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

* Synthetix: SynthetixBridgeToOptimism.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/SynthetixBridgeToOptimism.sol
* Docs: https://docs.synthetix.io/contracts/SynthetixBridgeToOptimism
*
* Contract Dependencies: 
*	- BaseSynthetixBridge
*	- IAddressResolver
*	- IBaseSynthetixBridge
*	- ISynthetixBridgeToOptimism
*	- MixinResolver
*	- MixinSystemSettings
*	- Owned
*	- iOVM_L1TokenGateway
* Libraries: 
*	- Address
*	- Math
*	- SafeDecimalMath
*	- SafeERC20
*	- SafeMath
*	- VestingEntries
*
* MIT License
* ===========
*
* Copyright (c) 2022 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

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

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

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

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

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

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

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


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

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

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


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

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

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

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

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

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


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

    function setCurrentPeriodId(uint128 periodId) external;

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

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


// Inheritance


// Internal references


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

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

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

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

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

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

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

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

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

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

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

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

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

    event AddressImported(bytes32 name, address destination);
}


// Internal references


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

    mapping(bytes32 => address) private addressCache;

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

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

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

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

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

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

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

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

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

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

        return true;
    }

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

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

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

    event CacheUpdated(bytes32 name, address destination);
}


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

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

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

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

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

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

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

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

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

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

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

    function deleteIntValue(bytes32 contractName, bytes32 record) external;

    function deleteAddressValue(bytes32 contractName, bytes32 record) external;

    function deleteBoolValue(bytes32 contractName, bytes32 record) external;

    function deleteBytes32Value(bytes32 contractName, bytes32 record) external;

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

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

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

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

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

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

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

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

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

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


// Internal references


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

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

    bytes32 internal constant CONTRACT_FLEXIBLESTORAGE = "FlexibleStorage";

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    function 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);
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


pragma experimental ABIEncoderV2;

interface IBaseSynthetixBridge {
    function suspendInitiation() external;

    function resumeInitiation() external;
}


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

        return c;
    }

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

        return c;
    }

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

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

        return c;
    }

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

        return c;
    }

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


// Libraries


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

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

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

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

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

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

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

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

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

        return quotientTimesTen / 10;
    }

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

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

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

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

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

        return resultTimesTen / 10;
    }

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

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

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

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

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

        return quotientTimesTen / 10;
    }

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

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

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


// Libraries


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

    /**
     * @dev Uses "exponentiation by squaring" algorithm where cost is 0(logN)
     * vs 0(N) for naive repeated multiplication.
     * Calculates x^n with x as fixed-point and n as regular unsigned int.
     * Calculates to 18 digits of precision with SafeDecimalMath.unit()
     */
    function powDecimal(uint x, uint n) internal pure returns (uint) {
        // https://mpark.github.io/programming/2014/08/18/exponentiation-by-squaring/

        uint result = SafeDecimalMath.unit();
        while (n > 0) {
            if (n % 2 != 0) {
                result = result.multiplyDecimal(x);
            }
            x = x.multiplyDecimal(x);
            n /= 2;
        }
        return result;
    }
}


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 exchangeAtomically(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        bytes32 trackingCode,
        uint minAmount
    ) external returns (uint amountReceived);

    function issueMaxSynths() external;

    function issueMaxSynthsOnBehalf(address issueForAddress) external;

    function issueSynths(uint amount) external;

    function issueSynthsOnBehalf(address issueForAddress, uint amount) external;

    function mint() external returns (bool);

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

    // Liquidations
    function liquidateDelinquentAccount(address account, 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;
}


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/ifeepool
interface IFeePool {
    // Views

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

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

    function feePeriodDuration() external view returns (uint);

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

    function targetThreshold() external view returns (uint);

    function totalFeesAvailable() external view returns (uint);

    function totalRewardsAvailable() external view returns (uint);

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

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

    function closeCurrentFeePeriod() external;

    function closeSecondary(uint snxBackedDebt, uint debtShareSupply) external;

    function recordFeePaid(uint sUSDAmount) external;

    function setRewardsToDistribute(uint amount) external;
}


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

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

    function aggregatorWarningFlags() external view returns (address);

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

    function anyRateIsInvalidAtRound(bytes32[] calldata currencyKeys, uint[] calldata roundIds) external view returns (bool);

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

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

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

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

    function effectiveAtomicValueAndRates(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint value,
            uint systemValue,
            uint systemSourceRate,
            uint systemDestinationRate
        );

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

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

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

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

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

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

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

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

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

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

    function rateStalePeriod() external view returns (uint);

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

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

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

    function synthTooVolatileForAtomicExchange(bytes32 currencyKey) external view returns (bool);
}


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

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

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

    function requireSystemActive() external view;

    function systemSuspended() external view returns (bool);

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireFuturesActive() external view;

    function requireFuturesMarketActive(bytes32 marketKey) external view;

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

    function requireSynthActive(bytes32 currencyKey) external view;

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

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

    function systemSuspension() external view returns (bool suspended, uint248 reason);

    function issuanceSuspension() external view returns (bool suspended, uint248 reason);

    function exchangeSuspension() external view returns (bool suspended, uint248 reason);

    function futuresSuspension() external view returns (bool suspended, uint248 reason);

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

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

    function futuresMarketSuspension(bytes32 marketKey) external view returns (bool suspended, uint248 reason);

    function getSynthExchangeSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory exchangeSuspensions, uint256[] memory reasons);

    function getSynthSuspensions(bytes32[] calldata synths)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    function getFuturesMarketSuspensions(bytes32[] calldata marketKeys)
        external
        view
        returns (bool[] memory suspensions, uint256[] memory reasons);

    // Restricted functions
    function suspendIssuance(uint256 reason) external;

    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function suspendFuturesMarket(bytes32 marketKey, uint256 reason) external;

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


// SPDX-License-Identifier: MIT


/**
 * @title iAbs_BaseCrossDomainMessenger
 */
interface iAbs_BaseCrossDomainMessenger {

    /**********
     * Events *
     **********/

    event SentMessage(bytes message);
    event RelayedMessage(bytes32 msgHash);
    event FailedRelayedMessage(bytes32 msgHash);


    /*************
     * Variables *
     *************/

    function xDomainMessageSender() external view returns (address);


    /********************
     * Public Functions *
     ********************/

    /**
     * Sends a cross domain message to the target messenger.
     * @param _target Target contract address.
     * @param _message Message to send to the target.
     * @param _gasLimit Gas limit for the provided message.
     */
    function sendMessage(
        address _target,
        bytes calldata _message,
        uint32 _gasLimit
    ) external;
}


// Inheritance


// Libraries


// Internal references


contract BaseSynthetixBridge is Owned, MixinSystemSettings, IBaseSynthetixBridge {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */
    bytes32 private constant CONTRACT_EXT_MESSENGER = "ext:Messenger";
    bytes32 internal constant CONTRACT_SYNTHETIX = "Synthetix";
    bytes32 private constant CONTRACT_REWARDESCROW = "RewardEscrowV2";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_FEEPOOL = "FeePool";
    bytes32 private constant CONTRACT_FLEXIBLESTORAGE = "FlexibleStorage";
    bytes32 private constant CONTRACT_EXCHANGERATES = "ExchangeRates";
    bytes32 private constant CONTRACT_SYSTEM_STATUS = "SystemStatus";

    // have to define this function like this here because contract name is required for FlexibleStorage
    function CONTRACT_NAME() public pure returns (bytes32);

    bool public initiationActive;

    bytes32 private constant SYNTH_TRANSFER_NAMESPACE = "SynthTransfer";
    bytes32 private constant SYNTH_TRANSFER_SENT = "Sent";
    bytes32 private constant SYNTH_TRANSFER_RECV = "Recv";

    // ========== CONSTRUCTOR ==========

    constructor(address _owner, address _resolver) public Owned(_owner) MixinSystemSettings(_resolver) {
        initiationActive = true;
    }

    // ========== INTERNALS ============

    function messenger() internal view returns (iAbs_BaseCrossDomainMessenger) {
        return iAbs_BaseCrossDomainMessenger(requireAndGetAddress(CONTRACT_EXT_MESSENGER));
    }

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

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

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

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

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

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

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

    function initiatingActive() internal view {
        require(initiationActive, "Initiation deactivated");
    }

    function counterpart() internal view returns (address);

    function onlyAllowFromCounterpart() internal view {
        // ensure function only callable from the L2 bridge via messenger (aka relayer)
        iAbs_BaseCrossDomainMessenger _messenger = messenger();
        require(msg.sender == address(_messenger), "Only the relayer can call this");
        require(_messenger.xDomainMessageSender() == counterpart(), "Only a counterpart bridge can invoke");
    }

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

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = MixinSystemSettings.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](8);
        newAddresses[0] = CONTRACT_EXT_MESSENGER;
        newAddresses[1] = CONTRACT_SYNTHETIX;
        newAddresses[2] = CONTRACT_REWARDESCROW;
        newAddresses[3] = CONTRACT_ISSUER;
        newAddresses[4] = CONTRACT_FEEPOOL;
        newAddresses[5] = CONTRACT_FLEXIBLESTORAGE;
        newAddresses[6] = CONTRACT_EXCHANGERATES;
        newAddresses[7] = CONTRACT_SYSTEM_STATUS;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    function synthTransferSent() external view returns (uint) {
        return _sumTransferAmounts(SYNTH_TRANSFER_SENT);
    }

    function synthTransferReceived() external view returns (uint) {
        return _sumTransferAmounts(SYNTH_TRANSFER_RECV);
    }

    // ========== MODIFIERS ============

    modifier requireInitiationActive() {
        initiatingActive();
        _;
    }

    modifier onlyCounterpart() {
        onlyAllowFromCounterpart();
        _;
    }

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

    function suspendInitiation() external onlyOwner {
        require(initiationActive, "Initiation suspended");
        initiationActive = false;
        emit InitiationSuspended();
    }

    function resumeInitiation() external onlyOwner {
        require(!initiationActive, "Initiation not suspended");
        initiationActive = true;
        emit InitiationResumed();
    }

    function initiateSynthTransfer(
        bytes32 currencyKey,
        address destination,
        uint amount
    ) external requireInitiationActive {
        require(destination != address(0), "Cannot send to zero address");
        require(getCrossChainSynthTransferEnabled(currencyKey) > 0, "Synth not enabled for cross chain transfer");
        systemStatus().requireSynthActive(currencyKey);

        _incrementSynthsTransferCounter(SYNTH_TRANSFER_SENT, currencyKey, amount);

        bool rateInvalid = issuer().burnSynthsWithoutDebt(currencyKey, msg.sender, amount);
        require(!rateInvalid, "Cannot initiate if synth rate is invalid");

        // create message payload
        bytes memory messageData =
            abi.encodeWithSelector(this.finalizeSynthTransfer.selector, currencyKey, destination, amount);

        // relay the message to Bridge on L1 via L2 Messenger
        messenger().sendMessage(
            counterpart(),
            messageData,
            uint32(getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits.Withdrawal))
        );

        emit InitiateSynthTransfer(currencyKey, destination, amount);
    }

    function finalizeSynthTransfer(
        bytes32 currencyKey,
        address destination,
        uint amount
    ) external onlyCounterpart {
        _incrementSynthsTransferCounter(SYNTH_TRANSFER_RECV, currencyKey, amount);

        issuer().issueSynthsWithoutDebt(currencyKey, destination, amount);

        emit FinalizeSynthTransfer(currencyKey, destination, amount);
    }

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

    function _incrementSynthsTransferCounter(
        bytes32 group,
        bytes32 currencyKey,
        uint amount
    ) internal {
        bytes32 key = keccak256(abi.encodePacked(SYNTH_TRANSFER_NAMESPACE, group, currencyKey));

        uint currentSynths = flexibleStorage().getUIntValue(CONTRACT_NAME(), key);

        flexibleStorage().setUIntValue(CONTRACT_NAME(), key, currentSynths.add(amount));
    }

    function _sumTransferAmounts(bytes32 group) internal view returns (uint sum) {
        // get list of synths from issuer
        bytes32[] memory currencyKeys = issuer().availableCurrencyKeys();

        // get all synth rates
        (uint[] memory rates, bool isInvalid) = exchangeRates().ratesAndInvalidForCurrencies(currencyKeys);

        require(!isInvalid, "Rates are invalid");

        // get all values
        bytes32[] memory transferAmountKeys = new bytes32[](currencyKeys.length);
        for (uint i = 0; i < currencyKeys.length; i++) {
            transferAmountKeys[i] = keccak256(abi.encodePacked(SYNTH_TRANSFER_NAMESPACE, group, currencyKeys[i]));
        }

        uint[] memory transferAmounts = flexibleStorage().getUIntValues(CONTRACT_NAME(), transferAmountKeys);

        for (uint i = 0; i < currencyKeys.length; i++) {
            sum = sum.add(transferAmounts[i].multiplyDecimalRound(rates[i]));
        }
    }

    // ========== EVENTS ==========

    event InitiationSuspended();

    event InitiationResumed();

    event InitiateSynthTransfer(bytes32 indexed currencyKey, address indexed destination, uint256 amount);
    event FinalizeSynthTransfer(bytes32 indexed currencyKey, address indexed destination, uint256 amount);
}


interface ISynthetixBridgeToOptimism {
    function closeFeePeriod(uint snxBackedDebt, uint debtSharesSupply) external;

    function migrateEscrow(uint256[][] calldata entryIDs) external;

    function depositReward(uint amount) external;

    function depositAndMigrateEscrow(uint256 depositAmount, uint256[][] calldata entryIDs) external;
}


// SPDX-License-Identifier: MIT


/**
 * @title iOVM_L1TokenGateway
 */
interface iOVM_L1TokenGateway {

    /**********
     * Events *
     **********/

    event DepositInitiated(
        address indexed _from,
        address _to,
        uint256 _amount
    );

    event WithdrawalFinalized(
        address indexed _to,
        uint256 _amount
    );


    /********************
     * Public Functions *
     ********************/

    function deposit(
        uint _amount
    )
        external;

    function depositTo(
        address _to,
        uint _amount
    )
        external;


    /*************************
     * Cross-chain Functions *
     *************************/

    function finalizeWithdrawal(
        address _to,
        uint _amount
    )
        external;
}


/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

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

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

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

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

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

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


/**
 * @dev Collection of functions related to the address type,
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing a contract.
     *
     * > It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

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


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

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

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

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

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

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}


interface ISynthetixBridgeToBase {
    // invoked by the xDomain messenger on L2
    function finalizeEscrowMigration(
        address account,
        uint256 escrowedAmount,
        VestingEntries.VestingEntry[] calldata vestingEntries
    ) external;

    // invoked by the xDomain messenger on L2
    function finalizeRewardDeposit(address from, uint amount) external;

    function finalizeFeePeriodClose(uint snxBackedDebt, uint debtSharesSupply) external;
}


// SPDX-License-Identifier: MIT


/**
 * @title iOVM_L2DepositedToken
 */
interface iOVM_L2DepositedToken {

    /**********
     * Events *
     **********/

    event WithdrawalInitiated(
        address indexed _from,
        address _to,
        uint256 _amount
    );

    event DepositFinalized(
        address indexed _to,
        uint256 _amount
    );


    /********************
     * Public Functions *
     ********************/

    function withdraw(
        uint _amount
    )
        external;

    function withdrawTo(
        address _to,
        uint _amount
    )
        external;


    /*************************
     * Cross-chain Functions *
     *************************/

    function finalizeDeposit(
        address _to,
        uint _amount
    )
        external;
}


// Inheritance


// Internal references


contract SynthetixBridgeToOptimism is BaseSynthetixBridge, ISynthetixBridgeToOptimism, iOVM_L1TokenGateway {
    using SafeERC20 for IERC20;

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_REWARDSDISTRIBUTION = "RewardsDistribution";
    bytes32 private constant CONTRACT_OVM_SYNTHETIXBRIDGETOBASE = "ovm:SynthetixBridgeToBase";
    bytes32 private constant CONTRACT_SYNTHETIXBRIDGEESCROW = "SynthetixBridgeEscrow";

    uint8 private constant MAX_ENTRIES_MIGRATED_PER_MESSAGE = 26;

    function CONTRACT_NAME() public pure returns (bytes32) {
        return "SynthetixBridgeToOptimism";
    }

    // ========== CONSTRUCTOR ==========

    constructor(address _owner, address _resolver) public BaseSynthetixBridge(_owner, _resolver) {}

    // ========== INTERNALS ============

    function synthetixERC20() internal view returns (IERC20) {
        return IERC20(requireAndGetAddress(CONTRACT_SYNTHETIX));
    }

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

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

    function synthetixBridgeToBase() internal view returns (address) {
        return requireAndGetAddress(CONTRACT_OVM_SYNTHETIXBRIDGETOBASE);
    }

    function synthetixBridgeEscrow() internal view returns (address) {
        return requireAndGetAddress(CONTRACT_SYNTHETIXBRIDGEESCROW);
    }

    function hasZeroDebt() internal view {
        require(issuer().debtBalanceOf(msg.sender, "sUSD") == 0, "Cannot deposit or migrate with debt");
    }

    function counterpart() internal view returns (address) {
        return synthetixBridgeToBase();
    }

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

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        bytes32[] memory existingAddresses = BaseSynthetixBridge.resolverAddressesRequired();
        bytes32[] memory newAddresses = new bytes32[](4);
        newAddresses[0] = CONTRACT_ISSUER;
        newAddresses[1] = CONTRACT_REWARDSDISTRIBUTION;
        newAddresses[2] = CONTRACT_OVM_SYNTHETIXBRIDGETOBASE;
        newAddresses[3] = CONTRACT_SYNTHETIXBRIDGEESCROW;
        addresses = combineArrays(existingAddresses, newAddresses);
    }

    // ========== MODIFIERS ============

    modifier requireZeroDebt() {
        hasZeroDebt();
        _;
    }

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

    function deposit(uint256 amount) external requireInitiationActive requireZeroDebt {
        _initiateDeposit(msg.sender, amount);
    }

    function depositTo(address to, uint amount) external requireInitiationActive requireZeroDebt {
        _initiateDeposit(to, amount);
    }

    function migrateEscrow(uint256[][] memory entryIDs) public requireInitiationActive requireZeroDebt {
        _migrateEscrow(entryIDs);
    }

    // invoked by a generous user on L1
    function depositReward(uint amount) external requireInitiationActive {
        // move the SNX into the deposit escrow
        synthetixERC20().transferFrom(msg.sender, synthetixBridgeEscrow(), amount);

        _depositReward(msg.sender, amount);
    }

    // forward any accidental tokens sent here to the escrow
    function forwardTokensToEscrow(address token) external {
        IERC20 erc20 = IERC20(token);
        erc20.safeTransfer(synthetixBridgeEscrow(), erc20.balanceOf(address(this)));
    }

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

    function closeFeePeriod(uint snxBackedAmount, uint totalDebtShares) external requireInitiationActive {
        require(msg.sender == address(feePool()), "Only the fee pool can call this");

        ISynthetixBridgeToBase bridgeToBase;
        bytes memory messageData =
            abi.encodeWithSelector(bridgeToBase.finalizeFeePeriodClose.selector, snxBackedAmount, totalDebtShares);

        // relay the message to this contract on L2 via L1 Messenger
        messenger().sendMessage(
            synthetixBridgeToBase(),
            messageData,
            uint32(getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits.CloseFeePeriod))
        );

        emit FeePeriodClosed(snxBackedAmount, totalDebtShares);
    }

    // invoked by Messenger on L1 after L2 waiting period elapses
    function finalizeWithdrawal(address to, uint256 amount) external onlyCounterpart {
        // transfer amount back to user
        synthetixERC20().transferFrom(synthetixBridgeEscrow(), to, amount);

        // no escrow actions - escrow remains on L2
        emit iOVM_L1TokenGateway.WithdrawalFinalized(to, amount);
    }

    // invoked by RewardsDistribution on L1 (takes SNX)
    function notifyRewardAmount(uint256 amount) external {
        require(msg.sender == address(rewardsDistribution()), "Caller is not RewardsDistribution contract");

        // NOTE: transfer SNX to synthetixBridgeEscrow because RewardsDistribution transfers them initially to this contract.
        synthetixERC20().transfer(synthetixBridgeEscrow(), amount);

        // to be here means I've been given an amount of SNX to distribute onto L2
        _depositReward(msg.sender, amount);
    }

    function depositAndMigrateEscrow(uint256 depositAmount, uint256[][] memory entryIDs)
        public
        requireInitiationActive
        requireZeroDebt
    {
        if (entryIDs.length > 0) {
            _migrateEscrow(entryIDs);
        }

        if (depositAmount > 0) {
            _initiateDeposit(msg.sender, depositAmount);
        }
    }

    // ========== PRIVATE/INTERNAL FUNCTIONS =========

    function _depositReward(address _from, uint256 _amount) internal {
        // create message payload for L2
        ISynthetixBridgeToBase bridgeToBase;
        bytes memory messageData = abi.encodeWithSelector(bridgeToBase.finalizeRewardDeposit.selector, _from, _amount);

        // relay the message to this contract on L2 via L1 Messenger
        messenger().sendMessage(
            synthetixBridgeToBase(),
            messageData,
            uint32(getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits.Reward))
        );

        emit RewardDepositInitiated(_from, _amount);
    }

    function _initiateDeposit(address _to, uint256 _depositAmount) private {
        // Transfer SNX to L2
        // First, move the SNX into the deposit escrow
        synthetixERC20().transferFrom(msg.sender, synthetixBridgeEscrow(), _depositAmount);
        // create message payload for L2
        iOVM_L2DepositedToken bridgeToBase;
        bytes memory messageData = abi.encodeWithSelector(bridgeToBase.finalizeDeposit.selector, _to, _depositAmount);

        // relay the message to this contract on L2 via L1 Messenger
        messenger().sendMessage(
            synthetixBridgeToBase(),
            messageData,
            uint32(getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits.Deposit))
        );

        emit iOVM_L1TokenGateway.DepositInitiated(msg.sender, _to, _depositAmount);
    }

    function _migrateEscrow(uint256[][] memory _entryIDs) private {
        // loop through the entryID array
        for (uint256 i = 0; i < _entryIDs.length; i++) {
            // Cannot send more than MAX_ENTRIES_MIGRATED_PER_MESSAGE entries due to ovm gas restrictions
            require(_entryIDs[i].length <= MAX_ENTRIES_MIGRATED_PER_MESSAGE, "Exceeds max entries per migration");
            // Burn their reward escrow first
            // Note: escrowSummary would lose the fidelity of the weekly escrows, so this may not be sufficient
            uint256 escrowedAccountBalance;
            VestingEntries.VestingEntry[] memory vestingEntries;
            (escrowedAccountBalance, vestingEntries) = rewardEscrowV2().burnForMigration(msg.sender, _entryIDs[i]);

            // if there is an escrow amount to be migrated
            if (escrowedAccountBalance > 0) {
                // NOTE: transfer SNX to synthetixBridgeEscrow because burnForMigration() transfers them to this contract.
                synthetixERC20().transfer(synthetixBridgeEscrow(), escrowedAccountBalance);
                // create message payload for L2
                ISynthetixBridgeToBase bridgeToBase;
                bytes memory messageData =
                    abi.encodeWithSelector(
                        bridgeToBase.finalizeEscrowMigration.selector,
                        msg.sender,
                        escrowedAccountBalance,
                        vestingEntries
                    );
                // relay the message to this contract on L2 via L1 Messenger
                messenger().sendMessage(
                    synthetixBridgeToBase(),
                    messageData,
                    uint32(getCrossDomainMessageGasLimit(CrossDomainMessageGasLimits.Escrow))
                );

                emit ExportedVestingEntries(msg.sender, escrowedAccountBalance, vestingEntries);
            }
        }
    }

    // ========== EVENTS ==========

    event ExportedVestingEntries(
        address indexed account,
        uint256 escrowedAccountBalance,
        VestingEntries.VestingEntry[] vestingEntries
    );

    event RewardDepositInitiated(address indexed account, uint256 amount);

    event FeePeriodClosed(uint snxBackedDebt, uint totalDebtShares);
}