt shares
        liquidatorRewards().updateEntry(from);

        ISynthetixDebtShare sds = synthetixDebtShare();

        // it is possible (eg in tests, system initialized with extra debt) to have issued debt without any shares issued
        // in which case, the first account to mint gets the debt. yw.
        uint debtShares = _sharesForDebt(amount);
        if (debtShares == 0) {
            sds.mintShare(from, amount);
        } else {
            sds.mintShare(from, debtShares);
        }
    }

    function _removeFromDebtRegister(
        address from,
        uint debtToRemove,
        uint existingDebt
    ) internal {
        // important: this has to happen before any updates to user's debt shares
        liquidatorRewards().updateEntry(from);

        ISynthetixDebtShare sds = synthetixDebtShare();

        uint currentDebtShare = _debtShareBalanceOf(from);

        if (debtToRemove == existingDebt) {
            sds.burnShare(from, currentDebtShare);
        } else {
            uint sharesToRemove = _sharesForDebt(debtToRemove);
            sds.burnShare(from, sharesToRemove < currentDebtShare ? sharesToRemove : currentDebtShare);
        }
    }

    // trips the breaker and returns boolean, where true means the breaker has tripped state
    function _verifyCircuitBreakers() internal returns (bool) {
        address debtRatioAggregator = requireAndGetAddress(CONTRACT_EXT_AGGREGATOR_DEBT_RATIO);
        (, int256 rawRatio, , , ) = AggregatorV2V3Interface(debtRatioAggregator).latestRoundData();
        (, bool broken, ) = exchangeRates().rateWithSafetyChecks(SNX);

        return circuitBreaker().probeCircuitBreaker(debtRatioAggregator, uint(rawRatio)) || broken;
    }

    /* ========== MODIFIERS ========== */
    modifier onlySynthetix() {
        require(msg.sender == address(synthetixERC20()), "Only Synthetix");
        _;
    }

    modifier onlyTrustedMinters() {
        address bridgeL1 = resolver.getAddress(CONTRACT_SYNTHETIXBRIDGETOOPTIMISM);
        address bridgeL2 = resolver.getAddress(CONTRACT_SYNTHETIXBRIDGETOBASE);
        address feePool = resolver.getAddress(CONTRACT_FEEPOOL);
        require(msg.sender == bridgeL1 || msg.sender == bridgeL2 || msg.sender == feePool, "only trusted minters");
        _;
    }

    modifier onlyTrustedMigrators() {
        address migratorL1 = resolver.getAddress(CONTRACT_DEBT_MIGRATOR_ON_ETHEREUM);
        address migratorL2 = resolver.getAddress(CONTRACT_DEBT_MIGRATOR_ON_OPTIMISM);
        require(msg.sender == migratorL1 || msg.sender == migratorL2, "only trusted migrators");
        require(migratorL1 == address(0) || migratorL2 == address(0), "one migrator must be 0x0");
        _;
    }

    function _onlySynthRedeemer() internal view {
        require(msg.sender == address(synthRedeemer()), "Only SynthRedeemer");
    }

    modifier onlySynthRedeemer() {
        _onlySynthRedeemer();
        _;
    }

    /* ========== EVENTS ========== */

    event SynthAdded(bytes32 currencyKey, address synth);
    event SynthRemoved(bytes32 currencyKey, address synth);
}

    

/*

⚠⚠⚠ WARNING WARNING WARNING ⚠⚠⚠

This is a TARGET contract - DO NOT CONNECT TO IT DIRECTLY IN YOUR CONTRACTS or DAPPS!

This contract has an associated PROXY that MUST be used for all integrations - this TARGET will be REPLACED in an upcoming Synthetix release!
The proxy can be found by looking up the PROXY property on this contract.

*//*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: MultiCollateralSynth.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/MultiCollateralSynth.sol
* Docs: https://docs.synthetix.io/contracts/MultiCollateralSynth
*
* Contract Dependencies: 
*	- ExternStateToken
*	- IAddressResolver
*	- IERC20
*	- ISynth
*	- MixinResolver
*	- Owned
*	- Proxyable
*	- State
*	- Synth
* Libraries: 
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2022 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxy
contract Proxy is Owned {
    Proxyable public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(Proxyable _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(_target);
    }

    function _emit(
        bytes calldata callData,
        uint numTopics,
        bytes32 topic1,
        bytes32 topic2,
        bytes32 topic3,
        bytes32 topic4
    ) external onlyTarget {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi).
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
                case 0 {
                    log0(add(_callData, 32), size)
                }
                case 1 {
                    log1(add(_callData, 32), size, topic1)
                }
                case 2 {
                    log2(add(_callData, 32), size, topic1, topic2)
                }
                case 3 {
                    log3(add(_callData, 32), size, topic1, topic2, topic3)
                }
                case 4 {
                    log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
                }
        }
    }

    // solhint-disable no-complex-fallback
    function() external payable {
        // Mutable call setting Proxyable.messageSender as this is using call not delegatecall
        target.setMessageSender(msg.sender);

        assembly {
            let free_ptr := mload(0x40)
            calldatacopy(free_ptr, 0, calldatasize)

            /* We must explicitly forward ether to the underlying contract as well. */
            let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
            returndatacopy(free_ptr, 0, returndatasize)

            if iszero(result) {
                revert(free_ptr, returndatasize)
            }
            return(free_ptr, returndatasize)
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxyable
contract Proxyable is Owned {
    // This contract should be treated like an abstract contract

    /* The proxy this contract exists behind. */
    Proxy public proxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address public messageSender;

    constructor(address payable _proxy) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address payable _proxy) external onlyOwner {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setMessageSender(address sender) external onlyProxy {
        messageSender = sender;
    }

    modifier onlyProxy {
        _onlyProxy();
        _;
    }

    function _onlyProxy() private view {
        require(Proxy(msg.sender) == proxy, "Only the proxy can call");
    }

    modifier optionalProxy {
        _optionalProxy();
        _;
    }

    function _optionalProxy() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
    }

    modifier optionalProxy_onlyOwner {
        _optionalProxy_onlyOwner();
        _;
    }

    // solhint-disable-next-line func-name-mixedcase
    function _optionalProxy_onlyOwner() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }

    /* ---------- Utilities ---------- */
    /*
     * Absolute value of the input, returned as a signed number.
     */
    function signedAbs(int x) internal pure returns (int) {
        return x < 0 ? -x : x;
    }

    /*
     * Absolute value of the input, returned as an unsigned number.
     */
    function abs(int x) internal pure returns (uint) {
        return uint(signedAbs(x));
    }
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/state
contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;

    constructor(address _associatedContract) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract) external onlyOwner {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract {
        require(msg.sender == associatedContract, "Only the associated contract can perform this action");
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address associatedContract);
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/tokenstate
contract TokenState is Owned, State {
    /* ERC20 fields. */
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    constructor(address _owner, address _associatedContract) public Owned(_owner) State(_associatedContract) {}

    /* ========== SETTERS ========== */

    /**
     * @notice Set ERC20 allowance.
     * @dev Only the associated contract may call this.
     * @param tokenOwner The authorising party.
     * @param spender The authorised party.
     * @param value The total value the authorised party may spend on the
     * authorising party's behalf.
     */
    function setAllowance(
        address tokenOwner,
        address spender,
        uint value
    ) external onlyAssociatedContract {
        allowance[tokenOwner][spender] = value;
    }

    /**
     * @notice Set the balance in a given account
     * @dev Only the associated contract may call this.
     * @param account The account whose value to set.
     * @param value The new balance of the given account.
     */
    function setBalanceOf(address account, uint value) external onlyAssociatedContract {
        balanceOf[account] = value;
    }
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/externstatetoken
contract ExternStateToken is Owned, Proxyable {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /* ========== STATE VARIABLES ========== */

    /* Stores balances and allowances. */
    TokenState public tokenState;

    /* Other ERC20 fields. */
    string public name;
    string public symbol;
    uint public totalSupply;
    uint8 public decimals;

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _name,
        string memory _symbol,
        uint _totalSupply,
        uint8 _decimals,
        address _owner
    ) public Owned(_owner) Proxyable(_proxy) {
        tokenState = _tokenState;

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

    /* ========== VIEWS ========== */

    /**
     * @notice Returns the ERC20 allowance of one party to spend on behalf of another.
     * @param owner The party authorising spending of their funds.
     * @param spender The party spending tokenOwner's funds.
     */
    function allowance(address owner, address spender) public view returns (uint) {
        return tokenState.allowance(owner, spender);
    }

    /**
     * @notice Returns the ERC20 token balance of a given account.
     */
    function balanceOf(address account) external view returns (uint) {
        return tokenState.balanceOf(account);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    /**
     * @notice Set the address of the TokenState contract.
     * @dev This can be used to "pause" transfer functionality, by pointing the tokenState at 0x000..
     * as balances would be unreachable.
     */
    function setTokenState(TokenState _tokenState) external optionalProxy_onlyOwner {
        tokenState = _tokenState;
        emitTokenStateUpdated(address(_tokenState));
    }

    function _internalTransfer(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Disallow transfers to irretrievable-addresses. */
        require(to != address(0) && to != address(this) && to != address(proxy), "Cannot transfer to this address");

        // Insufficient balance will be handled by the safe subtraction.
        tokenState.setBalanceOf(from, tokenState.balanceOf(from).sub(value));
        tokenState.setBalanceOf(to, tokenState.balanceOf(to).add(value));

        // Emit a standard ERC20 transfer event
        emitTransfer(from, to, value);

        return true;
    }

    /**
     * @dev Perform an ERC20 token transfer. Designed to be called by transfer functions possessing
     * the onlyProxy or optionalProxy modifiers.
     */
    function _transferByProxy(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        return _internalTransfer(from, to, value);
    }

    /*
     * @dev Perform an ERC20 token transferFrom. Designed to be called by transferFrom functions
     * possessing the optionalProxy or optionalProxy modifiers.
     */
    function _transferFromByProxy(
        address sender,
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Insufficient allowance will be handled by the safe subtraction. */
        tokenState.setAllowance(from, sender, tokenState.allowance(from, sender).sub(value));
        return _internalTransfer(from, to, value);
    }

    /**
     * @notice Approves spender to transfer on the message sender's behalf.
     */
    function approve(address spender, uint value) public optionalProxy returns (bool) {
        address sender = messageSender;

        tokenState.setAllowance(sender, spender, value);
        emitApproval(sender, spender, value);
        return true;
    }

    /* ========== EVENTS ========== */
    function addressToBytes32(address input) internal pure returns (bytes32) {
        return bytes32(uint256(uint160(input)));
    }

    event Transfer(address indexed from, address indexed to, uint value);
    bytes32 internal constant TRANSFER_SIG = keccak256("Transfer(address,address,uint256)");

    function emitTransfer(
        address from,
        address to,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, TRANSFER_SIG, addressToBytes32(from), addressToBytes32(to), 0);
    }

    event Approval(address indexed owner, address indexed spender, uint value);
    bytes32 internal constant APPROVAL_SIG = keccak256("Approval(address,address,uint256)");

    function emitApproval(
        address owner,
        address spender,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, APPROVAL_SIG, addressToBytes32(owner), addressToBytes32(spender), 0);
    }

    event TokenStateUpdated(address newTokenState);
    bytes32 internal constant TOKENSTATEUPDATED_SIG = keccak256("TokenStateUpdated(address)");

    function emitTokenStateUpdated(address newTokenState) internal {
        proxy._emit(abi.encode(newTokenState), 1, TOKENSTATEUPDATED_SIG, 0, 0, 0);
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views

    function allNetworksDebtInfo()
        external
        view
        returns (
            uint256 debt,
            uint256 sharesSupply,
            bool isStale
        );

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    // Restricted: used internally to Synthetix
    function addSynths(ISynth[] calldata synthsToAdd) external;

    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external;

    function setCurrentPeriodId(uint128 periodId) external;

    function liquidateAccount(address account, bool isSelfLiquidation)
        external
        returns (uint totalRedeemed, uint amountToLiquidate);

    function issueSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);

    function burnSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination =
                resolver.requireAndGetAddress(name, string(abi.encodePacked("Resolver missing target: ", name)));
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


// https://docs.synthetix.io/contracts/source/interfaces/isystemstatus
interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function systemSuspended() external view returns (bool);

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireFuturesActive() external view;

    function requireFuturesMarketActive(bytes32 marketKey) external view;

    function requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function synthSuspended(bytes32 currencyKey) external view returns (bool);

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function systemSuspension() external view returns (bool suspended, uint248 reason);

    function issuanceSuspension() external view returns (bool suspended, uint248 reason);

    function exchangeSuspension() external view returns (bool suspended, uint248 reason);

    function futuresSuspension() external view returns (bool suspended, uint248 reason);

    function synthExchangeSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function futuresMarketSuspension(bytes32 marketKey) external view returns (bool suspended, uint248 reason);

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons);

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    // Restricted functions
    function suspendIssuance(uint256 reason) external;

    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/ifeepool
interface IFeePool {
    // Views

    // solhint-disable-next-line func-name-mixedcase
    function FEE_ADDRESS() external view returns (address);

    function feesAvailable(address account) external view returns (uint, uint);

    function feePeriodDuration() external view returns (uint);

    function isFeesClaimable(address account) external view returns (bool);

    function targetThreshold() external view returns (uint);

    function totalFeesAvailable() external view returns (uint);

    function totalRewardsAvailable() external view returns (uint);

    // Mutative Functions
    function claimFees() external returns (bool);

    function claimOnBehalf(address claimingForAddress) external returns (bool);

    function closeCurrentFeePeriod() external;

    function closeSecondary(uint snxBackedDebt, uint debtShareSupply) external;

    function recordFeePaid(uint sUSDAmount) external;

    function setRewardsToDistribute(uint amount) external;
}


interface IVirtualSynth {
    // Views
    function balanceOfUnderlying(address account) external view returns (uint);

    function rate() external view returns (uint);

    function readyToSettle() external view returns (bool);

    function secsLeftInWaitingPeriod() external view returns (uint);

    function settled() external view returns (bool);

    function synth() external view returns (ISynth);

    // Mutative functions
    function settle(address account) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchanger
interface IExchanger {
    struct ExchangeEntrySettlement {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint reclaim;
        uint rebate;
        uint srcRoundIdAtPeriodEnd;
        uint destRoundIdAtPeriodEnd;
        uint timestamp;
    }

    struct ExchangeEntry {
        uint sourceRate;
        uint destinationRate;
        uint destinationAmount;
        uint exchangeFeeRate;
        uint exchangeDynamicFeeRate;
        uint roundIdForSrc;
        uint roundIdForDest;
    }

    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view returns (uint);

    function dynamicFeeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint feeRate, bool tooVolatile);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    function lastExchangeRate(bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function exchange(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    function suspendSynthWithInvalidRate(bytes32 currencyKey) external;
}


interface IFuturesMarketManager {
    function markets(uint index, uint pageSize) external view returns (address[] memory);

    function numMarkets() external view returns (uint);

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

    function marketForKey(bytes32 marketKey) external view returns (address);

    function marketsForKeys(bytes32[] calldata marketKeys) external view returns (address[] memory);

    function totalDebt() external view returns (uint debt, bool isInvalid);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/synth
contract Synth is Owned, IERC20, ExternStateToken, MixinResolver, ISynth {
    bytes32 public constant CONTRACT_NAME = "Synth";

    /* ========== STATE VARIABLES ========== */

    // Currency key which identifies this Synth to the Synthetix system
    bytes32 public currencyKey;

    uint8 public constant DECIMALS = 18;

    // Where fees are pooled in sUSD
    address public constant FEE_ADDRESS = 0xfeEFEEfeefEeFeefEEFEEfEeFeefEEFeeFEEFEeF;

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 private constant CONTRACT_EXCHANGER = "Exchanger";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";
    bytes32 private constant CONTRACT_FUTURESMARKETMANAGER = "FuturesMarketManager";

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _tokenName,
        string memory _tokenSymbol,
        address _owner,
        bytes32 _currencyKey,
        uint _totalSupply,
        address _resolver
    )
        public
        ExternStateToken(_proxy, _tokenState, _tokenName, _tokenSymbol, _totalSupply, DECIMALS, _owner)
        MixinResolver(_resolver)
    {
        require(_proxy != address(0), "_proxy cannot be 0");
        require(_owner != address(0), "_owner cannot be 0");

        currencyKey = _currencyKey;
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function transfer(address to, uint value) public onlyProxyOrInternal returns (bool) {
        _ensureCanTransfer(messageSender, value);

        // transfers to FEE_ADDRESS will be exchanged into sUSD and recorded as fee
        if (to == FEE_ADDRESS) {
            return _transferToFeeAddress(to, value);
        }

        // transfers to 0x address will be burned
        if (to == address(0)) {
            return _internalBurn(messageSender, value);
        }

        return super._internalTransfer(messageSender, to, value);
    }

    function transferAndSettle(address to, uint value) public onlyProxyOrInternal returns (bool) {
        // Exchanger.settle ensures synth is active
        (, , uint numEntriesSettled) = exchanger().settle(messageSender, currencyKey);

        // Save gas instead of calling transferableSynths
        uint balanceAfter = value;

        if (numEntriesSettled > 0) {
            balanceAfter = tokenState.balanceOf(messageSender);
        }

        // Reduce the value to transfer if balance is insufficient after reclaimed
        value = value > balanceAfter ? balanceAfter : value;

        return super._internalTransfer(messageSender, to, value);
    }

    function transferFrom(
        address from,
        address to,
        uint value
    ) public onlyProxyOrInternal returns (bool) {
        _ensureCanTransfer(from, value);

        return _internalTransferFrom(from, to, value);
    }

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) public onlyProxyOrInternal returns (bool) {
        // Exchanger.settle() ensures synth is active
        (, , uint numEntriesSettled) = exchanger().settle(from, currencyKey);

        // Save gas instead of calling transferableSynths
        uint balanceAfter = value;

        if (numEntriesSettled > 0) {
            balanceAfter = tokenState.balanceOf(from);
        }

        // Reduce the value to transfer if balance is insufficient after reclaimed
        value = value >= balanceAfter ? balanceAfter : value;

        return _internalTransferFrom(from, to, value);
    }

    /**
     * @notice _transferToFeeAddress function
     * non-sUSD synths are exchanged into sUSD via synthInitiatedExchange
     * notify feePool to record amount as fee paid to feePool */
    function _transferToFeeAddress(address to, uint value) internal returns (bool) {
        uint amountInUSD;

        // sUSD can be transferred to FEE_ADDRESS directly
        if (currencyKey == "sUSD") {
            amountInUSD = value;
            super._internalTransfer(messageSender, to, value);
        } else {
            // else exchange synth into sUSD and send to FEE_ADDRESS
            (amountInUSD, ) = exchanger().exchange(
                messageSender,
                messageSender,
                currencyKey,
                value,
                "sUSD",
                FEE_ADDRESS,
                false,
                address(0),
                bytes32(0)
            );
        }

        // Notify feePool to record sUSD to distribute as fees
        feePool().recordFeePaid(amountInUSD);

        return true;
    }

    function issue(address account, uint amount) external onlyInternalContracts {
        _internalIssue(account, amount);
    }

    function burn(address account, uint amount) external onlyInternalContracts {
        _internalBurn(account, amount);
    }

    function _internalIssue(address account, uint amount) internal {
        tokenState.setBalanceOf(account, tokenState.balanceOf(account).add(amount));
        totalSupply = totalSupply.add(amount);
        emitTransfer(address(0), account, amount);
        emitIssued(account, amount);
    }

    function _internalBurn(address account, uint amount) internal returns (bool) {
        tokenState.setBalanceOf(account, tokenState.balanceOf(account).sub(amount));
        totalSupply = totalSupply.sub(amount);
        emitTransfer(account, address(0), amount);
        emitBurned(account, amount);

        return true;
    }

    // Allow owner to set the total supply on import.
    function setTotalSupply(uint amount) external optionalProxy_onlyOwner {
        totalSupply = amount;
    }

    /* ========== VIEWS ========== */

    // Note: use public visibility so that it can be invoked in a subclass
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](5);
        addresses[0] = CONTRACT_SYSTEMSTATUS;
        addresses[1] = CONTRACT_EXCHANGER;
        addresses[2] = CONTRACT_ISSUER;
        addresses[3] = CONTRACT_FEEPOOL;
        addresses[4] = CONTRACT_FUTURESMARKETMANAGER;
    }

    function systemStatus() internal view returns (ISystemStatus) {
        return ISystemStatus(requireAndGetAddress(CONTRACT_SYSTEMSTATUS));
    }

    function feePool() internal view returns (IFeePool) {
        return IFeePool(requireAndGetAddress(CONTRACT_FEEPOOL));
    }

    function exchanger() internal view returns (IExchanger) {
        return IExchanger(requireAndGetAddress(CONTRACT_EXCHANGER));
    }

    function issuer() internal view returns (IIssuer) {
        return IIssuer(requireAndGetAddress(CONTRACT_ISSUER));
    }

    function futuresMarketManager() internal view returns (IFuturesMarketManager) {
        return IFuturesMarketManager(requireAndGetAddress(CONTRACT_FUTURESMARKETMANAGER));
    }

    function _ensureCanTransfer(address from, uint value) internal view {
        require(exchanger().maxSecsLeftInWaitingPeriod(from, currencyKey) == 0, "Cannot transfer during waiting period");
        require(transferableSynths(from) >= value, "Insufficient balance after any settlement owing");
        systemStatus().requireSynthActive(currencyKey);
    }

    function transferableSynths(address account) public view returns (uint) {
        (uint reclaimAmount, , ) = exchanger().settlementOwing(account, currencyKey);

        // Note: ignoring rebate amount here because a settle() is required in order to
        // allow the transfer to actually work

        uint balance = tokenState.balanceOf(account);

        if (reclaimAmount > balance) {
            return 0;
        } else {
            return balance.sub(reclaimAmount);
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _internalTransferFrom(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        // Skip allowance update in case of infinite allowance
        if (tokenState.allowance(from, messageSender) != uint(-1)) {
            // Reduce the allowance by the amount we're transferring.
            // The safeSub call will handle an insufficient allowance.
            tokenState.setAllowance(from, messageSender, tokenState.allowance(from, messageSender).sub(value));
        }

        return super._internalTransfer(from, to, value);
    }

    /* ========== MODIFIERS ========== */

    function _isInternalContract(address account) internal view returns (bool) {
        return
            account == address(feePool()) ||
            account == address(exchanger()) ||
            account == address(issuer()) ||
            account == address(futuresMarketManager());
    }

    modifier onlyInternalContracts() {
        require(_isInternalContract(msg.sender), "Only internal contracts allowed");
        _;
    }

    modifier onlyProxyOrInternal {
        _onlyProxyOrInternal();
        _;
    }

    function _onlyProxyOrInternal() internal {
        if (msg.sender == address(proxy)) {
            // allow proxy through, messageSender should be already set correctly
            return;
        } else if (_isInternalTransferCaller(msg.sender)) {
            // optionalProxy behaviour only for the internal legacy contracts
            messageSender = msg.sender;
        } else {
            revert("Only the proxy can call");
        }
    }

    /// some legacy internal contracts use transfer methods directly on implementation
    /// which isn't supported due to SIP-238 for other callers
    function _isInternalTransferCaller(address caller) internal view returns (bool) {
        // These entries are not required or cached in order to allow them to not exist (==address(0))
        // e.g. due to not being available on L2 or at some future point in time.
        return
            // ordered to reduce gas for more frequent calls
            caller == resolver.getAddress("CollateralShort") ||
            // not used frequently
            caller == resolver.getAddress("SynthRedeemer") ||
            caller == resolver.getAddress("WrapperFactory") || // transfer not used by users
            // legacy
            caller == resolver.getAddress("NativeEtherWrapper") ||
            caller == resolver.getAddress("Depot");
    }

    /* ========== EVENTS ========== */
    event Issued(address indexed account, uint value);

    bytes32 private constant ISSUED_SIG = keccak256("Issued(address,uint256)");

    function emitIssued(address account, uint value) internal {
        proxy._emit(abi.encode(value), 2, ISSUED_SIG, addressToBytes32(account), 0, 0);
    }

    event Burned(address indexed account, uint value);

    bytes32 private constant BURNED_SIG = keccak256("Burned(address,uint256)");

    function emitBurned(address account, uint value) internal {
        proxy._emit(abi.encode(value), 2, BURNED_SIG, addressToBytes32(account), 0, 0);
    }
}


interface ICollateralManager {
    // Manager information
    function hasCollateral(address collateral) external view returns (bool);

    function isSynthManaged(bytes32 currencyKey) external view returns (bool);

    // State information
    function long(bytes32 synth) external view returns (uint amount);

    function short(bytes32 synth) external view returns (uint amount);

    function totalLong() external view returns (uint susdValue, bool anyRateIsInvalid);

    function totalShort() external view returns (uint susdValue, bool anyRateIsInvalid);

    function getBorrowRate() external view returns (uint borrowRate, bool anyRateIsInvalid);

    function getShortRate(bytes32 synth) external view returns (uint shortRate, bool rateIsInvalid);

    function getRatesAndTime(uint index)
        external
        view
        returns (
            uint entryRate,
            uint lastRate,
            uint lastUpdated,
            uint newIndex
        );

    function getShortRatesAndTime(bytes32 currency, uint index)
        external
        view
        returns (
            uint entryRate,
            uint lastRate,
            uint lastUpdated,
            uint newIndex
        );

    function exceedsDebtLimit(uint amount, bytes32 currency) external view returns (bool canIssue, bool anyRateIsInvalid);

    function areSynthsAndCurrenciesSet(bytes32[] calldata requiredSynthNamesInResolver, bytes32[] calldata synthKeys)
        external
        view
        returns (bool);

    function areShortableSynthsSet(bytes32[] calldata requiredSynthNamesInResolver, bytes32[] calldata synthKeys)
        external
        view
        returns (bool);

    // Loans
    function getNewLoanId() external returns (uint id);

    // Manager mutative
    function addCollaterals(address[] calldata collaterals) external;

    function removeCollaterals(address[] calldata collaterals) external;

    function addSynths(bytes32[] calldata synthNamesInResolver, bytes32[] calldata synthKeys) external;

    function removeSynths(bytes32[] calldata synths, bytes32[] calldata synthKeys) external;

    function addShortableSynths(bytes32[] calldata requiredSynthNamesInResolver, bytes32[] calldata synthKeys) external;

    function removeShortableSynths(bytes32[] calldata synths) external;

    // State mutative

    function incrementLongs(bytes32 synth, uint amount) external;

    function decrementLongs(bytes32 synth, uint amount) external;

    function incrementShorts(bytes32 synth, uint amount) external;

    function decrementShorts(bytes32 synth, uint amount) external;

    function accrueInterest(
        uint interestIndex,
        bytes32 currency,
        bool isShort
    ) external returns (uint difference, uint index);

    function updateBorrowRatesCollateral(uint rate) external;

    function updateShortRatesCollateral(bytes32 currency, uint rate) external;
}


interface IWETH {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // WETH-specific functions.
    function deposit() external payable;

    function withdraw(uint amount) external;

    // Events
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint value);
    event Deposit(address indexed to, uint amount);
    event Withdrawal(address indexed to, uint amount);
}


// https://docs.synthetix.io/contracts/source/interfaces/ietherwrapper
contract IEtherWrapper {
    function mint(uint amount) external;

    function burn(uint amount) external;

    function distributeFees() external;

    function capacity() external view returns (uint);

    function getReserves() external view returns (uint);

    function totalIssuedSynths() external view returns (uint);

    function calculateMintFee(uint amount) public view returns (uint);

    function calculateBurnFee(uint amount) public view returns (uint);

    function maxETH() public view returns (uint256);

    function mintFeeRate() public view returns (uint256);

    function burnFeeRate() public view returns (uint256);

    function weth() public view returns (IWETH);
}


// https://docs.synthetix.io/contracts/source/interfaces/iwrapperfactory
interface IWrapperFactory {
    function isWrapper(address possibleWrapper) external view returns (bool);

    function createWrapper(
        IERC20 token,
        bytes32 currencyKey,
        bytes32 synthContractName
    ) external returns (address);

    function distributeFees() external;
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/multicollateralsynth
contract MultiCollateralSynth is Synth {
    bytes32 public constant CONTRACT_NAME = "MultiCollateralSynth";

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_COLLATERALMANAGER = "CollateralManager";
    bytes32 private constant CONTRACT_ETHER_WRAPPER = "EtherWrapper";
    bytes32 private constant CONTRACT_WRAPPER_FACTORY = "WrapperFactory";

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _tokenName,
        string memory _tokenSymbol,
        address _owner,
        bytes32 _currencyKey,
        uint _totalSupply,
        address _resolver
    ) public Synth(_proxy, _tokenState, _tokenName, _tokenSymbol, _owner, _currencyKey, _totalSupply, _resolver) {}

    /* ========== VIEWS ======================= */

    function collateralManager() internal view returns (ICollateralManager) {
        return ICollateralManager(requireAndGetAddress(CONTRACT_COLLATERALMANAGER));
    }

    function etherWrapper() internal view returns (IEtherWrapper) {
        return IEtherWrapper(requireAndGetAddress(CONTRACT_ETHER_WRAPPER));
    }

    function wrapperFactory() internal view returns (IWrapperFactory) {
        return IWrapperFactory(requireAndGetAddress(CONTRACT_WRAPPER_FACTORY));
    }

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = Synth.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](3);
        newAddresses[0] = CONTRACT_COLLATERALMANAGER;
        newAddresses[1] = CONTRACT_ETHER_WRAPPER;
        newAddresses[2] = CONTRACT_WRAPPER_FACTORY;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    /**
     * @notice Function that allows multi Collateral to issue a certain number of synths from an account.
     * @param account Account to issue synths to
     * @param amount Number of synths
     */
    function issue(address account, uint amount) external onlyInternalContracts {
        super._internalIssue(account, amount);
    }

    /**
     * @notice Function that allows multi Collateral to burn a certain number of synths from an account.
     * @param account Account to burn synths from
     * @param amount Number of synths
     */
    function burn(address account, uint amount) external onlyInternalContracts {
        super._internalBurn(account, amount);
    }

    /* ========== MODIFIERS ========== */

    // overriding modifier from super to add more internal contracts and checks
    function _isInternalContract(address account) internal view returns (bool) {
        return
            super._isInternalContract(account) ||
            collateralManager().hasCollateral(account) ||
            wrapperFactory().isWrapper(account) ||
            (account == address(etherWrapper()));
    }
}

    

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: ReadProxy.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/ReadProxy.sol
* Docs: https://docs.synthetix.io/contracts/ReadProxy
*
* Contract Dependencies: 
*	- Owned
* Libraries: (none)
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/

/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


pragma solidity ^0.5.16;


// https://docs.synthetix.io/contracts/Owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// solhint-disable payable-fallback

// https://docs.synthetix.io/contracts/ReadProxy
contract ReadProxy is Owned {
    address public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(address _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(target);
    }

    function() external {
        // The basics of a proxy read call
        // Note that msg.sender in the underlying will always be the address of this contract.
        assembly {
            calldatacopy(0, 0, calldatasize)

            // Use of staticcall - this will revert if the underlying function mutates state
            let result := staticcall(gas, sload(target_slot), 0, calldatasize, 0, 0)
            returndatacopy(0, 0, returndatasize)

            if iszero(result) {
                revert(0, returndatasize)
            }
            return(0, returndatasize)
        }
    }

    event TargetUpdated(address newTarget);
}


    

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: AddressResolver.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/AddressResolver.sol
* Docs: https://docs.synthetix.io/contracts/AddressResolver
*
* Contract Dependencies: 
*	- IAddressResolver
*	- Owned
* Libraries: (none)
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;


// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeEtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    // Restricted: used internally to Synthetix
    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function liquidateDelinquentAccount(
        address account,
        uint susdAmount,
        address liquidator
    ) external returns (uint totalRedeemed, uint amountToLiquidate);
}


// solhint-disable payable-fallback

// https://docs.synthetix.io/contracts/source/contracts/readproxy
contract ReadProxy is Owned {
    address public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(address _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(target);
    }

    function() external {
        // The basics of a proxy read call
        // Note that msg.sender in the underlying will always be the address of this contract.
        assembly {
            calldatacopy(0, 0, calldatasize)

            // Use of staticcall - this will revert if the underlying function mutates state
            let result := staticcall(gas, sload(target_slot), 0, calldatasize, 0, 0)
            returndatacopy(0, 0, returndatasize)

            if iszero(result) {
                revert(0, returndatasize)
            }
            return(0, returndatasize)
        }
    }

    event TargetUpdated(address newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination = resolver.requireAndGetAddress(
                name,
                string(abi.encodePacked("Resolver missing target: ", name))
            );
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}

    

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: ExchangerWithFeeRecAlternatives.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/ExchangerWithFeeRecAlternatives.sol
* Docs: https://docs.synthetix.io/contracts/ExchangerWithFeeRecAlternatives
*
* Contract Dependencies: 
*	- Exchanger
*	- IAddressResolver
*	- IExchanger
*	- MinimalProxyFactory
*	- MixinResolver
*	- MixinSystemSettings
*	- Owned
* Libraries: 
*	- ExchangeSettlementLib
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2022 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/iaddressresolver
interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views

    function allNetworksDebtInfo()
        external
        view
        returns (
            uint256 debt,
            uint256 sharesSupply,
            bool isStale
        );

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    function liquidationAmounts(address account, bool isSelfLiquidation)
        external
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint initialDebtBalance
        );

    // Restricted: used internally to Synthetix
    function addSynths(ISynth[] calldata synthsToAdd) external;

    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external;

    function setCurrentPeriodId(uint128 periodId) external;

    function liquidateAccount(address account, bool isSelfLiquidation)
        external
        returns (
            uint totalRedeemed,
            uint debtRemoved,
            uint escrowToLiquidate
        );

    function issueSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);

    function burnSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/addressresolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== RESTRICTED FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            bytes32 name = names[i];
            address destination = destinations[i];
            repository[name] = destination;
            emit AddressImported(name, destination);
        }
    }

    /* ========= PUBLIC FUNCTIONS ========== */

    function rebuildCaches(MixinResolver[] calldata destinations) external {
        for (uint i = 0; i < destinations.length; i++) {
            destinations[i].rebuildCache();
        }
    }

    /* ========== VIEWS ========== */

    function areAddressesImported(bytes32[] calldata names, address[] calldata destinations) external view returns (bool) {
        for (uint i = 0; i < names.length; i++) {
            if (repository[names[i]] != destinations[i]) {
                return false;
            }
        }
        return true;
    }

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }

    /* ========== EVENTS ========== */

    event AddressImported(bytes32 name, address destination);
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinresolver
contract MixinResolver {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    constructor(address _resolver) internal {
        resolver = AddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function combineArrays(bytes32[] memory first, bytes32[] memory second)
        internal
        pure
        returns (bytes32[] memory combination)
    {
        combination = new bytes32[](first.length + second.length);

        for (uint i = 0; i < first.length; i++) {
            combination[i] = first[i];
        }

        for (uint j = 0; j < second.length; j++) {
            combination[first.length + j] = second[j];
        }
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    // Note: this function is public not external in order for it to be overridden and invoked via super in subclasses
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {}

    function rebuildCache() public {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        // The resolver must call this function whenver it updates its state
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            address destination =
                resolver.requireAndGetAddress(name, string(abi.encodePacked("Resolver missing target: ", name)));
            addressCache[name] = destination;
            emit CacheUpdated(name, destination);
        }
    }

    /* ========== VIEWS ========== */

    function isResolverCached() external view returns (bool) {
        bytes32[] memory requiredAddresses = resolverAddressesRequired();
        for (uint i = 0; i < requiredAddresses.length; i++) {
            bytes32 name = requiredAddresses[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function requireAndGetAddress(bytes32 name) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), string(abi.encodePacked("Missing address: ", name)));
        return _foundAddress;
    }

    /* ========== EVENTS ========== */

    event CacheUpdated(bytes32 name, address destination);
}


// https://docs.synthetix.io/contracts/source/interfaces/iflexiblestorage
interface IFlexibleStorage {
    // Views
    function getUIntValue(bytes32 contractName, bytes32 record) external view returns (uint);

    function getUIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (uint[] memory);

    function getIntValue(bytes32 contractName, bytes32 record) external view returns (int);

    function getIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (int[] memory);

    function getAddressValue(bytes32 contractName, bytes32 record) external view returns (address);

    function getAddressValues(bytes32 contractName, bytes32[] calldata records) external view returns (address[] memory);

    function getBoolValue(bytes32 contractName, bytes32 record) external view returns (bool);

    function getBoolValues(bytes32 contractName, bytes32[] calldata records) external view returns (bool[] memory);

    function getBytes32Value(bytes32 contractName, bytes32 record) external view returns (bytes32);

    function getBytes32Values(bytes32 contractName, bytes32[] calldata records) external view returns (bytes32[] memory);

    // Mutative functions
    function deleteUIntValue(bytes32 contractName, bytes32 record) external;

    function deleteIntValue(bytes32 contractName, bytes32 record) external;

    function deleteAddressValue(bytes32 contractName, bytes32 record) external;

    function deleteBoolValue(bytes32 contractName, bytes32 record) external;

    function deleteBytes32Value(bytes32 contractName, bytes32 record) external;

    function setUIntValue(
        bytes32 contractName,
        bytes32 record,
        uint value
    ) external;

    function setUIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        uint[] calldata values
    ) external;

    function setIntValue(
        bytes32 contractName,
        bytes32 record,
        int value
    ) external;

    function setIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        int[] calldata values
    ) external;

    function setAddressValue(
        bytes32 contractName,
        bytes32 record,
        address value
    ) external;

    function setAddressValues(
        bytes32 contractName,
        bytes32[] calldata records,
        address[] calldata values
    ) external;

    function setBoolValue(
        bytes32 contractName,
        bytes32 record,
        bool value
    ) external;

    function setBoolValues(
        bytes32 contractName,
        bytes32[] calldata records,
        bool[] calldata values
    ) external;

    function setBytes32Value(
        bytes32 contractName,
        bytes32 record,
        bytes32 value
    ) external;

    function setBytes32Values(
        bytes32 contractName,
        bytes32[] calldata records,
        bytes32[] calldata values
    ) external;
}


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/mixinsystemsettings
contract MixinSystemSettings is MixinResolver {
    // must match the one defined SystemSettingsLib, defined in both places due to sol v0.5 limitations
    bytes32 internal constant SETTING_CONTRACT_NAME = "SystemSettings";

    bytes32 internal constant SETTING_WAITING_PERIOD_SECS = "waitingPeriodSecs";
    bytes32 internal constant SETTING_PRICE_DEVIATION_THRESHOLD_FACTOR = "priceDeviationThresholdFactor";
    bytes32 internal constant SETTING_ISSUANCE_RATIO = "issuanceRatio";
    bytes32 internal constant SETTING_FEE_PERIOD_DURATION = "feePeriodDuration";
    bytes32 internal constant SETTING_TARGET_THRESHOLD = "targetThreshold";
    bytes32 internal constant SETTING_LIQUIDATION_DELAY = "liquidationDelay";
    bytes32 internal constant SETTING_LIQUIDATION_RATIO = "liquidationRatio";
    bytes32 internal constant SETTING_LIQUIDATION_ESCROW_DURATION = "liquidationEscrowDuration";
    bytes32 internal constant SETTING_LIQUIDATION_PENALTY = "liquidationPenalty";
    bytes32 internal constant SETTING_SNX_LIQUIDATION_PENALTY = "snxLiquidationPenalty";
    bytes32 internal constant SETTING_SELF_LIQUIDATION_PENALTY = "selfLiquidationPenalty";
    bytes32 internal constant SETTING_FLAG_REWARD = "flagReward";
    bytes32 internal constant SETTING_LIQUIDATE_REWARD = "liquidateReward";
    bytes32 internal constant SETTING_RATE_STALE_PERIOD = "rateStalePeriod";
    /* ========== Exchange Fees Related ========== */
    bytes32 internal constant SETTING_EXCHANGE_FEE_RATE = "exchangeFeeRate";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD = "exchangeDynamicFeeThreshold";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY = "exchangeDynamicFeeWeightDecay";
    bytes32 internal constant SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS = "exchangeDynamicFeeRounds";
    bytes32 internal constant SETTING_EXCHANGE_MAX_DYNAMIC_FEE = "exchangeMaxDynamicFee";
    /* ========== End Exchange Fees Related ========== */
    bytes32 internal constant SETTING_MINIMUM_STAKE_TIME = "minimumStakeTime";
    bytes32 internal constant SETTING_AGGREGATOR_WARNING_FLAGS = "aggregatorWarningFlags";
    bytes32 internal constant SETTING_TRADING_REWARDS_ENABLED = "tradingRewardsEnabled";
    bytes32 internal constant SETTING_DEBT_SNAPSHOT_STALE_TIME = "debtSnapshotStaleTime";
    bytes32 internal constant SETTING_CROSS_DOMAIN_DEPOSIT_GAS_LIMIT = "crossDomainDepositGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_ESCROW_GAS_LIMIT = "crossDomainEscrowGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_REWARD_GAS_LIMIT = "crossDomainRewardGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_WITHDRAWAL_GAS_LIMIT = "crossDomainWithdrawalGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_FEE_PERIOD_CLOSE_GAS_LIMIT = "crossDomainCloseGasLimit";
    bytes32 internal constant SETTING_CROSS_DOMAIN_RELAY_GAS_LIMIT = "crossDomainRelayGasLimit";
    bytes32 internal constant SETTING_ETHER_WRAPPER_MAX_ETH = "etherWrapperMaxETH";
    bytes32 internal constant SETTING_ETHER_WRAPPER_MINT_FEE_RATE = "etherWrapperMintFeeRate";
    bytes32 internal constant SETTING_ETHER_WRAPPER_BURN_FEE_RATE = "etherWrapperBurnFeeRate";
    bytes32 internal constant SETTING_WRAPPER_MAX_TOKEN_AMOUNT = "wrapperMaxTokens";
    bytes32 internal constant SETTING_WRAPPER_MINT_FEE_RATE = "wrapperMintFeeRate";
    bytes32 internal constant SETTING_WRAPPER_BURN_FEE_RATE = "wrapperBurnFeeRate";
    bytes32 internal constant SETTING_INTERACTION_DELAY = "interactionDelay";
    bytes32 internal constant SETTING_COLLAPSE_FEE_RATE = "collapseFeeRate";
    bytes32 internal constant SETTING_ATOMIC_MAX_VOLUME_PER_BLOCK = "atomicMaxVolumePerBlock";
    bytes32 internal constant SETTING_ATOMIC_TWAP_WINDOW = "atomicTwapWindow";
    bytes32 internal constant SETTING_ATOMIC_EQUIVALENT_FOR_DEX_PRICING = "atomicEquivalentForDexPricing";
    bytes32 internal constant SETTING_ATOMIC_EXCHANGE_FEE_RATE = "atomicExchangeFeeRate";
    bytes32 internal constant SETTING_ATOMIC_VOLATILITY_CONSIDERATION_WINDOW = "atomicVolConsiderationWindow";
    bytes32 internal constant SETTING_ATOMIC_VOLATILITY_UPDATE_THRESHOLD = "atomicVolUpdateThreshold";
    bytes32 internal constant SETTING_PURE_CHAINLINK_PRICE_FOR_ATOMIC_SWAPS_ENABLED = "pureChainlinkForAtomicsEnabled";
    bytes32 internal constant SETTING_CROSS_SYNTH_TRANSFER_ENABLED = "crossChainSynthTransferEnabled";

    bytes32 internal constant CONTRACT_FLEXIBLESTORAGE = "FlexibleStorage";

    enum CrossDomainMessageGasLimits {Deposit, Escrow, Reward, Withdrawal, CloseFeePeriod, Relay}

    struct DynamicFeeConfig {
        uint threshold;
        uint weightDecay;
        uint rounds;
        uint maxFee;
    }

    constructor(address _resolver) internal MixinResolver(_resolver) {}

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](1);
        addresses[0] = CONTRACT_FLEXIBLESTORAGE;
    }

    function flexibleStorage() internal view returns (IFlexibleStorage) {
        return IFlexibleStorage(requireAndGetAddress(CONTRACT_FLEXIBLESTORAGE));
    }

    function _getGasLimitSetting(CrossDomainMessageGasLimits gasLimitType) internal pure returns (bytes32) {
        if (gasLimitType == CrossDomainMessageGasLimits.Deposit) {
            return SETTING_CROSS_DOMAIN_DEPOSIT_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Escrow) {
            return SETTING_CROSS_DOMAIN_ESCROW_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Reward) {
            return SETTING_CROSS_DOMAIN_REWARD_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Withdrawal) {
            return SETTING_CROSS_DOMAIN_WITHDRAWAL_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.Relay) {
            return SETTING_CROSS_DOMAIN_RELAY_GAS_LIMIT;
        } else if (gasLimitType == CrossDomainMessageGasLimits.CloseFeePeriod) {
            return SETTING_CROSS_DOMAIN_FEE_PERIOD_CLOSE_GAS_LIMIT;
        } else {
            revert("Unknown gas limit type");
        }
    }

    function getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits gasLimitType) internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, _getGasLimitSetting(gasLimitType));
    }

    function getTradingRewardsEnabled() internal view returns (bool) {
        return flexibleStorage().getBoolValue(SETTING_CONTRACT_NAME, SETTING_TRADING_REWARDS_ENABLED);
    }

    function getWaitingPeriodSecs() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_WAITING_PERIOD_SECS);
    }

    function getPriceDeviationThresholdFactor() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_PRICE_DEVIATION_THRESHOLD_FACTOR);
    }

    function getIssuanceRatio() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ISSUANCE_RATIO);
    }

    function getFeePeriodDuration() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_FEE_PERIOD_DURATION);
    }

    function getTargetThreshold() internal view returns (uint) {
        // lookup on flexible storage directly for gas savings (rather than via SystemSettings)
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_TARGET_THRESHOLD);
    }

    function getLiquidationDelay() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_DELAY);
    }

    function getLiquidationRatio() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_RATIO);
    }

    function getLiquidationEscrowDuration() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_ESCROW_DURATION);
    }

    function getLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATION_PENALTY);
    }

    function getSnxLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_SNX_LIQUIDATION_PENALTY);
    }

    function getSelfLiquidationPenalty() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_SELF_LIQUIDATION_PENALTY);
    }

    function getFlagReward() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_FLAG_REWARD);
    }

    function getLiquidateReward() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_LIQUIDATE_REWARD);
    }

    function getRateStalePeriod() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_RATE_STALE_PERIOD);
    }

    /* ========== Exchange Related Fees ========== */
    function getExchangeFeeRate(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_EXCHANGE_FEE_RATE, currencyKey))
            );
    }

    /// @notice Get exchange dynamic fee related keys
    /// @return threshold, weight decay, rounds, and max fee
    function getExchangeDynamicFeeConfig() internal view returns (DynamicFeeConfig memory) {
        bytes32[] memory keys = new bytes32[](4);
        keys[0] = SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD;
        keys[1] = SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY;
        keys[2] = SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS;
        keys[3] = SETTING_EXCHANGE_MAX_DYNAMIC_FEE;
        uint[] memory values = flexibleStorage().getUIntValues(SETTING_CONTRACT_NAME, keys);
        return DynamicFeeConfig({threshold: values[0], weightDecay: values[1], rounds: values[2], maxFee: values[3]});
    }

    /* ========== End Exchange Related Fees ========== */

    function getMinimumStakeTime() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_MINIMUM_STAKE_TIME);
    }

    function getAggregatorWarningFlags() internal view returns (address) {
        return flexibleStorage().getAddressValue(SETTING_CONTRACT_NAME, SETTING_AGGREGATOR_WARNING_FLAGS);
    }

    function getDebtSnapshotStaleTime() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_DEBT_SNAPSHOT_STALE_TIME);
    }

    function getEtherWrapperMaxETH() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_MAX_ETH);
    }

    function getEtherWrapperMintFeeRate() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_MINT_FEE_RATE);
    }

    function getEtherWrapperBurnFeeRate() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ETHER_WRAPPER_BURN_FEE_RATE);
    }

    function getWrapperMaxTokenAmount(address wrapper) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_MAX_TOKEN_AMOUNT, wrapper))
            );
    }

    function getWrapperMintFeeRate(address wrapper) internal view returns (int) {
        return
            flexibleStorage().getIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_MINT_FEE_RATE, wrapper))
            );
    }

    function getWrapperBurnFeeRate(address wrapper) internal view returns (int) {
        return
            flexibleStorage().getIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_WRAPPER_BURN_FEE_RATE, wrapper))
            );
    }

    function getInteractionDelay(address collateral) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_INTERACTION_DELAY, collateral))
            );
    }

    function getCollapseFeeRate(address collateral) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_COLLAPSE_FEE_RATE, collateral))
            );
    }

    function getAtomicMaxVolumePerBlock() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ATOMIC_MAX_VOLUME_PER_BLOCK);
    }

    function getAtomicTwapWindow() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_ATOMIC_TWAP_WINDOW);
    }

    function getAtomicEquivalentForDexPricing(bytes32 currencyKey) internal view returns (address) {
        return
            flexibleStorage().getAddressValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_EQUIVALENT_FOR_DEX_PRICING, currencyKey))
            );
    }

    function getAtomicExchangeFeeRate(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_EXCHANGE_FEE_RATE, currencyKey))
            );
    }

    function getAtomicVolatilityConsiderationWindow(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_VOLATILITY_CONSIDERATION_WINDOW, currencyKey))
            );
    }

    function getAtomicVolatilityUpdateThreshold(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_ATOMIC_VOLATILITY_UPDATE_THRESHOLD, currencyKey))
            );
    }

    function getPureChainlinkPriceForAtomicSwapsEnabled(bytes32 currencyKey) internal view returns (bool) {
        return
            flexibleStorage().getBoolValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_PURE_CHAINLINK_PRICE_FOR_ATOMIC_SWAPS_ENABLED, currencyKey))
            );
    }

    function getCrossChainSynthTransferEnabled(bytes32 currencyKey) internal view returns (uint) {
        return
            flexibleStorage().getUIntValue(
                SETTING_CONTRACT_NAME,
                keccak256(abi.encodePacked(SETTING_CROSS_SYNTH_TRANSFER_ENABLED, currencyKey))
            );
    }

    function getExchangeMaxDynamicFee() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_MAX_DYNAMIC_FEE);
    }

    function getExchangeDynamicFeeRounds() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_ROUNDS);
    }

    function getExchangeDynamicFeeThreshold() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_THRESHOLD);
    }

    function getExchangeDynamicFeeWeightDecay() internal view returns (uint) {
        return flexibleStorage().getUIntValue(SETTING_CONTRACT_NAME, SETTING_EXCHANGE_DYNAMIC_FEE_WEIGHT_DECAY);
    }
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }

    /* ---------- Utilities ---------- */
    /*
     * Absolute value of the input, returned as a signed number.
     */
    function signedAbs(int x) internal pure returns (int) {
        return x < 0 ? -x : x;
    }

    /*
     * Absolute value of the input, returned as an unsigned number.
     */
    function abs(int x) internal pure returns (uint) {
        return uint(signedAbs(x));
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/isystemstatus
interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function systemSuspended() external view returns (bool);

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireFuturesActive() external view;

    function requireFuturesMarketActive(bytes32 marketKey) external view;

    function requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function synthSuspended(bytes32 currencyKey) external view returns (bool);

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function systemSuspension() external view returns (bool suspended, uint248 reason);

    function issuanceSuspension() external view returns (bool suspended, uint248 reason);

    function exchangeSuspension() external view returns (bool suspended, uint248 reason);

    function futuresSuspension() external view returns (bool suspended, uint248 reason);

    function synthExchangeSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function futuresMarketSuspension(bytes32 marketKey) external view returns (bool suspended, uint248 reason);

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons);

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    // Restricted functions
    function suspendIssuance(uint256 reason) external;

    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


// https://docs.synthetix.io/contracts/source/interfaces/ICircuitBreaker
interface ICircuitBreaker {
    // Views
    function isInvalid(address oracleAddress, uint value) external view returns (bool);

    function priceDeviationThresholdFactor() external view returns (uint);

    function isDeviationAboveThreshold(uint base, uint comparison) external view returns (bool);

    function lastValue(address oracleAddress) external view returns (uint);

    function circuitBroken(address oracleAddress) external view returns (bool);

    // Mutative functions
    function resetLastValue(address[] calldata oracleAddresses, uint[] calldata values) external;

    function probeCircuitBreaker(address oracleAddress, uint value) external returns (bool circuitBroken);
}


// https://docs.synthetix.io/contracts/source/interfaces/ifeepool
interface IFeePool {
    // Views

    // solhint-disable-next-line func-name-mixedcase
    function FEE_ADDRESS() external view returns (address);

    function feesAvailable(address account) external view returns (uint, uint);

    function feePeriodDuration() external view returns (uint);

    function isFeesClaimable(address account) external view returns (bool);

    function targetThreshold() external view returns (uint);

    function totalFeesAvailable() external view returns (uint);

    function totalRewardsAvailable() external view returns (uint);

    // Mutative Functions
    function claimFees() external returns (bool);

    function claimOnBehalf(address claimingForAddress) external returns (bool);

    function closeCurrentFeePeriod() external;

    function closeSecondary(uint snxBackedDebt, uint debtShareSupply) external;

    function recordFeePaid(uint sUSDAmount) external;

    function setRewardsToDistribute(uint amount) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/idelegateapprovals
interface IDelegateApprovals {
    // Views
    function canBurnFor(address authoriser, address delegate) external view returns (bool);

    function canIssueFor(address authoriser, address delegate) external view returns (bool);

    function canClaimFor(address authoriser, address delegate) external view returns (bool);

    function canExchangeFor(address authoriser, address delegate) external view returns (bool);

    // Mutative
    function approveAllDelegatePowers(address delegate) external;

    function removeAllDelegatePowers(address delegate) external;

    function approveBurnOnBehalf(address delegate) external;

    function removeBurnOnBehalf(address delegate) external;

    function approveIssueOnBehalf(address delegate) external;

    function removeIssueOnBehalf(address delegate) external;

    function approveClaimOnBehalf(address delegate) external;

    function removeClaimOnBehalf(address delegate) external;

    function approveExchangeOnBehalf(address delegate) external;

    function removeExchangeOnBehalf(address delegate) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/itradingrewards
interface ITradingRewards {
    /* ========== VIEWS ========== */

    function getAvailableRewards() external view returns (uint);

    function getUnassignedRewards() external view returns (uint);

    function getRewardsToken() external view returns (address);

    function getPeriodController() external view returns (address);

    function getCurrentPeriod() external view returns (uint);

    function getPeriodIsClaimable(uint periodID) external view returns (bool);

    function getPeriodIsFinalized(uint periodID) external view returns (bool);

    function getPeriodRecordedFees(uint periodID) external view returns (uint);

    function getPeriodTotalRewards(uint periodID) external view returns (uint);

    function getPeriodAvailableRewards(uint periodID) external view returns (uint);

    function getUnaccountedFeesForAccountForPeriod(address account, uint periodID) external view returns (uint);

    function getAvailableRewardsForAccountForPeriod(address account, uint periodID) external view returns (uint);

    function getAvailableRewardsForAccountForPeriods(address account, uint[] calldata periodIDs)
        external
        view
        returns (uint totalRewards);

    /* ========== MUTATIVE FUNCTIONS ========== */

    function claimRewardsForPeriod(uint periodID) external;

    function claimRewardsForPeriods(uint[] calldata periodIDs) external;

    /* ========== RESTRICTED FUNCTIONS ========== */

    function recordExchangeFeeForAccount(uint usdFeeAmount, address account) external;

    function closeCurrentPeriodWithRewards(uint rewards) external;

    function recoverTokens(address tokenAddress, address recoverAddress) external;

    function recoverUnassignedRewardTokens(address recoverAddress) external;

    function recoverAssignedRewardTokensAndDestroyPeriod(address recoverAddress, uint periodID) external;

    function setPeriodController(address newPeriodController) external;
}


interface IVirtualSynth {
    // Views
    function balanceOfUnderlying(address account) external view returns (uint);

    function rate() external view returns (uint);

    function readyToSettle() external view returns (bool);

    function secsLeftInWaitingPeriod() external view returns (uint);

    function settled() external view returns (bool);

    function synth() external view returns (ISynth);

    // Mutative functions
    function settle(address account) external;
}


pragma experimental ABIEncoderV2;


// https://docs.synthetix.io/contracts/source/interfaces/iexchanger
interface IExchanger {
    struct ExchangeEntrySettlement {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint reclaim;
        uint rebate;
        uint srcRoundIdAtPeriodEnd;
        uint destRoundIdAtPeriodEnd;
        uint timestamp;
    }

    struct ExchangeEntry {
        uint sourceRate;
        uint destinationRate;
        uint destinationAmount;
        uint exchangeFeeRate;
        uint exchangeDynamicFeeRate;
        uint roundIdForSrc;
        uint roundIdForDest;
        uint sourceAmountAfterSettlement;
    }

    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view returns (uint);

    function dynamicFeeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint feeRate, bool tooVolatile);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    function lastExchangeRate(bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function exchange(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );
}

// Used to have strongly-typed access to internal mutative functions in Synthetix
interface ISynthetixInternal {
    function emitExchangeTracking(
        bytes32 trackingCode,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        uint256 fee
    ) external;

    function emitSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitAtomicSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitExchangeReclaim(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;

    function emitExchangeRebate(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;
}

interface IExchangerInternalDebtCache {
    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateCachedSynthDebts(bytes32[] calldata currencyKeys) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/IDirectIntegration
interface IDirectIntegrationManager {
    struct ParameterIntegrationSettings {
        bytes32 currencyKey;
        address dexPriceAggregator;
        address atomicEquivalentForDexPricing;
        uint atomicExchangeFeeRate;
        uint atomicTwapWindow;
        uint atomicMaxVolumePerBlock;
        uint atomicVolatilityConsiderationWindow;
        uint atomicVolatilityUpdateThreshold;
        uint exchangeFeeRate;
        uint exchangeMaxDynamicFee;
        uint exchangeDynamicFeeRounds;
        uint exchangeDynamicFeeThreshold;
        uint exchangeDynamicFeeWeightDecay;
    }

    function getExchangeParameters(address integration, bytes32 key)
        external
        view
        returns (ParameterIntegrationSettings memory settings);

    function setExchangeParameters(
        address integration,
        bytes32[] calldata currencyKeys,
        ParameterIntegrationSettings calldata params
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangerates
interface IExchangeRates {
    // Structs
    struct RateAndUpdatedTime {
        uint216 rate;
        uint40 time;
    }

    // Views
    function aggregators(bytes32 currencyKey) external view returns (address);

    function aggregatorWarningFlags() external view returns (address);

    function anyRateIsInvalid(bytes32[] calldata currencyKeys) external view returns (bool);

    function anyRateIsInvalidAtRound(bytes32[] calldata currencyKeys, uint[] calldata roundIds) external view returns (bool);

    function currenciesUsingAggregator(address aggregator) external view returns (bytes32[] memory);

    function effectiveValue(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external view returns (uint value);

    function effectiveValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveValueAndRatesAtRound(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        uint roundIdForSrc,
        uint roundIdForDest
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveAtomicValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function effectiveAtomicValueAndRates(
        IDirectIntegrationManager.ParameterIntegrationSettings calldata sourceSettings,
        uint sourceAmount,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata destinationSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata usdSettings
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function getCurrentRoundId(bytes32 currencyKey) external view returns (uint);

    function getLastRoundIdBeforeElapsedSecs(
        bytes32 currencyKey,
        uint startingRoundId,
        uint startingTimestamp,
        uint timediff
    ) external view returns (uint);

    function lastRateUpdateTimes(bytes32 currencyKey) external view returns (uint256);

    function rateAndTimestampAtRound(bytes32 currencyKey, uint roundId) external view returns (uint rate, uint time);

    function rateAndUpdatedTime(bytes32 currencyKey) external view returns (uint rate, uint time);

    function rateAndInvalid(bytes32 currencyKey) external view returns (uint rate, bool isInvalid);

    function rateForCurrency(bytes32 currencyKey) external view returns (uint);

    function rateIsFlagged(bytes32 currencyKey) external view returns (bool);

    function rateIsInvalid(bytes32 currencyKey) external view returns (bool);

    function rateIsStale(bytes32 currencyKey) external view returns (bool);

    function rateStalePeriod() external view returns (uint);

    function ratesAndUpdatedTimeForCurrencyLastNRounds(
        bytes32 currencyKey,
        uint numRounds,
        uint roundId
    ) external view returns (uint[] memory rates, uint[] memory times);

    function ratesAndInvalidForCurrencies(bytes32[] calldata currencyKeys)
        external
        view
        returns (uint[] memory rates, bool anyRateInvalid);

    function ratesForCurrencies(bytes32[] calldata currencyKeys) external view returns (uint[] memory);

    function synthTooVolatileForAtomicExchange(bytes32 currencyKey) external view returns (bool);

    function synthTooVolatileForAtomicExchange(IDirectIntegrationManager.ParameterIntegrationSettings calldata settings)
        external
        view
        returns (bool);

    function rateWithSafetyChecks(bytes32 currencyKey)
        external
        returns (
            uint rate,
            bool broken,
            bool invalid
        );
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangestate
interface IExchangeState {
    // Views
    struct ExchangeEntry {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint amountReceived;
        uint exchangeFeeRate;
        uint timestamp;
        uint roundIdForSrc;
        uint roundIdForDest;
    }

    function getLengthOfEntries(address account, bytes32 currencyKey) external view returns (uint);

    function getEntryAt(
        address account,
        bytes32 currencyKey,
        uint index
    )
        external
        view
        returns (
            bytes32 src,
            uint amount,
            bytes32 dest,
            uint amountReceived,
            uint exchangeFeeRate,
            uint timestamp,
            uint roundIdForSrc,
            uint roundIdForDest
        );

    function getMaxTimestamp(address account, bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function appendExchangeEntry(
        address account,
        bytes32 src,
        uint amount,
        bytes32 dest,
        uint amountReceived,
        uint exchangeFeeRate,
        uint timestamp,
        uint roundIdForSrc,
        uint roundIdForDest
    ) external;

    function removeEntries(address account, bytes32 currencyKey) external;
}


interface IDebtCache {
    // Views

    function cachedDebt() external view returns (uint);

    function cachedSynthDebt(bytes32 currencyKey) external view returns (uint);

    function cacheTimestamp() external view returns (uint);

    function cacheInvalid() external view returns (bool);

    function cacheStale() external view returns (bool);

    function isInitialized() external view returns (bool);

    function currentSynthDebts(bytes32[] calldata currencyKeys)
        external
        view
        returns (
            uint[] memory debtValues,
            uint futuresDebt,
            uint excludedDebt,
            bool anyRateIsInvalid
        );

    function cachedSynthDebts(bytes32[] calldata currencyKeys) external view returns (uint[] memory debtValues);

    function totalNonSnxBackedDebt() external view returns (uint excludedDebt, bool isInvalid);

    function currentDebt() external view returns (uint debt, bool anyRateIsInvalid);

    function cacheInfo()
        external
        view
        returns (
            uint debt,
            uint timestamp,
            bool isInvalid,
            bool isStale
        );

    function excludedIssuedDebts(bytes32[] calldata currencyKeys) external view returns (uint[] memory excludedDebts);

    // Mutative functions

    function updateCachedSynthDebts(bytes32[] calldata currencyKeys) external;

    function updateCachedSynthDebtWithRate(bytes32 currencyKey, uint currencyRate) external;

    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateDebtCacheValidity(bool currentlyInvalid) external;

    function purgeCachedSynthDebt(bytes32 currencyKey) external;

    function takeDebtSnapshot() external;

    function recordExcludedDebtChange(bytes32 currencyKey, int256 delta) external;

    function updateCachedsUSDDebt(int amount) external;

    function importExcludedIssuedDebts(IDebtCache prevDebtCache, IIssuer prevIssuer) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/isynthetix
interface ISynthetix {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint);

    function isWaitingPeriod(bytes32 currencyKey) external view returns (bool);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey) external view returns (uint);

    function totalIssuedSynthsExcludeOtherCollateral(bytes32 currencyKey) external view returns (uint);

    function transferableSynthetix(address account) external view returns (uint transferable);

    function getFirstNonZeroEscrowIndex(address account) external view returns (uint);

    // Mutative Functions
    function burnSynths(uint amount) external;

    function burnSynthsOnBehalf(address burnForAddress, uint amount) external;

    function burnSynthsToTarget() external;

    function burnSynthsToTargetOnBehalf(address burnForAddress) external;

    function exchange(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeOnBehalf(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeWithTracking(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeWithTrackingForInitiator(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeWithVirtual(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function issueMaxSynths() external;

    function issueMaxSynthsOnBehalf(address issueForAddress) external;

    function issueSynths(uint amount) external;

    function issueSynthsOnBehalf(address issueForAddress, uint amount) external;

    function mint() external returns (bool);

    function settle(bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    // Liquidations
    function liquidateDelinquentAccount(address account) external returns (bool);

    function liquidateDelinquentAccountEscrowIndex(address account, uint escrowStartIndex) external returns (bool);

    function liquidateSelf() external returns (bool);

    // Restricted Functions

    function mintSecondary(address account, uint amount) external;

    function mintSecondaryRewards(uint amount) external;

    function burnSecondary(address account, uint amount) external;
}


library ExchangeSettlementLib {
    using SafeMath for uint256;
    using SafeDecimalMath for uint256;

    struct ResolvedAddresses {
        IExchangeState exchangeState;
        IExchangeRates exchangeRates;
        ICircuitBreaker circuitBreaker;
        IExchangerInternalDebtCache debtCache;
        IIssuer issuer;
        ISynthetix synthetix;
    }

    bytes32 internal constant sUSD = "sUSD";

    function internalSettle(
        ResolvedAddresses calldata resolvedAddresses,
        address from,
        bytes32 currencyKey,
        bool updateCache,
        uint waitingPeriod
    )
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntriesSettled
        )
    {
        require(
            maxSecsLeftInWaitingPeriod(resolvedAddresses.exchangeState, from, currencyKey, waitingPeriod) == 0,
            "Cannot settle during waiting period"
        );

        (uint reclaimAmount, uint rebateAmount, uint entries, IExchanger.ExchangeEntrySettlement[] memory settlements) =
            _settlementOwing(resolvedAddresses, from, currencyKey, waitingPeriod);

        if (reclaimAmount > rebateAmount) {
            reclaimed = reclaimAmount.sub(rebateAmount);
            _reclaim(resolvedAddresses, from, currencyKey, reclaimed);
        } else if (rebateAmount > reclaimAmount) {
            refunded = rebateAmount.sub(reclaimAmount);
            _refund(resolvedAddresses, from, currencyKey, refunded);
        }

        // by checking a reclaim or refund we also check that the currency key is still a valid synth,
        // as the deviation check will return 0 if the synth has been removed.
        if (updateCache && (reclaimed > 0 || refunded > 0)) {
            bytes32[] memory key = new bytes32[](1);
            key[0] = currencyKey;
            resolvedAddresses.debtCache.updateCachedSynthDebts(key);
        }

        // emit settlement event for each settled exchange entry
        for (uint i = 0; i < settlements.length; i++) {
            emit ExchangeEntrySettled(
                from,
                settlements[i].src,
                settlements[i].amount,
                settlements[i].dest,
                settlements[i].reclaim,
                settlements[i].rebate,
                settlements[i].srcRoundIdAtPeriodEnd,
                settlements[i].destRoundIdAtPeriodEnd,
                settlements[i].timestamp
            );
        }

        numEntriesSettled = entries;

        // Now remove all entries, even if no reclaim and no rebate
        resolvedAddresses.exchangeState.removeEntries(from, currencyKey);
    }

    function maxSecsLeftInWaitingPeriod(
        IExchangeState exchangeState,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    ) public view returns (uint) {
        return _secsLeftInWaitingPeriodForExchange(exchangeState.getMaxTimestamp(account, currencyKey), waitingPeriod);
    }

    function _secsLeftInWaitingPeriodForExchange(uint timestamp, uint waitingPeriod) internal view returns (uint) {
        if (timestamp == 0 || now >= timestamp.add(waitingPeriod)) {
            return 0;
        }

        return timestamp.add(waitingPeriod).sub(now);
    }

    function _reclaim(
        ResolvedAddresses memory resolvedAddresses,
        address from,
        bytes32 currencyKey,
        uint amount
    ) internal {
        // burn amount from user
        resolvedAddresses.issuer.synths(currencyKey).burn(from, amount);
        ISynthetixInternal(address(resolvedAddresses.synthetix)).emitExchangeReclaim(from, currencyKey, amount);
    }

    function _refund(
        ResolvedAddresses memory resolvedAddresses,
        address from,
        bytes32 currencyKey,
        uint amount
    ) internal {
        // issue amount to user
        resolvedAddresses.issuer.synths(currencyKey).issue(from, amount);
        ISynthetixInternal(address(resolvedAddresses.synthetix)).emitExchangeRebate(from, currencyKey, amount);
    }

    function hasWaitingPeriodOrSettlementOwing(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    ) external view returns (bool) {
        if (maxSecsLeftInWaitingPeriod(resolvedAddresses.exchangeState, account, currencyKey, waitingPeriod) != 0) {
            return true;
        }

        (uint reclaimAmount, , , ) = _settlementOwing(resolvedAddresses, account, currencyKey, waitingPeriod);

        return reclaimAmount > 0;
    }

    function settlementOwing(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    )
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries,
            IExchanger.ExchangeEntrySettlement[] memory
        )
    {
        return _settlementOwing(resolvedAddresses, account, currencyKey, waitingPeriod);
    }

    // Internal function to aggregate each individual rebate and reclaim entry for a synth
    function _settlementOwing(
        ResolvedAddresses memory resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    )
        internal
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries,
            IExchanger.ExchangeEntrySettlement[] memory
        )
    {
        // Need to sum up all reclaim and rebate amounts for the user and the currency key
        numEntries = resolvedAddresses.exchangeState.getLengthOfEntries(account, currencyKey);

        // For each unsettled exchange
        IExchanger.ExchangeEntrySettlement[] memory settlements = new IExchanger.ExchangeEntrySettlement[](numEntries);
        for (uint i = 0; i < numEntries; i++) {
            // fetch the entry from storage
            IExchangeState.ExchangeEntry memory exchangeEntry =
                _getExchangeEntry(resolvedAddresses.exchangeState, account, currencyKey, i);

            // determine the last round ids for src and dest pairs when period ended or latest if not over
            (uint srcRoundIdAtPeriodEnd, uint destRoundIdAtPeriodEnd) =
                _getRoundIdsAtPeriodEnd(resolvedAddresses.exchangeRates, exchangeEntry, waitingPeriod);

            // given these round ids, determine what effective value they should have received
            uint amountShouldHaveReceived;
            {
                (uint destinationAmount, , ) =
                    resolvedAddresses.exchangeRates.effectiveValueAndRatesAtRound(
                        exchangeEntry.src,
                        exchangeEntry.amount,
                        exchangeEntry.dest,
                        srcRoundIdAtPeriodEnd,
                        destRoundIdAtPeriodEnd
                    );

                // and deduct the fee from this amount using the exchangeFeeRate from storage
                amountShouldHaveReceived = _deductFeesFromAmount(destinationAmount, exchangeEntry.exchangeFeeRate);
            }

            // SIP-65 settlements where the amount at end of waiting period is beyond the threshold, then
            // settle with no reclaim or rebate
            bool sip65condition =
                resolvedAddresses.circuitBreaker.isDeviationAboveThreshold(
                    exchangeEntry.amountReceived,
                    amountShouldHaveReceived
                );

            uint reclaim;
            uint rebate;

            if (!sip65condition) {
                if (exchangeEntry.amountReceived > amountShouldHaveReceived) {
                    // if they received more than they should have, add to the reclaim tally
                    reclaim = exchangeEntry.amountReceived.sub(amountShouldHaveReceived);
                    reclaimAmount = reclaimAmount.add(reclaim);
                } else if (amountShouldHaveReceived > exchangeEntry.amountReceived) {
                    // if less, add to the rebate tally
                    rebate = amountShouldHaveReceived.sub(exchangeEntry.amountReceived);
                    rebateAmount = rebateAmount.add(rebate);
                }
            }

            settlements[i] = IExchanger.ExchangeEntrySettlement({
                src: exchangeEntry.src,
                amount: exchangeEntry.amount,
                dest: exchangeEntry.dest,
                reclaim: reclaim,
                rebate: rebate,
                srcRoundIdAtPeriodEnd: srcRoundIdAtPeriodEnd,
                destRoundIdAtPeriodEnd: destRoundIdAtPeriodEnd,
                timestamp: exchangeEntry.timestamp
            });
        }

        return (reclaimAmount, rebateAmount, numEntries, settlements);
    }

    function _getExchangeEntry(
        IExchangeState exchangeState,
        address account,
        bytes32 currencyKey,
        uint index
    ) internal view returns (IExchangeState.ExchangeEntry memory) {
        (
            bytes32 src,
            uint amount,
            bytes32 dest,
            uint amountReceived,
            uint exchangeFeeRate,
            uint timestamp,
            uint roundIdForSrc,
            uint roundIdForDest
        ) = exchangeState.getEntryAt(account, currencyKey, index);

        return
            IExchangeState.ExchangeEntry({
                src: src,
                amount: amount,
                dest: dest,
                amountReceived: amountReceived,
                exchangeFeeRate: exchangeFeeRate,
                timestamp: timestamp,
                roundIdForSrc: roundIdForSrc,
                roundIdForDest: roundIdForDest
            });
    }

    function _getRoundIdsAtPeriodEnd(
        IExchangeRates exRates,
        IExchangeState.ExchangeEntry memory exchangeEntry,
        uint waitingPeriod
    ) internal view returns (uint srcRoundIdAtPeriodEnd, uint destRoundIdAtPeriodEnd) {
        srcRoundIdAtPeriodEnd = exRates.getLastRoundIdBeforeElapsedSecs(
            exchangeEntry.src,
            exchangeEntry.roundIdForSrc,
            exchangeEntry.timestamp,
            waitingPeriod
        );
        destRoundIdAtPeriodEnd = exRates.getLastRoundIdBeforeElapsedSecs(
            exchangeEntry.dest,
            exchangeEntry.roundIdForDest,
            exchangeEntry.timestamp,
            waitingPeriod
        );
    }

    function _deductFeesFromAmount(uint destinationAmount, uint exchangeFeeRate)
        internal
        pure
        returns (uint amountReceived)
    {
        amountReceived = destinationAmount.multiplyDecimal(SafeDecimalMath.unit().sub(exchangeFeeRate));
    }

    function appendExchange(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 src,
        uint amount,
        bytes32 dest,
        uint amountReceived,
        uint exchangeFeeRate
    ) external {
        uint roundIdForSrc = resolvedAddresses.exchangeRates.getCurrentRoundId(src);
        uint roundIdForDest = resolvedAddresses.exchangeRates.getCurrentRoundId(dest);
        resolvedAddresses.exchangeState.appendExchangeEntry(
            account,
            src,
            amount,
            dest,
            amountReceived,
            exchangeFeeRate,
            now,
            roundIdForSrc,
            roundIdForDest
        );

        emit ExchangeEntryAppended(
            account,
            src,
            amount,
            dest,
            amountReceived,
            exchangeFeeRate,
            roundIdForSrc,
            roundIdForDest
        );
    }

    // ========== EVENTS ==========
    event ExchangeEntryAppended(
        address indexed account,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 amountReceived,
        uint256 exchangeFeeRate,
        uint256 roundIdForSrc,
        uint256 roundIdForDest
    );

    event ExchangeEntrySettled(
        address indexed from,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 reclaim,
        uint256 rebate,
        uint256 srcRoundIdAtPeriodEnd,
        uint256 destRoundIdAtPeriodEnd,
        uint256 exchangeTimestamp
    );
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxy
contract Proxy is Owned {
    Proxyable public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(Proxyable _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(_target);
    }

    function _emit(
        bytes calldata callData,
        uint numTopics,
        bytes32 topic1,
        bytes32 topic2,
        bytes32 topic3,
        bytes32 topic4
    ) external onlyTarget {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi).
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
                case 0 {
                    log0(add(_callData, 32), size)
                }
                case 1 {
                    log1(add(_callData, 32), size, topic1)
                }
                case 2 {
                    log2(add(_callData, 32), size, topic1, topic2)
                }
                case 3 {
                    log3(add(_callData, 32), size, topic1, topic2, topic3)
                }
                case 4 {
                    log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
                }
        }
    }

    // solhint-disable no-complex-fallback
    function() external payable {
        // Mutable call setting Proxyable.messageSender as this is using call not delegatecall
        target.setMessageSender(msg.sender);

        assembly {
            let free_ptr := mload(0x40)
            calldatacopy(free_ptr, 0, calldatasize)

            /* We must explicitly forward ether to the underlying contract as well. */
            let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
            returndatacopy(free_ptr, 0, returndatasize)

            if iszero(result) {
                revert(free_ptr, returndatasize)
            }
            return(free_ptr, returndatasize)
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/proxyable
contract Proxyable is Owned {
    // This contract should be treated like an abstract contract

    /* The proxy this contract exists behind. */
    Proxy public proxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address public messageSender;

    constructor(address payable _proxy) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address payable _proxy) external onlyOwner {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setMessageSender(address sender) external onlyProxy {
        messageSender = sender;
    }

    modifier onlyProxy {
        _onlyProxy();
        _;
    }

    function _onlyProxy() private view {
        require(Proxy(msg.sender) == proxy, "Only the proxy can call");
    }

    modifier optionalProxy {
        _optionalProxy();
        _;
    }

    function _optionalProxy() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
    }

    modifier optionalProxy_onlyOwner {
        _optionalProxy_onlyOwner();
        _;
    }

    // solhint-disable-next-line func-name-mixedcase
    function _optionalProxy_onlyOwner() private {
        if (Proxy(msg.sender) != proxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
    }

    event ProxyUpdated(address proxyAddress);
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/exchanger
contract Exchanger is Owned, MixinSystemSettings, IExchanger {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    bytes32 public constant CONTRACT_NAME = "Exchanger";

    bytes32 internal constant sUSD = "sUSD";

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 private constant CONTRACT_EXCHANGESTATE = "ExchangeState";
    bytes32 private constant CONTRACT_EXRATES = "ExchangeRates";
    bytes32 private constant CONTRACT_SYNTHETIX = "Synthetix";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";
    bytes32 private constant CONTRACT_TRADING_REWARDS = "TradingRewards";
    bytes32 private constant CONTRACT_DELEGATEAPPROVALS = "DelegateApprovals";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_DEBTCACHE = "DebtCache";
    bytes32 private constant CONTRACT_CIRCUIT_BREAKER = "CircuitBreaker";
    bytes32 private constant CONTRACT_DIRECT_INTEGRATION_MANAGER = "DirectIntegrationManager";

    constructor(address _owner, address _resolver) public Owned(_owner) MixinSystemSettings(_resolver) {}

    /* ========== VIEWS ========== */

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = MixinSystemSettings.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](11);
        newAddresses[0] = CONTRACT_SYSTEMSTATUS;
        newAddresses[1] = CONTRACT_EXCHANGESTATE;
        newAddresses[2] = CONTRACT_EXRATES;
        newAddresses[3] = CONTRACT_SYNTHETIX;
        newAddresses[4] = CONTRACT_FEEPOOL;
        newAddresses[5] = CONTRACT_TRADING_REWARDS;
        newAddresses[6] = CONTRACT_DELEGATEAPPROVALS;
        newAddresses[7] = CONTRACT_ISSUER;
        newAddresses[8] = CONTRACT_DEBTCACHE;
        newAddresses[9] = CONTRACT_CIRCUIT_BREAKER;
        newAddresses[10] = CONTRACT_DIRECT_INTEGRATION_MANAGER;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    function systemStatus() internal view returns (ISystemStatus) {
        return ISystemStatus(requireAndGetAddress(CONTRACT_SYSTEMSTATUS));
    }

    function exchangeState() internal view returns (IExchangeState) {
        return IExchangeState(requireAndGetAddress(CONTRACT_EXCHANGESTATE));
    }

    function exchangeRates() internal view returns (IExchangeRates) {
        return IExchangeRates(requireAndGetAddress(CONTRACT_EXRATES));
    }

    function circuitBreaker() internal view returns (ICircuitBreaker) {
        return ICircuitBreaker(requireAndGetAddress(CONTRACT_CIRCUIT_BREAKER));
    }

    function synthetix() internal view returns (ISynthetix) {
        return ISynthetix(requireAndGetAddress(CONTRACT_SYNTHETIX));
    }

    function feePool() internal view returns (IFeePool) {
        return IFeePool(requireAndGetAddress(CONTRACT_FEEPOOL));
    }

    function tradingRewards() internal view returns (ITradingRewards) {
        return ITradingRewards(requireAndGetAddress(CONTRACT_TRADING_REWARDS));
    }

    function delegateApprovals() internal view returns (IDelegateApprovals) {
        return IDelegateApprovals(requireAndGetAddress(CONTRACT_DELEGATEAPPROVALS));
    }

    function issuer() internal view returns (IIssuer) {
        return IIssuer(requireAndGetAddress(CONTRACT_ISSUER));
    }

    function debtCache() internal view returns (IExchangerInternalDebtCache) {
        return IExchangerInternalDebtCache(requireAndGetAddress(CONTRACT_DEBTCACHE));
    }

    function directIntegrationManager() internal view returns (IDirectIntegrationManager) {
        return IDirectIntegrationManager(requireAndGetAddress(CONTRACT_DIRECT_INTEGRATION_MANAGER));
    }

    function resolvedAddresses() internal view returns (ExchangeSettlementLib.ResolvedAddresses memory) {
        return
            ExchangeSettlementLib.ResolvedAddresses(
                exchangeState(),
                exchangeRates(),
                circuitBreaker(),
                debtCache(),
                issuer(),
                synthetix()
            );
    }

    function waitingPeriodSecs() external view returns (uint) {
        return getWaitingPeriodSecs();
    }

    function tradingRewardsEnabled() external view returns (bool) {
        return getTradingRewardsEnabled();
    }

    function priceDeviationThresholdFactor() external view returns (uint) {
        return getPriceDeviationThresholdFactor();
    }

    function lastExchangeRate(bytes32 currencyKey) external view returns (uint) {
        return circuitBreaker().lastValue(address(exchangeRates().aggregators(currencyKey)));
    }

    function settlementOwing(address account, bytes32 currencyKey)
        public
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        )
    {
        (reclaimAmount, rebateAmount, numEntries, ) = ExchangeSettlementLib.settlementOwing(
            resolvedAddresses(),
            account,
            currencyKey,
            getWaitingPeriodSecs()
        );
    }

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool) {
        return
            ExchangeSettlementLib.hasWaitingPeriodOrSettlementOwing(
                resolvedAddresses(),
                account,
                currencyKey,
                getWaitingPeriodSecs()
            );
    }

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) public view returns (uint) {
        return
            ExchangeSettlementLib._secsLeftInWaitingPeriodForExchange(
                exchangeState().getMaxTimestamp(account, currencyKey),
                getWaitingPeriodSecs()
            );
    }

    /* ========== SETTERS ========== */

    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) public view returns (uint amountAfterSettlement) {
        amountAfterSettlement = amount;

        // balance of a synth will show an amount after settlement
        uint balanceOfSourceAfterSettlement = IERC20(address(issuer().synths(currencyKey))).balanceOf(from);

        // when there isn't enough supply (either due to reclamation settlement or because the number is too high)
        if (amountAfterSettlement > balanceOfSourceAfterSettlement) {
            // then the amount to exchange is reduced to their remaining supply
            amountAfterSettlement = balanceOfSourceAfterSettlement;
        }

        if (refunded > 0) {
            amountAfterSettlement = amountAfterSettlement.add(refunded);
        }
    }

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool) {
        (, bool invalid) = exchangeRates().rateAndInvalid(currencyKey);
        return invalid;
    }

    /* ========== MUTATIVE FUNCTIONS ========== */
    function exchange(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        bytes32 trackingCode
    ) external onlySynthetixorSynth returns (uint amountReceived, IVirtualSynth vSynth) {
        uint fee;
        if (from != exchangeForAddress) {
            require(delegateApprovals().canExchangeFor(exchangeForAddress, from), "Not approved to act on behalf");
        }

        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(from, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(from, destinationCurrencyKey);

        (amountReceived, fee, vSynth) = _exchange(
            exchangeForAddress,
            sourceSettings,
            sourceAmount,
            destinationSettings,
            destinationAddress,
            virtualSynth
        );

        _processTradingRewards(fee, rewardAddress);

        if (trackingCode != bytes32(0)) {
            _emitTrackingEvent(trackingCode, destinationCurrencyKey, amountReceived, fee);
        }
    }

    function exchangeAtomically(
        address,
        bytes32,
        uint,
        bytes32,
        address,
        bytes32,
        uint
    ) external returns (uint) {
        _notImplemented();
    }

    function _emitTrackingEvent(
        bytes32 trackingCode,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        uint256 fee
    ) internal {
        ISynthetixInternal(address(synthetix())).emitExchangeTracking(trackingCode, toCurrencyKey, toAmount, fee);
    }

    function _processTradingRewards(uint fee, address rewardAddress) internal {
        if (fee > 0 && rewardAddress != address(0) && getTradingRewardsEnabled()) {
            tradingRewards().recordExchangeFeeForAccount(fee, rewardAddress);
        }
    }

    function _updateSNXIssuedDebtOnExchange(bytes32[2] memory currencyKeys, uint[2] memory currencyRates) internal {
        bool includesSUSD = currencyKeys[0] == sUSD || currencyKeys[1] == sUSD;
        uint numKeys = includesSUSD ? 2 : 3;

        bytes32[] memory keys = new bytes32[](numKeys);
        keys[0] = currencyKeys[0];
        keys[1] = currencyKeys[1];

        uint[] memory rates = new uint[](numKeys);
        rates[0] = currencyRates[0];
        rates[1] = currencyRates[1];

        if (!includesSUSD) {
            keys[2] = sUSD; // And we'll also update sUSD to account for any fees if it wasn't one of the exchanged currencies
            rates[2] = SafeDecimalMath.unit();
        }

        // Note that exchanges can't invalidate the debt cache, since if a rate is invalid,
        // the exchange will have failed already.
        debtCache().updateCachedSynthDebtsWithRates(keys, rates);
    }

    function _settleAndCalcSourceAmountRemaining(
        uint sourceAmount,
        address from,
        bytes32 sourceCurrencyKey
    ) internal returns (uint sourceAmountAfterSettlement) {
        (, uint refunded, uint numEntriesSettled) =
            ExchangeSettlementLib.internalSettle(
                resolvedAddresses(),
                from,
                sourceCurrencyKey,
                false,
                getWaitingPeriodSecs()
            );

        sourceAmountAfterSettlement = sourceAmount;

        // when settlement was required
        if (numEntriesSettled > 0) {
            // ensure the sourceAmount takes this into account
            sourceAmountAfterSettlement = calculateAmountAfterSettlement(from, sourceCurrencyKey, sourceAmount, refunded);
        }
    }

    function _exchange(
        address from,
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        uint sourceAmount,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings,
        address destinationAddress,
        bool virtualSynth
    )
        internal
        returns (
            uint amountReceived,
            uint fee,
            IVirtualSynth vSynth
        )
    {
        if (!_ensureCanExchange(sourceSettings.currencyKey, destinationSettings.currencyKey, sourceAmount)) {
            return (0, 0, IVirtualSynth(0));
        }

        // Using struct to resolve stack too deep error
        IExchanger.ExchangeEntry memory entry;
        ExchangeSettlementLib.ResolvedAddresses memory addrs = resolvedAddresses();

        entry.roundIdForSrc = addrs.exchangeRates.getCurrentRoundId(sourceSettings.currencyKey);
        entry.roundIdForDest = addrs.exchangeRates.getCurrentRoundId(destinationSettings.currencyKey);

        entry.sourceAmountAfterSettlement = _settleAndCalcSourceAmountRemaining(
            sourceAmount,
            from,
            sourceSettings.currencyKey
        );

        // If, after settlement the user has no balance left (highly unlikely), then return to prevent
        // emitting events of 0 and don't revert so as to ensure the settlement queue is emptied
        if (entry.sourceAmountAfterSettlement == 0) {
            return (0, 0, IVirtualSynth(0));
        }

        (entry.destinationAmount, entry.sourceRate, entry.destinationRate) = addrs
            .exchangeRates
            .effectiveValueAndRatesAtRound(
            sourceSettings.currencyKey,
            entry.sourceAmountAfterSettlement,
            destinationSettings.currencyKey,
            entry.roundIdForSrc,
            entry.roundIdForDest
        );

        // rates must also be good for the round we are doing
        _ensureCanExchangeAtRound(
            sourceSettings.currencyKey,
            destinationSettings.currencyKey,
            entry.roundIdForSrc,
            entry.roundIdForDest
        );

        bool tooVolatile;
        (entry.exchangeFeeRate, tooVolatile) = _feeRateForExchangeAtRounds(
            sourceSettings,
            destinationSettings,
            entry.roundIdForSrc,
            entry.roundIdForDest
        );

        if (tooVolatile) {
            // do not exchange if rates are too volatile, this to prevent charging
            // dynamic fees that are over the max value
            return (0, 0, IVirtualSynth(0));
        }

        amountReceived = ExchangeSettlementLib._deductFeesFromAmount(entry.destinationAmount, entry.exchangeFeeRate);
        // Note: `fee` is denominated in the destinationCurrencyKey.
        fee = entry.destinationAmount.sub(amountReceived);

        // Note: We don't need to check their balance as the _convert() below will do a safe subtraction which requires
        // the subtraction to not overflow, which would happen if their balance is not sufficient.
        vSynth = _convert(
            sourceSettings.currencyKey,
            from,
            entry.sourceAmountAfterSettlement,
            destinationSettings.currencyKey,
            amountReceived,
            destinationAddress,
            virtualSynth
        );

        // When using a virtual synth, it becomes the destinationAddress for event and settlement tracking
        if (vSynth != IVirtualSynth(0)) {
            destinationAddress = address(vSynth);
        }

        // Remit the fee if required
        if (fee > 0) {
            // Normalize fee to sUSD
            // Note: `fee` is being reused to avoid stack too deep errors.
            fee = addrs.exchangeRates.effectiveValue(destinationSettings.currencyKey, fee, sUSD);

            // Remit the fee in sUSDs
            issuer().synths(sUSD).issue(feePool().FEE_ADDRESS(), fee);

            // Tell the fee pool about this
            feePool().recordFeePaid(fee);
        }

        // Note: As of this point, `fee` is denominated in sUSD.

        // Nothing changes as far as issuance data goes because the total value in the system hasn't changed.
        // But we will update the debt snapshot in case exchange rates have fluctuated since the last exchange
        // in these currencies
        _updateSNXIssuedDebtOnExchange(
            [sourceSettings.currencyKey, destinationSettings.currencyKey],
            [entry.sourceRate, entry.destinationRate]
        );

        // Let the DApps know there was a Synth exchange
        ISynthetixInternal(address(synthetix())).emitSynthExchange(
            from,
            sourceSettings.currencyKey,
            entry.sourceAmountAfterSettlement,
            destinationSettings.currencyKey,
            amountReceived,
            destinationAddress
        );

        // iff the waiting period is gt 0
        if (getWaitingPeriodSecs() > 0) {
            // persist the exchange information for the dest key
            ExchangeSettlementLib.appendExchange(
                addrs,
                destinationAddress,
                sourceSettings.currencyKey,
                entry.sourceAmountAfterSettlement,
                destinationSettings.currencyKey,
                amountReceived,
                entry.exchangeFeeRate
            );
        }
    }

    function _convert(
        bytes32 sourceCurrencyKey,
        address from,
        uint sourceAmountAfterSettlement,
        bytes32 destinationCurrencyKey,
        uint amountReceived,
        address recipient,
        bool virtualSynth
    ) internal returns (IVirtualSynth vSynth) {
        // Burn the source amount
        issuer().synths(sourceCurrencyKey).burn(from, sourceAmountAfterSettlement);

        // Issue their new synths
        ISynth dest = issuer().synths(destinationCurrencyKey);

        if (virtualSynth) {
            Proxyable synth = Proxyable(address(dest));
            vSynth = _createVirtualSynth(IERC20(address(synth.proxy())), recipient, amountReceived, destinationCurrencyKey);
            dest.issue(address(vSynth), amountReceived);
        } else {
            dest.issue(recipient, amountReceived);
        }
    }

    function _createVirtualSynth(
        IERC20,
        address,
        uint,
        bytes32
    ) internal returns (IVirtualSynth) {
        _notImplemented();
    }

    // Note: this function can intentionally be called by anyone on behalf of anyone else (the caller just pays the gas)
    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntriesSettled
        )
    {
        systemStatus().requireSynthActive(currencyKey);
        return ExchangeSettlementLib.internalSettle(resolvedAddresses(), from, currencyKey, true, getWaitingPeriodSecs());
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    // gets the exchange parameters for a given direct integration (returns default params if no overrides exist)
    function _exchangeSettings(address from, bytes32 currencyKey)
        internal
        view
        returns (IDirectIntegrationManager.ParameterIntegrationSettings memory settings)
    {
        settings = directIntegrationManager().getExchangeParameters(from, currencyKey);
    }

    // runs basic checks and calls `rateWithSafetyChecks` (which can trigger circuit breakers)
    // returns if there are any problems found with the rate of the given currencyKey but not reverted
    function _ensureCanExchange(
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey,
        uint sourceAmount
    ) internal returns (bool) {
        require(sourceCurrencyKey != destinationCurrencyKey, "Can't be same synth");
        require(sourceAmount > 0, "Zero amount");

        (, bool srcBroken, bool srcStaleOrInvalid) =
            sourceCurrencyKey != sUSD ? exchangeRates().rateWithSafetyChecks(sourceCurrencyKey) : (0, false, false);
        (, bool dstBroken, bool dstStaleOrInvalid) =
            destinationCurrencyKey != sUSD
                ? exchangeRates().rateWithSafetyChecks(destinationCurrencyKey)
                : (0, false, false);

        require(!srcStaleOrInvalid, "src rate stale or flagged");
        require(!dstStaleOrInvalid, "dest rate stale or flagged");

        return !srcBroken && !dstBroken;
    }

    // runs additional checks to verify a rate is valid at a specific round`
    function _ensureCanExchangeAtRound(
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey,
        uint roundIdForSrc,
        uint roundIdForDest
    ) internal view {
        require(sourceCurrencyKey != destinationCurrencyKey, "Can't be same synth");

        bytes32[] memory synthKeys = new bytes32[](2);
        synthKeys[0] = sourceCurrencyKey;
        synthKeys[1] = destinationCurrencyKey;

        uint[] memory roundIds = new uint[](2);
        roundIds[0] = roundIdForSrc;
        roundIds[1] = roundIdForDest;
        require(!exchangeRates().anyRateIsInvalidAtRound(synthKeys, roundIds), "src/dest rate stale or flagged");
    }

    /* ========== Exchange Related Fees ========== */
    /// @notice public function to get the total fee rate for a given exchange
    /// @param sourceCurrencyKey The source currency key
    /// @param destinationCurrencyKey The destination currency key
    /// @return The exchange fee rate, and whether the rates are too volatile
    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view returns (uint) {
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(msg.sender, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(msg.sender, destinationCurrencyKey);

        (uint feeRate, bool tooVolatile) = _feeRateForExchange(sourceSettings, destinationSettings);
        require(!tooVolatile, "too volatile");
        return feeRate;
    }

    /// @notice public function to get the dynamic fee rate for a given exchange
    /// @param sourceCurrencyKey The source currency key
    /// @param destinationCurrencyKey The destination currency key
    /// @return The exchange dynamic fee rate and if rates are too volatile
    function dynamicFeeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint feeRate, bool tooVolatile)
    {
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(msg.sender, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(msg.sender, destinationCurrencyKey);

        return _dynamicFeeRateForExchange(sourceSettings, destinationSettings);
    }

    /// @notice Calculate the exchange fee for a given source and destination currency key
    /// @param sourceSettings The source currency key
    /// @param destinationSettings The destination currency key
    /// @return The exchange fee rate
    /// @return The exchange dynamic fee rate and if rates are too volatile
    function _feeRateForExchange(
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings
    ) internal view returns (uint feeRate, bool tooVolatile) {
        // Get the exchange fee rate as per the source currencyKey and destination currencyKey
        uint baseRate = sourceSettings.exchangeFeeRate.add(destinationSettings.exchangeFeeRate);
        uint dynamicFee;
        (dynamicFee, tooVolatile) = _dynamicFeeRateForExchange(sourceSettings, destinationSettings);
        return (baseRate.add(dynamicFee), tooVolatile);
    }

    /// @notice Calculate the exchange fee for a given source and destination currency key
    /// @param sourceSettings The source currency key
    /// @param destinationSettings The destination currency key
    /// @param roundIdForSrc The round id of the source currency.
    /// @param roundIdForDest The round id of the target currency.
    /// @return The exchange fee rate
    /// @return The exchange dynamic fee rate
    function _feeRateForExchangeAtRounds(
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings,
        uint roundIdForSrc,
        uint roundIdForDest
    ) internal view returns (uint feeRate, bool tooVolatile) {
        // Get the exchange fee rate as per the source currencyKey and destination currencyKey
        uint baseRate = sourceSettings.exchangeFeeRate.add(destinationSettings.exchangeFeeRate);
        uint dynamicFee;
        (dynamicFee, tooVolatile) = _dynamicFeeRateForExchangeAtRounds(
            sourceSettings,
            destinationSettings,
            roundIdForSrc,
            roundIdForDest
        );
        return (baseRate.add(dynamicFee), tooVolatile);
    }

    function _dynamicFeeRateForExchange(
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings
    ) internal view returns (uint dynamicFee, bool tooVolatile) {
        (uint dynamicFeeDst, bool dstVolatile) = _dynamicFeeRateForCurrency(destinationSettings);
        (uint dynamicFeeSrc, bool srcVolatile) = _dynamicFeeRateForCurrency(sourceSettings);
        dynamicFee = dynamicFeeDst.add(dynamicFeeSrc);
        // cap to maxFee
        bool overMax = dynamicFee > sourceSettings.exchangeMaxDynamicFee;
        dynamicFee = overMax ? sourceSettings.exchangeMaxDynamicFee : dynamicFee;
        return (dynamicFee, overMax || dstVolatile || srcVolatile);
    }

    function _dynamicFeeRateForExchangeAtRounds(
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings,
        uint roundIdForSrc,
        uint roundIdForDest
    ) internal view returns (uint dynamicFee, bool tooVolatile) {
        (uint dynamicFeeDst, bool dstVolatile) = _dynamicFeeRateForCurrencyRound(destinationSettings, roundIdForDest);
        (uint dynamicFeeSrc, bool srcVolatile) = _dynamicFeeRateForCurrencyRound(sourceSettings, roundIdForSrc);
        dynamicFee = dynamicFeeDst.add(dynamicFeeSrc);
        // cap to maxFee
        bool overMax = dynamicFee > sourceSettings.exchangeMaxDynamicFee;
        dynamicFee = overMax ? sourceSettings.exchangeMaxDynamicFee : dynamicFee;
        return (dynamicFee, overMax || dstVolatile || srcVolatile);
    }

    /// @notice Get dynamic dynamicFee for a given currency key (SIP-184)
    /// @param settings The given currency key
    /// @return The dynamic fee and if it exceeds max dynamic fee set in config
    function _dynamicFeeRateForCurrency(IDirectIntegrationManager.ParameterIntegrationSettings memory settings)
        internal
        view
        returns (uint dynamicFee, bool tooVolatile)
    {
        // no dynamic dynamicFee for sUSD or too few rounds
        if (settings.currencyKey == sUSD || settings.exchangeDynamicFeeRounds <= 1) {
            return (0, false);
        }
        uint roundId = exchangeRates().getCurrentRoundId(settings.currencyKey);
        return _dynamicFeeRateForCurrencyRound(settings, roundId);
    }

    /// @notice Get dynamicFee for a given currency key (SIP-184)
    /// @param settings The given currency key
    /// @param roundId The round id
    /// @return The dynamic fee and if it exceeds max dynamic fee set in config
    function _dynamicFeeRateForCurrencyRound(
        IDirectIntegrationManager.ParameterIntegrationSettings memory settings,
        uint roundId
    ) internal view returns (uint dynamicFee, bool tooVolatile) {
        // no dynamic dynamicFee for sUSD or too few rounds
        if (settings.currencyKey == sUSD || settings.exchangeDynamicFeeRounds <= 1) {
            return (0, false);
        }
        uint[] memory prices;
        (prices, ) = exchangeRates().ratesAndUpdatedTimeForCurrencyLastNRounds(
            settings.currencyKey,
            settings.exchangeDynamicFeeRounds,
            roundId
        );
        dynamicFee = _dynamicFeeCalculation(
            prices,
            settings.exchangeDynamicFeeThreshold,
            settings.exchangeDynamicFeeWeightDecay
        );
        // cap to maxFee
        bool overMax = dynamicFee > settings.exchangeMaxDynamicFee;
        dynamicFee = overMax ? settings.exchangeMaxDynamicFee : dynamicFee;
        return (dynamicFee, overMax);
    }

    /// @notice Calculate dynamic fee according to SIP-184
    /// @param prices A list of prices from the current round to the previous rounds
    /// @param threshold A threshold to clip the price deviation ratop
    /// @param weightDecay A weight decay constant
    /// @return uint dynamic fee rate as decimal
    function _dynamicFeeCalculation(
        uint[] memory prices,
        uint threshold,
        uint weightDecay
    ) internal pure returns (uint) {
        // don't underflow
        if (prices.length == 0) {
            return 0;
        }

        uint dynamicFee = 0; // start with 0
        // go backwards in price array
        for (uint i = prices.length - 1; i > 0; i--) {
            // apply decay from previous round (will be 0 for first round)
            dynamicFee = dynamicFee.multiplyDecimal(weightDecay);
            // calculate price deviation
            uint deviation = _thresholdedAbsDeviationRatio(prices[i - 1], prices[i], threshold);
            // add to total fee
            dynamicFee = dynamicFee.add(deviation);
        }
        return dynamicFee;
    }

    /// absolute price deviation ratio used by dynamic fee calculation
    /// deviationRatio = (abs(current - previous) / previous) - threshold
    /// if negative, zero is returned
    function _thresholdedAbsDeviationRatio(
        uint price,
        uint previousPrice,
        uint threshold
    ) internal pure returns (uint) {
        if (previousPrice == 0) {
            return 0; // don't divide by zero
        }
        // abs difference between prices
        uint absDelta = price > previousPrice ? price - previousPrice : previousPrice - price;
        // relative to previous price
        uint deviationRatio = absDelta.divideDecimal(previousPrice);
        // only the positive difference from threshold
        return deviationRatio > threshold ? deviationRatio - threshold : 0;
    }

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        )
    {
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(msg.sender, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(msg.sender, destinationCurrencyKey);

        require(sourceCurrencyKey == sUSD || !exchangeRates().rateIsInvalid(sourceCurrencyKey), "src synth rate invalid");

        require(
            destinationCurrencyKey == sUSD || !exchangeRates().rateIsInvalid(destinationCurrencyKey),
            "dest synth rate invalid"
        );

        // The checks are added for consistency with the checks performed in _exchange()
        // The reverts (instead of no-op returns) are used order to prevent incorrect usage in calling contracts
        // (The no-op in _exchange() is in order to trigger system suspension if needed)

        // check synths active
        systemStatus().requireSynthActive(sourceCurrencyKey);
        systemStatus().requireSynthActive(destinationCurrencyKey);

        bool tooVolatile;
        (exchangeFeeRate, tooVolatile) = _feeRateForExchange(sourceSettings, destinationSettings);

        // check rates volatility result
        require(!tooVolatile, "exchange rates too volatile");

        (uint destinationAmount, , ) =
            exchangeRates().effectiveValueAndRates(sourceCurrencyKey, sourceAmount, destinationCurrencyKey);

        amountReceived = ExchangeSettlementLib._deductFeesFromAmount(destinationAmount, exchangeFeeRate);
        fee = destinationAmount.sub(amountReceived);
    }

    function _notImplemented() internal pure {
        revert("Cannot be run on this layer");
    }

    // ========== MODIFIERS ==========

    modifier onlySynthetixorSynth() {
        ISynthetix _synthetix = synthetix();
        require(
            msg.sender == address(_synthetix) || _synthetix.synthsByAddress(msg.sender) != bytes32(0),
            "Exchanger: Only synthetix or a synth contract can perform this action"
        );
        _;
    }

    // ========== EVENTS ==========
    // note bot hof these events are actually emitted from `ExchangeSettlementLib`
    // but they are defined here for interface reasons
    event ExchangeEntryAppended(
        address indexed account,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 amountReceived,
        uint256 exchangeFeeRate,
        uint256 roundIdForSrc,
        uint256 roundIdForDest
    );

    event ExchangeEntrySettled(
        address indexed from,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 reclaim,
        uint256 rebate,
        uint256 srcRoundIdAtPeriodEnd,
        uint256 destRoundIdAtPeriodEnd,
        uint256 exchangeTimestamp
    );
}


// https://docs.synthetix.io/contracts/source/contracts/minimalproxyfactory
contract MinimalProxyFactory {
    function _cloneAsMinimalProxy(address _base, string memory _revertMsg) internal returns (address clone) {
        bytes memory createData = _generateMinimalProxyCreateData(_base);

        assembly {
            clone := create(
                0, // no value
                add(createData, 0x20), // data
                55 // data is always 55 bytes (10 constructor + 45 code)
            )
        }

        // If CREATE fails for some reason, address(0) is returned
        require(clone != address(0), _revertMsg);
    }

    function _generateMinimalProxyCreateData(address _base) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                //---- constructor -----
                bytes10(0x3d602d80600a3d3981f3),
                //---- proxy code -----
                bytes10(0x363d3d373d3d3d363d73),
                _base,
                bytes15(0x5af43d82803e903d91602b57fd5bf3)
            );
    }
}


// Inheritance


// Internal references


interface IVirtualSynthInternal {
    function initialize(
        IERC20 _synth,
        IAddressResolver _resolver,
        address _recipient,
        uint _amount,
        bytes32 _currencyKey
    ) external;
}

// https://docs.synthetix.io/contracts/source/contracts/exchangerwithfeereclamationalternatives
contract ExchangerWithFeeRecAlternatives is MinimalProxyFactory, Exchanger {
    bytes32 public constant CONTRACT_NAME = "ExchangerWithFeeRecAlternatives";

    using SafeMath for uint;

    struct ExchangeVolumeAtPeriod {
        uint64 time;
        uint192 volume;
    }

    ExchangeVolumeAtPeriod public lastAtomicVolume;

    constructor(address _owner, address _resolver) public MinimalProxyFactory() Exchanger(_owner, _resolver) {}

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_VIRTUALSYNTH_MASTERCOPY = "VirtualSynthMastercopy";

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = Exchanger.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](1);
        newAddresses[0] = CONTRACT_VIRTUALSYNTH_MASTERCOPY;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    /* ========== VIEWS ========== */

    function atomicMaxVolumePerBlock() external view returns (uint) {
        return getAtomicMaxVolumePerBlock();
    }

    function feeRateForAtomicExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint exchangeFeeRate)
    {
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(msg.sender, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(msg.sender, destinationCurrencyKey);
        exchangeFeeRate = _feeRateForAtomicExchange(sourceSettings, destinationSettings);
    }

    function getAmountsForAtomicExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        )
    {
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
            _exchangeSettings(msg.sender, sourceCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
            _exchangeSettings(msg.sender, destinationCurrencyKey);
        IDirectIntegrationManager.ParameterIntegrationSettings memory usdSettings = _exchangeSettings(msg.sender, sUSD);

        (amountReceived, fee, exchangeFeeRate, , , ) = _getAmountsForAtomicExchangeMinusFees(
            sourceAmount,
            sourceSettings,
            destinationSettings,
            usdSettings
        );
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode,
        uint minAmount
    ) external onlySynthetixorSynth returns (uint amountReceived) {
        uint fee;
        (amountReceived, fee) = _exchangeAtomically(
            from,
            sourceCurrencyKey,
            sourceAmount,
            destinationCurrencyKey,
            destinationAddress
        );

        require(amountReceived >= minAmount, "The amount received is below the minimum amount specified.");

        _processTradingRewards(fee, destinationAddress);

        if (trackingCode != bytes32(0)) {
            _emitTrackingEvent(trackingCode, destinationCurrencyKey, amountReceived, fee);
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _virtualSynthMastercopy() internal view returns (address) {
        return requireAndGetAddress(CONTRACT_VIRTUALSYNTH_MASTERCOPY);
    }

    function _createVirtualSynth(
        IERC20 synth,
        address recipient,
        uint amount,
        bytes32 currencyKey
    ) internal returns (IVirtualSynth) {
        // prevent inverse synths from being allowed due to purgeability
        require(currencyKey[0] != 0x69, "Cannot virtualize this synth");

        IVirtualSynthInternal vSynth =
            IVirtualSynthInternal(_cloneAsMinimalProxy(_virtualSynthMastercopy(), "Could not create new vSynth"));
        vSynth.initialize(synth, resolver, recipient, amount, currencyKey);
        emit VirtualSynthCreated(address(synth), recipient, address(vSynth), currencyKey, amount);

        return IVirtualSynth(address(vSynth));
    }

    function _exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress
    ) internal returns (uint amountReceived, uint fee) {
        uint sourceAmountAfterSettlement;
        uint exchangeFeeRate;
        uint systemSourceRate;
        uint systemDestinationRate;

        {
            IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings =
                _exchangeSettings(from, sourceCurrencyKey);
            IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings =
                _exchangeSettings(from, destinationCurrencyKey);

            if (!_ensureCanExchange(sourceCurrencyKey, destinationCurrencyKey, sourceAmount)) {
                return (0, 0);
            }
            require(!exchangeRates().synthTooVolatileForAtomicExchange(sourceSettings), "Src synth too volatile");
            require(!exchangeRates().synthTooVolatileForAtomicExchange(destinationSettings), "Dest synth too volatile");

            sourceAmountAfterSettlement = _settleAndCalcSourceAmountRemaining(sourceAmount, from, sourceCurrencyKey);

            // If, after settlement the user has no balance left (highly unlikely), then return to prevent
            // emitting events of 0 and don't revert so as to ensure the settlement queue is emptied
            if (sourceAmountAfterSettlement == 0) {
                return (0, 0);
            }

            // sometimes we need parameters for USD and USD has parameters which could be overridden
            IDirectIntegrationManager.ParameterIntegrationSettings memory usdSettings = _exchangeSettings(from, sUSD);

            uint systemConvertedAmount;

            // Note: also ensures the given synths are allowed to be atomically exchanged
            (
                amountReceived, // output amount with fee taken out (denominated in dest currency)
                fee, // fee amount (denominated in dest currency)
                exchangeFeeRate, // applied fee rate
                systemConvertedAmount, // current system value without fees (denominated in dest currency)
                systemSourceRate, // current system rate for src currency
                systemDestinationRate // current system rate for dest currency
            ) = _getAmountsForAtomicExchangeMinusFees(
                sourceAmountAfterSettlement,
                sourceSettings,
                destinationSettings,
                usdSettings
            );

            // Sanity check atomic output's value against current system value (checking atomic rates)
            require(
                !circuitBreaker().isDeviationAboveThreshold(systemConvertedAmount, amountReceived.add(fee)),
                "Atomic rate deviates too much"
            );

            // Determine sUSD value of exchange
            uint sourceSusdValue;
            if (sourceCurrencyKey == sUSD) {
                // Use after-settled amount as this is amount converted (not sourceAmount)
                sourceSusdValue = sourceAmountAfterSettlement;
            } else if (destinationCurrencyKey == sUSD) {
                // In this case the systemConvertedAmount would be the fee-free sUSD value of the source synth
                sourceSusdValue = systemConvertedAmount;
            } else {
                // Otherwise, convert source to sUSD value
                (uint amountReceivedInUSD, uint sUsdFee, , , , ) =
                    _getAmountsForAtomicExchangeMinusFees(
                        sourceAmountAfterSettlement,
                        sourceSettings,
                        usdSettings,
                        usdSettings
                    );
                sourceSusdValue = amountReceivedInUSD.add(sUsdFee);
            }

            // Check and update atomic volume limit
            _checkAndUpdateAtomicVolume(sourceSettings, sourceSusdValue);
        }

        // Note: We don't need to check their balance as the _convert() below will do a safe subtraction which requires
        // the subtraction to not overflow, which would happen if their balance is not sufficient.

        _convert(
            sourceCurrencyKey,
            from,
            sourceAmountAfterSettlement,
            destinationCurrencyKey,
            amountReceived,
            destinationAddress,
            false // no vsynths
        );

        // Remit the fee if required
        if (fee > 0) {
            // Normalize fee to sUSD
            // Note: `fee` is being reused to avoid stack too deep errors.
            fee = exchangeRates().effectiveValue(destinationCurrencyKey, fee, sUSD);

            // Remit the fee in sUSDs
            issuer().synths(sUSD).issue(feePool().FEE_ADDRESS(), fee);

            // Tell the fee pool about this
            feePool().recordFeePaid(fee);
        }

        // Note: As of this point, `fee` is denominated in sUSD.

        // Note: this update of the debt snapshot will not be accurate because the atomic exchange
        // was executed with a different rate than the system rate. To be perfect, issuance data,
        // priced in system rates, should have been adjusted on the src and dest synth.
        // The debt pool is expected to be deprecated soon, and so we don't bother with being
        // perfect here. For now, an inaccuracy will slowly accrue over time with increasing atomic
        // exchange volume.
        _updateSNXIssuedDebtOnExchange(
            [sourceCurrencyKey, destinationCurrencyKey],
            [systemSourceRate, systemDestinationRate]
        );

        // Let the DApps know there was a Synth exchange
        ISynthetixInternal(address(synthetix())).emitSynthExchange(
            from,
            sourceCurrencyKey,
            sourceAmountAfterSettlement,
            destinationCurrencyKey,
            amountReceived,
            destinationAddress
        );

        // Emit separate event to track atomic exchanges
        ISynthetixInternal(address(synthetix())).emitAtomicSynthExchange(
            from,
            sourceCurrencyKey,
            sourceAmountAfterSettlement,
            destinationCurrencyKey,
            amountReceived,
            destinationAddress
        );

        // No need to persist any exchange information, as no settlement is required for atomic exchanges
    }

    function _checkAndUpdateAtomicVolume(
        IDirectIntegrationManager.ParameterIntegrationSettings memory settings,
        uint sourceSusdValue
    ) internal {
        uint currentVolume =
            uint(lastAtomicVolume.time) == block.timestamp
                ? uint(lastAtomicVolume.volume).add(sourceSusdValue)
                : sourceSusdValue;
        require(currentVolume <= settings.atomicMaxVolumePerBlock, "Surpassed volume limit");
        lastAtomicVolume.time = uint64(block.timestamp);
        lastAtomicVolume.volume = uint192(currentVolume); // Protected by volume limit check above
    }

    function _feeRateForAtomicExchange(
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings
    ) internal view returns (uint) {
        // Get the exchange fee rate as per source and destination currencyKey
        uint baseRate = sourceSettings.atomicExchangeFeeRate.add(destinationSettings.atomicExchangeFeeRate);
        if (baseRate == 0) {
            // If no atomic rate was set, fallback to the regular exchange rate
            baseRate = sourceSettings.exchangeFeeRate.add(destinationSettings.exchangeFeeRate);
        }

        return baseRate;
    }

    function _getAmountsForAtomicExchangeMinusFees(
        uint sourceAmount,
        IDirectIntegrationManager.ParameterIntegrationSettings memory sourceSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory destinationSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings memory usdSettings
    )
        internal
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate,
            uint systemConvertedAmount,
            uint systemSourceRate,
            uint systemDestinationRate
        )
    {
        uint destinationAmount;
        (destinationAmount, systemConvertedAmount, systemSourceRate, systemDestinationRate) = exchangeRates()
            .effectiveAtomicValueAndRates(sourceSettings, sourceAmount, destinationSettings, usdSettings);

        exchangeFeeRate = _feeRateForAtomicExchange(sourceSettings, destinationSettings);
        amountReceived = ExchangeSettlementLib._deductFeesFromAmount(destinationAmount, exchangeFeeRate);
        fee = destinationAmount.sub(amountReceived);
    }

    event VirtualSynthCreated(
        address indexed synth,
        address indexed recipient,
        address vSynth,
        bytes32 currencyKey,
        uint amount
    );
}

    

/*
* Synthetix - ExchangeState.sol
*
* https://github.com/Synthetixio/synthetix
* https://synthetix.io
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,	
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/
    
/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski

date:       2018-2-26

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).

-----------------------------------------------------------------
*/

pragma solidity 0.4.25;


/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;

    /**
     * @dev Owned Constructor
     */
    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       State.sol
version:    1.1
author:     Dominic Romanowski
            Anton Jurisevic

date:       2018-05-15

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

This contract is used side by side with external state token
contracts, such as Synthetix and Synth.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.

The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.

-----------------------------------------------------------------
*/


contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;

    constructor(address _owner, address _associatedContract) public Owned(_owner) {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract) external onlyOwner {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract {
        require(msg.sender == associatedContract, "Only the associated contract can perform this action");
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address associatedContract);
}


contract ExchangeState is State {
    struct ExchangeEntry {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint amountReceived;
        uint exchangeFeeRate;
        uint timestamp;
        uint roundIdForSrc;
        uint roundIdForDest;
    }

    mapping(address => mapping(bytes32 => ExchangeEntry[])) public exchanges;

    uint public maxEntriesInQueue = 12;

    constructor(address _owner, address _associatedContract) public State(_owner, _associatedContract) {}

    /* ========== SETTERS ========== */

    function setMaxEntriesInQueue(uint _maxEntriesInQueue) external onlyOwner {
        maxEntriesInQueue = _maxEntriesInQueue;
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function appendExchangeEntry(
        address account,
        bytes32 src,
        uint amount,
        bytes32 dest,
        uint amountReceived,
        uint exchangeFeeRate,
        uint timestamp,
        uint roundIdForSrc,
        uint roundIdForDest
    ) external onlyAssociatedContract {
        require(exchanges[account][dest].length < maxEntriesInQueue, "Max queue length reached");

        exchanges[account][dest].push(
            ExchangeEntry({
                src: src,
                amount: amount,
                dest: dest,
                amountReceived: amountReceived,
                exchangeFeeRate: exchangeFeeRate,
                timestamp: timestamp,
                roundIdForSrc: roundIdForSrc,
                roundIdForDest: roundIdForDest
            })
        );
    }

    function removeEntries(address account, bytes32 currencyKey) external onlyAssociatedContract {
        delete exchanges[account][currencyKey];
    }

    /* ========== VIEWS ========== */

    function getLengthOfEntries(address account, bytes32 currencyKey) external view returns (uint) {
        return exchanges[account][currencyKey].length;
    }

    function getEntryAt(address account, bytes32 currencyKey, uint index)
        external
        view
        returns (
            bytes32 src,
            uint amount,
            bytes32 dest,
            uint amountReceived,
            uint exchangeFeeRate,
            uint timestamp,
            uint roundIdForSrc,
            uint roundIdForDest
        )
    {
        ExchangeEntry storage entry = exchanges[account][currencyKey][index];
        return (
            entry.src,
            entry.amount,
            entry.dest,
            entry.amountReceived,
            entry.exchangeFeeRate,
            entry.timestamp,
            entry.roundIdForSrc,
            entry.roundIdForDest
        );
    }

    function getMaxTimestamp(address account, bytes32 currencyKey) external view returns (uint) {
        ExchangeEntry[] storage userEntries = exchanges[account][currencyKey];
        uint timestamp = 0;
        for (uint i = 0; i < userEntries.length; i++) {
            if (userEntries[i].timestamp > timestamp) {
                timestamp = userEntries[i].timestamp;
            }
        }
        return timestamp;
    }
}


    

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: FlexibleStorage.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/FlexibleStorage.sol
* Docs: https://docs.synthetix.io/contracts/FlexibleStorage
*
* Contract Dependencies: 
*	- ContractStorage
*	- IFlexibleStorage
* Libraries: (none)
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity >=0.4.24;


interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


// Internal References


// https://docs.synthetix.io/contracts/source/contracts/ContractStorage
contract ContractStorage {
    IAddressResolver public resolverProxy;

    mapping(bytes32 => bytes32) public hashes;

    constructor(address _resolver) internal {
        // ReadProxyAddressResolver
        resolverProxy = IAddressResolver(_resolver);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _memoizeHash(bytes32 contractName) internal returns (bytes32) {
        bytes32 hashKey = hashes[contractName];
        if (hashKey == bytes32(0)) {
            // set to unique hash at the time of creation
            hashKey = keccak256(abi.encodePacked(msg.sender, contractName, block.number));
            hashes[contractName] = hashKey;
        }
        return hashKey;
    }

    /* ========== VIEWS ========== */

    /* ========== RESTRICTED FUNCTIONS ========== */

    function migrateContractKey(
        bytes32 fromContractName,
        bytes32 toContractName,
        bool removeAccessFromPreviousContract
    ) external onlyContract(fromContractName) {
        require(hashes[fromContractName] != bytes32(0), "Cannot migrate empty contract");

        hashes[toContractName] = hashes[fromContractName];

        if (removeAccessFromPreviousContract) {
            delete hashes[fromContractName];
        }

        emit KeyMigrated(fromContractName, toContractName, removeAccessFromPreviousContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyContract(bytes32 contractName) {
        address callingContract = resolverProxy.requireAndGetAddress(
            contractName,
            "Cannot find contract in Address Resolver"
        );
        require(callingContract == msg.sender, "Can only be invoked by the configured contract");
        _;
    }

    /* ========== EVENTS ========== */

    event KeyMigrated(bytes32 fromContractName, bytes32 toContractName, bool removeAccessFromPreviousContract);
}


interface IFlexibleStorage {
    // Views
    function getUIntValue(bytes32 contractName, bytes32 record) external view returns (uint);

    function getUIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (uint[] memory);

    function getIntValue(bytes32 contractName, bytes32 record) external view returns (int);

    function getIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (int[] memory);

    function getAddressValue(bytes32 contractName, bytes32 record) external view returns (address);

    function getAddressValues(bytes32 contractName, bytes32[] calldata records) external view returns (address[] memory);

    function getBoolValue(bytes32 contractName, bytes32 record) external view returns (bool);

    function getBoolValues(bytes32 contractName, bytes32[] calldata records) external view returns (bool[] memory);

    function getBytes32Value(bytes32 contractName, bytes32 record) external view returns (bytes32);

    function getBytes32Values(bytes32 contractName, bytes32[] calldata records) external view returns (bytes32[] memory);

    // Mutative functions
    function deleteUIntValue(bytes32 contractName, bytes32 record) external;

    function deleteIntValue(bytes32 contractName, bytes32 record) external;

    function deleteAddressValue(bytes32 contractName, bytes32 record) external;

    function deleteBoolValue(bytes32 contractName, bytes32 record) external;

    function deleteBytes32Value(bytes32 contractName, bytes32 record) external;

    function setUIntValue(
        bytes32 contractName,
        bytes32 record,
        uint value
    ) external;

    function setUIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        uint[] calldata values
    ) external;

    function setIntValue(
        bytes32 contractName,
        bytes32 record,
        int value
    ) external;

    function setIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        int[] calldata values
    ) external;

    function setAddressValue(
        bytes32 contractName,
        bytes32 record,
        address value
    ) external;

    function setAddressValues(
        bytes32 contractName,
        bytes32[] calldata records,
        address[] calldata values
    ) external;

    function setBoolValue(
        bytes32 contractName,
        bytes32 record,
        bool value
    ) external;

    function setBoolValues(
        bytes32 contractName,
        bytes32[] calldata records,
        bool[] calldata values
    ) external;

    function setBytes32Value(
        bytes32 contractName,
        bytes32 record,
        bytes32 value
    ) external;

    function setBytes32Values(
        bytes32 contractName,
        bytes32[] calldata records,
        bytes32[] calldata values
    ) external;
}


// Inheritance


// Internal References


// https://docs.synthetix.io/contracts/source/contracts/FlexibleStorage
contract FlexibleStorage is ContractStorage, IFlexibleStorage {
    mapping(bytes32 => mapping(bytes32 => uint)) internal uintStorage;
    mapping(bytes32 => mapping(bytes32 => int)) internal intStorage;
    mapping(bytes32 => mapping(bytes32 => address)) internal addressStorage;
    mapping(bytes32 => mapping(bytes32 => bool)) internal boolStorage;
    mapping(bytes32 => mapping(bytes32 => bytes32)) internal bytes32Storage;

    constructor(address _resolver) public ContractStorage(_resolver) {}

    /* ========== INTERNAL FUNCTIONS ========== */

    function _setUIntValue(
        bytes32 contractName,
        bytes32 record,
        uint value
    ) internal {
        uintStorage[_memoizeHash(contractName)][record] = value;
        emit ValueSetUInt(contractName, record, value);
    }

    function _setIntValue(
        bytes32 contractName,
        bytes32 record,
        int value
    ) internal {
        intStorage[_memoizeHash(contractName)][record] = value;
        emit ValueSetInt(contractName, record, value);
    }

    function _setAddressValue(
        bytes32 contractName,
        bytes32 record,
        address value
    ) internal {
        addressStorage[_memoizeHash(contractName)][record] = value;
        emit ValueSetAddress(contractName, record, value);
    }

    function _setBoolValue(
        bytes32 contractName,
        bytes32 record,
        bool value
    ) internal {
        boolStorage[_memoizeHash(contractName)][record] = value;
        emit ValueSetBool(contractName, record, value);
    }

    function _setBytes32Value(
        bytes32 contractName,
        bytes32 record,
        bytes32 value
    ) internal {
        bytes32Storage[_memoizeHash(contractName)][record] = value;
        emit ValueSetBytes32(contractName, record, value);
    }

    /* ========== VIEWS ========== */

    function getUIntValue(bytes32 contractName, bytes32 record) external view returns (uint) {
        return uintStorage[hashes[contractName]][record];
    }

    function getUIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (uint[] memory) {
        uint[] memory results = new uint[](records.length);

        mapping(bytes32 => uint) storage data = uintStorage[hashes[contractName]];
        for (uint i = 0; i < records.length; i++) {
            results[i] = data[records[i]];
        }
        return results;
    }

    function getIntValue(bytes32 contractName, bytes32 record) external view returns (int) {
        return intStorage[hashes[contractName]][record];
    }

    function getIntValues(bytes32 contractName, bytes32[] calldata records) external view returns (int[] memory) {
        int[] memory results = new int[](records.length);

        mapping(bytes32 => int) storage data = intStorage[hashes[contractName]];
        for (uint i = 0; i < records.length; i++) {
            results[i] = data[records[i]];
        }
        return results;
    }

    function getAddressValue(bytes32 contractName, bytes32 record) external view returns (address) {
        return addressStorage[hashes[contractName]][record];
    }

    function getAddressValues(bytes32 contractName, bytes32[] calldata records) external view returns (address[] memory) {
        address[] memory results = new address[](records.length);

        mapping(bytes32 => address) storage data = addressStorage[hashes[contractName]];
        for (uint i = 0; i < records.length; i++) {
            results[i] = data[records[i]];
        }
        return results;
    }

    function getBoolValue(bytes32 contractName, bytes32 record) external view returns (bool) {
        return boolStorage[hashes[contractName]][record];
    }

    function getBoolValues(bytes32 contractName, bytes32[] calldata records) external view returns (bool[] memory) {
        bool[] memory results = new bool[](records.length);

        mapping(bytes32 => bool) storage data = boolStorage[hashes[contractName]];
        for (uint i = 0; i < records.length; i++) {
            results[i] = data[records[i]];
        }
        return results;
    }

    function getBytes32Value(bytes32 contractName, bytes32 record) external view returns (bytes32) {
        return bytes32Storage[hashes[contractName]][record];
    }

    function getBytes32Values(bytes32 contractName, bytes32[] calldata records) external view returns (bytes32[] memory) {
        bytes32[] memory results = new bytes32[](records.length);

        mapping(bytes32 => bytes32) storage data = bytes32Storage[hashes[contractName]];
        for (uint i = 0; i < records.length; i++) {
            results[i] = data[records[i]];
        }
        return results;
    }

    /* ========== RESTRICTED FUNCTIONS ========== */
    function setUIntValue(
        bytes32 contractName,
        bytes32 record,
        uint value
    ) external onlyContract(contractName) {
        _setUIntValue(contractName, record, value);
    }

    function setUIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        uint[] calldata values
    ) external onlyContract(contractName) {
        require(records.length == values.length, "Input lengths must match");

        for (uint i = 0; i < records.length; i++) {
            _setUIntValue(contractName, records[i], values[i]);
        }
    }

    function deleteUIntValue(bytes32 contractName, bytes32 record) external onlyContract(contractName) {
        uint value = uintStorage[hashes[contractName]][record];
        emit ValueDeletedUInt(contractName, record, value);
        delete uintStorage[hashes[contractName]][record];
    }

    function setIntValue(
        bytes32 contractName,
        bytes32 record,
        int value
    ) external onlyContract(contractName) {
        _setIntValue(contractName, record, value);
    }

    function setIntValues(
        bytes32 contractName,
        bytes32[] calldata records,
        int[] calldata values
    ) external onlyContract(contractName) {
        require(records.length == values.length, "Input lengths must match");

        for (uint i = 0; i < records.length; i++) {
            _setIntValue(contractName, records[i], values[i]);
        }
    }

    function deleteIntValue(bytes32 contractName, bytes32 record) external onlyContract(contractName) {
        int value = intStorage[hashes[contractName]][record];
        emit ValueDeletedInt(contractName, record, value);
        delete intStorage[hashes[contractName]][record];
    }

    function setAddressValue(
        bytes32 contractName,
        bytes32 record,
        address value
    ) external onlyContract(contractName) {
        _setAddressValue(contractName, record, value);
    }

    function setAddressValues(
        bytes32 contractName,
        bytes32[] calldata records,
        address[] calldata values
    ) external onlyContract(contractName) {
        require(records.length == values.length, "Input lengths must match");

        for (uint i = 0; i < records.length; i++) {
            _setAddressValue(contractName, records[i], values[i]);
        }
    }

    function deleteAddressValue(bytes32 contractName, bytes32 record) external onlyContract(contractName) {
        address value = addressStorage[hashes[contractName]][record];
        emit ValueDeletedAddress(contractName, record, value);
        delete addressStorage[hashes[contractName]][record];
    }

    function setBoolValue(
        bytes32 contractName,
        bytes32 record,
        bool value
    ) external onlyContract(contractName) {
        _setBoolValue(contractName, record, value);
    }

    function setBoolValues(
        bytes32 contractName,
        bytes32[] calldata records,
        bool[] calldata values
    ) external onlyContract(contractName) {
        require(records.length == values.length, "Input lengths must match");

        for (uint i = 0; i < records.length; i++) {
            _setBoolValue(contractName, records[i], values[i]);
        }
    }

    function deleteBoolValue(bytes32 contractName, bytes32 record) external onlyContract(contractName) {
        bool value = boolStorage[hashes[contractName]][record];
        emit ValueDeletedBool(contractName, record, value);
        delete boolStorage[hashes[contractName]][record];
    }

    function setBytes32Value(
        bytes32 contractName,
        bytes32 record,
        bytes32 value
    ) external onlyContract(contractName) {
        _setBytes32Value(contractName, record, value);
    }

    function setBytes32Values(
        bytes32 contractName,
        bytes32[] calldata records,
        bytes32[] calldata values
    ) external onlyContract(contractName) {
        require(records.length == values.length, "Input lengths must match");

        for (uint i = 0; i < records.length; i++) {
            _setBytes32Value(contractName, records[i], values[i]);
        }
    }

    function deleteBytes32Value(bytes32 contractName, bytes32 record) external onlyContract(contractName) {
        bytes32 value = bytes32Storage[hashes[contractName]][record];
        emit ValueDeletedBytes32(contractName, record, value);
        delete bytes32Storage[hashes[contractName]][record];
    }

    /* ========== EVENTS ========== */

    event ValueSetUInt(bytes32 contractName, bytes32 record, uint value);
    event ValueDeletedUInt(bytes32 contractName, bytes32 record, uint value);

    event ValueSetInt(bytes32 contractName, bytes32 record, int value);
    event ValueDeletedInt(bytes32 contractName, bytes32 record, int value);

    event ValueSetAddress(bytes32 contractName, bytes32 record, address value);
    event ValueDeletedAddress(bytes32 contractName, bytes32 record, address value);

    event ValueSetBool(bytes32 contractName, bytes32 record, bool value);
    event ValueDeletedBool(bytes32 contractName, bytes32 record, bool value);

    event ValueSetBytes32(bytes32 contractName, bytes32 record, bytes32 value);
    event ValueDeletedBytes32(bytes32 contractName, bytes32 record, bytes32 value);
}

    

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: ExchangeSettlementLib.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/ExchangeSettlementLib.sol
* Docs: https://docs.synthetix.io/contracts/ExchangeSettlementLib
*
* Contract Dependencies: (none)
* Libraries: 
*	- ExchangeSettlementLib
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2022 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity >=0.4.24;

// https://docs.synthetix.io/contracts/source/interfaces/isynth
interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


interface IVirtualSynth {
    // Views
    function balanceOfUnderlying(address account) external view returns (uint);

    function rate() external view returns (uint);

    function readyToSettle() external view returns (bool);

    function secsLeftInWaitingPeriod() external view returns (uint);

    function settled() external view returns (bool);

    function synth() external view returns (ISynth);

    // Mutative functions
    function settle(address account) external;
}


pragma experimental ABIEncoderV2;


// https://docs.synthetix.io/contracts/source/interfaces/iexchanger
interface IExchanger {
    struct ExchangeEntrySettlement {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint reclaim;
        uint rebate;
        uint srcRoundIdAtPeriodEnd;
        uint destRoundIdAtPeriodEnd;
        uint timestamp;
    }

    struct ExchangeEntry {
        uint sourceRate;
        uint destinationRate;
        uint destinationAmount;
        uint exchangeFeeRate;
        uint exchangeDynamicFeeRate;
        uint roundIdForSrc;
        uint roundIdForDest;
        uint sourceAmountAfterSettlement;
    }

    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view returns (uint);

    function dynamicFeeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint feeRate, bool tooVolatile);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    function lastExchangeRate(bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function exchange(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );
}

// Used to have strongly-typed access to internal mutative functions in Synthetix
interface ISynthetixInternal {
    function emitExchangeTracking(
        bytes32 trackingCode,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        uint256 fee
    ) external;

    function emitSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitAtomicSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint fromAmount,
        bytes32 toCurrencyKey,
        uint toAmount,
        address toAddress
    ) external;

    function emitExchangeReclaim(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;

    function emitExchangeRebate(
        address account,
        bytes32 currencyKey,
        uint amount
    ) external;
}

interface IExchangerInternalDebtCache {
    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateCachedSynthDebts(bytes32[] calldata currencyKeys) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/ICircuitBreaker
interface ICircuitBreaker {
    // Views
    function isInvalid(address oracleAddress, uint value) external view returns (bool);

    function priceDeviationThresholdFactor() external view returns (uint);

    function isDeviationAboveThreshold(uint base, uint comparison) external view returns (bool);

    function lastValue(address oracleAddress) external view returns (uint);

    function circuitBroken(address oracleAddress) external view returns (bool);

    // Mutative functions
    function resetLastValue(address[] calldata oracleAddresses, uint[] calldata values) external;

    function probeCircuitBreaker(address oracleAddress, uint value) external returns (bool circuitBroken);
}


// https://docs.synthetix.io/contracts/source/interfaces/IDirectIntegration
interface IDirectIntegrationManager {
    struct ParameterIntegrationSettings {
        bytes32 currencyKey;
        address dexPriceAggregator;
        address atomicEquivalentForDexPricing;
        uint atomicExchangeFeeRate;
        uint atomicTwapWindow;
        uint atomicMaxVolumePerBlock;
        uint atomicVolatilityConsiderationWindow;
        uint atomicVolatilityUpdateThreshold;
        uint exchangeFeeRate;
        uint exchangeMaxDynamicFee;
        uint exchangeDynamicFeeRounds;
        uint exchangeDynamicFeeThreshold;
        uint exchangeDynamicFeeWeightDecay;
    }

    function getExchangeParameters(address integration, bytes32 key)
        external
        view
        returns (ParameterIntegrationSettings memory settings);

    function setExchangeParameters(
        address integration,
        bytes32[] calldata currencyKeys,
        ParameterIntegrationSettings calldata params
    ) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangerates
interface IExchangeRates {
    // Structs
    struct RateAndUpdatedTime {
        uint216 rate;
        uint40 time;
    }

    // Views
    function aggregators(bytes32 currencyKey) external view returns (address);

    function aggregatorWarningFlags() external view returns (address);

    function anyRateIsInvalid(bytes32[] calldata currencyKeys) external view returns (bool);

    function anyRateIsInvalidAtRound(bytes32[] calldata currencyKeys, uint[] calldata roundIds) external view returns (bool);

    function currenciesUsingAggregator(address aggregator) external view returns (bytes32[] memory);

    function effectiveValue(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external view returns (uint value);

    function effectiveValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveValueAndRatesAtRound(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        uint roundIdForSrc,
        uint roundIdForDest
    )
        external
        view
        returns (
            uint value,
            uint sourceRate,
            uint destinationRate
        );

    function effectiveAtomicValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function effectiveAtomicValueAndRates(
        IDirectIntegrationManager.ParameterIntegrationSettings calldata sourceSettings,
        uint sourceAmount,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata destinationSettings,
        IDirectIntegrationManager.ParameterIntegrationSettings calldata usdSettings
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

    function getCurrentRoundId(bytes32 currencyKey) external view returns (uint);

    function getLastRoundIdBeforeElapsedSecs(
        bytes32 currencyKey,
        uint startingRoundId,
        uint startingTimestamp,
        uint timediff
    ) external view returns (uint);

    function lastRateUpdateTimes(bytes32 currencyKey) external view returns (uint256);

    function rateAndTimestampAtRound(bytes32 currencyKey, uint roundId) external view returns (uint rate, uint time);

    function rateAndUpdatedTime(bytes32 currencyKey) external view returns (uint rate, uint time);

    function rateAndInvalid(bytes32 currencyKey) external view returns (uint rate, bool isInvalid);

    function rateForCurrency(bytes32 currencyKey) external view returns (uint);

    function rateIsFlagged(bytes32 currencyKey) external view returns (bool);

    function rateIsInvalid(bytes32 currencyKey) external view returns (bool);

    function rateIsStale(bytes32 currencyKey) external view returns (bool);

    function rateStalePeriod() external view returns (uint);

    function ratesAndUpdatedTimeForCurrencyLastNRounds(
        bytes32 currencyKey,
        uint numRounds,
        uint roundId
    ) external view returns (uint[] memory rates, uint[] memory times);

    function ratesAndInvalidForCurrencies(bytes32[] calldata currencyKeys)
        external
        view
        returns (uint[] memory rates, bool anyRateInvalid);

    function ratesForCurrencies(bytes32[] calldata currencyKeys) external view returns (uint[] memory);

    function synthTooVolatileForAtomicExchange(bytes32 currencyKey) external view returns (bool);

    function synthTooVolatileForAtomicExchange(IDirectIntegrationManager.ParameterIntegrationSettings calldata settings)
        external
        view
        returns (bool);

    function rateWithSafetyChecks(bytes32 currencyKey)
        external
        returns (
            uint rate,
            bool broken,
            bool invalid
        );
}


// https://docs.synthetix.io/contracts/source/interfaces/iexchangestate
interface IExchangeState {
    // Views
    struct ExchangeEntry {
        bytes32 src;
        uint amount;
        bytes32 dest;
        uint amountReceived;
        uint exchangeFeeRate;
        uint timestamp;
        uint roundIdForSrc;
        uint roundIdForDest;
    }

    function getLengthOfEntries(address account, bytes32 currencyKey) external view returns (uint);

    function getEntryAt(
        address account,
        bytes32 currencyKey,
        uint index
    )
        external
        view
        returns (
            bytes32 src,
            uint amount,
            bytes32 dest,
            uint amountReceived,
            uint exchangeFeeRate,
            uint timestamp,
            uint roundIdForSrc,
            uint roundIdForDest
        );

    function getMaxTimestamp(address account, bytes32 currencyKey) external view returns (uint);

    // Mutative functions
    function appendExchangeEntry(
        address account,
        bytes32 src,
        uint amount,
        bytes32 dest,
        uint amountReceived,
        uint exchangeFeeRate,
        uint timestamp,
        uint roundIdForSrc,
        uint roundIdForDest
    ) external;

    function removeEntries(address account, bytes32 currencyKey) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/iissuer
interface IIssuer {
    // Views

    function allNetworksDebtInfo()
        external
        view
        returns (
            uint256 debt,
            uint256 sharesSupply,
            bool isStale
        );

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function getSynths(bytes32[] calldata currencyKeys) external view returns (ISynth[] memory);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeOtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    function liquidationAmounts(address account, bool isSelfLiquidation)
        external
        view
        returns (
            uint totalRedeemed,
            uint debtToRemove,
            uint escrowToLiquidate,
            uint initialDebtBalance
        );

    // Restricted: used internally to Synthetix
    function addSynths(ISynth[] calldata synthsToAdd) external;

    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function burnForRedemption(
        address deprecatedSynthProxy,
        address account,
        uint balance
    ) external;

    function setCurrentPeriodId(uint128 periodId) external;

    function liquidateAccount(address account, bool isSelfLiquidation)
        external
        returns (
            uint totalRedeemed,
            uint debtRemoved,
            uint escrowToLiquidate
        );

    function issueSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);

    function burnSynthsWithoutDebt(
        bytes32 currencyKey,
        address to,
        uint amount
    ) external returns (bool rateInvalid);
}


interface IDebtCache {
    // Views

    function cachedDebt() external view returns (uint);

    function cachedSynthDebt(bytes32 currencyKey) external view returns (uint);

    function cacheTimestamp() external view returns (uint);

    function cacheInvalid() external view returns (bool);

    function cacheStale() external view returns (bool);

    function isInitialized() external view returns (bool);

    function currentSynthDebts(bytes32[] calldata currencyKeys)
        external
        view
        returns (
            uint[] memory debtValues,
            uint futuresDebt,
            uint excludedDebt,
            bool anyRateIsInvalid
        );

    function cachedSynthDebts(bytes32[] calldata currencyKeys) external view returns (uint[] memory debtValues);

    function totalNonSnxBackedDebt() external view returns (uint excludedDebt, bool isInvalid);

    function currentDebt() external view returns (uint debt, bool anyRateIsInvalid);

    function cacheInfo()
        external
        view
        returns (
            uint debt,
            uint timestamp,
            bool isInvalid,
            bool isStale
        );

    function excludedIssuedDebts(bytes32[] calldata currencyKeys) external view returns (uint[] memory excludedDebts);

    // Mutative functions

    function updateCachedSynthDebts(bytes32[] calldata currencyKeys) external;

    function updateCachedSynthDebtWithRate(bytes32 currencyKey, uint currencyRate) external;

    function updateCachedSynthDebtsWithRates(bytes32[] calldata currencyKeys, uint[] calldata currencyRates) external;

    function updateDebtCacheValidity(bool currentlyInvalid) external;

    function purgeCachedSynthDebt(bytes32 currencyKey) external;

    function takeDebtSnapshot() external;

    function recordExcludedDebtChange(bytes32 currencyKey, int256 delta) external;

    function updateCachedsUSDDebt(int amount) external;

    function importExcludedIssuedDebts(IDebtCache prevDebtCache, IIssuer prevIssuer) external;
}


// https://docs.synthetix.io/contracts/source/interfaces/isynthetix
interface ISynthetix {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint);

    function isWaitingPeriod(bytes32 currencyKey) external view returns (bool);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey) external view returns (uint);

    function totalIssuedSynthsExcludeOtherCollateral(bytes32 currencyKey) external view returns (uint);

    function transferableSynthetix(address account) external view returns (uint transferable);

    function getFirstNonZeroEscrowIndex(address account) external view returns (uint);

    // Mutative Functions
    function burnSynths(uint amount) external;

    function burnSynthsOnBehalf(address burnForAddress, uint amount) external;

    function burnSynthsToTarget() external;

    function burnSynthsToTargetOnBehalf(address burnForAddress) external;

    function exchange(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeOnBehalf(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeWithTracking(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeWithTrackingForInitiator(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address rewardAddress,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeWithVirtual(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        bytes32 trackingCode
    ) external returns (uint amountReceived, IVirtualSynth vSynth);

    function exchangeAtomically(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function issueMaxSynths() external;

    function issueMaxSynthsOnBehalf(address issueForAddress) external;

    function issueSynths(uint amount) external;

    function issueSynthsOnBehalf(address issueForAddress, uint amount) external;

    function mint() external returns (bool);

    function settle(bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    // Liquidations
    function liquidateDelinquentAccount(address account) external returns (bool);

    function liquidateDelinquentAccountEscrowIndex(address account, uint escrowStartIndex) external returns (bool);

    function liquidateSelf() external returns (bool);

    // Restricted Functions

    function mintSecondary(address account, uint amount) external;

    function mintSecondaryRewards(uint amount) external;

    function burnSecondary(address account, uint amount) external;
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }

    /* ---------- Utilities ---------- */
    /*
     * Absolute value of the input, returned as a signed number.
     */
    function signedAbs(int x) internal pure returns (int) {
        return x < 0 ? -x : x;
    }

    /*
     * Absolute value of the input, returned as an unsigned number.
     */
    function abs(int x) internal pure returns (uint) {
        return uint(signedAbs(x));
    }
}


library ExchangeSettlementLib {
    using SafeMath for uint256;
    using SafeDecimalMath for uint256;

    struct ResolvedAddresses {
        IExchangeState exchangeState;
        IExchangeRates exchangeRates;
        ICircuitBreaker circuitBreaker;
        IExchangerInternalDebtCache debtCache;
        IIssuer issuer;
        ISynthetix synthetix;
    }

    bytes32 internal constant sUSD = "sUSD";

    function internalSettle(
        ResolvedAddresses calldata resolvedAddresses,
        address from,
        bytes32 currencyKey,
        bool updateCache,
        uint waitingPeriod
    )
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntriesSettled
        )
    {
        require(
            maxSecsLeftInWaitingPeriod(resolvedAddresses.exchangeState, from, currencyKey, waitingPeriod) == 0,
            "Cannot settle during waiting period"
        );

        (uint reclaimAmount, uint rebateAmount, uint entries, IExchanger.ExchangeEntrySettlement[] memory settlements) =
            _settlementOwing(resolvedAddresses, from, currencyKey, waitingPeriod);

        if (reclaimAmount > rebateAmount) {
            reclaimed = reclaimAmount.sub(rebateAmount);
            _reclaim(resolvedAddresses, from, currencyKey, reclaimed);
        } else if (rebateAmount > reclaimAmount) {
            refunded = rebateAmount.sub(reclaimAmount);
            _refund(resolvedAddresses, from, currencyKey, refunded);
        }

        // by checking a reclaim or refund we also check that the currency key is still a valid synth,
        // as the deviation check will return 0 if the synth has been removed.
        if (updateCache && (reclaimed > 0 || refunded > 0)) {
            bytes32[] memory key = new bytes32[](1);
            key[0] = currencyKey;
            resolvedAddresses.debtCache.updateCachedSynthDebts(key);
        }

        // emit settlement event for each settled exchange entry
        for (uint i = 0; i < settlements.length; i++) {
            emit ExchangeEntrySettled(
                from,
                settlements[i].src,
                settlements[i].amount,
                settlements[i].dest,
                settlements[i].reclaim,
                settlements[i].rebate,
                settlements[i].srcRoundIdAtPeriodEnd,
                settlements[i].destRoundIdAtPeriodEnd,
                settlements[i].timestamp
            );
        }

        numEntriesSettled = entries;

        // Now remove all entries, even if no reclaim and no rebate
        resolvedAddresses.exchangeState.removeEntries(from, currencyKey);
    }

    function maxSecsLeftInWaitingPeriod(
        IExchangeState exchangeState,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    ) public view returns (uint) {
        return _secsLeftInWaitingPeriodForExchange(exchangeState.getMaxTimestamp(account, currencyKey), waitingPeriod);
    }

    function _secsLeftInWaitingPeriodForExchange(uint timestamp, uint waitingPeriod) internal view returns (uint) {
        if (timestamp == 0 || now >= timestamp.add(waitingPeriod)) {
            return 0;
        }

        return timestamp.add(waitingPeriod).sub(now);
    }

    function _reclaim(
        ResolvedAddresses memory resolvedAddresses,
        address from,
        bytes32 currencyKey,
        uint amount
    ) internal {
        // burn amount from user
        resolvedAddresses.issuer.synths(currencyKey).burn(from, amount);
        ISynthetixInternal(address(resolvedAddresses.synthetix)).emitExchangeReclaim(from, currencyKey, amount);
    }

    function _refund(
        ResolvedAddresses memory resolvedAddresses,
        address from,
        bytes32 currencyKey,
        uint amount
    ) internal {
        // issue amount to user
        resolvedAddresses.issuer.synths(currencyKey).issue(from, amount);
        ISynthetixInternal(address(resolvedAddresses.synthetix)).emitExchangeRebate(from, currencyKey, amount);
    }

    function hasWaitingPeriodOrSettlementOwing(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    ) external view returns (bool) {
        if (maxSecsLeftInWaitingPeriod(resolvedAddresses.exchangeState, account, currencyKey, waitingPeriod) != 0) {
            return true;
        }

        (uint reclaimAmount, , , ) = _settlementOwing(resolvedAddresses, account, currencyKey, waitingPeriod);

        return reclaimAmount > 0;
    }

    function settlementOwing(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    )
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries,
            IExchanger.ExchangeEntrySettlement[] memory
        )
    {
        return _settlementOwing(resolvedAddresses, account, currencyKey, waitingPeriod);
    }

    // Internal function to aggregate each individual rebate and reclaim entry for a synth
    function _settlementOwing(
        ResolvedAddresses memory resolvedAddresses,
        address account,
        bytes32 currencyKey,
        uint waitingPeriod
    )
        internal
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries,
            IExchanger.ExchangeEntrySettlement[] memory
        )
    {
        // Need to sum up all reclaim and rebate amounts for the user and the currency key
        numEntries = resolvedAddresses.exchangeState.getLengthOfEntries(account, currencyKey);

        // For each unsettled exchange
        IExchanger.ExchangeEntrySettlement[] memory settlements = new IExchanger.ExchangeEntrySettlement[](numEntries);
        for (uint i = 0; i < numEntries; i++) {
            // fetch the entry from storage
            IExchangeState.ExchangeEntry memory exchangeEntry =
                _getExchangeEntry(resolvedAddresses.exchangeState, account, currencyKey, i);

            // determine the last round ids for src and dest pairs when period ended or latest if not over
            (uint srcRoundIdAtPeriodEnd, uint destRoundIdAtPeriodEnd) =
                _getRoundIdsAtPeriodEnd(resolvedAddresses.exchangeRates, exchangeEntry, waitingPeriod);

            // given these round ids, determine what effective value they should have received
            uint amountShouldHaveReceived;
            {
                (uint destinationAmount, , ) =
                    resolvedAddresses.exchangeRates.effectiveValueAndRatesAtRound(
                        exchangeEntry.src,
                        exchangeEntry.amount,
                        exchangeEntry.dest,
                        srcRoundIdAtPeriodEnd,
                        destRoundIdAtPeriodEnd
                    );

                // and deduct the fee from this amount using the exchangeFeeRate from storage
                amountShouldHaveReceived = _deductFeesFromAmount(destinationAmount, exchangeEntry.exchangeFeeRate);
            }

            // SIP-65 settlements where the amount at end of waiting period is beyond the threshold, then
            // settle with no reclaim or rebate
            bool sip65condition =
                resolvedAddresses.circuitBreaker.isDeviationAboveThreshold(
                    exchangeEntry.amountReceived,
                    amountShouldHaveReceived
                );

            uint reclaim;
            uint rebate;

            if (!sip65condition) {
                if (exchangeEntry.amountReceived > amountShouldHaveReceived) {
                    // if they received more than they should have, add to the reclaim tally
                    reclaim = exchangeEntry.amountReceived.sub(amountShouldHaveReceived);
                    reclaimAmount = reclaimAmount.add(reclaim);
                } else if (amountShouldHaveReceived > exchangeEntry.amountReceived) {
                    // if less, add to the rebate tally
                    rebate = amountShouldHaveReceived.sub(exchangeEntry.amountReceived);
                    rebateAmount = rebateAmount.add(rebate);
                }
            }

            settlements[i] = IExchanger.ExchangeEntrySettlement({
                src: exchangeEntry.src,
                amount: exchangeEntry.amount,
                dest: exchangeEntry.dest,
                reclaim: reclaim,
                rebate: rebate,
                srcRoundIdAtPeriodEnd: srcRoundIdAtPeriodEnd,
                destRoundIdAtPeriodEnd: destRoundIdAtPeriodEnd,
                timestamp: exchangeEntry.timestamp
            });
        }

        return (reclaimAmount, rebateAmount, numEntries, settlements);
    }

    function _getExchangeEntry(
        IExchangeState exchangeState,
        address account,
        bytes32 currencyKey,
        uint index
    ) internal view returns (IExchangeState.ExchangeEntry memory) {
        (
            bytes32 src,
            uint amount,
            bytes32 dest,
            uint amountReceived,
            uint exchangeFeeRate,
            uint timestamp,
            uint roundIdForSrc,
            uint roundIdForDest
        ) = exchangeState.getEntryAt(account, currencyKey, index);

        return
            IExchangeState.ExchangeEntry({
                src: src,
                amount: amount,
                dest: dest,
                amountReceived: amountReceived,
                exchangeFeeRate: exchangeFeeRate,
                timestamp: timestamp,
                roundIdForSrc: roundIdForSrc,
                roundIdForDest: roundIdForDest
            });
    }

    function _getRoundIdsAtPeriodEnd(
        IExchangeRates exRates,
        IExchangeState.ExchangeEntry memory exchangeEntry,
        uint waitingPeriod
    ) internal view returns (uint srcRoundIdAtPeriodEnd, uint destRoundIdAtPeriodEnd) {
        srcRoundIdAtPeriodEnd = exRates.getLastRoundIdBeforeElapsedSecs(
            exchangeEntry.src,
            exchangeEntry.roundIdForSrc,
            exchangeEntry.timestamp,
            waitingPeriod
        );
        destRoundIdAtPeriodEnd = exRates.getLastRoundIdBeforeElapsedSecs(
            exchangeEntry.dest,
            exchangeEntry.roundIdForDest,
            exchangeEntry.timestamp,
            waitingPeriod
        );
    }

    function _deductFeesFromAmount(uint destinationAmount, uint exchangeFeeRate)
        internal
        pure
        returns (uint amountReceived)
    {
        amountReceived = destinationAmount.multiplyDecimal(SafeDecimalMath.unit().sub(exchangeFeeRate));
    }

    function appendExchange(
        ResolvedAddresses calldata resolvedAddresses,
        address account,
        bytes32 src,
        uint amount,
        bytes32 dest,
        uint amountReceived,
        uint exchangeFeeRate
    ) external {
        uint roundIdForSrc = resolvedAddresses.exchangeRates.getCurrentRoundId(src);
        uint roundIdForDest = resolvedAddresses.exchangeRates.getCurrentRoundId(dest);
        resolvedAddresses.exchangeState.appendExchangeEntry(
            account,
            src,
            amount,
            dest,
            amountReceived,
            exchangeFeeRate,
            now,
            roundIdForSrc,
            roundIdForDest
        );

        emit ExchangeEntryAppended(
            account,
            src,
            amount,
            dest,
            amountReceived,
            exchangeFeeRate,
            roundIdForSrc,
            roundIdForDest
        );
    }

    // ========== EVENTS ==========
    event ExchangeEntryAppended(
        address indexed account,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 amountReceived,
        uint256 exchangeFeeRate,
        uint256 roundIdForSrc,
        uint256 roundIdForDest
    );

    event ExchangeEntrySettled(
        address indexed from,
        bytes32 src,
        uint256 amount,
        bytes32 dest,
        uint256 reclaim,
        uint256 rebate,
        uint256 srcRoundIdAtPeriodEnd,
        uint256 destRoundIdAtPeriodEnd,
        uint256 exchangeTimestamp
    );
}

    

/*
 * Nomin TokenState Contract
 *
 * Stores ERC20 balance and approval information for the
 * nomin component of the Havven stablecoin system.
 *
 * version: nUSDa.1
 * date: 29 Jun 2018
 * url: https://github.com/Havven/havven/releases/tag/nUSDa.1
 */
 
 
pragma solidity 0.4.24;
 
 
/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------
 
file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski
 
date:       2018-2-26
 
-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------
 
An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.
 
To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).
 
-----------------------------------------------------------------
*/
 
 
/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;
 
    /**
     * @dev Owned Constructor
     */
    constructor(address _owner)
        public
    {
        require(_owner != address(0));
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }
 
    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }
 
    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner);
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }
 
    modifier onlyOwner
    {
        require(msg.sender == owner);
        _;
    }
 
    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}
 
 
/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------
 
file:       State.sol
version:    1.1
author:     Dominic Romanowski
            Anton Jurisevic
 
date:       2018-05-15
 
-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------
 
This contract is used side by side with external state token
contracts, such as Havven and Nomin.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.
 
The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.
 
-----------------------------------------------------------------
*/
 
 
contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;
 
 
    constructor(address _owner, address _associatedContract)
        Owned(_owner)
        public
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }
 
    /* ========== SETTERS ========== */
 
    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract)
        external
        onlyOwner
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }
 
    /* ========== MODIFIERS ========== */
 
    modifier onlyAssociatedContract
    {
        require(msg.sender == associatedContract);
        _;
    }
 
    /* ========== EVENTS ========== */
 
    event AssociatedContractUpdated(address associatedContract);
}
 
 
/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------
 
file:       TokenState.sol
version:    1.1
author:     Dominic Romanowski
            Anton Jurisevic
 
date:       2018-05-15
 
-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------
 
A contract that holds the state of an ERC20 compliant token.
 
This contract is used side by side with external state token
contracts, such as Havven and Nomin.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.
 
The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.
 
-----------------------------------------------------------------
*/
 
 
/**
 * @title ERC20 Token State
 * @notice Stores balance information of an ERC20 token contract.
 */
contract TokenState is State {
 
    /* ERC20 fields. */
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;
 
    /**
     * @dev Constructor
     * @param _owner The address which controls this contract.
     * @param _associatedContract The ERC20 contract whose state this composes.
     */
    constructor(address _owner, address _associatedContract)
        State(_owner, _associatedContract)
        public
    {}
 
    /* ========== SETTERS ========== */
 
    /**
     * @notice Set ERC20 allowance.
     * @dev Only the associated contract may call this.
     * @param tokenOwner The authorising party.
     * @param spender The authorised party.
     * @param value The total value the authorised party may spend on the
     * authorising party's behalf.
     */
    function setAllowance(address tokenOwner, address spender, uint value)
        external
        onlyAssociatedContract
    {
        allowance[tokenOwner][spender] = value;
    }
 
    /**
     * @notice Set the balance in a given account
     * @dev Only the associated contract may call this.
     * @param account The account whose value to set.
     * @param value The new balance of the given account.
     */
    function setBalanceOf(address account, uint value)
        external
        onlyAssociatedContract
    {
        balanceOf[account] = value;
    }
}

/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: SystemStatus.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/SystemStatus.sol
* Docs: https://docs.synthetix.io/contracts/SystemStatus
*
* Contract Dependencies: 
*	- ISystemStatus
*	- Owned
* Libraries: (none)
*
* MIT License
* ===========
*
* Copyright (c) 2022 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/isystemstatus
interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function systemSuspended() external view returns (bool);

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireFuturesActive() external view;

    function requireFuturesMarketActive(bytes32 marketKey) external view;

    function requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function synthSuspended(bytes32 currencyKey) external view returns (bool);

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function systemSuspension() external view returns (bool suspended, uint248 reason);

    function issuanceSuspension() external view returns (bool suspended, uint248 reason);

    function exchangeSuspension() external view returns (bool suspended, uint248 reason);

    function futuresSuspension() external view returns (bool suspended, uint248 reason);

    function synthExchangeSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    function futuresMarketSuspension(bytes32 marketKey) external view returns (bool suspended, uint248 reason);

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons);

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    // Restricted functions
    function suspendIssuance(uint256 reason) external;

    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/systemstatus
contract SystemStatus is Owned, ISystemStatus {
    mapping(bytes32 => mapping(address => Status)) public accessControl;

    uint248 public constant SUSPENSION_REASON_UPGRADE = 1;

    bytes32 public constant SECTION_SYSTEM = "System";
    bytes32 public constant SECTION_ISSUANCE = "Issuance";
    bytes32 public constant SECTION_EXCHANGE = "Exchange";
    bytes32 public constant SECTION_FUTURES = "Futures";
    bytes32 public constant SECTION_SYNTH_EXCHANGE = "SynthExchange";
    bytes32 public constant SECTION_SYNTH = "Synth";

    bytes32 public constant CONTRACT_NAME = "SystemStatus";

    Suspension public systemSuspension;

    Suspension public issuanceSuspension;

    Suspension public exchangeSuspension;

    Suspension public futuresSuspension;

    mapping(bytes32 => Suspension) public synthExchangeSuspension;

    mapping(bytes32 => Suspension) public synthSuspension;

    mapping(bytes32 => Suspension) public futuresMarketSuspension;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== VIEWS ========== */
    function requireSystemActive() external view {
        _internalRequireSystemActive();
    }

    function systemSuspended() external view returns (bool) {
        return systemSuspension.suspended;
    }

    function requireIssuanceActive() external view {
        // Issuance requires the system be active
        _internalRequireSystemActive();

        // and issuance itself of course
        _internalRequireIssuanceActive();
    }

    function requireExchangeActive() external view {
        // Exchanging requires the system be active
        _internalRequireSystemActive();

        // and exchanging itself of course
        _internalRequireExchangeActive();
    }

    function requireSynthExchangeActive(bytes32 currencyKey) external view {
        // Synth exchange and transfer requires the system be active
        _internalRequireSystemActive();
        _internalRequireSynthExchangeActive(currencyKey);
    }

    function requireFuturesActive() external view {
        _internalRequireSystemActive();
        _internalRequireExchangeActive();
        _internalRequireFuturesActive();
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function requireFuturesMarketActive(bytes32 marketKey) external view {
        _internalRequireSystemActive();
        _internalRequireExchangeActive(); // exchanging implicitely used
        _internalRequireFuturesActive(); // futures global flag
        _internalRequireFuturesMarketActive(marketKey); // specific futures market flag
    }

    function synthSuspended(bytes32 currencyKey) external view returns (bool) {
        return systemSuspension.suspended || synthSuspension[currencyKey].suspended;
    }

    function requireSynthActive(bytes32 currencyKey) external view {
        // Synth exchange and transfer requires the system be active
        _internalRequireSystemActive();
        _internalRequireSynthActive(currencyKey);
    }

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view {
        // Synth exchange and transfer requires the system be active
        _internalRequireSystemActive();
        _internalRequireSynthActive(sourceCurrencyKey);
        _internalRequireSynthActive(destinationCurrencyKey);
    }

    function requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view {
        // Synth exchange and transfer requires the system be active
        _internalRequireSystemActive();

        // and exchanging must be active
        _internalRequireExchangeActive();

        // and the synth exchanging between the synths must be active
        _internalRequireSynthExchangeActive(sourceCurrencyKey);
        _internalRequireSynthExchangeActive(destinationCurrencyKey);

        // and finally, the synths cannot be suspended
        _internalRequireSynthActive(sourceCurrencyKey);
        _internalRequireSynthActive(destinationCurrencyKey);
    }

    function isSystemUpgrading() external view returns (bool) {
        return systemSuspension.suspended && systemSuspension.reason == SUSPENSION_REASON_UPGRADE;
    }

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons)
    {
        exchangeSuspensions = new bool[](synths.length);
        reasons = new uint256[](synths.length);

        for (uint i = 0; i < synths.length; i++) {
            exchangeSuspensions[i] = synthExchangeSuspension[synths[i]].suspended;
            reasons[i] = synthExchangeSuspension[synths[i]].reason;
        }
    }

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons)
    {
        suspensions = new bool[](synths.length);
        reasons = new uint256[](synths.length);

        for (uint i = 0; i < synths.length; i++) {
            suspensions[i] = synthSuspension[synths[i]].suspended;
            reasons[i] = synthSuspension[synths[i]].reason;
        }
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons)
    {
        suspensions = new bool[](marketKeys.length);
        reasons = new uint256[](marketKeys.length);

        for (uint i = 0; i < marketKeys.length; i++) {
            suspensions[i] = futuresMarketSuspension[marketKeys[i]].suspended;
            reasons[i] = futuresMarketSuspension[marketKeys[i]].reason;
        }
    }

    /* ========== MUTATIVE FUNCTIONS ========== */
    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external onlyOwner {
        _internalUpdateAccessControl(section, account, canSuspend, canResume);
    }

    function updateAccessControls(
        bytes32[] calldata sections,
        address[] calldata accounts,
        bool[] calldata canSuspends,
        bool[] calldata canResumes
    ) external onlyOwner {
        require(
            sections.length == accounts.length &&
                accounts.length == canSuspends.length &&
                canSuspends.length == canResumes.length,
            "Input array lengths must match"
        );
        for (uint i = 0; i < sections.length; i++) {
            _internalUpdateAccessControl(sections[i], accounts[i], canSuspends[i], canResumes[i]);
        }
    }

    function suspendSystem(uint256 reason) external {
        _requireAccessToSuspend(SECTION_SYSTEM);
        systemSuspension.suspended = true;
        systemSuspension.reason = uint248(reason);
        emit SystemSuspended(systemSuspension.reason);
    }

    function resumeSystem() external {
        _requireAccessToResume(SECTION_SYSTEM);
        systemSuspension.suspended = false;
        emit SystemResumed(uint256(systemSuspension.reason));
        systemSuspension.reason = 0;
    }

    function suspendIssuance(uint256 reason) external {
        _requireAccessToSuspend(SECTION_ISSUANCE);
        issuanceSuspension.suspended = true;
        issuanceSuspension.reason = uint248(reason);
        emit IssuanceSuspended(reason);
    }

    function resumeIssuance() external {
        _requireAccessToResume(SECTION_ISSUANCE);
        issuanceSuspension.suspended = false;
        emit IssuanceResumed(uint256(issuanceSuspension.reason));
        issuanceSuspension.reason = 0;
    }

    function suspendExchange(uint256 reason) external {
        _requireAccessToSuspend(SECTION_EXCHANGE);
        exchangeSuspension.suspended = true;
        exchangeSuspension.reason = uint248(reason);
        emit ExchangeSuspended(reason);
    }

    function resumeExchange() external {
        _requireAccessToResume(SECTION_EXCHANGE);
        exchangeSuspension.suspended = false;
        emit ExchangeResumed(uint256(exchangeSuspension.reason));
        exchangeSuspension.reason = 0;
    }

    function suspendFutures(uint256 reason) external {
        _requireAccessToSuspend(SECTION_FUTURES);
        futuresSuspension.suspended = true;
        futuresSuspension.reason = uint248(reason);
        emit FuturesSuspended(reason);
    }

    function resumeFutures() external {
        _requireAccessToResume(SECTION_FUTURES);
        futuresSuspension.suspended = false;
        emit FuturesResumed(uint256(futuresSuspension.reason));
        futuresSuspension.reason = 0;
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external {
        bytes32[] memory marketKeys = new bytes32[](1);
        marketKeys[0] = marketKey;
        _internalSuspendFuturesMarkets(marketKeys, reason);
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function suspendFuturesMarkets(bytes32[] calldata marketKeys, uint256 reason) external {
        _internalSuspendFuturesMarkets(marketKeys, reason);
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function resumeFuturesMarket(bytes32 marketKey) external {
        bytes32[] memory marketKeys = new bytes32[](1);
        marketKeys[0] = marketKey;
        _internalResumeFuturesMarkets(marketKeys);
    }

    /// @notice marketKey doesn't necessarily correspond to asset key
    function resumeFuturesMarkets(bytes32[] calldata marketKeys) external {
        _internalResumeFuturesMarkets(marketKeys);
    }

    function suspendSynthExchange(bytes32 currencyKey, uint256 reason) external {
        bytes32[] memory currencyKeys = new bytes32[](1);
        currencyKeys[0] = currencyKey;
        _internalSuspendSynthExchange(currencyKeys, reason);
    }

    function suspendSynthsExchange(bytes32[] calldata currencyKeys, uint256 reason) external {
        _internalSuspendSynthExchange(currencyKeys, reason);
    }

    function resumeSynthExchange(bytes32 currencyKey) external {
        bytes32[] memory currencyKeys = new bytes32[](1);
        currencyKeys[0] = currencyKey;
        _internalResumeSynthsExchange(currencyKeys);
    }

    function resumeSynthsExchange(bytes32[] calldata currencyKeys) external {
        _internalResumeSynthsExchange(currencyKeys);
    }

    function suspendSynth(bytes32 currencyKey, uint256 reason) external {
        bytes32[] memory currencyKeys = new bytes32[](1);
        currencyKeys[0] = currencyKey;
        _internalSuspendSynths(currencyKeys, reason);
    }

    function suspendSynths(bytes32[] calldata currencyKeys, uint256 reason) external {
        _internalSuspendSynths(currencyKeys, reason);
    }

    function resumeSynth(bytes32 currencyKey) external {
        bytes32[] memory currencyKeys = new bytes32[](1);
        currencyKeys[0] = currencyKey;
        _internalResumeSynths(currencyKeys);
    }

    function resumeSynths(bytes32[] calldata currencyKeys) external {
        _internalResumeSynths(currencyKeys);
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    function _requireAccessToSuspend(bytes32 section) internal view {
        require(accessControl[section][msg.sender].canSuspend, "Restricted to access control list");
    }

    function _requireAccessToResume(bytes32 section) internal view {
        require(accessControl[section][msg.sender].canResume, "Restricted to access control list");
    }

    function _internalRequireSystemActive() internal view {
        require(
            !systemSuspension.suspended,
            systemSuspension.reason == SUSPENSION_REASON_UPGRADE
                ? "Synthetix is suspended, upgrade in progress... please stand by"
                : "Synthetix is suspended. Operation prohibited"
        );
    }

    function _internalRequireIssuanceActive() internal view {
        require(!issuanceSuspension.suspended, "Issuance is suspended. Operation prohibited");
    }

    function _internalRequireExchangeActive() internal view {
        require(!exchangeSuspension.suspended, "Exchange is suspended. Operation prohibited");
    }

    function _internalRequireFuturesActive() internal view {
        require(!futuresSuspension.suspended, "Futures markets are suspended. Operation prohibited");
    }

    function _internalRequireSynthExchangeActive(bytes32 currencyKey) internal view {
        require(!synthExchangeSuspension[currencyKey].suspended, "Synth exchange suspended. Operation prohibited");
    }

    function _internalRequireSynthActive(bytes32 currencyKey) internal view {
        require(!synthSuspension[currencyKey].suspended, "Synth is suspended. Operation prohibited");
    }

    function _internalRequireFuturesMarketActive(bytes32 marketKey) internal view {
        require(!futuresMarketSuspension[marketKey].suspended, "Market suspended");
    }

    function _internalSuspendSynths(bytes32[] memory currencyKeys, uint256 reason) internal {
        _requireAccessToSuspend(SECTION_SYNTH);
        for (uint i = 0; i < currencyKeys.length; i++) {
            bytes32 currencyKey = currencyKeys[i];
            synthSuspension[currencyKey].suspended = true;
            synthSuspension[currencyKey].reason = uint248(reason);
            emit SynthSuspended(currencyKey, reason);
        }
    }

    function _internalResumeSynths(bytes32[] memory currencyKeys) internal {
        _requireAccessToResume(SECTION_SYNTH);
        for (uint i = 0; i < currencyKeys.length; i++) {
            bytes32 currencyKey = currencyKeys[i];
            emit SynthResumed(currencyKey, uint256(synthSuspension[currencyKey].reason));
            delete synthSuspension[currencyKey];
        }
    }

    function _internalSuspendSynthExchange(bytes32[] memory currencyKeys, uint256 reason) internal {
        _requireAccessToSuspend(SECTION_SYNTH_EXCHANGE);
        for (uint i = 0; i < currencyKeys.length; i++) {
            bytes32 currencyKey = currencyKeys[i];
            synthExchangeSuspension[currencyKey].suspended = true;
            synthExchangeSuspension[currencyKey].reason = uint248(reason);
            emit SynthExchangeSuspended(currencyKey, reason);
        }
    }

    function _internalResumeSynthsExchange(bytes32[] memory currencyKeys) internal {
        _requireAccessToResume(SECTION_SYNTH_EXCHANGE);
        for (uint i = 0; i < currencyKeys.length; i++) {
            bytes32 currencyKey = currencyKeys[i];
            emit SynthExchangeResumed(currencyKey, uint256(synthExchangeSuspension[currencyKey].reason));
            delete synthExchangeSuspension[currencyKey];
        }
    }

    function _internalSuspendFuturesMarkets(bytes32[] memory marketKeys, uint256 reason) internal {
        _requireAccessToSuspend(SECTION_FUTURES);
        for (uint i = 0; i < marketKeys.length; i++) {
            bytes32 marketKey = marketKeys[i];
            futuresMarketSuspension[marketKey].suspended = true;
            futuresMarketSuspension[marketKey].reason = uint248(reason);
            emit FuturesMarketSuspended(marketKey, reason);
        }
    }

    function _internalResumeFuturesMarkets(bytes32[] memory marketKeys) internal {
        _requireAccessToResume(SECTION_FUTURES);
        for (uint i = 0; i < marketKeys.length; i++) {
            bytes32 marketKey = marketKeys[i];
            emit FuturesMarketResumed(marketKey, uint256(futuresMarketSuspension[marketKey].reason));
            delete futuresMarketSuspension[marketKey];
        }
    }

    function _internalUpdateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) internal {
        require(
            section == SECTION_SYSTEM ||
                section == SECTION_ISSUANCE ||
                section == SECTION_EXCHANGE ||
                section == SECTION_FUTURES ||
                section == SECTION_SYNTH_EXCHANGE ||
                section == SECTION_SYNTH,
            "Invalid section supplied"
        );
        accessControl[section][account].canSuspend = canSuspend;
        accessControl[section][account].canResume = canResume;
        emit AccessControlUpdated(section, account, canSuspend, canResume);
    }

    /* ========== EVENTS ========== */

    event SystemSuspended(uint256 reason);
    event SystemResumed(uint256 reason);

    event IssuanceSuspended(uint256 reason);
    event IssuanceResumed(uint256 reason);

    event ExchangeSuspended(uint256 reason);
    event ExchangeResumed(uint256 reason);

    event FuturesSuspended(uint256 reason);
    event FuturesResumed(uint256 reason);

    event SynthExchangeSuspended(bytes32 currencyKey, uint256 reason);
    event SynthExchangeResumed(bytes32 currencyKey, uint256 reason);

    event SynthSuspended(bytes32 currencyKey, uint256 reason);
    event SynthResumed(bytes32 currencyKey, uint256 reason);

    event FuturesMarketSuspended(bytes32 marketKey, uint256 reason);
    event FuturesMarketResumed(bytes32 marketKey, uint256 reason);

    event AccessControlUpdated(bytes32 indexed section, address indexed account, bool canSuspend, bool canResume);
}