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

* Synthetix: migrations/Migration_Mirfak.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/migrations/Migration_Mirfak.sol
* Docs: https://docs.synthetix.io/contracts/migrations/Migration_Mirfak
*
* Contract Dependencies: 
*	- BaseMigration
*	- EternalStorage
*	- ExternStateToken
*	- IAddressResolver
*	- IERC20
*	- IExchangeState
*	- IFeePool
*	- IIssuer
*	- IRewardEscrow
*	- IRewardsDistribution
*	- ISynth
*	- ISynthetixState
*	- ISystemStatus
*	- LegacyOwned
*	- LimitedSetup
*	- MixinResolver
*	- MixinSystemSettings
*	- Owned
*	- Proxy
*	- Proxyable
*	- State
*	- Synth
* Libraries: 
*	- SafeDecimalMath
*	- SafeMath
*	- VestingEntries
*
* 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);
}


contract BaseMigration is Owned {
    address public deployer;

    constructor(address _owner) internal Owned(_owner) {
        deployer = msg.sender;
    }

    // safety value to return ownership (anyone can invoke)
    function returnOwnership(address forContract) public {
        bytes memory payload = abi.encodeWithSignature("nominateNewOwner(address)", owner);

        // solhint-disable avoid-low-level-calls
        (bool success, ) = forContract.call(payload);

        if (!success) {
            // then try legacy way
            bytes memory legacyPayload = abi.encodeWithSignature("nominateOwner(address)", owner);

            // solhint-disable avoid-low-level-calls
            (bool legacySuccess, ) = forContract.call(legacyPayload);

            require(legacySuccess, "Legacy nomination failed");
        }
    }

    function _requireDeployer() private view {
        require(msg.sender == deployer, "Only the deployer can invoke this");
    }

    modifier onlyDeployer() {
        _requireDeployer();
        _;
    }
}


// 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);
}


// 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);
}


// 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);
}


// 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


// 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/eternalstorage
/**
 * @notice  This contract is based on the code available from this blog
 * https://blog.colony.io/writing-upgradeable-contracts-in-solidity-6743f0eecc88/
 * Implements support for storing a keccak256 key and value pairs. It is the more flexible
 * and extensible option. This ensures data schema changes can be implemented without
 * requiring upgrades to the storage contract.
 */
contract EternalStorage is Owned, State {
    constructor(address _owner, address _associatedContract) public Owned(_owner) State(_associatedContract) {}

    /* ========== DATA TYPES ========== */
    mapping(bytes32 => uint) internal UIntStorage;
    mapping(bytes32 => string) internal StringStorage;
    mapping(bytes32 => address) internal AddressStorage;
    mapping(bytes32 => bytes) internal BytesStorage;
    mapping(bytes32 => bytes32) internal Bytes32Storage;
    mapping(bytes32 => bool) internal BooleanStorage;
    mapping(bytes32 => int) internal IntStorage;

    // UIntStorage;
    function getUIntValue(bytes32 record) external view returns (uint) {
        return UIntStorage[record];
    }

    function setUIntValue(bytes32 record, uint value) external onlyAssociatedContract {
        UIntStorage[record] = value;
    }

    function deleteUIntValue(bytes32 record) external onlyAssociatedContract {
        delete UIntStorage[record];
    }

    // StringStorage
    function getStringValue(bytes32 record) external view returns (string memory) {
        return StringStorage[record];
    }

    function setStringValue(bytes32 record, string calldata value) external onlyAssociatedContract {
        StringStorage[record] = value;
    }

    function deleteStringValue(bytes32 record) external onlyAssociatedContract {
        delete StringStorage[record];
    }

    // AddressStorage
    function getAddressValue(bytes32 record) external view returns (address) {
        return AddressStorage[record];
    }

    function setAddressValue(bytes32 record, address value) external onlyAssociatedContract {
        AddressStorage[record] = value;
    }

    function deleteAddressValue(bytes32 record) external onlyAssociatedContract {
        delete AddressStorage[record];
    }

    // BytesStorage
    function getBytesValue(bytes32 record) external view returns (bytes memory) {
        return BytesStorage[record];
    }

    function setBytesValue(bytes32 record, bytes calldata value) external onlyAssociatedContract {
        BytesStorage[record] = value;
    }

    function deleteBytesValue(bytes32 record) external onlyAssociatedContract {
        delete BytesStorage[record];
    }

    // Bytes32Storage
    function getBytes32Value(bytes32 record) external view returns (bytes32) {
        return Bytes32Storage[record];
    }

    function setBytes32Value(bytes32 record, bytes32 value) external onlyAssociatedContract {
        Bytes32Storage[record] = value;
    }

    function deleteBytes32Value(bytes32 record) external onlyAssociatedContract {
        delete Bytes32Storage[record];
    }

    // BooleanStorage
    function getBooleanValue(bytes32 record) external view returns (bool) {
        return BooleanStorage[record];
    }

    function setBooleanValue(bytes32 record, bool value) external onlyAssociatedContract {
        BooleanStorage[record] = value;
    }

    function deleteBooleanValue(bytes32 record) external onlyAssociatedContract {
        delete BooleanStorage[record];
    }

    // IntStorage
    function getIntValue(bytes32 record) external view returns (int) {
        return IntStorage[record];
    }

    function setIntValue(bytes32 record, int value) external onlyAssociatedContract {
        IntStorage[record] = value;
    }

    function deleteIntValue(bytes32 record) external onlyAssociatedContract {
        delete IntStorage[record];
    }
}


// https://docs.synthetix.io/contracts/source/contracts/limitedsetup
contract LimitedSetup {
    uint public setupExpiryTime;

    /**
     * @dev LimitedSetup Constructor.
     * @param setupDuration The time the setup period will last for.
     */
    constructor(uint setupDuration) internal {
        setupExpiryTime = now + setupDuration;
    }

    modifier onlyDuringSetup {
        require(now < setupExpiryTime, "Can only perform this action during setup");
        _;
    }
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/feepooleternalstorage
contract FeePoolEternalStorage is EternalStorage, LimitedSetup {
    bytes32 internal constant LAST_FEE_WITHDRAWAL = "last_fee_withdrawal";

    constructor(address _owner, address _feePool) public EternalStorage(_owner, _feePool) LimitedSetup(6 weeks) {}

    function importFeeWithdrawalData(address[] calldata accounts, uint[] calldata feePeriodIDs)
        external
        onlyOwner
        onlyDuringSetup
    {
        require(accounts.length == feePeriodIDs.length, "Length mismatch");

        for (uint8 i = 0; i < accounts.length; i++) {
            this.setUIntValue(keccak256(abi.encodePacked(LAST_FEE_WITHDRAWAL, accounts[i])), feePeriodIDs[i]);
        }
    }
}


/**
 * @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;
    }
}


// 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;
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/feepoolstate
contract FeePoolState is Owned, LimitedSetup {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

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

    uint8 public constant FEE_PERIOD_LENGTH = 6;

    address public feePool;

    // The IssuanceData activity that's happened in a fee period.
    struct IssuanceData {
        uint debtPercentage;
        uint debtEntryIndex;
    }

    // The IssuanceData activity that's happened in a fee period.
    mapping(address => IssuanceData[FEE_PERIOD_LENGTH]) public accountIssuanceLedger;

    constructor(address _owner, IFeePool _feePool) public Owned(_owner) LimitedSetup(6 weeks) {
        feePool = address(_feePool);
    }

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

    /**
     * @notice set the FeePool contract as it is the only authority to be able to call
     * appendAccountIssuanceRecord with the onlyFeePool modifer
     * @dev Must be set by owner when FeePool logic is upgraded
     */
    function setFeePool(IFeePool _feePool) external onlyOwner {
        feePool = address(_feePool);
    }

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

    /**
     * @notice Get an accounts issuanceData for
     * @param account users account
     * @param index Index in the array to retrieve. Upto FEE_PERIOD_LENGTH
     */
    function getAccountsDebtEntry(address account, uint index)
        public
        view
        returns (uint debtPercentage, uint debtEntryIndex)
    {
        require(index < FEE_PERIOD_LENGTH, "index exceeds the FEE_PERIOD_LENGTH");

        debtPercentage = accountIssuanceLedger[account][index].debtPercentage;
        debtEntryIndex = accountIssuanceLedger[account][index].debtEntryIndex;
    }

    /**
     * @notice Find the oldest debtEntryIndex for the corresponding closingDebtIndex
     * @param account users account
     * @param closingDebtIndex the last periods debt index on close
     */
    function applicableIssuanceData(address account, uint closingDebtIndex) external view returns (uint, uint) {
        IssuanceData[FEE_PERIOD_LENGTH] memory issuanceData = accountIssuanceLedger[account];

        // We want to use the user's debtEntryIndex at when the period closed
        // Find the oldest debtEntryIndex for the corresponding closingDebtIndex
        for (uint i = 0; i < FEE_PERIOD_LENGTH; i++) {
            if (closingDebtIndex >= issuanceData[i].debtEntryIndex) {
                return (issuanceData[i].debtPercentage, issuanceData[i].debtEntryIndex);
            }
        }
    }

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

    /**
     * @notice Logs an accounts issuance data in the current fee period which is then stored historically
     * @param account Message.Senders account address
     * @param debtRatio Debt of this account as a percentage of the global debt.
     * @param debtEntryIndex The index in the global debt ledger. synthetix.synthetixState().issuanceData(account)
     * @param currentPeriodStartDebtIndex The startingDebtIndex of the current fee period
     * @dev onlyFeePool to call me on synthetix.issue() & synthetix.burn() calls to store the locked SNX
     * per fee period so we know to allocate the correct proportions of fees and rewards per period
      accountIssuanceLedger[account][0] has the latest locked amount for the current period. This can be update as many time
      accountIssuanceLedger[account][1-2] has the last locked amount for a previous period they minted or burned
     */
    function appendAccountIssuanceRecord(
        address account,
        uint debtRatio,
        uint debtEntryIndex,
        uint currentPeriodStartDebtIndex
    ) external onlyFeePool {
        // Is the current debtEntryIndex within this fee period
        if (accountIssuanceLedger[account][0].debtEntryIndex < currentPeriodStartDebtIndex) {
            // If its older then shift the previous IssuanceData entries periods down to make room for the new one.
            issuanceDataIndexOrder(account);
        }

        // Always store the latest IssuanceData entry at [0]
        accountIssuanceLedger[account][0].debtPercentage = debtRatio;
        accountIssuanceLedger[account][0].debtEntryIndex = debtEntryIndex;
    }

    /**
     * @notice Pushes down the entire array of debt ratios per fee period
     */
    function issuanceDataIndexOrder(address account) private {
        for (uint i = FEE_PERIOD_LENGTH - 2; i < FEE_PERIOD_LENGTH; i--) {
            uint next = i + 1;
            accountIssuanceLedger[account][next].debtPercentage = accountIssuanceLedger[account][i].debtPercentage;
            accountIssuanceLedger[account][next].debtEntryIndex = accountIssuanceLedger[account][i].debtEntryIndex;
        }
    }

    /**
     * @notice Import issuer data from synthetixState.issuerData on FeePeriodClose() block #
     * @dev Only callable by the contract owner, and only for 6 weeks after deployment.
     * @param accounts Array of issuing addresses
     * @param ratios Array of debt ratios
     * @param periodToInsert The Fee Period to insert the historical records into
     * @param feePeriodCloseIndex An accounts debtEntryIndex is valid when within the fee peroid,
     * since the input ratio will be an average of the pervious periods it just needs to be
     * > recentFeePeriods[periodToInsert].startingDebtIndex
     * < recentFeePeriods[periodToInsert - 1].startingDebtIndex
     */
    function importIssuerData(
        address[] calldata accounts,
        uint[] calldata ratios,
        uint periodToInsert,
        uint feePeriodCloseIndex
    ) external onlyOwner onlyDuringSetup {
        require(accounts.length == ratios.length, "Length mismatch");

        for (uint i = 0; i < accounts.length; i++) {
            accountIssuanceLedger[accounts[i]][periodToInsert].debtPercentage = ratios[i];
            accountIssuanceLedger[accounts[i]][periodToInsert].debtEntryIndex = feePeriodCloseIndex;
            emit IssuanceDebtRatioEntry(accounts[i], ratios[i], feePeriodCloseIndex);
        }
    }

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

    modifier onlyFeePool {
        require(msg.sender == address(feePool), "Only the FeePool contract can perform this action");
        _;
    }

    /* ========== Events ========== */
    event IssuanceDebtRatioEntry(address indexed account, uint debtRatio, uint feePeriodCloseIndex);
}


// 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);
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/proxyerc20
contract ProxyERC20 is Proxy, IERC20 {
    constructor(address _owner) public Proxy(_owner) {}

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

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

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

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

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

    /**
     * @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(address(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(address(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(address(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(address(target)).transferFrom(from, to, value);

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


// 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;
}


// Inheritance


// https://docs.synthetix.io/contracts/source/contracts/exchangestate
contract ExchangeState is Owned, State, IExchangeState {
    mapping(address => mapping(bytes32 => IExchangeState.ExchangeEntry[])) public exchanges;

    uint public maxEntriesInQueue = 12;

    constructor(address _owner, address _associatedContract) public Owned(_owner) State(_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;
    }
}


// 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 requireExchangeBetweenSynthsAllowed(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function requireSynthActive(bytes32 currencyKey) external view;

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

    function synthSuspension(bytes32 currencyKey) 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);

    // Restricted functions
    function suspendSynth(bytes32 currencyKey, 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_SYNTH_EXCHANGE = "SynthExchange";
    bytes32 public constant SECTION_SYNTH = "Synth";

    Suspension public systemSuspension;

    Suspension public issuanceSuspension;

    Suspension public exchangeSuspension;

    mapping(bytes32 => Suspension) public synthExchangeSuspension;

    mapping(bytes32 => Suspension) public synthSuspension;

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

    /* ========== VIEWS ========== */
    function requireSystemActive() external view {
        _internalRequireSystemActive();
    }

    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 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;
        }
    }

    /* ========== 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 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 _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 _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 _internalUpdateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) internal {
        require(
            section == SECTION_SYSTEM ||
                section == SECTION_ISSUANCE ||
                section == SECTION_EXCHANGE ||
                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 SynthExchangeSuspended(bytes32 currencyKey, uint256 reason);
    event SynthExchangeResumed(bytes32 currencyKey, uint256 reason);

    event SynthSuspended(bytes32 currencyKey, uint256 reason);
    event SynthResumed(bytes32 currencyKey, uint256 reason);

    event AccessControlUpdated(bytes32 indexed section, address indexed account, bool canSuspend, bool canResume);
}


contract LegacyOwned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        owner = _owner;
    }

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


contract LegacyTokenState is LegacyOwned {
    // the address of the contract that can modify balances and allowances
    // this can only be changed by the owner of this contract
    address public associatedContract;

    // ERC20 fields.
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    constructor(address _owner, address _associatedContract) public LegacyOwned(_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);
    }

    function setAllowance(
        address tokenOwner,
        address spender,
        uint value
    ) external onlyAssociatedContract {
        allowance[tokenOwner][spender] = value;
    }

    function setBalanceOf(address account, uint value) external onlyAssociatedContract {
        balanceOf[account] = value;
    }

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

    modifier onlyAssociatedContract {
        require(msg.sender == associatedContract);
        _;
    }

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

    event AssociatedContractUpdated(address _associatedContract);
}


// https://docs.synthetix.io/contracts/source/interfaces/isynthetixstate
interface ISynthetixState {
    // Views
    function debtLedger(uint index) external view returns (uint);

    function issuanceData(address account) external view returns (uint initialDebtOwnership, uint debtEntryIndex);

    function debtLedgerLength() external view returns (uint);

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

    function lastDebtLedgerEntry() external view returns (uint);

    // Mutative functions
    function incrementTotalIssuerCount() external;

    function decrementTotalIssuerCount() external;

    function setCurrentIssuanceData(address account, uint initialDebtOwnership) external;

    function appendDebtLedgerValue(uint value) external;

    function clearIssuanceData(address account) external;
}


// Inheritance


// Libraries


// https://docs.synthetix.io/contracts/source/contracts/synthetixstate
contract SynthetixState is Owned, State, ISynthetixState {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    // A struct for handing values associated with an individual user's debt position
    struct IssuanceData {
        // Percentage of the total debt owned at the time
        // of issuance. This number is modified by the global debt
        // delta array. You can figure out a user's exit price and
        // collateralisation ratio using a combination of their initial
        // debt and the slice of global debt delta which applies to them.
        uint initialDebtOwnership;
        // This lets us know when (in relative terms) the user entered
        // the debt pool so we can calculate their exit price and
        // collateralistion ratio
        uint debtEntryIndex;
    }

    // Issued synth balances for individual fee entitlements and exit price calculations
    mapping(address => IssuanceData) public issuanceData;

    // The total count of people that have outstanding issued synths in any flavour
    uint public totalIssuerCount;

    // Global debt pool tracking
    uint[] public debtLedger;

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

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

    /**
     * @notice Set issuance data for an address
     * @dev Only the associated contract may call this.
     * @param account The address to set the data for.
     * @param initialDebtOwnership The initial debt ownership for this address.
     */
    function setCurrentIssuanceData(address account, uint initialDebtOwnership) external onlyAssociatedContract {
        issuanceData[account].initialDebtOwnership = initialDebtOwnership;
        issuanceData[account].debtEntryIndex = debtLedger.length;
    }

    /**
     * @notice Clear issuance data for an address
     * @dev Only the associated contract may call this.
     * @param account The address to clear the data for.
     */
    function clearIssuanceData(address account) external onlyAssociatedContract {
        delete issuanceData[account];
    }

    /**
     * @notice Increment the total issuer count
     * @dev Only the associated contract may call this.
     */
    function incrementTotalIssuerCount() external onlyAssociatedContract {
        totalIssuerCount = totalIssuerCount.add(1);
    }

    /**
     * @notice Decrement the total issuer count
     * @dev Only the associated contract may call this.
     */
    function decrementTotalIssuerCount() external onlyAssociatedContract {
        totalIssuerCount = totalIssuerCount.sub(1);
    }

    /**
     * @notice Append a value to the debt ledger
     * @dev Only the associated contract may call this.
     * @param value The new value to be added to the debt ledger.
     */
    function appendDebtLedgerValue(uint value) external onlyAssociatedContract {
        debtLedger.push(value);
    }

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

    /**
     * @notice Retrieve the length of the debt ledger array
     */
    function debtLedgerLength() external view returns (uint) {
        return debtLedger.length;
    }

    /**
     * @notice Retrieve the most recent entry from the debt ledger
     */
    function lastDebtLedgerEntry() external view returns (uint) {
        return debtLedger[debtLedger.length - 1];
    }

    /**
     * @notice Query whether an account has issued and has an outstanding debt balance
     * @param account The address to query for
     */
    function hasIssued(address account) external view returns (bool) {
        return issuanceData[account].initialDebtOwnership > 0;
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/irewardescrow
interface IRewardEscrow {
    // Views
    function balanceOf(address account) external view returns (uint);

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

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

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

    function getVestingScheduleEntry(address account, uint index) external view returns (uint[2] memory);

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

    // Mutative functions
    function appendVestingEntry(address account, uint quantity) external;

    function vest() 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/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);

    // 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 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, uint susdAmount) external returns (bool);

    // Restricted Functions

    function mintSecondary(address account, uint amount) external;

    function mintSecondaryRewards(uint amount) external;

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


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/rewardescrow
contract RewardEscrow is Owned, IRewardEscrow {
    using SafeMath for uint;

    /* The corresponding Synthetix contract. */
    ISynthetix public synthetix;

    IFeePool public feePool;

    /* Lists of (timestamp, quantity) pairs per account, sorted in ascending time order.
     * These are the times at which each given quantity of SNX vests. */
    mapping(address => uint[2][]) public vestingSchedules;

    /* An account's total escrowed synthetix balance to save recomputing this for fee extraction purposes. */
    mapping(address => uint) public totalEscrowedAccountBalance;

    /* An account's total vested reward synthetix. */
    mapping(address => uint) public totalVestedAccountBalance;

    /* The total remaining escrowed balance, for verifying the actual synthetix balance of this contract against. */
    uint public totalEscrowedBalance;

    uint internal constant TIME_INDEX = 0;
    uint internal constant QUANTITY_INDEX = 1;

    /* Limit vesting entries to disallow unbounded iteration over vesting schedules.
     * There are 5 years of the supply schedule */
    uint public constant MAX_VESTING_ENTRIES = 52 * 5;

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

    constructor(
        address _owner,
        ISynthetix _synthetix,
        IFeePool _feePool
    ) public Owned(_owner) {
        synthetix = _synthetix;
        feePool = _feePool;
    }

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

    /**
     * @notice set the synthetix contract address as we need to transfer SNX when the user vests
     */
    function setSynthetix(ISynthetix _synthetix) external onlyOwner {
        synthetix = _synthetix;
        emit SynthetixUpdated(address(_synthetix));
    }

    /**
     * @notice set the FeePool contract as it is the only authority to be able to call
     * appendVestingEntry with the onlyFeePool modifer
     */
    function setFeePool(IFeePool _feePool) external onlyOwner {
        feePool = _feePool;
        emit FeePoolUpdated(address(_feePool));
    }

    /* ========== VIEW FUNCTIONS ========== */

    /**
     * @notice A simple alias to totalEscrowedAccountBalance: provides ERC20 balance integration.
     */
    function balanceOf(address account) public view returns (uint) {
        return totalEscrowedAccountBalance[account];
    }

    function _numVestingEntries(address account) internal view returns (uint) {
        return vestingSchedules[account].length;
    }

    /**
     * @notice The number of vesting dates in an account's schedule.
     */
    function numVestingEntries(address account) external view returns (uint) {
        return vestingSchedules[account].length;
    }

    /**
     * @notice Get a particular schedule entry for an account.
     * @return A pair of uints: (timestamp, synthetix quantity).
     */
    function getVestingScheduleEntry(address account, uint index) public view returns (uint[2] memory) {
        return vestingSchedules[account][index];
    }

    /**
     * @notice Get the time at which a given schedule entry will vest.
     */
    function getVestingTime(address account, uint index) public view returns (uint) {
        return getVestingScheduleEntry(account, index)[TIME_INDEX];
    }

    /**
     * @notice Get the quantity of SNX associated with a given schedule entry.
     */
    function getVestingQuantity(address account, uint index) public view returns (uint) {
        return getVestingScheduleEntry(account, index)[QUANTITY_INDEX];
    }

    /**
     * @notice Obtain the index of the next schedule entry that will vest for a given user.
     */
    function getNextVestingIndex(address account) public view returns (uint) {
        uint len = _numVestingEntries(account);
        for (uint i = 0; i < len; i++) {
            if (getVestingTime(account, i) != 0) {
                return i;
            }
        }
        return len;
    }

    /**
     * @notice Obtain the next schedule entry that will vest for a given user.
     * @return A pair of uints: (timestamp, synthetix quantity). */
    function getNextVestingEntry(address account) public view returns (uint[2] memory) {
        uint index = getNextVestingIndex(account);
        if (index == _numVestingEntries(account)) {
            return [uint(0), 0];
        }
        return getVestingScheduleEntry(account, index);
    }

    /**
     * @notice Obtain the time at which the next schedule entry will vest for a given user.
     */
    function getNextVestingTime(address account) external view returns (uint) {
        return getNextVestingEntry(account)[TIME_INDEX];
    }

    /**
     * @notice Obtain the quantity which the next schedule entry will vest for a given user.
     */
    function getNextVestingQuantity(address account) external view returns (uint) {
        return getNextVestingEntry(account)[QUANTITY_INDEX];
    }

    /**
     * @notice return the full vesting schedule entries vest for a given user.
     * @dev For DApps to display the vesting schedule for the
     * inflationary supply over 5 years. Solidity cant return variable length arrays
     * so this is returning pairs of data. Vesting Time at [0] and quantity at [1] and so on
     */
    function checkAccountSchedule(address account) public view returns (uint[520] memory) {
        uint[520] memory _result;
        uint schedules = _numVestingEntries(account);
        for (uint i = 0; i < schedules; i++) {
            uint[2] memory pair = getVestingScheduleEntry(account, i);
            _result[i * 2] = pair[0];
            _result[i * 2 + 1] = pair[1];
        }
        return _result;
    }

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

    function _appendVestingEntry(address account, uint quantity) internal {
        /* No empty or already-passed vesting entries allowed. */
        require(quantity != 0, "Quantity cannot be zero");

        /* There must be enough balance in the contract to provide for the vesting entry. */
        totalEscrowedBalance = totalEscrowedBalance.add(quantity);
        require(
            totalEscrowedBalance <= IERC20(address(synthetix)).balanceOf(address(this)),
            "Must be enough balance in the contract to provide for the vesting entry"
        );

        /* Disallow arbitrarily long vesting schedules in light of the gas limit. */
        uint scheduleLength = vestingSchedules[account].length;
        require(scheduleLength <= MAX_VESTING_ENTRIES, "Vesting schedule is too long");

        /* Escrow the tokens for 1 year. */
        uint time = now + 52 weeks;

        if (scheduleLength == 0) {
            totalEscrowedAccountBalance[account] = quantity;
        } else {
            /* Disallow adding new vested SNX earlier than the last one.
             * Since entries are only appended, this means that no vesting date can be repeated. */
            require(
                getVestingTime(account, scheduleLength - 1) < time,
                "Cannot add new vested entries earlier than the last one"
            );
            totalEscrowedAccountBalance[account] = totalEscrowedAccountBalance[account].add(quantity);
        }

        vestingSchedules[account].push([time, quantity]);

        emit VestingEntryCreated(account, now, quantity);
    }

    /**
     * @notice Add a new vesting entry at a given time and quantity to an account's schedule.
     * @dev A call to this should accompany a previous successful call to synthetix.transfer(rewardEscrow, amount),
     * to ensure that when the funds are withdrawn, there is enough balance.
     * Note; although this function could technically be used to produce unbounded
     * arrays, it's only withinn the 4 year period of the weekly inflation schedule.
     * @param account The account to append a new vesting entry to.
     * @param quantity The quantity of SNX that will be escrowed.
     */
    function appendVestingEntry(address account, uint quantity) external onlyFeePool {
        _appendVestingEntry(account, quantity);
    }

    /**
     * @notice Allow a user to withdraw any SNX in their schedule that have vested.
     */
    function vest() external {
        uint numEntries = _numVestingEntries(msg.sender);
        uint total;
        for (uint i = 0; i < numEntries; i++) {
            uint time = getVestingTime(msg.sender, i);
            /* The list is sorted; when we reach the first future time, bail out. */
            if (time > now) {
                break;
            }
            uint qty = getVestingQuantity(msg.sender, i);
            if (qty > 0) {
                vestingSchedules[msg.sender][i] = [0, 0];
                total = total.add(qty);
            }
        }

        if (total != 0) {
            totalEscrowedBalance = totalEscrowedBalance.sub(total);
            totalEscrowedAccountBalance[msg.sender] = totalEscrowedAccountBalance[msg.sender].sub(total);
            totalVestedAccountBalance[msg.sender] = totalVestedAccountBalance[msg.sender].add(total);
            IERC20(address(synthetix)).transfer(msg.sender, total);
            emit Vested(msg.sender, now, total);
        }
    }

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

    modifier onlyFeePool() {
        bool isFeePool = msg.sender == address(feePool);

        require(isFeePool, "Only the FeePool contracts can perform this action");
        _;
    }

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

    event SynthetixUpdated(address newSynthetix);

    event FeePoolUpdated(address newFeePool);

    event Vested(address indexed beneficiary, uint time, uint value);

    event VestingEntryCreated(address indexed beneficiary, uint time, uint value);
}


// https://docs.synthetix.io/contracts/source/interfaces/irewardsdistribution
interface IRewardsDistribution {
    // Structs
    struct DistributionData {
        address destination;
        uint amount;
    }

    // Views
    function authority() external view returns (address);

    function distributions(uint index) external view returns (address destination, uint amount); // DistributionData

    function distributionsLength() external view returns (uint);

    // Mutative Functions
    function distributeRewards(uint amount) external returns (bool);
}


// Inheritance


// Libraires


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/rewardsdistribution
contract RewardsDistribution is Owned, IRewardsDistribution {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /**
     * @notice Authorised address able to call distributeRewards
     */
    address public authority;

    /**
     * @notice Address of the Synthetix ProxyERC20
     */
    address public synthetixProxy;

    /**
     * @notice Address of the RewardEscrow contract
     */
    address public rewardEscrow;

    /**
     * @notice Address of the FeePoolProxy
     */
    address public feePoolProxy;

    /**
     * @notice An array of addresses and amounts to send
     */
    DistributionData[] public distributions;

    /**
     * @dev _authority maybe the underlying synthetix contract.
     * Remember to set the authority on a synthetix upgrade
     */
    constructor(
        address _owner,
        address _authority,
        address _synthetixProxy,
        address _rewardEscrow,
        address _feePoolProxy
    ) public Owned(_owner) {
        authority = _authority;
        synthetixProxy = _synthetixProxy;
        rewardEscrow = _rewardEscrow;
        feePoolProxy = _feePoolProxy;
    }

    // ========== EXTERNAL SETTERS ==========

    function setSynthetixProxy(address _synthetixProxy) external onlyOwner {
        synthetixProxy = _synthetixProxy;
    }

    function setRewardEscrow(address _rewardEscrow) external onlyOwner {
        rewardEscrow = _rewardEscrow;
    }

    function setFeePoolProxy(address _feePoolProxy) external onlyOwner {
        feePoolProxy = _feePoolProxy;
    }

    /**
     * @notice Set the address of the contract authorised to call distributeRewards()
     * @param _authority Address of the authorised calling contract.
     */
    function setAuthority(address _authority) external onlyOwner {
        authority = _authority;
    }

    // ========== EXTERNAL FUNCTIONS ==========

    /**
     * @notice Adds a Rewards DistributionData struct to the distributions
     * array. Any entries here will be iterated and rewards distributed to
     * each address when tokens are sent to this contract and distributeRewards()
     * is called by the autority.
     * @param destination An address to send rewards tokens too
     * @param amount The amount of rewards tokens to send
     */
    function addRewardDistribution(address destination, uint amount) external onlyOwner returns (bool) {
        require(destination != address(0), "Cant add a zero address");
        require(amount != 0, "Cant add a zero amount");

        DistributionData memory rewardsDistribution = DistributionData(destination, amount);
        distributions.push(rewardsDistribution);

        emit RewardDistributionAdded(distributions.length - 1, destination, amount);
        return true;
    }

    /**
     * @notice Deletes a RewardDistribution from the distributions
     * so it will no longer be included in the call to distributeRewards()
     * @param index The index of the DistributionData to delete
     */
    function removeRewardDistribution(uint index) external onlyOwner {
        require(index <= distributions.length - 1, "index out of bounds");

        // shift distributions indexes across
        for (uint i = index; i < distributions.length - 1; i++) {
            distributions[i] = distributions[i + 1];
        }
        distributions.length--;

        // Since this function must shift all later entries down to fill the
        // gap from the one it removed, it could in principle consume an
        // unbounded amount of gas. However, the number of entries will
        // presumably always be very low.
    }

    /**
     * @notice Edits a RewardDistribution in the distributions array.
     * @param index The index of the DistributionData to edit
     * @param destination The destination address. Send the same address to keep or different address to change it.
     * @param amount The amount of tokens to edit. Send the same number to keep or change the amount of tokens to send.
     */
    function editRewardDistribution(
        uint index,
        address destination,
        uint amount
    ) external onlyOwner returns (bool) {
        require(index <= distributions.length - 1, "index out of bounds");

        distributions[index].destination = destination;
        distributions[index].amount = amount;

        return true;
    }

    function distributeRewards(uint amount) external returns (bool) {
        require(amount > 0, "Nothing to distribute");
        require(msg.sender == authority, "Caller is not authorised");
        require(rewardEscrow != address(0), "RewardEscrow is not set");
        require(synthetixProxy != address(0), "SynthetixProxy is not set");
        require(feePoolProxy != address(0), "FeePoolProxy is not set");
        require(
            IERC20(synthetixProxy).balanceOf(address(this)) >= amount,
            "RewardsDistribution contract does not have enough tokens to distribute"
        );

        uint remainder = amount;

        // Iterate the array of distributions sending the configured amounts
        for (uint i = 0; i < distributions.length; i++) {
            if (distributions[i].destination != address(0) || distributions[i].amount != 0) {
                remainder = remainder.sub(distributions[i].amount);

                // Transfer the SNX
                IERC20(synthetixProxy).transfer(distributions[i].destination, distributions[i].amount);

                // If the contract implements RewardsDistributionRecipient.sol, inform it how many SNX its received.
                bytes memory payload = abi.encodeWithSignature("notifyRewardAmount(uint256)", distributions[i].amount);

                // solhint-disable avoid-low-level-calls
                (bool success, ) = distributions[i].destination.call(payload);

                if (!success) {
                    // Note: we're ignoring the return value as it will fail for contracts that do not implement RewardsDistributionRecipient.sol
                }
            }
        }

        // After all ditributions have been sent, send the remainder to the RewardsEscrow contract
        IERC20(synthetixProxy).transfer(rewardEscrow, remainder);

        // Tell the FeePool how much it has to distribute to the stakers
        IFeePool(feePoolProxy).setRewardsToDistribute(remainder);

        emit RewardsDistributed(amount);
        return true;
    }

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

    /**
     * @notice Retrieve the length of the distributions array
     */
    function distributionsLength() external view returns (uint) {
        return distributions.length;
    }

    /* ========== Events ========== */

    event RewardDistributionAdded(uint index, address destination, uint amount);
    event RewardsDistributed(uint amount);
}


// 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 {
    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_PENALTY = "liquidationPenalty";
    bytes32 internal constant SETTING_RATE_STALE_PERIOD = "rateStalePeriod";
    bytes32 internal constant SETTING_EXCHANGE_FEE_RATE = "exchangeFeeRate";
    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_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 CONTRACT_FLEXIBLESTORAGE = "FlexibleStorage";

    enum CrossDomainMessageGasLimits {Deposit, Escrow, Reward, Withdrawal}

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

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

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

    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);
    }
}


// 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 exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        bool virtualSynth,
        address rewardAddress,
        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 resetLastExchangeRate(bytes32[] calldata currencyKeys) external;

    function suspendSynthWithInvalidRate(bytes32 currencyKey) external;
}


pragma experimental ABIEncoderV2;

library VestingEntries {
    struct VestingEntry {
        uint64 endTime;
        uint256 escrowAmount;
    }
    struct VestingEntryWithID {
        uint64 endTime;
        uint256 escrowAmount;
        uint256 entryID;
    }
}

interface IRewardEscrowV2 {
    // Views
    function balanceOf(address account) external view returns (uint);

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

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

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

    function getVestingQuantity(address account, uint256[] calldata entryIDs) external view returns (uint);

    function getVestingSchedules(
        address account,
        uint256 index,
        uint256 pageSize
    ) external view returns (VestingEntries.VestingEntryWithID[] memory);

    function getAccountVestingEntryIDs(
        address account,
        uint256 index,
        uint256 pageSize
    ) external view returns (uint256[] memory);

    function getVestingEntryClaimable(address account, uint256 entryID) external view returns (uint);

    function getVestingEntry(address account, uint256 entryID) external view returns (uint64, uint256);

    // Mutative functions
    function vest(uint256[] calldata entryIDs) external;

    function createEscrowEntry(
        address beneficiary,
        uint256 deposit,
        uint256 duration
    ) external;

    function appendVestingEntry(
        address account,
        uint256 quantity,
        uint256 duration
    ) external;

    function migrateVestingSchedule(address _addressToMigrate) external;

    function migrateAccountEscrowBalances(
        address[] calldata accounts,
        uint256[] calldata escrowBalances,
        uint256[] calldata vestedBalances
    ) external;

    // Account Merging
    function startMergingWindow() external;

    function mergeAccount(address accountToMerge, uint256[] calldata entryIDs) external;

    function nominateAccountToMerge(address account) external;

    function accountMergingIsOpen() external view returns (bool);

    // L2 Migration
    function importVestingEntries(
        address account,
        uint256 escrowedAmount,
        VestingEntries.VestingEntry[] calldata vestingEntries
    ) external;

    // Return amount of SNX transfered to SynthetixBridgeToOptimism deposit contract
    function burnForMigration(address account, uint256[] calldata entryIDs)
        external
        returns (uint256 escrowedAccountBalance, VestingEntries.VestingEntry[] memory vestingEntries);
}


// 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;
}


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[2][] calldata requiredSynthAndInverseNamesInResolver, bytes32[] calldata synthKeys)
        external;

    function removeShortableSynths(bytes32[] calldata synths) external;

    // State mutative
    function updateBorrowRates(uint rate) external;

    function updateShortRates(bytes32 currency, uint rate) external;

    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;
}


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);
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/feepool
contract FeePool is Owned, Proxyable, LimitedSetup, MixinSystemSettings, IFeePool {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    bytes32 public constant CONTRACT_NAME = "FeePool";

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

    // sUSD currencyKey. Fees stored and paid in sUSD
    bytes32 private sUSD = "sUSD";

    // This struct represents the issuance activity that's happened in a fee period.
    struct FeePeriod {
        uint64 feePeriodId;
        uint64 startingDebtIndex;
        uint64 startTime;
        uint feesToDistribute;
        uint feesClaimed;
        uint rewardsToDistribute;
        uint rewardsClaimed;
    }

    // A staker(mintr) can claim from the previous fee period (7 days) only.
    // Fee Periods stored and managed from [0], such that [0] is always
    // the current active fee period which is not claimable until the
    // public function closeCurrentFeePeriod() is called closing the
    // current weeks collected fees. [1] is last weeks feeperiod
    uint8 public constant FEE_PERIOD_LENGTH = 2;

    FeePeriod[FEE_PERIOD_LENGTH] private _recentFeePeriods;
    uint256 private _currentFeePeriod;

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

    bytes32 private constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 private constant CONTRACT_SYNTHETIX = "Synthetix";
    bytes32 private constant CONTRACT_FEEPOOLSTATE = "FeePoolState";
    bytes32 private constant CONTRACT_FEEPOOLETERNALSTORAGE = "FeePoolEternalStorage";
    bytes32 private constant CONTRACT_EXCHANGER = "Exchanger";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_SYNTHETIXSTATE = "SynthetixState";
    bytes32 private constant CONTRACT_REWARDESCROW_V2 = "RewardEscrowV2";
    bytes32 private constant CONTRACT_DELEGATEAPPROVALS = "DelegateApprovals";
    bytes32 private constant CONTRACT_COLLATERALMANAGER = "CollateralManager";
    bytes32 private constant CONTRACT_REWARDSDISTRIBUTION = "RewardsDistribution";
    bytes32 private constant CONTRACT_ETHER_WRAPPER = "EtherWrapper";

    /* ========== ETERNAL STORAGE CONSTANTS ========== */

    bytes32 private constant LAST_FEE_WITHDRAWAL = "last_fee_withdrawal";

    constructor(
        address payable _proxy,
        address _owner,
        address _resolver
    ) public Owned(_owner) Proxyable(_proxy) LimitedSetup(3 weeks) MixinSystemSettings(_resolver) {
        // Set our initial fee period
        _recentFeePeriodsStorage(0).feePeriodId = 1;
        _recentFeePeriodsStorage(0).startTime = uint64(now);
    }

    /* ========== VIEWS ========== */
    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = MixinSystemSettings.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](12);
        newAddresses[0] = CONTRACT_SYSTEMSTATUS;
        newAddresses[1] = CONTRACT_SYNTHETIX;
        newAddresses[2] = CONTRACT_FEEPOOLSTATE;
        newAddresses[3] = CONTRACT_FEEPOOLETERNALSTORAGE;
        newAddresses[4] = CONTRACT_EXCHANGER;
        newAddresses[5] = CONTRACT_ISSUER;
        newAddresses[6] = CONTRACT_SYNTHETIXSTATE;
        newAddresses[7] = CONTRACT_REWARDESCROW_V2;
        newAddresses[8] = CONTRACT_DELEGATEAPPROVALS;
        newAddresses[9] = CONTRACT_REWARDSDISTRIBUTION;
        newAddresses[10] = CONTRACT_COLLATERALMANAGER;
        newAddresses[11] = CONTRACT_ETHER_WRAPPER;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

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

    function synthetix() internal view returns (ISynthetix) {
        return ISynthetix(requireAndGetAddress(CONTRACT_SYNTHETIX));
    }

    function feePoolState() internal view returns (FeePoolState) {
        return FeePoolState(requireAndGetAddress(CONTRACT_FEEPOOLSTATE));
    }

    function feePoolEternalStorage() internal view returns (FeePoolEternalStorage) {
        return FeePoolEternalStorage(requireAndGetAddress(CONTRACT_FEEPOOLETERNALSTORAGE));
    }

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

    function collateralManager() internal view returns (ICollateralManager) {
        return ICollateralManager(requireAndGetAddress(CONTRACT_COLLATERALMANAGER));
    }

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

    function synthetixState() internal view returns (ISynthetixState) {
        return ISynthetixState(requireAndGetAddress(CONTRACT_SYNTHETIXSTATE));
    }

    function rewardEscrowV2() internal view returns (IRewardEscrowV2) {
        return IRewardEscrowV2(requireAndGetAddress(CONTRACT_REWARDESCROW_V2));
    }

    function delegateApprovals() internal view returns (IDelegateApprovals) {
        return IDelegateApprovals(requireAndGetAddress(CONTRACT_DELEGATEAPPROVALS));
    }

    function rewardsDistribution() internal view returns (IRewardsDistribution) {
        return IRewardsDistribution(requireAndGetAddress(CONTRACT_REWARDSDISTRIBUTION));
    }

    function etherWrapper() internal view returns (IEtherWrapper) {
        return IEtherWrapper(requireAndGetAddress(CONTRACT_ETHER_WRAPPER));
    }

    function issuanceRatio() external view returns (uint) {
        return getIssuanceRatio();
    }

    function feePeriodDuration() external view returns (uint) {
        return getFeePeriodDuration();
    }

    function targetThreshold() external view returns (uint) {
        return getTargetThreshold();
    }

    function recentFeePeriods(uint index)
        external
        view
        returns (
            uint64 feePeriodId,
            uint64 startingDebtIndex,
            uint64 startTime,
            uint feesToDistribute,
            uint feesClaimed,
            uint rewardsToDistribute,
            uint rewardsClaimed
        )
    {
        FeePeriod memory feePeriod = _recentFeePeriodsStorage(index);
        return (
            feePeriod.feePeriodId,
            feePeriod.startingDebtIndex,
            feePeriod.startTime,
            feePeriod.feesToDistribute,
            feePeriod.feesClaimed,
            feePeriod.rewardsToDistribute,
            feePeriod.rewardsClaimed
        );
    }

    function _recentFeePeriodsStorage(uint index) internal view returns (FeePeriod storage) {
        return _recentFeePeriods[(_currentFeePeriod + index) % FEE_PERIOD_LENGTH];
    }

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

    /**
     * @notice Logs an accounts issuance data per fee period
     * @param account Message.Senders account address
     * @param debtRatio Debt percentage this account has locked after minting or burning their synth
     * @param debtEntryIndex The index in the global debt ledger. synthetixState.issuanceData(account)
     * @dev onlyIssuer to call me on synthetix.issue() & synthetix.burn() calls to store the locked SNX
     * per fee period so we know to allocate the correct proportions of fees and rewards per period
     */
    function appendAccountIssuanceRecord(
        address account,
        uint debtRatio,
        uint debtEntryIndex
    ) external onlyIssuerAndSynthetixState {
        feePoolState().appendAccountIssuanceRecord(
            account,
            debtRatio,
            debtEntryIndex,
            _recentFeePeriodsStorage(0).startingDebtIndex
        );

        emitIssuanceDebtRatioEntry(account, debtRatio, debtEntryIndex, _recentFeePeriodsStorage(0).startingDebtIndex);
    }

    /**
     * @notice The Exchanger contract informs us when fees are paid.
     * @param amount susd amount in fees being paid.
     */
    function recordFeePaid(uint amount) external onlyInternalContracts {
        // Keep track off fees in sUSD in the open fee pool period.
        _recentFeePeriodsStorage(0).feesToDistribute = _recentFeePeriodsStorage(0).feesToDistribute.add(amount);
    }

    /**
     * @notice The RewardsDistribution contract informs us how many SNX rewards are sent to RewardEscrow to be claimed.
     */
    function setRewardsToDistribute(uint amount) external {
        address rewardsAuthority = address(rewardsDistribution());
        require(messageSender == rewardsAuthority || msg.sender == rewardsAuthority, "Caller is not rewardsAuthority");
        // Add the amount of SNX rewards to distribute on top of any rolling unclaimed amount
        _recentFeePeriodsStorage(0).rewardsToDistribute = _recentFeePeriodsStorage(0).rewardsToDistribute.add(amount);
    }

    /**
     * @notice Close the current fee period and start a new one.
     */
    function closeCurrentFeePeriod() external issuanceActive {
        require(getFeePeriodDuration() > 0, "Fee Period Duration not set");
        require(_recentFeePeriodsStorage(0).startTime <= (now - getFeePeriodDuration()), "Too early to close fee period");

        etherWrapper().distributeFees();

        // Note:  when FEE_PERIOD_LENGTH = 2, periodClosing is the current period & periodToRollover is the last open claimable period
        FeePeriod storage periodClosing = _recentFeePeriodsStorage(FEE_PERIOD_LENGTH - 2);
        FeePeriod storage periodToRollover = _recentFeePeriodsStorage(FEE_PERIOD_LENGTH - 1);

        // Any unclaimed fees from the last period in the array roll back one period.
        // Because of the subtraction here, they're effectively proportionally redistributed to those who
        // have already claimed from the old period, available in the new period.
        // The subtraction is important so we don't create a ticking time bomb of an ever growing
        // number of fees that can never decrease and will eventually overflow at the end of the fee pool.
        _recentFeePeriodsStorage(FEE_PERIOD_LENGTH - 2).feesToDistribute = periodToRollover
            .feesToDistribute
            .sub(periodToRollover.feesClaimed)
            .add(periodClosing.feesToDistribute);
        _recentFeePeriodsStorage(FEE_PERIOD_LENGTH - 2).rewardsToDistribute = periodToRollover
            .rewardsToDistribute
            .sub(periodToRollover.rewardsClaimed)
            .add(periodClosing.rewardsToDistribute);

        // Shift the previous fee periods across to make room for the new one.
        _currentFeePeriod = _currentFeePeriod.add(FEE_PERIOD_LENGTH).sub(1).mod(FEE_PERIOD_LENGTH);

        // Clear the first element of the array to make sure we don't have any stale values.
        delete _recentFeePeriods[_currentFeePeriod];

        // Open up the new fee period.
        // Increment periodId from the recent closed period feePeriodId
        _recentFeePeriodsStorage(0).feePeriodId = uint64(uint256(_recentFeePeriodsStorage(1).feePeriodId).add(1));
        _recentFeePeriodsStorage(0).startingDebtIndex = uint64(synthetixState().debtLedgerLength());
        _recentFeePeriodsStorage(0).startTime = uint64(now);

        emitFeePeriodClosed(_recentFeePeriodsStorage(1).feePeriodId);
    }

    /**
     * @notice Claim fees for last period when available or not already withdrawn.
     */
    function claimFees() external issuanceActive optionalProxy returns (bool) {
        return _claimFees(messageSender);
    }

    /**
     * @notice Delegated claimFees(). Call from the deletegated address
     * and the fees will be sent to the claimingForAddress.
     * approveClaimOnBehalf() must be called first to approve the deletage address
     * @param claimingForAddress The account you are claiming fees for
     */
    function claimOnBehalf(address claimingForAddress) external issuanceActive optionalProxy returns (bool) {
        require(delegateApprovals().canClaimFor(claimingForAddress, messageSender), "Not approved to claim on behalf");

        return _claimFees(claimingForAddress);
    }

    function _claimFees(address claimingAddress) internal returns (bool) {
        uint rewardsPaid = 0;
        uint feesPaid = 0;
        uint availableFees;
        uint availableRewards;

        // Address won't be able to claim fees if it is too far below the target c-ratio.
        // It will need to burn synths then try claiming again.
        (bool feesClaimable, bool anyRateIsInvalid) = _isFeesClaimableAndAnyRatesInvalid(claimingAddress);

        require(feesClaimable, "C-Ratio below penalty threshold");

        require(!anyRateIsInvalid, "A synth or SNX rate is invalid");

        // Get the claimingAddress available fees and rewards
        (availableFees, availableRewards) = feesAvailable(claimingAddress);

        require(
            availableFees > 0 || availableRewards > 0,
            "No fees or rewards available for period, or fees already claimed"
        );

        // Record the address has claimed for this period
        _setLastFeeWithdrawal(claimingAddress, _recentFeePeriodsStorage(1).feePeriodId);

        if (availableFees > 0) {
            // Record the fee payment in our recentFeePeriods
            feesPaid = _recordFeePayment(availableFees);

            // Send them their fees
            _payFees(claimingAddress, feesPaid);
        }

        if (availableRewards > 0) {
            // Record the reward payment in our recentFeePeriods
            rewardsPaid = _recordRewardPayment(availableRewards);

            // Send them their rewards
            _payRewards(claimingAddress, rewardsPaid);
        }

        emitFeesClaimed(claimingAddress, feesPaid, rewardsPaid);

        return true;
    }

    /**
     * @notice Admin function to import the FeePeriod data from the previous contract
     */
    function importFeePeriod(
        uint feePeriodIndex,
        uint feePeriodId,
        uint startingDebtIndex,
        uint startTime,
        uint feesToDistribute,
        uint feesClaimed,
        uint rewardsToDistribute,
        uint rewardsClaimed
    ) public optionalProxy_onlyOwner onlyDuringSetup {
        require(startingDebtIndex <= synthetixState().debtLedgerLength(), "Cannot import bad data");

        _recentFeePeriods[_currentFeePeriod.add(feePeriodIndex).mod(FEE_PERIOD_LENGTH)] = FeePeriod({
            feePeriodId: uint64(feePeriodId),
            startingDebtIndex: uint64(startingDebtIndex),
            startTime: uint64(startTime),
            feesToDistribute: feesToDistribute,
            feesClaimed: feesClaimed,
            rewardsToDistribute: rewardsToDistribute,
            rewardsClaimed: rewardsClaimed
        });
    }

    /**
     * @notice Record the fee payment in our recentFeePeriods.
     * @param sUSDAmount The amount of fees priced in sUSD.
     */
    function _recordFeePayment(uint sUSDAmount) internal returns (uint) {
        // Don't assign to the parameter
        uint remainingToAllocate = sUSDAmount;

        uint feesPaid;
        // Start at the oldest period and record the amount, moving to newer periods
        // until we've exhausted the amount.
        // The condition checks for overflow because we're going to 0 with an unsigned int.
        for (uint i = FEE_PERIOD_LENGTH - 1; i < FEE_PERIOD_LENGTH; i--) {
            uint feesAlreadyClaimed = _recentFeePeriodsStorage(i).feesClaimed;
            uint delta = _recentFeePeriodsStorage(i).feesToDistribute.sub(feesAlreadyClaimed);

            if (delta > 0) {
                // Take the smaller of the amount left to claim in the period and the amount we need to allocate
                uint amountInPeriod = delta < remainingToAllocate ? delta : remainingToAllocate;

                _recentFeePeriodsStorage(i).feesClaimed = feesAlreadyClaimed.add(amountInPeriod);
                remainingToAllocate = remainingToAllocate.sub(amountInPeriod);
                feesPaid = feesPaid.add(amountInPeriod);

                // No need to continue iterating if we've recorded the whole amount;
                if (remainingToAllocate == 0) return feesPaid;

                // We've exhausted feePeriods to distribute and no fees remain in last period
                // User last to claim would in this scenario have their remainder slashed
                if (i == 0 && remainingToAllocate > 0) {
                    remainingToAllocate = 0;
                }
            }
        }

        return feesPaid;
    }

    /**
     * @notice Record the reward payment in our recentFeePeriods.
     * @param snxAmount The amount of SNX tokens.
     */
    function _recordRewardPayment(uint snxAmount) internal returns (uint) {
        // Don't assign to the parameter
        uint remainingToAllocate = snxAmount;

        uint rewardPaid;

        // Start at the oldest period and record the amount, moving to newer periods
        // until we've exhausted the amount.
        // The condition checks for overflow because we're going to 0 with an unsigned int.
        for (uint i = FEE_PERIOD_LENGTH - 1; i < FEE_PERIOD_LENGTH; i--) {
            uint toDistribute =
                _recentFeePeriodsStorage(i).rewardsToDistribute.sub(_recentFeePeriodsStorage(i).rewardsClaimed);

            if (toDistribute > 0) {
                // Take the smaller of the amount left to claim in the period and the amount we need to allocate
                uint amountInPeriod = toDistribute < remainingToAllocate ? toDistribute : remainingToAllocate;

                _recentFeePeriodsStorage(i).rewardsClaimed = _recentFeePeriodsStorage(i).rewardsClaimed.add(amountInPeriod);
                remainingToAllocate = remainingToAllocate.sub(amountInPeriod);
                rewardPaid = rewardPaid.add(amountInPeriod);

                // No need to continue iterating if we've recorded the whole amount;
                if (remainingToAllocate == 0) return rewardPaid;

                // We've exhausted feePeriods to distribute and no rewards remain in last period
                // User last to claim would in this scenario have their remainder slashed
                // due to rounding up of PreciseDecimal
                if (i == 0 && remainingToAllocate > 0) {
                    remainingToAllocate = 0;
                }
            }
        }
        return rewardPaid;
    }

    /**
     * @notice Send the fees to claiming address.
     * @param account The address to send the fees to.
     * @param sUSDAmount The amount of fees priced in sUSD.
     */
    function _payFees(address account, uint sUSDAmount) internal notFeeAddress(account) {
        // Grab the sUSD Synth
        ISynth sUSDSynth = issuer().synths(sUSD);

        // NOTE: we do not control the FEE_ADDRESS so it is not possible to do an
        // ERC20.approve() transaction to allow this feePool to call ERC20.transferFrom
        // to the accounts address

        // Burn the source amount
        sUSDSynth.burn(FEE_ADDRESS, sUSDAmount);

        // Mint their new synths
        sUSDSynth.issue(account, sUSDAmount);
    }

    /**
     * @notice Send the rewards to claiming address - will be locked in rewardEscrow.
     * @param account The address to send the fees to.
     * @param snxAmount The amount of SNX.
     */
    function _payRewards(address account, uint snxAmount) internal notFeeAddress(account) {
        /* Escrow the tokens for 1 year. */
        uint escrowDuration = 52 weeks;

        // Record vesting entry for claiming address and amount
        // SNX already minted to rewardEscrow balance
        rewardEscrowV2().appendVestingEntry(account, snxAmount, escrowDuration);
    }

    /**
     * @notice The total fees available in the system to be withdrawnn in sUSD
     */
    function totalFeesAvailable() external view returns (uint) {
        uint totalFees = 0;

        // Fees in fee period [0] are not yet available for withdrawal
        for (uint i = 1; i < FEE_PERIOD_LENGTH; i++) {
            totalFees = totalFees.add(_recentFeePeriodsStorage(i).feesToDistribute);
            totalFees = totalFees.sub(_recentFeePeriodsStorage(i).feesClaimed);
        }

        return totalFees;
    }

    /**
     * @notice The total SNX rewards available in the system to be withdrawn
     */
    function totalRewardsAvailable() external view returns (uint) {
        uint totalRewards = 0;

        // Rewards in fee period [0] are not yet available for withdrawal
        for (uint i = 1; i < FEE_PERIOD_LENGTH; i++) {
            totalRewards = totalRewards.add(_recentFeePeriodsStorage(i).rewardsToDistribute);
            totalRewards = totalRewards.sub(_recentFeePeriodsStorage(i).rewardsClaimed);
        }

        return totalRewards;
    }

    /**
     * @notice The fees available to be withdrawn by a specific account, priced in sUSD
     * @dev Returns two amounts, one for fees and one for SNX rewards
     */
    function feesAvailable(address account) public view returns (uint, uint) {
        // Add up the fees
        uint[2][FEE_PERIOD_LENGTH] memory userFees = feesByPeriod(account);

        uint totalFees = 0;
        uint totalRewards = 0;

        // Fees & Rewards in fee period [0] are not yet available for withdrawal
        for (uint i = 1; i < FEE_PERIOD_LENGTH; i++) {
            totalFees = totalFees.add(userFees[i][0]);
            totalRewards = totalRewards.add(userFees[i][1]);
        }

        // And convert totalFees to sUSD
        // Return totalRewards as is in SNX amount
        return (totalFees, totalRewards);
    }

    function _isFeesClaimableAndAnyRatesInvalid(address account) internal view returns (bool, bool) {
        // Threshold is calculated from ratio % above the target ratio (issuanceRatio).
        //  0  <  10%:   Claimable
        // 10% > above:  Unable to claim
        (uint ratio, bool anyRateIsInvalid) = issuer().collateralisationRatioAndAnyRatesInvalid(account);
        uint targetRatio = getIssuanceRatio();

        // Claimable if collateral ratio below target ratio
        if (ratio < targetRatio) {
            return (true, anyRateIsInvalid);
        }

        // Calculate the threshold for collateral ratio before fees can't be claimed.
        uint ratio_threshold = targetRatio.multiplyDecimal(SafeDecimalMath.unit().add(getTargetThreshold()));

        // Not claimable if collateral ratio above threshold
        if (ratio > ratio_threshold) {
            return (false, anyRateIsInvalid);
        }

        return (true, anyRateIsInvalid);
    }

    function isFeesClaimable(address account) external view returns (bool feesClaimable) {
        (feesClaimable, ) = _isFeesClaimableAndAnyRatesInvalid(account);
    }

    /**
     * @notice Calculates fees by period for an account, priced in sUSD
     * @param account The address you want to query the fees for
     */
    function feesByPeriod(address account) public view returns (uint[2][FEE_PERIOD_LENGTH] memory results) {
        // What's the user's debt entry index and the debt they owe to the system at current feePeriod
        uint userOwnershipPercentage;
        uint debtEntryIndex;
        FeePoolState _feePoolState = feePoolState();

        (userOwnershipPercentage, debtEntryIndex) = _feePoolState.getAccountsDebtEntry(account, 0);

        // If they don't have any debt ownership and they never minted, they don't have any fees.
        // User ownership can reduce to 0 if user burns all synths,
        // however they could have fees applicable for periods they had minted in before so we check debtEntryIndex.
        if (debtEntryIndex == 0 && userOwnershipPercentage == 0) {
            uint[2][FEE_PERIOD_LENGTH] memory nullResults;
            return nullResults;
        }

        // The [0] fee period is not yet ready to claim, but it is a fee period that they can have
        // fees owing for, so we need to report on it anyway.
        uint feesFromPeriod;
        uint rewardsFromPeriod;
        (feesFromPeriod, rewardsFromPeriod) = _feesAndRewardsFromPeriod(0, userOwnershipPercentage, debtEntryIndex);

        results[0][0] = feesFromPeriod;
        results[0][1] = rewardsFromPeriod;

        // Retrieve user's last fee claim by periodId
        uint lastFeeWithdrawal = getLastFeeWithdrawal(account);

        // Go through our fee periods from the oldest feePeriod[FEE_PERIOD_LENGTH - 1] and figure out what we owe them.
        // Condition checks for periods > 0
        for (uint i = FEE_PERIOD_LENGTH - 1; i > 0; i--) {
            uint next = i - 1;
            uint nextPeriodStartingDebtIndex = _recentFeePeriodsStorage(next).startingDebtIndex;

            // We can skip the period, as no debt minted during period (next period's startingDebtIndex is still 0)
            if (nextPeriodStartingDebtIndex > 0 && lastFeeWithdrawal < _recentFeePeriodsStorage(i).feePeriodId) {
                // We calculate a feePeriod's closingDebtIndex by looking at the next feePeriod's startingDebtIndex
                // we can use the most recent issuanceData[0] for the current feePeriod
                // else find the applicableIssuanceData for the feePeriod based on the StartingDebtIndex of the period
                uint closingDebtIndex = uint256(nextPeriodStartingDebtIndex).sub(1);

                // Gas optimisation - to reuse debtEntryIndex if found new applicable one
                // if applicable is 0,0 (none found) we keep most recent one from issuanceData[0]
                // return if userOwnershipPercentage = 0)
                (userOwnershipPercentage, debtEntryIndex) = _feePoolState.applicableIssuanceData(account, closingDebtIndex);

                (feesFromPeriod, rewardsFromPeriod) = _feesAndRewardsFromPeriod(i, userOwnershipPercentage, debtEntryIndex);

                results[i][0] = feesFromPeriod;
                results[i][1] = rewardsFromPeriod;
            }
        }
    }

    /**
     * @notice ownershipPercentage is a high precision decimals uint based on
     * wallet's debtPercentage. Gives a precise amount of the feesToDistribute
     * for fees in the period. Precision factor is removed before results are
     * returned.
     * @dev The reported fees owing for the current period [0] are just a
     * running balance until the fee period closes
     */
    function _feesAndRewardsFromPeriod(
        uint period,
        uint ownershipPercentage,
        uint debtEntryIndex
    ) internal view returns (uint, uint) {
        // If it's zero, they haven't issued, and they have no fees OR rewards.
        if (ownershipPercentage == 0) return (0, 0);

        uint debtOwnershipForPeriod = ownershipPercentage;

        // If period has closed we want to calculate debtPercentage for the period
        if (period > 0) {
            uint closingDebtIndex = uint256(_recentFeePeriodsStorage(period - 1).startingDebtIndex).sub(1);
            debtOwnershipForPeriod = _effectiveDebtRatioForPeriod(closingDebtIndex, ownershipPercentage, debtEntryIndex);
        }

        // Calculate their percentage of the fees / rewards in this period
        // This is a high precision integer.
        uint feesFromPeriod = _recentFeePeriodsStorage(period).feesToDistribute.multiplyDecimal(debtOwnershipForPeriod);

        uint rewardsFromPeriod =
            _recentFeePeriodsStorage(period).rewardsToDistribute.multiplyDecimal(debtOwnershipForPeriod);

        return (feesFromPeriod.preciseDecimalToDecimal(), rewardsFromPeriod.preciseDecimalToDecimal());
    }

    function _effectiveDebtRatioForPeriod(
        uint closingDebtIndex,
        uint ownershipPercentage,
        uint debtEntryIndex
    ) internal view returns (uint) {
        // Figure out their global debt percentage delta at end of fee Period.
        // This is a high precision integer.
        ISynthetixState _synthetixState = synthetixState();
        uint feePeriodDebtOwnership =
            _synthetixState
                .debtLedger(closingDebtIndex)
                .divideDecimalRoundPrecise(_synthetixState.debtLedger(debtEntryIndex))
                .multiplyDecimalRoundPrecise(ownershipPercentage);

        return feePeriodDebtOwnership;
    }

    function effectiveDebtRatioForPeriod(address account, uint period) external view returns (uint) {
        require(period != 0, "Current period is not closed yet");
        require(period < FEE_PERIOD_LENGTH, "Exceeds the FEE_PERIOD_LENGTH");

        // If the period being checked is uninitialised then return 0. This is only at the start of the system.
        if (_recentFeePeriodsStorage(period - 1).startingDebtIndex == 0) return 0;

        uint closingDebtIndex = uint256(_recentFeePeriodsStorage(period - 1).startingDebtIndex).sub(1);

        uint ownershipPercentage;
        uint debtEntryIndex;
        (ownershipPercentage, debtEntryIndex) = feePoolState().applicableIssuanceData(account, closingDebtIndex);

        // internal function will check closingDebtIndex has corresponding debtLedger entry
        return _effectiveDebtRatioForPeriod(closingDebtIndex, ownershipPercentage, debtEntryIndex);
    }

    /**
     * @notice Get the feePeriodID of the last claim this account made
     * @param _claimingAddress account to check the last fee period ID claim for
     * @return uint of the feePeriodID this account last claimed
     */
    function getLastFeeWithdrawal(address _claimingAddress) public view returns (uint) {
        return feePoolEternalStorage().getUIntValue(keccak256(abi.encodePacked(LAST_FEE_WITHDRAWAL, _claimingAddress)));
    }

    /**
     * @notice Calculate the collateral ratio before user is blocked from claiming.
     */
    function getPenaltyThresholdRatio() public view returns (uint) {
        return getIssuanceRatio().multiplyDecimal(SafeDecimalMath.unit().add(getTargetThreshold()));
    }

    /**
     * @notice Set the feePeriodID of the last claim this account made
     * @param _claimingAddress account to set the last feePeriodID claim for
     * @param _feePeriodID the feePeriodID this account claimed fees for
     */
    function _setLastFeeWithdrawal(address _claimingAddress, uint _feePeriodID) internal {
        feePoolEternalStorage().setUIntValue(
            keccak256(abi.encodePacked(LAST_FEE_WITHDRAWAL, _claimingAddress)),
            _feePeriodID
        );
    }

    /* ========== Modifiers ========== */
    modifier onlyInternalContracts {
        bool isExchanger = msg.sender == address(exchanger());
        bool isSynth = issuer().synthsByAddress(msg.sender) != bytes32(0);
        bool isCollateral = collateralManager().hasCollateral(msg.sender);
        bool isEtherWrapper = msg.sender == address(etherWrapper());

        require(isExchanger || isSynth || isCollateral || isEtherWrapper, "Only Internal Contracts");
        _;
    }

    modifier onlyIssuerAndSynthetixState {
        bool isIssuer = msg.sender == address(issuer());
        bool isSynthetixState = msg.sender == address(synthetixState());
        require(isIssuer || isSynthetixState, "Issuer and SynthetixState only");
        _;
    }

    modifier notFeeAddress(address account) {
        require(account != FEE_ADDRESS, "Fee address not allowed");
        _;
    }

    modifier issuanceActive() {
        systemStatus().requireIssuanceActive();
        _;
    }

    /* ========== Proxy Events ========== */

    event IssuanceDebtRatioEntry(
        address indexed account,
        uint debtRatio,
        uint debtEntryIndex,
        uint feePeriodStartingDebtIndex
    );
    bytes32 private constant ISSUANCEDEBTRATIOENTRY_SIG =
        keccak256("IssuanceDebtRatioEntry(address,uint256,uint256,uint256)");

    function emitIssuanceDebtRatioEntry(
        address account,
        uint debtRatio,
        uint debtEntryIndex,
        uint feePeriodStartingDebtIndex
    ) internal {
        proxy._emit(
            abi.encode(debtRatio, debtEntryIndex, feePeriodStartingDebtIndex),
            2,
            ISSUANCEDEBTRATIOENTRY_SIG,
            bytes32(uint256(uint160(account))),
            0,
            0
        );
    }

    event FeePeriodClosed(uint feePeriodId);
    bytes32 private constant FEEPERIODCLOSED_SIG = keccak256("FeePeriodClosed(uint256)");

    function emitFeePeriodClosed(uint feePeriodId) internal {
        proxy._emit(abi.encode(feePeriodId), 1, FEEPERIODCLOSED_SIG, 0, 0, 0);
    }

    event FeesClaimed(address account, uint sUSDAmount, uint snxRewards);
    bytes32 private constant FEESCLAIMED_SIG = keccak256("FeesClaimed(address,uint256,uint256)");

    function emitFeesClaimed(
        address account,
        uint sUSDAmount,
        uint snxRewards
    ) internal {
        proxy._emit(abi.encode(account, sUSDAmount, snxRewards), 1, FEESCLAIMED_SIG, 0, 0, 0);
    }
}


// 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);
    }
}


// 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";

    /* ========== 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,
                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[](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);
    }
}


// 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";

    /* ========== 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 resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = Synth.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](2);
        newAddresses[0] = CONTRACT_COLLATERALMANAGER;
        newAddresses[1] = CONTRACT_ETHER_WRAPPER;
        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 ========== */

    // Contracts directly interacting with multiCollateralSynth to issue and burn
    modifier onlyInternalContracts() {
        bool isFeePool = msg.sender == address(feePool());
        bool isExchanger = msg.sender == address(exchanger());
        bool isIssuer = msg.sender == address(issuer());
        bool isEtherWrapper = msg.sender == address(etherWrapper());
        bool isMultiCollateral = collateralManager().hasCollateral(msg.sender);

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


// 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;
}


// 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/iliquidations
interface ILiquidations {
    // Views
    function isOpenForLiquidation(address account) external view returns (bool);

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

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

    function liquidationDelay() external view returns (uint);

    function liquidationRatio() external view returns (uint);

    function liquidationPenalty() external view returns (uint);

    function calculateAmountToFixCollateral(uint debtBalance, uint collateral) external view returns (uint);

    // Mutative Functions
    function flagAccountForLiquidation(address account) external;

    // Restricted: used internally to Synthetix
    function removeAccountInLiquidation(address account) external;

    function checkAndRemoveAccountInLiquidation(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;
}


// 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
        );
}

// 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 sETH = "sETH";
    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_SYNTHETIXSTATE = "SynthetixState";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";
    bytes32 private constant CONTRACT_DELEGATEAPPROVALS = "DelegateApprovals";
    bytes32 private constant CONTRACT_COLLATERALMANAGER = "CollateralManager";
    bytes32 private constant CONTRACT_REWARDESCROW_V2 = "RewardEscrowV2";
    bytes32 private constant CONTRACT_SYNTHETIXESCROW = "SynthetixEscrow";
    bytes32 private constant CONTRACT_LIQUIDATIONS = "Liquidations";
    bytes32 private constant CONTRACT_DEBTCACHE = "DebtCache";
    bytes32 private constant CONTRACT_SYNTHREDEEMER = "SynthRedeemer";

    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[](12);
        newAddresses[0] = CONTRACT_SYNTHETIX;
        newAddresses[1] = CONTRACT_EXCHANGER;
        newAddresses[2] = CONTRACT_EXRATES;
        newAddresses[3] = CONTRACT_SYNTHETIXSTATE;
        newAddresses[4] = CONTRACT_FEEPOOL;
        newAddresses[5] = CONTRACT_DELEGATEAPPROVALS;
        newAddresses[6] = CONTRACT_REWARDESCROW_V2;
        newAddresses[7] = CONTRACT_SYNTHETIXESCROW;
        newAddresses[8] = CONTRACT_LIQUIDATIONS;
        newAddresses[9] = CONTRACT_DEBTCACHE;
        newAddresses[10] = CONTRACT_COLLATERALMANAGER;
        newAddresses[11] = CONTRACT_SYNTHREDEEMER;
        return combineArrays(existingAddresses, newAddresses);
    }

    function synthetix() internal view returns (ISynthetix) {
        return ISynthetix(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 synthetixState() internal view returns (ISynthetixState) {
        return ISynthetixState(requireAndGetAddress(CONTRACT_SYNTHETIXSTATE));
    }

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

    function liquidations() internal view returns (ILiquidations) {
        return ILiquidations(requireAndGetAddress(CONTRACT_LIQUIDATIONS));
    }

    function delegateApprovals() internal view returns (IDelegateApprovals) {
        return IDelegateApprovals(requireAndGetAddress(CONTRACT_DELEGATEAPPROVALS));
    }

    function collateralManager() internal view returns (ICollateralManager) {
        return ICollateralManager(requireAndGetAddress(CONTRACT_COLLATERALMANAGER));
    }

    function rewardEscrowV2() internal view returns (IRewardEscrowV2) {
        return IRewardEscrowV2(requireAndGetAddress(CONTRACT_REWARDESCROW_V2));
    }

    function synthetixEscrow() internal view returns (IHasBalance) {
        return IHasBalance(requireAndGetAddress(CONTRACT_SYNTHETIXESCROW));
    }

    function debtCache() internal view returns (IIssuerInternalDebtCache) {
        return IIssuerInternalDebtCache(requireAndGetAddress(CONTRACT_DEBTCACHE));
    }

    function synthRedeemer() internal view returns (ISynthRedeemer) {
        return ISynthRedeemer(requireAndGetAddress(CONTRACT_SYNTHREDEEMER));
    }

    function issuanceRatio() external view returns (uint) {
        return getIssuanceRatio();
    }

    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;

        IExchangeRates exRates = exchangeRates();

        // 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) = exRates.rateAndInvalid(currencyKey);
        return (debt.divideDecimalRound(currencyRate), anyRateIsInvalid || currencyRateInvalid);
    }

    function _debtBalanceOfAndTotalDebt(address _issuer, bytes32 currencyKey)
        internal
        view
        returns (
            uint debtBalance,
            uint totalSystemValue,
            bool anyRateIsInvalid
        )
    {
        ISynthetixState state = synthetixState();

        // What was their initial debt ownership?
        (uint initialDebtOwnership, uint debtEntryIndex) = state.issuanceData(_issuer);

        // What's the total value of the system excluding ETH backed synths in their requested currency?
        (totalSystemValue, anyRateIsInvalid) = _totalIssuedSynths(currencyKey, true);

        // If it's zero, they haven't issued, and they have no debt.
        // Note: it's more gas intensive to put this check here rather than before _totalIssuedSynths
        // if they have 0 SNX, but it's a necessary trade-off
        if (initialDebtOwnership == 0) return (0, totalSystemValue, anyRateIsInvalid);

        // Figure out the global debt percentage delta from when they entered the system.
        // This is a high precision integer of 27 (1e27) decimals.
        uint currentDebtOwnership =
            state
                .lastDebtLedgerEntry()
                .divideDecimalRoundPrecise(state.debtLedger(debtEntryIndex))
                .multiplyDecimalRoundPrecise(initialDebtOwnership);

        // Their debt balance is their portion of the total system value.
        uint highPrecisionBalance =
            totalSystemValue.decimalToPreciseDecimal().multiplyDecimalRoundPrecise(currentDebtOwnership);

        // Convert back into 18 decimals (1e18)
        debtBalance = highPrecisionBalance.preciseDecimalToDecimal();
    }

    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(_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) = exchangeRates().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(_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) {
        uint balance = IERC20(address(synthetix())).balanceOf(account);

        if (address(synthetixEscrow()) != address(0)) {
            balance = balance.add(synthetixEscrow().balanceOf(account));
        }

        if (address(rewardEscrowV2()) != address(0)) {
            balance = balance.add(rewardEscrowV2().balanceOf(account));
        }

        return balance;
    }

    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) {
        ISynthetixState state = synthetixState();

        // What was their initial debt ownership?
        (uint initialDebtOwnership, ) = state.issuanceData(_issuer);

        // If it's zero, they haven't issued, and they have no debt.
        if (initialDebtOwnership == 0) return 0;

        (debtBalance, , ) = _debtBalanceOfAndTotalDebt(_issuer, 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(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;
    }

    /* ========== 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 synth to redeem without rate");
            ISynthRedeemer _synthRedeemer = synthRedeemer();
            synths[sUSD].issue(address(_synthRedeemer), amountOfsUSD);
            // ensure the debt cache is aware of the new sUSD issued
            debtCache().updateCachedSynthDebtWithRate(sUSD, SafeDecimalMath.unit());
            _synthRedeemer.deprecate(IERC20(address(Proxyable(address(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 issueSynths(address from, uint amount) external onlySynthetix {
        _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);
    }

    function liquidateDelinquentAccount(
        address account,
        uint susdAmount,
        address liquidator
    ) external onlySynthetix returns (uint totalRedeemed, uint amountToLiquidate) {
        // Ensure waitingPeriod and sUSD balance is settled as burning impacts the size of debt pool
        require(!exchanger().hasWaitingPeriodOrSettlementOwing(liquidator, sUSD), "sUSD needs to be settled");

        // Check account is liquidation open
        require(liquidations().isOpenForLiquidation(account), "Account not open for liquidation");

        // require liquidator has enough sUSD
        require(IERC20(address(synths[sUSD])).balanceOf(liquidator) >= susdAmount, "Not enough sUSD");

        uint liquidationPenalty = liquidations().liquidationPenalty();

        // What is their debt in sUSD?
        (uint debtBalance, uint totalDebtIssued, bool anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(account, sUSD);
        (uint snxRate, bool snxRateInvalid) = exchangeRates().rateAndInvalid(SNX);
        _requireRatesNotInvalid(anyRateIsInvalid || snxRateInvalid);

        uint collateralForAccount = _collateral(account);
        uint amountToFixRatio =
            liquidations().calculateAmountToFixCollateral(debtBalance, _snxToUSD(collateralForAccount, snxRate));

        // Cap amount to liquidate to repair collateral ratio based on issuance ratio
        amountToLiquidate = amountToFixRatio < susdAmount ? amountToFixRatio : susdAmount;

        // what's the equivalent amount of snx for the amountToLiquidate?
        uint snxRedeemed = _usdToSnx(amountToLiquidate, snxRate);

        // Add penalty
        totalRedeemed = snxRedeemed.multiplyDecimal(SafeDecimalMath.unit().add(liquidationPenalty));

        // if total SNX to redeem is greater than account's collateral
        // account is under collateralised, liquidate all collateral and reduce sUSD to burn
        if (totalRedeemed > collateralForAccount) {
            // set totalRedeemed to all transferable collateral
            totalRedeemed = collateralForAccount;

            // whats the equivalent sUSD to burn for all collateral less penalty
            amountToLiquidate = _snxToUSD(
                collateralForAccount.divideDecimal(SafeDecimalMath.unit().add(liquidationPenalty)),
                snxRate
            );
        }

        // burn sUSD from messageSender (liquidator) and reduce account's debt
        _burnSynths(account, liquidator, amountToLiquidate, debtBalance, totalDebtIssued);

        // Remove liquidation flag if amount liquidated fixes ratio
        if (amountToLiquidate == amountToFixRatio) {
            // Remove liquidation
            liquidations().removeAccountInLiquidation(account);
        }
    }

    /* ========== 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 {
        (uint maxIssuable, uint existingDebt, uint totalSystemDebt, 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, existingDebt, totalSystemDebt);

        // record issue timestamp
        _setLastIssueEvent(from);

        // Create their synths
        synths[sUSD].issue(from, amount);

        // Account for the issued debt in the cache
        debtCache().updateCachedSynthDebtWithRate(sUSD, SafeDecimalMath.unit());

        // Store their locked SNX amount to determine their fee % for the period
        _appendAccountIssuanceRecord(from);
    }

    function _burnSynths(
        address debtAccount,
        address burnAccount,
        uint amount,
        uint existingDebt,
        uint totalDebtIssued
    ) internal returns (uint amountBurnt) {
        // 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, totalDebtIssued);

        // 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().updateCachedSynthDebtWithRate(sUSD, SafeDecimalMath.unit());

        // Store their debtRatio against a fee period to determine their fee/rewards % for the period
        _appendAccountIssuanceRecord(debtAccount);
    }

    // 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 (!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, uint totalSystemValue, bool anyRateIsInvalid) = _debtBalanceOfAndTotalDebt(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, totalSystemValue);

        // Check and remove liquidation if existingDebt after burning is <= maxIssuableSynths
        // Issuance ratio is fixed so should remove any liquidations
        if (existingDebt.sub(amountBurnt) <= maxIssuableSynthsForAccount) {
            liquidations().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 _appendAccountIssuanceRecord(address from) internal {
        uint initialDebtOwnership;
        uint debtEntryIndex;
        (initialDebtOwnership, debtEntryIndex) = synthetixState().issuanceData(from);
        feePool().appendAccountIssuanceRecord(from, initialDebtOwnership, debtEntryIndex);
    }

    function _addToDebtRegister(
        address from,
        uint amount,
        uint existingDebt,
        uint totalDebtIssued
    ) internal {
        ISynthetixState state = synthetixState();

        // What will the new total be including the new value?
        uint newTotalDebtIssued = amount.add(totalDebtIssued);

        // What is their percentage (as a high precision int) of the total debt?
        uint debtPercentage = amount.divideDecimalRoundPrecise(newTotalDebtIssued);

        // And what effect does this percentage change have on the global debt holding of other issuers?
        // The delta specifically needs to not take into account any existing debt as it's already
        // accounted for in the delta from when they issued previously.
        // The delta is a high precision integer.
        uint delta = SafeDecimalMath.preciseUnit().sub(debtPercentage);

        // And what does their debt ownership look like including this previous stake?
        if (existingDebt > 0) {
            debtPercentage = amount.add(existingDebt).divideDecimalRoundPrecise(newTotalDebtIssued);
        } else {
            // If they have no debt, they're a new issuer; record this.
            state.incrementTotalIssuerCount();
        }

        // Save the debt entry parameters
        state.setCurrentIssuanceData(from, debtPercentage);

        // And if we're the first, push 1 as there was no effect to any other holders, otherwise push
        // the change for the rest of the debt holders. The debt ledger holds high precision integers.
        if (state.debtLedgerLength() > 0) {
            state.appendDebtLedgerValue(state.lastDebtLedgerEntry().multiplyDecimalRoundPrecise(delta));
        } else {
            state.appendDebtLedgerValue(SafeDecimalMath.preciseUnit());
        }
    }

    function _removeFromDebtRegister(
        address from,
        uint debtToRemove,
        uint existingDebt,
        uint totalDebtIssued
    ) internal {
        ISynthetixState state = synthetixState();

        // What will the new total after taking out the withdrawn amount
        uint newTotalDebtIssued = totalDebtIssued.sub(debtToRemove);

        uint delta = 0;

        // What will the debt delta be if there is any debt left?
        // Set delta to 0 if no more debt left in system after user
        if (newTotalDebtIssued > 0) {
            // What is the percentage of the withdrawn debt (as a high precision int) of the total debt after?
            uint debtPercentage = debtToRemove.divideDecimalRoundPrecise(newTotalDebtIssued);

            // And what effect does this percentage change have on the global debt holding of other issuers?
            // The delta specifically needs to not take into account any existing debt as it's already
            // accounted for in the delta from when they issued previously.
            delta = SafeDecimalMath.preciseUnit().add(debtPercentage);
        }

        // Are they exiting the system, or are they just decreasing their debt position?
        if (debtToRemove == existingDebt) {
            state.setCurrentIssuanceData(from, 0);
            state.decrementTotalIssuerCount();
        } else {
            // What percentage of the debt will they be left with?
            uint newDebt = existingDebt.sub(debtToRemove);
            uint newDebtPercentage = newDebt.divideDecimalRoundPrecise(newTotalDebtIssued);

            // Store the debt percentage and debt ledger as high precision integers
            state.setCurrentIssuanceData(from, newDebtPercentage);
        }

        // Update our cumulative ledger. This is also a high precision integer.
        state.appendDebtLedgerValue(state.lastDebtLedgerEntry().multiplyDecimalRoundPrecise(delta));
    }

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

    function _onlySynthetix() internal view {
        require(msg.sender == address(synthetix()), "Issuer: Only the synthetix contract can perform this action");
    }

    modifier onlySynthetix() {
        _onlySynthetix(); // Use an internal function to save code size.
        _;
    }

    function _onlySynthRedeemer() internal view {
        require(msg.sender == address(synthRedeemer()), "Issuer: Only the SynthRedeemer contract can perform this action");
    }

    modifier onlySynthRedeemer() {
        _onlySynthRedeemer();
        _;
    }

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

    event SynthAdded(bytes32 currencyKey, address synth);
    event SynthRemoved(bytes32 currencyKey, address synth);
}


interface ISynthetixNamedContract {
    // solhint-disable func-name-mixedcase
    function CONTRACT_NAME() external view returns (bytes32);
}

// solhint-disable contract-name-camelcase
contract Migration_Mirfak is BaseMigration {
    // https://etherscan.io/address/0xEb3107117FEAd7de89Cd14D463D340A2E6917769;
    address public constant OWNER = 0xEb3107117FEAd7de89Cd14D463D340A2E6917769;

    // ----------------------------
    // EXISTING SYNTHETIX CONTRACTS
    // ----------------------------

    // https://etherscan.io/address/0x823bE81bbF96BEc0e25CA13170F5AaCb5B79ba83
    AddressResolver public constant addressresolver_i = AddressResolver(0x823bE81bbF96BEc0e25CA13170F5AaCb5B79ba83);
    // https://etherscan.io/address/0xb440DD674e1243644791a4AdfE3A2AbB0A92d309
    Proxy public constant proxyfeepool_i = Proxy(0xb440DD674e1243644791a4AdfE3A2AbB0A92d309);
    // https://etherscan.io/address/0xC9DFff5fA5605fd94F8B7927b892F2B57391e8bB
    FeePoolEternalStorage public constant feepooleternalstorage_i =
        FeePoolEternalStorage(0xC9DFff5fA5605fd94F8B7927b892F2B57391e8bB);
    // https://etherscan.io/address/0x11164F6a47C3f8472D19b9aDd516Fc780cb7Ee02
    FeePoolState public constant feepoolstate_i = FeePoolState(0x11164F6a47C3f8472D19b9aDd516Fc780cb7Ee02);
    // https://etherscan.io/address/0xC011a73ee8576Fb46F5E1c5751cA3B9Fe0af2a6F
    ProxyERC20 public constant proxyerc20_i = ProxyERC20(0xC011a73ee8576Fb46F5E1c5751cA3B9Fe0af2a6F);
    // https://etherscan.io/address/0xC011A72400E58ecD99Ee497CF89E3775d4bd732F
    Proxy public constant proxysynthetix_i = Proxy(0xC011A72400E58ecD99Ee497CF89E3775d4bd732F);
    // https://etherscan.io/address/0x545973f28950f50fc6c7F52AAb4Ad214A27C0564
    ExchangeState public constant exchangestate_i = ExchangeState(0x545973f28950f50fc6c7F52AAb4Ad214A27C0564);
    // https://etherscan.io/address/0x1c86B3CDF2a60Ae3a574f7f71d44E2C50BDdB87E
    SystemStatus public constant systemstatus_i = SystemStatus(0x1c86B3CDF2a60Ae3a574f7f71d44E2C50BDdB87E);
    // https://etherscan.io/address/0x5b1b5fEa1b99D83aD479dF0C222F0492385381dD
    LegacyTokenState public constant tokenstatesynthetix_i = LegacyTokenState(0x5b1b5fEa1b99D83aD479dF0C222F0492385381dD);
    // https://etherscan.io/address/0x4b9Ca5607f1fF8019c1C6A3c2f0CC8de622D5B82
    SynthetixState public constant synthetixstate_i = SynthetixState(0x4b9Ca5607f1fF8019c1C6A3c2f0CC8de622D5B82);
    // https://etherscan.io/address/0xb671F2210B1F6621A2607EA63E6B2DC3e2464d1F
    RewardEscrow public constant rewardescrow_i = RewardEscrow(0xb671F2210B1F6621A2607EA63E6B2DC3e2464d1F);
    // https://etherscan.io/address/0x29C295B046a73Cde593f21f63091B072d407e3F2
    RewardsDistribution public constant rewardsdistribution_i =
        RewardsDistribution(0x29C295B046a73Cde593f21f63091B072d407e3F2);
    // https://etherscan.io/address/0x510adfDF6E7554C571b7Cd9305Ce91473610015e
    FeePool public constant feepool_i = FeePool(0x510adfDF6E7554C571b7Cd9305Ce91473610015e);
    // https://etherscan.io/address/0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b
    MultiCollateralSynth public constant synthsusd_i = MultiCollateralSynth(0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b);
    // https://etherscan.io/address/0x05a9CBe762B36632b3594DA4F082340E0e5343e8
    TokenState public constant tokenstatesusd_i = TokenState(0x05a9CBe762B36632b3594DA4F082340E0e5343e8);
    // https://etherscan.io/address/0x57Ab1E02fEE23774580C119740129eAC7081e9D3
    Proxy public constant proxysusd_i = Proxy(0x57Ab1E02fEE23774580C119740129eAC7081e9D3);
    // https://etherscan.io/address/0x57Ab1ec28D129707052df4dF418D58a2D46d5f51
    ProxyERC20 public constant proxyerc20susd_i = ProxyERC20(0x57Ab1ec28D129707052df4dF418D58a2D46d5f51);
    // https://etherscan.io/address/0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9
    MultiCollateralSynth public constant synthsbtc_i = MultiCollateralSynth(0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9);
    // https://etherscan.io/address/0x4F6296455F8d754c19821cF1EC8FeBF2cD456E67
    TokenState public constant tokenstatesbtc_i = TokenState(0x4F6296455F8d754c19821cF1EC8FeBF2cD456E67);
    // https://etherscan.io/address/0xfE18be6b3Bd88A2D2A7f928d00292E7a9963CfC6
    ProxyERC20 public constant proxysbtc_i = ProxyERC20(0xfE18be6b3Bd88A2D2A7f928d00292E7a9963CfC6);
    // https://etherscan.io/address/0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6
    MultiCollateralSynth public constant synthseth_i = MultiCollateralSynth(0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6);
    // https://etherscan.io/address/0x34A5ef81d18F3a305aE9C2d7DF42beef4c79031c
    TokenState public constant tokenstateseth_i = TokenState(0x34A5ef81d18F3a305aE9C2d7DF42beef4c79031c);
    // https://etherscan.io/address/0x5e74C9036fb86BD7eCdcb084a0673EFc32eA31cb
    ProxyERC20 public constant proxyseth_i = ProxyERC20(0x5e74C9036fb86BD7eCdcb084a0673EFc32eA31cb);
    // https://etherscan.io/address/0x922C84B3894298296C34842D866BfC0d36C54778
    Issuer public constant issuer_i = Issuer(0x922C84B3894298296C34842D866BfC0d36C54778);

    // ----------------------------------
    // NEW CONTRACTS DEPLOYED TO BE ADDED
    // ----------------------------------

    // https://etherscan.io/address/0x510adfDF6E7554C571b7Cd9305Ce91473610015e
    address public constant new_FeePool_contract = 0x510adfDF6E7554C571b7Cd9305Ce91473610015e;
    // https://etherscan.io/address/0x54f25546260C7539088982bcF4b7dC8EDEF19f21
    address public constant new_Synthetix_contract = 0x54f25546260C7539088982bcF4b7dC8EDEF19f21;
    // https://etherscan.io/address/0x7634F2A1741a683ccda37Dce864c187F990D7B4b
    address public constant new_Exchanger_contract = 0x7634F2A1741a683ccda37Dce864c187F990D7B4b;
    // https://etherscan.io/address/0xe92B4c7428152052B0930c81F4c687a5F1A12292
    address public constant new_DebtCache_contract = 0xe92B4c7428152052B0930c81F4c687a5F1A12292;
    // https://etherscan.io/address/0x922C84B3894298296C34842D866BfC0d36C54778
    address public constant new_Issuer_contract = 0x922C84B3894298296C34842D866BfC0d36C54778;
    // https://etherscan.io/address/0xe533139Af961c9747356D947838c98451015e234
    address public constant new_SynthRedeemer_contract = 0xe533139Af961c9747356D947838c98451015e234;
    // https://etherscan.io/address/0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b
    address public constant new_SynthsUSD_contract = 0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b;
    // https://etherscan.io/address/0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9
    address public constant new_SynthsBTC_contract = 0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9;
    // https://etherscan.io/address/0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6
    address public constant new_SynthsETH_contract = 0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6;

    constructor() public BaseMigration(OWNER) {}

    function contractsRequiringOwnership() public pure returns (address[] memory contracts) {
        contracts = new address[](24);
        contracts[0] = address(addressresolver_i);
        contracts[1] = address(proxyfeepool_i);
        contracts[2] = address(feepooleternalstorage_i);
        contracts[3] = address(feepoolstate_i);
        contracts[4] = address(proxyerc20_i);
        contracts[5] = address(proxysynthetix_i);
        contracts[6] = address(exchangestate_i);
        contracts[7] = address(systemstatus_i);
        contracts[8] = address(tokenstatesynthetix_i);
        contracts[9] = address(synthetixstate_i);
        contracts[10] = address(rewardescrow_i);
        contracts[11] = address(rewardsdistribution_i);
        contracts[12] = address(feepool_i);
        contracts[13] = address(synthsusd_i);
        contracts[14] = address(tokenstatesusd_i);
        contracts[15] = address(proxysusd_i);
        contracts[16] = address(proxyerc20susd_i);
        contracts[17] = address(synthsbtc_i);
        contracts[18] = address(tokenstatesbtc_i);
        contracts[19] = address(proxysbtc_i);
        contracts[20] = address(synthseth_i);
        contracts[21] = address(tokenstateseth_i);
        contracts[22] = address(proxyseth_i);
        contracts[23] = address(issuer_i);
    }

    function migrate(address currentOwner) external onlyDeployer {
        require(owner == currentOwner, "Only the assigned owner can be re-assigned when complete");

        require(
            ISynthetixNamedContract(new_FeePool_contract).CONTRACT_NAME() == "FeePool",
            "Invalid contract supplied for FeePool"
        );
        require(
            ISynthetixNamedContract(new_Synthetix_contract).CONTRACT_NAME() == "Synthetix",
            "Invalid contract supplied for Synthetix"
        );
        require(
            ISynthetixNamedContract(new_Exchanger_contract).CONTRACT_NAME() == "ExchangerWithVirtualSynth",
            "Invalid contract supplied for Exchanger"
        );
        require(
            ISynthetixNamedContract(new_DebtCache_contract).CONTRACT_NAME() == "DebtCache",
            "Invalid contract supplied for DebtCache"
        );
        require(
            ISynthetixNamedContract(new_Issuer_contract).CONTRACT_NAME() == "Issuer",
            "Invalid contract supplied for Issuer"
        );
        require(
            ISynthetixNamedContract(new_SynthRedeemer_contract).CONTRACT_NAME() == "SynthRedeemer",
            "Invalid contract supplied for SynthRedeemer"
        );
        require(
            ISynthetixNamedContract(new_SynthsUSD_contract).CONTRACT_NAME() == "MultiCollateralSynth",
            "Invalid contract supplied for SynthsUSD"
        );
        require(
            ISynthetixNamedContract(new_SynthsBTC_contract).CONTRACT_NAME() == "MultiCollateralSynth",
            "Invalid contract supplied for SynthsBTC"
        );
        require(
            ISynthetixNamedContract(new_SynthsETH_contract).CONTRACT_NAME() == "MultiCollateralSynth",
            "Invalid contract supplied for SynthsETH"
        );

        // ACCEPT OWNERSHIP for all contracts that require ownership to make changes
        acceptAll();

        // MIGRATION
        // Import all new contracts into the address resolver;
        addressresolver_importAddresses_0();
        // Rebuild the resolver caches in all MixinResolver contracts - batch 1;
        addressresolver_rebuildCaches_1();
        // Rebuild the resolver caches in all MixinResolver contracts - batch 2;
        addressresolver_rebuildCaches_2();
        // Rebuild the resolver caches in all MixinResolver contracts - batch 3;
        addressresolver_rebuildCaches_3();
        // Rebuild the resolver caches in all MixinResolver contracts - batch 4;
        addressresolver_rebuildCaches_4();
        // Rebuild the resolver caches in all MixinResolver contracts - batch 5;
        addressresolver_rebuildCaches_5();
        // Ensure the ProxyFeePool contract has the correct FeePool target set;
        proxyfeepool_i.setTarget(Proxyable(new_FeePool_contract));
        // Ensure the FeePool contract can write to its EternalStorage;
        feepooleternalstorage_i.setAssociatedContract(new_FeePool_contract);
        // Ensure the FeePool contract can write to its State;
        feepoolstate_i.setFeePool(IFeePool(new_FeePool_contract));
        // Ensure the SNX proxy has the correct Synthetix target set;
        proxyerc20_i.setTarget(Proxyable(new_Synthetix_contract));
        // Ensure the legacy SNX proxy has the correct Synthetix target set;
        proxysynthetix_i.setTarget(Proxyable(new_Synthetix_contract));
        // Ensure the Exchanger contract can write to its State;
        exchangestate_i.setAssociatedContract(new_Exchanger_contract);
        // Ensure the Exchanger contract can suspend synths - see SIP-65;
        systemstatus_i.updateAccessControl("Synth", new_Exchanger_contract, true, false);
        // Ensure the Synthetix contract can write to its TokenState contract;
        tokenstatesynthetix_i.setAssociatedContract(new_Synthetix_contract);
        // Ensure that Synthetix can write to its State contract;
        synthetixstate_i.setAssociatedContract(new_Issuer_contract);
        // Ensure the legacy RewardEscrow contract is connected to the Synthetix contract;
        rewardescrow_i.setSynthetix(ISynthetix(new_Synthetix_contract));
        // Ensure the legacy RewardEscrow contract is connected to the FeePool contract;
        rewardescrow_i.setFeePool(IFeePool(new_FeePool_contract));
        // Ensure the RewardsDistribution has Synthetix set as its authority for distribution;
        rewardsdistribution_i.setAuthority(new_Synthetix_contract);
        // Import fee period from existing fee pool at index 0;
        importFeePeriod_0();
        // Import fee period from existing fee pool at index 1;
        importFeePeriod_1();
        // Ensure the new synth has the totalSupply from the previous one;
        copyTotalSupplyFrom_sUSD();
        // Ensure the sUSD synth can write to its TokenState;
        tokenstatesusd_i.setAssociatedContract(new_SynthsUSD_contract);
        // Ensure the sUSD synth Proxy is correctly connected to the Synth;
        proxysusd_i.setTarget(Proxyable(new_SynthsUSD_contract));
        // Ensure the special ERC20 proxy for sUSD has its target set to the Synth;
        proxyerc20susd_i.setTarget(Proxyable(new_SynthsUSD_contract));
        // Ensure the new synth has the totalSupply from the previous one;
        copyTotalSupplyFrom_sBTC();
        // Ensure the sBTC synth can write to its TokenState;
        tokenstatesbtc_i.setAssociatedContract(new_SynthsBTC_contract);
        // Ensure the sBTC synth Proxy is correctly connected to the Synth;
        proxysbtc_i.setTarget(Proxyable(new_SynthsBTC_contract));
        // Ensure the new synth has the totalSupply from the previous one;
        copyTotalSupplyFrom_sETH();
        // Ensure the sETH synth can write to its TokenState;
        tokenstateseth_i.setAssociatedContract(new_SynthsETH_contract);
        // Ensure the sETH synth Proxy is correctly connected to the Synth;
        proxyseth_i.setTarget(Proxyable(new_SynthsETH_contract));
        // Add synths to the Issuer contract - batch 1;
        issuer_addSynths_39();
        // Add synths to the Issuer contract - batch 2;
        issuer_addSynths_40();
        // Add synths to the Issuer contract - batch 3;
        issuer_addSynths_41();
        // Add synths to the Issuer contract - batch 4;
        issuer_addSynths_42();
        // Add synths to the Issuer contract - batch 5;
        issuer_addSynths_43();

        // NOMINATE OWNERSHIP back to owner for aforementioned contracts
        nominateAll();
    }

    function acceptAll() internal {
        address[] memory contracts = contractsRequiringOwnership();
        for (uint i = 0; i < contracts.length; i++) {
            Owned(contracts[i]).acceptOwnership();
        }
    }

    function nominateAll() internal {
        address[] memory contracts = contractsRequiringOwnership();
        for (uint i = 0; i < contracts.length; i++) {
            returnOwnership(contracts[i]);
        }
    }

    function addressresolver_importAddresses_0() internal {
        bytes32[] memory addressresolver_importAddresses_names_0_0 = new bytes32[](9);
        addressresolver_importAddresses_names_0_0[0] = bytes32("FeePool");
        addressresolver_importAddresses_names_0_0[1] = bytes32("Synthetix");
        addressresolver_importAddresses_names_0_0[2] = bytes32("Exchanger");
        addressresolver_importAddresses_names_0_0[3] = bytes32("DebtCache");
        addressresolver_importAddresses_names_0_0[4] = bytes32("Issuer");
        addressresolver_importAddresses_names_0_0[5] = bytes32("SynthRedeemer");
        addressresolver_importAddresses_names_0_0[6] = bytes32("SynthsUSD");
        addressresolver_importAddresses_names_0_0[7] = bytes32("SynthsBTC");
        addressresolver_importAddresses_names_0_0[8] = bytes32("SynthsETH");
        address[] memory addressresolver_importAddresses_destinations_0_1 = new address[](9);
        addressresolver_importAddresses_destinations_0_1[0] = address(new_FeePool_contract);
        addressresolver_importAddresses_destinations_0_1[1] = address(new_Synthetix_contract);
        addressresolver_importAddresses_destinations_0_1[2] = address(new_Exchanger_contract);
        addressresolver_importAddresses_destinations_0_1[3] = address(new_DebtCache_contract);
        addressresolver_importAddresses_destinations_0_1[4] = address(new_Issuer_contract);
        addressresolver_importAddresses_destinations_0_1[5] = address(new_SynthRedeemer_contract);
        addressresolver_importAddresses_destinations_0_1[6] = address(new_SynthsUSD_contract);
        addressresolver_importAddresses_destinations_0_1[7] = address(new_SynthsBTC_contract);
        addressresolver_importAddresses_destinations_0_1[8] = address(new_SynthsETH_contract);
        addressresolver_i.importAddresses(
            addressresolver_importAddresses_names_0_0,
            addressresolver_importAddresses_destinations_0_1
        );
    }

    function addressresolver_rebuildCaches_1() internal {
        MixinResolver[] memory addressresolver_rebuildCaches_destinations_1_0 = new MixinResolver[](20);
        addressresolver_rebuildCaches_destinations_1_0[0] = MixinResolver(0xDA4eF8520b1A57D7d63f1E249606D1A459698876);
        addressresolver_rebuildCaches_destinations_1_0[1] = MixinResolver(new_Exchanger_contract);
        addressresolver_rebuildCaches_destinations_1_0[2] = MixinResolver(new_Issuer_contract);
        addressresolver_rebuildCaches_destinations_1_0[3] = MixinResolver(new_SynthsUSD_contract);
        addressresolver_rebuildCaches_destinations_1_0[4] = MixinResolver(0xC61b352fCc311Ae6B0301459A970150005e74b3E);
        addressresolver_rebuildCaches_destinations_1_0[5] = MixinResolver(0x388fD1A8a7d36e03eFA1ab100a1c5159a3A3d427);
        addressresolver_rebuildCaches_destinations_1_0[6] = MixinResolver(0x37B648a07476F4941D3D647f81118AFd55fa8a04);
        addressresolver_rebuildCaches_destinations_1_0[7] = MixinResolver(0xEF285D339c91aDf1dD7DE0aEAa6250805FD68258);
        addressresolver_rebuildCaches_destinations_1_0[8] = MixinResolver(0xcf9bB94b5d65589039607BA66e3DAC686d3eFf01);
        addressresolver_rebuildCaches_destinations_1_0[9] = MixinResolver(0xCeC4e038371d32212C6Dcdf36Fdbcb6F8a34C6d8);
        addressresolver_rebuildCaches_destinations_1_0[10] = MixinResolver(0x5eDf7dd83fE2889D264fa9D3b93d0a6e6A45D6C6);
        addressresolver_rebuildCaches_destinations_1_0[11] = MixinResolver(0x9745606DA6e162866DAD7bF80f2AbF145EDD7571);
        addressresolver_rebuildCaches_destinations_1_0[12] = MixinResolver(0x2962EA4E749e54b10CFA557770D597027BA67cB3);
        addressresolver_rebuildCaches_destinations_1_0[13] = MixinResolver(new_SynthsBTC_contract);
        addressresolver_rebuildCaches_destinations_1_0[14] = MixinResolver(new_SynthsETH_contract);
        addressresolver_rebuildCaches_destinations_1_0[15] = MixinResolver(0xda3c83750b1FA31Fda838136ef3f853b41cb7a5a);
        addressresolver_rebuildCaches_destinations_1_0[16] = MixinResolver(0x47bD14817d7684082E04934878EE2Dd3576Ae19d);
        addressresolver_rebuildCaches_destinations_1_0[17] = MixinResolver(0x6F927644d55E32318629198081923894FbFe5c07);
        addressresolver_rebuildCaches_destinations_1_0[18] = MixinResolver(0xe3D5E1c1bA874C0fF3BA31b999967F24d5ca04e5);
        addressresolver_rebuildCaches_destinations_1_0[19] = MixinResolver(0xA962208CDC8588F9238fae169d0F63306c353F4F);
        addressresolver_i.rebuildCaches(addressresolver_rebuildCaches_destinations_1_0);
    }

    function addressresolver_rebuildCaches_2() internal {
        MixinResolver[] memory addressresolver_rebuildCaches_destinations_2_0 = new MixinResolver[](20);
        addressresolver_rebuildCaches_destinations_2_0[0] = MixinResolver(0xcd980Fc5CcdAe62B18A52b83eC64200121A929db);
        addressresolver_rebuildCaches_destinations_2_0[1] = MixinResolver(0xAf090d6E583C082f2011908cf95c2518BE7A53ac);
        addressresolver_rebuildCaches_destinations_2_0[2] = MixinResolver(0x21ee4afBd6c151fD9A69c1389598170B1d45E0e3);
        addressresolver_rebuildCaches_destinations_2_0[3] = MixinResolver(0xcb6Cb218D558ae7fF6415f95BDA6616FCFF669Cb);
        addressresolver_rebuildCaches_destinations_2_0[4] = MixinResolver(0x7B29C9e188De18563B19d162374ce6836F31415a);
        addressresolver_rebuildCaches_destinations_2_0[5] = MixinResolver(0xC22e51FA362654ea453B4018B616ef6f6ab3b779);
        addressresolver_rebuildCaches_destinations_2_0[6] = MixinResolver(0xaB38249f4f56Ef868F6b5E01D9cFa26B952c1270);
        addressresolver_rebuildCaches_destinations_2_0[7] = MixinResolver(0xAa1b12E3e5F70aBCcd1714F4260A74ca21e7B17b);
        addressresolver_rebuildCaches_destinations_2_0[8] = MixinResolver(0x0F393ce493d8FB0b83915248a21a3104932ed97c);
        addressresolver_rebuildCaches_destinations_2_0[9] = MixinResolver(0xfD0435A588BF5c5a6974BA19Fa627b772833d4eb);
        addressresolver_rebuildCaches_destinations_2_0[10] = MixinResolver(0x4287dac1cC7434991119Eba7413189A66fFE65cF);
        addressresolver_rebuildCaches_destinations_2_0[11] = MixinResolver(0x34c76BC146b759E58886e821D62548AC1e0BA7Bc);
        addressresolver_rebuildCaches_destinations_2_0[12] = MixinResolver(0x0E8Fa2339314AB7E164818F26207897bBe29C3af);
        addressresolver_rebuildCaches_destinations_2_0[13] = MixinResolver(0xe615Df79AC987193561f37E77465bEC2aEfe9aDb);
        addressresolver_rebuildCaches_destinations_2_0[14] = MixinResolver(0x3E2dA260B4A85782A629320EB027A3B7c28eA9f1);
        addressresolver_rebuildCaches_destinations_2_0[15] = MixinResolver(0xc02DD182Ce029E6d7f78F37492DFd39E4FEB1f8b);
        addressresolver_rebuildCaches_destinations_2_0[16] = MixinResolver(0x0d1c4e5C07B071aa4E6A14A604D4F6478cAAC7B4);
        addressresolver_rebuildCaches_destinations_2_0[17] = MixinResolver(0x13D0F5B8630520eA04f694F17A001fb95eaFD30E);
        addressresolver_rebuildCaches_destinations_2_0[18] = MixinResolver(0x815CeF3b7773f35428B4353073B086ecB658f73C);
        addressresolver_rebuildCaches_destinations_2_0[19] = MixinResolver(0xb0e0BA880775B7F2ba813b3800b3979d719F0379);
        addressresolver_i.rebuildCaches(addressresolver_rebuildCaches_destinations_2_0);
    }

    function addressresolver_rebuildCaches_3() internal {
        MixinResolver[] memory addressresolver_rebuildCaches_destinations_3_0 = new MixinResolver[](20);
        addressresolver_rebuildCaches_destinations_3_0[0] = MixinResolver(0x8e082925e78538955bC0e2F363FC5d1Ab3be739b);
        addressresolver_rebuildCaches_destinations_3_0[1] = MixinResolver(0x399BA516a6d68d6Ad4D5f3999902D0DeAcaACDdd);
        addressresolver_rebuildCaches_destinations_3_0[2] = MixinResolver(0x9530FA32a3059114AC20A5812870Da12D97d1174);
        addressresolver_rebuildCaches_destinations_3_0[3] = MixinResolver(0x249612F641111022f2f48769f3Df5D85cb3E26a2);
        addressresolver_rebuildCaches_destinations_3_0[4] = MixinResolver(0x04720DbBD4599aD26811545595d97fB813E84964);
        addressresolver_rebuildCaches_destinations_3_0[5] = MixinResolver(0x2acfe6265D358d982cB1c3B521199973CD443C71);
        addressresolver_rebuildCaches_destinations_3_0[6] = MixinResolver(0x46A7Af405093B27DA6DeF193C508Bd9240A255FA);
        addressresolver_rebuildCaches_destinations_3_0[7] = MixinResolver(0x8350d1b2d6EF5289179fe49E5b0F208165B4e32e);
        addressresolver_rebuildCaches_destinations_3_0[8] = MixinResolver(0x29DD4A59F4D339226867e77aF211724eaBb45c02);
        addressresolver_rebuildCaches_destinations_3_0[9] = MixinResolver(0xf7B8dF8b16dA302d85603B8e7F95111a768458Cc);
        addressresolver_rebuildCaches_destinations_3_0[10] = MixinResolver(0x0517A56da8A517e3b2D484Cc5F1Da4BDCfE68ec3);
        addressresolver_rebuildCaches_destinations_3_0[11] = MixinResolver(0x099CfAd1640fc7EA686ab1D83F0A285Ba0470882);
        addressresolver_rebuildCaches_destinations_3_0[12] = MixinResolver(0x19cC1f63e344D74A87D955E3F3E95B28DDDc61d8);
        addressresolver_rebuildCaches_destinations_3_0[13] = MixinResolver(0x4D50A0e5f068ACdC80A1da2dd1f0Ad48845df2F8);
        addressresolver_rebuildCaches_destinations_3_0[14] = MixinResolver(0xb73c665825dAa926D6ef09417FbE5654473c1b49);
        addressresolver_rebuildCaches_destinations_3_0[15] = MixinResolver(0x806A599d60B2FdBda379D5890287D2fba1026cC0);
        addressresolver_rebuildCaches_destinations_3_0[16] = MixinResolver(0xCea42504874586a718954746A564B72bc7eba3E3);
        addressresolver_rebuildCaches_destinations_3_0[17] = MixinResolver(0x947d5656725fB9A8f9c826A91b6082b07E2745B7);
        addressresolver_rebuildCaches_destinations_3_0[18] = MixinResolver(0x186E56A62E7caCE1308f1A1B0dbb27f33F80f16f);
        addressresolver_rebuildCaches_destinations_3_0[19] = MixinResolver(0x931c5516EE121a177bD2B60e0122Da5B27630ABc);
        addressresolver_i.rebuildCaches(addressresolver_rebuildCaches_destinations_3_0);
    }

    function addressresolver_rebuildCaches_4() internal {
        MixinResolver[] memory addressresolver_rebuildCaches_destinations_4_0 = new MixinResolver[](20);
        addressresolver_rebuildCaches_destinations_4_0[0] = MixinResolver(0x6Dc6a64724399524184C2c44a526A2cff1BaA507);
        addressresolver_rebuildCaches_destinations_4_0[1] = MixinResolver(0x87eb6e935e3C7E3E3A0E31a5658498bC87dE646E);
        addressresolver_rebuildCaches_destinations_4_0[2] = MixinResolver(0x53869BDa4b8d85aEDCC9C6cAcf015AF9447Cade7);
        addressresolver_rebuildCaches_destinations_4_0[3] = MixinResolver(0x1cB27Ac646afAE192dF9928A2808C0f7f586Af7d);
        addressresolver_rebuildCaches_destinations_4_0[4] = MixinResolver(0x3dD7b893c25025CabFBd290A5E06BaFF3DE335b8);
        addressresolver_rebuildCaches_destinations_4_0[5] = MixinResolver(0x1A4505543C92084bE57ED80113eaB7241171e7a8);
        addressresolver_rebuildCaches_destinations_4_0[6] = MixinResolver(0xF6ce55E09De0F9F97210aAf6DB88Ed6b6792Ca1f);
        addressresolver_rebuildCaches_destinations_4_0[7] = MixinResolver(0xacAAB69C2BA65A2DB415605F309007e18D4F5E8C);
        addressresolver_rebuildCaches_destinations_4_0[8] = MixinResolver(0x9A5Ea0D8786B8d17a70410A905Aed1443fae5A38);
        addressresolver_rebuildCaches_destinations_4_0[9] = MixinResolver(0xC1AAE9d18bBe386B102435a8632C8063d31e747C);
        addressresolver_rebuildCaches_destinations_4_0[10] = MixinResolver(0x5c8344bcdC38F1aB5EB5C1d4a35DdEeA522B5DfA);
        addressresolver_rebuildCaches_destinations_4_0[11] = MixinResolver(0xaa03aB31b55DceEeF845C8d17890CC61cD98eD04);
        addressresolver_rebuildCaches_destinations_4_0[12] = MixinResolver(0x1F2c3a1046c32729862fcB038369696e3273a516);
        addressresolver_rebuildCaches_destinations_4_0[13] = MixinResolver(0xAD95C918af576c82Df740878C3E983CBD175daB6);
        addressresolver_rebuildCaches_destinations_4_0[14] = MixinResolver(new_FeePool_contract);
        addressresolver_rebuildCaches_destinations_4_0[15] = MixinResolver(0x62922670313bf6b41C580143d1f6C173C5C20019);
        addressresolver_rebuildCaches_destinations_4_0[16] = MixinResolver(0xCd9D4988C0AE61887B075bA77f08cbFAd2b65068);
        addressresolver_rebuildCaches_destinations_4_0[17] = MixinResolver(0xd69b189020EF614796578AfE4d10378c5e7e1138);
        addressresolver_rebuildCaches_destinations_4_0[18] = MixinResolver(new_Synthetix_contract);
        addressresolver_rebuildCaches_destinations_4_0[19] = MixinResolver(new_DebtCache_contract);
        addressresolver_i.rebuildCaches(addressresolver_rebuildCaches_destinations_4_0);
    }

    function addressresolver_rebuildCaches_5() internal {
        MixinResolver[] memory addressresolver_rebuildCaches_destinations_5_0 = new MixinResolver[](3);
        addressresolver_rebuildCaches_destinations_5_0[0] = MixinResolver(new_SynthRedeemer_contract);
        addressresolver_rebuildCaches_destinations_5_0[1] = MixinResolver(0x067e398605E84F2D0aEEC1806e62768C5110DCc6);
        addressresolver_rebuildCaches_destinations_5_0[2] = MixinResolver(0x7A3d898b717e50a96fd8b232E9d15F0A547A7eeb);
        addressresolver_i.rebuildCaches(addressresolver_rebuildCaches_destinations_5_0);
    }

    function importFeePeriod_0() internal {
        // https://etherscan.io/address/0xcf9E60005C9aca983caf65d3669a24fDd0775fc0;
        FeePool existingFeePool = FeePool(0xcf9E60005C9aca983caf65d3669a24fDd0775fc0);
        // https://etherscan.io/address/0x510adfDF6E7554C571b7Cd9305Ce91473610015e;
        FeePool newFeePool = FeePool(0x510adfDF6E7554C571b7Cd9305Ce91473610015e);
        (
            uint64 feePeriodId_0,
            uint64 startingDebtIndex_0,
            uint64 startTime_0,
            uint feesToDistribute_0,
            uint feesClaimed_0,
            uint rewardsToDistribute_0,
            uint rewardsClaimed_0
        ) = existingFeePool.recentFeePeriods(0);
        newFeePool.importFeePeriod(
            0,
            feePeriodId_0,
            startingDebtIndex_0,
            startTime_0,
            feesToDistribute_0,
            feesClaimed_0,
            rewardsToDistribute_0,
            rewardsClaimed_0
        );
    }

    function importFeePeriod_1() internal {
        // https://etherscan.io/address/0xcf9E60005C9aca983caf65d3669a24fDd0775fc0;
        FeePool existingFeePool = FeePool(0xcf9E60005C9aca983caf65d3669a24fDd0775fc0);
        // https://etherscan.io/address/0x510adfDF6E7554C571b7Cd9305Ce91473610015e;
        FeePool newFeePool = FeePool(0x510adfDF6E7554C571b7Cd9305Ce91473610015e);
        (
            uint64 feePeriodId_1,
            uint64 startingDebtIndex_1,
            uint64 startTime_1,
            uint feesToDistribute_1,
            uint feesClaimed_1,
            uint rewardsToDistribute_1,
            uint rewardsClaimed_1
        ) = existingFeePool.recentFeePeriods(1);
        newFeePool.importFeePeriod(
            1,
            feePeriodId_1,
            startingDebtIndex_1,
            startTime_1,
            feesToDistribute_1,
            feesClaimed_1,
            rewardsToDistribute_1,
            rewardsClaimed_1
        );
    }

    function copyTotalSupplyFrom_sUSD() internal {
        // https://etherscan.io/address/0x4D8dBD193d89b7B506BE5dC9Db75B91dA00D6a1d;
        Synth existingSynth = Synth(0x4D8dBD193d89b7B506BE5dC9Db75B91dA00D6a1d);
        // https://etherscan.io/address/0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b;
        Synth newSynth = Synth(0x967968963517AFDC9b8Ccc9AD6649bC507E83a7b);
        newSynth.setTotalSupply(existingSynth.totalSupply());
    }

    function copyTotalSupplyFrom_sBTC() internal {
        // https://etherscan.io/address/0xDB91E4B3b6E19bF22E810C43273eae48C9037e74;
        Synth existingSynth = Synth(0xDB91E4B3b6E19bF22E810C43273eae48C9037e74);
        // https://etherscan.io/address/0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9;
        Synth newSynth = Synth(0xC8a5f06858a1B49A7F703EacD433A1444a5e5bd9);
        newSynth.setTotalSupply(existingSynth.totalSupply());
    }

    function copyTotalSupplyFrom_sETH() internal {
        // https://etherscan.io/address/0xab4e760fEEe20C5c2509061b995e06b542D3112B;
        Synth existingSynth = Synth(0xab4e760fEEe20C5c2509061b995e06b542D3112B);
        // https://etherscan.io/address/0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6;
        Synth newSynth = Synth(0xCFA46B4923c0E75B7b84E9FBde70ED26feFefBf6);
        newSynth.setTotalSupply(existingSynth.totalSupply());
    }

    function issuer_addSynths_39() internal {
        ISynth[] memory issuer_addSynths_synthsToAdd_39_0 = new ISynth[](15);
        issuer_addSynths_synthsToAdd_39_0[0] = ISynth(new_SynthsUSD_contract);
        issuer_addSynths_synthsToAdd_39_0[1] = ISynth(0xC61b352fCc311Ae6B0301459A970150005e74b3E);
        issuer_addSynths_synthsToAdd_39_0[2] = ISynth(0x388fD1A8a7d36e03eFA1ab100a1c5159a3A3d427);
        issuer_addSynths_synthsToAdd_39_0[3] = ISynth(0x37B648a07476F4941D3D647f81118AFd55fa8a04);
        issuer_addSynths_synthsToAdd_39_0[4] = ISynth(0xEF285D339c91aDf1dD7DE0aEAa6250805FD68258);
        issuer_addSynths_synthsToAdd_39_0[5] = ISynth(0xcf9bB94b5d65589039607BA66e3DAC686d3eFf01);
        issuer_addSynths_synthsToAdd_39_0[6] = ISynth(0xCeC4e038371d32212C6Dcdf36Fdbcb6F8a34C6d8);
        issuer_addSynths_synthsToAdd_39_0[7] = ISynth(0x5eDf7dd83fE2889D264fa9D3b93d0a6e6A45D6C6);
        issuer_addSynths_synthsToAdd_39_0[8] = ISynth(0x9745606DA6e162866DAD7bF80f2AbF145EDD7571);
        issuer_addSynths_synthsToAdd_39_0[9] = ISynth(0x2962EA4E749e54b10CFA557770D597027BA67cB3);
        issuer_addSynths_synthsToAdd_39_0[10] = ISynth(new_SynthsBTC_contract);
        issuer_addSynths_synthsToAdd_39_0[11] = ISynth(new_SynthsETH_contract);
        issuer_addSynths_synthsToAdd_39_0[12] = ISynth(0xda3c83750b1FA31Fda838136ef3f853b41cb7a5a);
        issuer_addSynths_synthsToAdd_39_0[13] = ISynth(0x47bD14817d7684082E04934878EE2Dd3576Ae19d);
        issuer_addSynths_synthsToAdd_39_0[14] = ISynth(0x6F927644d55E32318629198081923894FbFe5c07);
        issuer_i.addSynths(issuer_addSynths_synthsToAdd_39_0);
    }

    function issuer_addSynths_40() internal {
        ISynth[] memory issuer_addSynths_synthsToAdd_40_0 = new ISynth[](15);
        issuer_addSynths_synthsToAdd_40_0[0] = ISynth(0xe3D5E1c1bA874C0fF3BA31b999967F24d5ca04e5);
        issuer_addSynths_synthsToAdd_40_0[1] = ISynth(0xA962208CDC8588F9238fae169d0F63306c353F4F);
        issuer_addSynths_synthsToAdd_40_0[2] = ISynth(0xcd980Fc5CcdAe62B18A52b83eC64200121A929db);
        issuer_addSynths_synthsToAdd_40_0[3] = ISynth(0xAf090d6E583C082f2011908cf95c2518BE7A53ac);
        issuer_addSynths_synthsToAdd_40_0[4] = ISynth(0x21ee4afBd6c151fD9A69c1389598170B1d45E0e3);
        issuer_addSynths_synthsToAdd_40_0[5] = ISynth(0xcb6Cb218D558ae7fF6415f95BDA6616FCFF669Cb);
        issuer_addSynths_synthsToAdd_40_0[6] = ISynth(0x7B29C9e188De18563B19d162374ce6836F31415a);
        issuer_addSynths_synthsToAdd_40_0[7] = ISynth(0xC22e51FA362654ea453B4018B616ef6f6ab3b779);
        issuer_addSynths_synthsToAdd_40_0[8] = ISynth(0xaB38249f4f56Ef868F6b5E01D9cFa26B952c1270);
        issuer_addSynths_synthsToAdd_40_0[9] = ISynth(0xAa1b12E3e5F70aBCcd1714F4260A74ca21e7B17b);
        issuer_addSynths_synthsToAdd_40_0[10] = ISynth(0x0F393ce493d8FB0b83915248a21a3104932ed97c);
        issuer_addSynths_synthsToAdd_40_0[11] = ISynth(0xfD0435A588BF5c5a6974BA19Fa627b772833d4eb);
        issuer_addSynths_synthsToAdd_40_0[12] = ISynth(0x4287dac1cC7434991119Eba7413189A66fFE65cF);
        issuer_addSynths_synthsToAdd_40_0[13] = ISynth(0x34c76BC146b759E58886e821D62548AC1e0BA7Bc);
        issuer_addSynths_synthsToAdd_40_0[14] = ISynth(0x0E8Fa2339314AB7E164818F26207897bBe29C3af);
        issuer_i.addSynths(issuer_addSynths_synthsToAdd_40_0);
    }

    function issuer_addSynths_41() internal {
        ISynth[] memory issuer_addSynths_synthsToAdd_41_0 = new ISynth[](15);
        issuer_addSynths_synthsToAdd_41_0[0] = ISynth(0xe615Df79AC987193561f37E77465bEC2aEfe9aDb);
        issuer_addSynths_synthsToAdd_41_0[1] = ISynth(0x3E2dA260B4A85782A629320EB027A3B7c28eA9f1);
        issuer_addSynths_synthsToAdd_41_0[2] = ISynth(0xc02DD182Ce029E6d7f78F37492DFd39E4FEB1f8b);
        issuer_addSynths_synthsToAdd_41_0[3] = ISynth(0x0d1c4e5C07B071aa4E6A14A604D4F6478cAAC7B4);
        issuer_addSynths_synthsToAdd_41_0[4] = ISynth(0x13D0F5B8630520eA04f694F17A001fb95eaFD30E);
        issuer_addSynths_synthsToAdd_41_0[5] = ISynth(0x815CeF3b7773f35428B4353073B086ecB658f73C);
        issuer_addSynths_synthsToAdd_41_0[6] = ISynth(0xb0e0BA880775B7F2ba813b3800b3979d719F0379);
        issuer_addSynths_synthsToAdd_41_0[7] = ISynth(0x8e082925e78538955bC0e2F363FC5d1Ab3be739b);
        issuer_addSynths_synthsToAdd_41_0[8] = ISynth(0x399BA516a6d68d6Ad4D5f3999902D0DeAcaACDdd);
        issuer_addSynths_synthsToAdd_41_0[9] = ISynth(0x9530FA32a3059114AC20A5812870Da12D97d1174);
        issuer_addSynths_synthsToAdd_41_0[10] = ISynth(0x249612F641111022f2f48769f3Df5D85cb3E26a2);
        issuer_addSynths_synthsToAdd_41_0[11] = ISynth(0x04720DbBD4599aD26811545595d97fB813E84964);
        issuer_addSynths_synthsToAdd_41_0[12] = ISynth(0x2acfe6265D358d982cB1c3B521199973CD443C71);
        issuer_addSynths_synthsToAdd_41_0[13] = ISynth(0x46A7Af405093B27DA6DeF193C508Bd9240A255FA);
        issuer_addSynths_synthsToAdd_41_0[14] = ISynth(0x8350d1b2d6EF5289179fe49E5b0F208165B4e32e);
        issuer_i.addSynths(issuer_addSynths_synthsToAdd_41_0);
    }

    function issuer_addSynths_42() internal {
        ISynth[] memory issuer_addSynths_synthsToAdd_42_0 = new ISynth[](15);
        issuer_addSynths_synthsToAdd_42_0[0] = ISynth(0x29DD4A59F4D339226867e77aF211724eaBb45c02);
        issuer_addSynths_synthsToAdd_42_0[1] = ISynth(0xf7B8dF8b16dA302d85603B8e7F95111a768458Cc);
        issuer_addSynths_synthsToAdd_42_0[2] = ISynth(0x0517A56da8A517e3b2D484Cc5F1Da4BDCfE68ec3);
        issuer_addSynths_synthsToAdd_42_0[3] = ISynth(0x099CfAd1640fc7EA686ab1D83F0A285Ba0470882);
        issuer_addSynths_synthsToAdd_42_0[4] = ISynth(0x19cC1f63e344D74A87D955E3F3E95B28DDDc61d8);
        issuer_addSynths_synthsToAdd_42_0[5] = ISynth(0x4D50A0e5f068ACdC80A1da2dd1f0Ad48845df2F8);
        issuer_addSynths_synthsToAdd_42_0[6] = ISynth(0xb73c665825dAa926D6ef09417FbE5654473c1b49);
        issuer_addSynths_synthsToAdd_42_0[7] = ISynth(0x806A599d60B2FdBda379D5890287D2fba1026cC0);
        issuer_addSynths_synthsToAdd_42_0[8] = ISynth(0xCea42504874586a718954746A564B72bc7eba3E3);
        issuer_addSynths_synthsToAdd_42_0[9] = ISynth(0x947d5656725fB9A8f9c826A91b6082b07E2745B7);
        issuer_addSynths_synthsToAdd_42_0[10] = ISynth(0x186E56A62E7caCE1308f1A1B0dbb27f33F80f16f);
        issuer_addSynths_synthsToAdd_42_0[11] = ISynth(0x931c5516EE121a177bD2B60e0122Da5B27630ABc);
        issuer_addSynths_synthsToAdd_42_0[12] = ISynth(0x6Dc6a64724399524184C2c44a526A2cff1BaA507);
        issuer_addSynths_synthsToAdd_42_0[13] = ISynth(0x87eb6e935e3C7E3E3A0E31a5658498bC87dE646E);
        issuer_addSynths_synthsToAdd_42_0[14] = ISynth(0x53869BDa4b8d85aEDCC9C6cAcf015AF9447Cade7);
        issuer_i.addSynths(issuer_addSynths_synthsToAdd_42_0);
    }

    function issuer_addSynths_43() internal {
        ISynth[] memory issuer_addSynths_synthsToAdd_43_0 = new ISynth[](6);
        issuer_addSynths_synthsToAdd_43_0[0] = ISynth(0x1cB27Ac646afAE192dF9928A2808C0f7f586Af7d);
        issuer_addSynths_synthsToAdd_43_0[1] = ISynth(0x3dD7b893c25025CabFBd290A5E06BaFF3DE335b8);
        issuer_addSynths_synthsToAdd_43_0[2] = ISynth(0x1A4505543C92084bE57ED80113eaB7241171e7a8);
        issuer_addSynths_synthsToAdd_43_0[3] = ISynth(0xF6ce55E09De0F9F97210aAf6DB88Ed6b6792Ca1f);
        issuer_addSynths_synthsToAdd_43_0[4] = ISynth(0xacAAB69C2BA65A2DB415605F309007e18D4F5E8C);
        issuer_addSynths_synthsToAdd_43_0[5] = ISynth(0x9A5Ea0D8786B8d17a70410A905Aed1443fae5A38);
        issuer_i.addSynths(issuer_addSynths_synthsToAdd_43_0);
    }
}

