// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/IFraxPool.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.5.7;

interface IFraxPool {
    function minting_fee() external returns (uint256);
    function redemption_fee() external returns (uint256);
    function buyback_fee() external returns (uint256);
    function recollat_fee() external returns (uint256);
    function collatDollarBalance() external returns (uint256);
    function availableExcessCollatDV() external returns (uint256);
    function getCollateralPrice() external returns (uint256);
    function setCollatETHOracle(address _collateral_weth_oracle_address, address _weth_address) external;
    function mint1t1FRAX(uint256 collateral_amount, uint256 FRAX_out_min) external;
    function mintAlgorithmicFRAX(uint256 fxs_amount_d18, uint256 FRAX_out_min) external;
    function mintFractionalFRAX(uint256 collateral_amount, uint256 fxs_amount, uint256 FRAX_out_min) external;
    function redeem1t1FRAX(uint256 FRAX_amount, uint256 COLLATERAL_out_min) external;
    function redeemFractionalFRAX(uint256 FRAX_amount, uint256 FXS_out_min, uint256 COLLATERAL_out_min) external;
    function redeemAlgorithmicFRAX(uint256 FRAX_amount, uint256 FXS_out_min) external;
    function collectRedemption() external;
    function recollateralizeFRAX(uint256 collateral_amount, uint256 FXS_out_min) external;
    function buyBackFXS(uint256 FXS_amount, uint256 COLLATERAL_out_min) external;
    function toggleMinting() external;
    function toggleRedeeming() external;
    function toggleRecollateralize() external;
    function toggleBuyBack() external;
    function toggleCollateralPrice(uint256 _new_price) external;
    function setPoolParameters(uint256 new_ceiling, uint256 new_bonus_rate, uint256 new_redemption_delay, uint256 new_mint_fee, uint256 new_redeem_fee, uint256 new_buyback_fee, uint256 new_recollat_fee) external;
    function setTimelock(address new_timelock) external;
    function setOwner(address _owner_address) external;
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/IOneSplit.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

//
//  [ msg.sender ]
//       | |
//       | |
//       \_/
// +---------------+ ________________________________
// | OneSplitAudit | _______________________________  \
// +---------------+                                 \ \
//       | |                      ______________      | | (staticcall)
//       | |                    /  ____________  \    | |
//       | | (call)            / /              \ \   | |
//       | |                  / /               | |   | |
//       \_/                  | |               \_/   \_/
// +--------------+           | |           +----------------------+
// | OneSplitWrap |           | |           |   OneSplitViewWrap   |
// +--------------+           | |           +----------------------+
//       | |                  | |                     | |
//       | | (delegatecall)   | | (staticcall)        | | (staticcall)
//       \_/                  | |                     \_/
// +--------------+           | |             +------------------+
// |   OneSplit   |           | |             |   OneSplitView   |
// +--------------+           | |             +------------------+
//       | |                  / /
//        \ \________________/ /
//         \__________________/
//


contract IOneSplitConsts {
    // flags = FLAG_DISABLE_UNISWAP + FLAG_DISABLE_BANCOR + ...
    uint256 internal constant FLAG_DISABLE_UNISWAP = 0x01;
    uint256 internal constant DEPRECATED_FLAG_DISABLE_KYBER = 0x02; // Deprecated
    uint256 internal constant FLAG_DISABLE_BANCOR = 0x04;
    uint256 internal constant FLAG_DISABLE_OASIS = 0x08;
    uint256 internal constant FLAG_DISABLE_COMPOUND = 0x10;
    uint256 internal constant FLAG_DISABLE_FULCRUM = 0x20;
    uint256 internal constant FLAG_DISABLE_CHAI = 0x40;
    uint256 internal constant FLAG_DISABLE_AAVE = 0x80;
    uint256 internal constant FLAG_DISABLE_SMART_TOKEN = 0x100;
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_ETH = 0x200; // Deprecated, Turned off by default
    uint256 internal constant FLAG_DISABLE_BDAI = 0x400;
    uint256 internal constant FLAG_DISABLE_IEARN = 0x800;
    uint256 internal constant FLAG_DISABLE_CURVE_COMPOUND = 0x1000;
    uint256 internal constant FLAG_DISABLE_CURVE_USDT = 0x2000;
    uint256 internal constant FLAG_DISABLE_CURVE_Y = 0x4000;
    uint256 internal constant FLAG_DISABLE_CURVE_BINANCE = 0x8000;
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_DAI = 0x10000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_USDC = 0x20000; // Deprecated, Turned off by default
    uint256 internal constant FLAG_DISABLE_CURVE_SYNTHETIX = 0x40000;
    uint256 internal constant FLAG_DISABLE_WETH = 0x80000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_COMPOUND = 0x100000; // Works only when one of assets is ETH or FLAG_ENABLE_MULTI_PATH_ETH
    uint256 internal constant FLAG_DISABLE_UNISWAP_CHAI = 0x200000; // Works only when ETH<>DAI or FLAG_ENABLE_MULTI_PATH_ETH
    uint256 internal constant FLAG_DISABLE_UNISWAP_AAVE = 0x400000; // Works only when one of assets is ETH or FLAG_ENABLE_MULTI_PATH_ETH
    uint256 internal constant FLAG_DISABLE_IDLE = 0x800000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP = 0x1000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_V2 = 0x2000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_V2_ETH = 0x4000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_V2_DAI = 0x8000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_V2_USDC = 0x10000000;
    uint256 internal constant FLAG_DISABLE_ALL_SPLIT_SOURCES = 0x20000000;
    uint256 internal constant FLAG_DISABLE_ALL_WRAP_SOURCES = 0x40000000;
    uint256 internal constant FLAG_DISABLE_CURVE_PAX = 0x80000000;
    uint256 internal constant FLAG_DISABLE_CURVE_RENBTC = 0x100000000;
    uint256 internal constant FLAG_DISABLE_CURVE_TBTC = 0x200000000;
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_USDT = 0x400000000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_WBTC = 0x800000000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_TBTC = 0x1000000000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_RENBTC = 0x2000000000; // Deprecated, Turned off by default
    uint256 internal constant FLAG_DISABLE_DFORCE_SWAP = 0x4000000000;
    uint256 internal constant FLAG_DISABLE_SHELL = 0x8000000000;
    uint256 internal constant FLAG_ENABLE_CHI_BURN = 0x10000000000;
    uint256 internal constant FLAG_DISABLE_MSTABLE_MUSD = 0x20000000000;
    uint256 internal constant FLAG_DISABLE_CURVE_SBTC = 0x40000000000;
    uint256 internal constant FLAG_DISABLE_DMM = 0x80000000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_ALL = 0x100000000000;
    uint256 internal constant FLAG_DISABLE_CURVE_ALL = 0x200000000000;
    uint256 internal constant FLAG_DISABLE_UNISWAP_V2_ALL = 0x400000000000;
    uint256 internal constant FLAG_DISABLE_SPLIT_RECALCULATION = 0x800000000000;
    uint256 internal constant FLAG_DISABLE_BALANCER_ALL = 0x1000000000000;
    uint256 internal constant FLAG_DISABLE_BALANCER_1 = 0x2000000000000;
    uint256 internal constant FLAG_DISABLE_BALANCER_2 = 0x4000000000000;
    uint256 internal constant FLAG_DISABLE_BALANCER_3 = 0x8000000000000;
    uint256 internal constant DEPRECATED_FLAG_ENABLE_KYBER_UNISWAP_RESERVE = 0x10000000000000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_KYBER_OASIS_RESERVE = 0x20000000000000; // Deprecated, Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_KYBER_BANCOR_RESERVE = 0x40000000000000; // Deprecated, Turned off by default
    uint256 internal constant FLAG_ENABLE_REFERRAL_GAS_SPONSORSHIP = 0x80000000000000; // Turned off by default
    uint256 internal constant DEPRECATED_FLAG_ENABLE_MULTI_PATH_COMP = 0x100000000000000; // Deprecated, Turned off by default
    uint256 internal constant FLAG_DISABLE_KYBER_ALL = 0x200000000000000;
    uint256 internal constant FLAG_DISABLE_KYBER_1 = 0x400000000000000;
    uint256 internal constant FLAG_DISABLE_KYBER_2 = 0x800000000000000;
    uint256 internal constant FLAG_DISABLE_KYBER_3 = 0x1000000000000000;
    uint256 internal constant FLAG_DISABLE_KYBER_4 = 0x2000000000000000;
    uint256 internal constant FLAG_ENABLE_CHI_BURN_BY_ORIGIN = 0x4000000000000000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP_ALL = 0x8000000000000000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP_ETH = 0x10000000000000000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP_DAI = 0x20000000000000000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP_USDC = 0x40000000000000000;
    uint256 internal constant FLAG_DISABLE_MOONISWAP_POOL_TOKEN = 0x80000000000000000;
}


contract IOneSplit is IOneSplitConsts {
    function getExpectedReturn(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 parts,
        uint256 flags // See constants in IOneSplit.sol
    )
        public
        view
        returns(
            uint256 returnAmount,
            uint256[] memory distribution
        );

    function getExpectedReturnWithGas(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 parts,
        uint256 flags, // See constants in IOneSplit.sol
        uint256 destTokenEthPriceTimesGasPrice
    )
        public
        view
        returns(
            uint256 returnAmount,
            uint256 estimateGasAmount,
            uint256[] memory distribution
        );

    function swap(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256 flags
    )
        public
        payable
        returns(uint256 returnAmount);
}


contract IOneSplitMulti is IOneSplit {
    function getExpectedReturnWithGasMulti(
        IERC20[] memory tokens,
        uint256 amount,
        uint256[] memory parts,
        uint256[] memory flags,
        uint256[] memory destTokenEthPriceTimesGasPrices
    )
        public
        view
        returns(
            uint256[] memory returnAmounts,
            uint256 estimateGasAmount,
            uint256[] memory distribution
        );

    function swapMulti(
        IERC20[] memory tokens,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256[] memory flags
    )
        public
        payable
        returns(uint256 returnAmount);
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/IUniswapV2Exchange.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./UniversalERC20.sol";


interface IUniswapV2Exchange {
    function getReserves() external view returns(uint112 _reserve0, uint112 _reserve1, uint32 _blockTimestampLast);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;
}


library UniswapV2ExchangeLib {
    using Math for uint256;
    using SafeMath for uint256;
    using UniversalERC20 for IERC20;

    function getReturn(
        IUniswapV2Exchange exchange,
        IERC20 fromToken,
        IERC20 destToken,
        uint amountIn
    ) internal view returns (uint256 result, bool needSync, bool needSkim) {
        uint256 reserveIn = fromToken.universalBalanceOf(address(exchange));
        uint256 reserveOut = destToken.universalBalanceOf(address(exchange));
        (uint112 reserve0, uint112 reserve1,) = exchange.getReserves();
        if (fromToken > destToken) {
            (reserve0, reserve1) = (reserve1, reserve0);
        }
        needSync = (reserveIn < reserve0 || reserveOut < reserve1);
        needSkim = !needSync && (reserveIn > reserve0 || reserveOut > reserve1);

        uint256 amountInWithFee = amountIn.mul(997);
        uint256 numerator = amountInWithFee.mul(Math.min(reserveOut, reserve1));
        uint256 denominator = Math.min(reserveIn, reserve0).mul(1000).add(amountInWithFee);
        result = (denominator == 0) ? 0 : numerator.div(denominator);
    }
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/IWETH.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";


contract IWETH is IERC20 {
    function deposit() external payable;

    function withdraw(uint256 amount) external;
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/MintUtilities.sol



pragma solidity ^0.5.7;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import './OneSplitAudit.sol';
import './IFraxPool.sol';
import './IWETH.sol';

// 1inch stuff here
// https://github.com/1inch-exchange/1inchProtocol/tree/master/contracts/interface
// https://github.com/1inch-exchange/1inchProtocol/blob/master/contracts/IOneSplit.sol
// https://github.com/1inch-exchange/1inchProtocol

contract MintUtilities {
    using SafeMath for uint256;
    address constant private USDC_ADDRESS = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48;
    address constant private WETH_ADDRESS = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address constant private FRAX_ADDRESS = 0x853d955aCEf822Db058eb8505911ED77F175b99e;
    address constant private FXS_ADDRESS = 0x3432B6A60D23Ca0dFCa7761B7ab56459D9C964D0;
    address payable constant public ONE_SPLIT_AUDIT_ADDRESS = 0xC586BeF4a0992C495Cf22e1aeEE4E446CECDee0E;
    address constant public REFERRAL_REWARD_ADDRESS = 0x234D953a9404Bf9DbC3b526271d440cD2870bCd2; // Frax main

    IERC20 constant internal USDC_ERC20 = IERC20(USDC_ADDRESS);
    IERC20 constant internal WETH_ERC20 = IERC20(WETH_ADDRESS);
    IERC20 constant internal FRAX_ERC20 = IERC20(FRAX_ADDRESS);
    IERC20 constant internal FXS_ERC20 = IERC20(FXS_ADDRESS);
    IERC20 constant internal ETH_ERC20 = IERC20(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);

    IWETH constant internal WETH_IWETH = IWETH(WETH_ADDRESS);

    OneSplitAudit constant internal OneSplit_Inst = OneSplitAudit(ONE_SPLIT_AUDIT_ADDRESS);

    address public owner_address;
    address payable public owner_address_payable;
    bool public is_paused;

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

    modifier notPaused {
        require(is_paused == false, "Contract is paused");
        _;
    }

    constructor () public {
        owner_address = msg.sender;
        owner_address_payable = msg.sender;
        is_paused = false;
    }

    function _swapWETHForUSDC(
        uint256 amountWETH,
        uint256 usdc_out_min,
        uint256[] memory distribution_WETH_USDC,
        uint256 max_slippage
    ) internal notPaused returns (uint256) {
        // Approve the WETH for 1inch
        WETH_ERC20.approve(address(this), amountWETH);

        // Swap some ETH for USDC
        (uint256 received_USDC) = OneSplit_Inst.swapWithReferral(
            WETH_ERC20,
            USDC_ERC20,
            amountWETH,
            usdc_out_min,
            distribution_WETH_USDC,
            0,
            REFERRAL_REWARD_ADDRESS,
            max_slippage
        );
        
        // Make sure enough USDC was recieved
        require(received_USDC >= usdc_out_min, "[_swapWETHForUSDC]: Not enough USDC received from swap");

        return received_USDC;
    }

    function _swapUSDCForFXS(
        uint256 received_USDC,
        uint256 fxs_out_min,
        uint256[] memory distribution_USDC_FXS,
        uint256 max_slippage
    ) internal notPaused returns (uint256) {
        // Approve the USDC for 1inch
        USDC_ERC20.approve(address(this), received_USDC);

        // Swap some USDC for FXS
        (uint256 received_FXS) = OneSplit_Inst.swapWithReferral(
            USDC_ERC20,
            FXS_ERC20,
            received_USDC,
            fxs_out_min,
            distribution_USDC_FXS,
            0,
            REFERRAL_REWARD_ADDRESS,
            max_slippage
        );

        // Make sure enough FXS was recieved
        require(received_FXS >= fxs_out_min, "[_swapUSDCForFXS]: Not enough FXS received from swap");

        return received_FXS;
    }

    function ethSwapToMintFF(
        uint256 amountETH,
        uint256 usdc_out_min,
        uint256[] calldata distribution_WETH_USDC,
        uint256 fxs_out_min,
        uint256[] calldata distribution_USDC_FXS,
        uint256 usdc_for_mint,
        uint256 frax_out_min,
        uint256 max_slippage,
        address _pool_address
    ) external payable notPaused {
        require(msg.value == amountETH, "msg.value doesn't match amountETH");

        // =================== Convert ETH to WETH first ===================
        WETH_IWETH.deposit.value(amountETH)();
        assert(WETH_IWETH.transfer(address(this), amountETH));

        // =================== ETH -> USDC via 1inch ===================
        (uint256 received_USDC) = _swapWETHForUSDC(amountETH, usdc_out_min, distribution_WETH_USDC, max_slippage);

        // =================== USDC -> FXS via 1inch ===================
        (uint256 received_FXS) = _swapUSDCForFXS(received_USDC, fxs_out_min, distribution_USDC_FXS, max_slippage);

        // =================== USDC + FXS -> FRAX via FraxPool mint ===================

        // Approve the Collat for the FraxPool
        USDC_ERC20.approve(_pool_address, (usdc_for_mint).mul(105).div(100));

        // Approve the FXS for the FraxPool
        FXS_ERC20.approve(_pool_address, (received_FXS).mul(105).div(100));

        // Mint
        IFraxPool(_pool_address).mintFractionalFRAX(usdc_for_mint, received_FXS, frax_out_min);

        // Return FRAX to owner. Note that there may be crumbs left over...
        FRAX_ERC20.transfer(msg.sender, frax_out_min);
    }

    // The smart contract should never end up having to need this as there should be no deposits. Just for emergency purposes
    function recoverERC20(address tokenAddress, uint256 tokenAmount) external onlyOwner {
        IERC20(tokenAddress).transfer(owner_address, tokenAmount);
    }

    function withdraw() external onlyOwner
    {
        msg.sender.transfer(address(this).balance);
    }

    function selfDestruct() external payable onlyOwner {
        selfdestruct(owner_address_payable);
    }

    function togglePaused() external onlyOwner {
        is_paused = !is_paused;
    } 
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/OneSplitAudit.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/ownership/Ownable.sol";
import "./IWETH.sol";
import "./IUniswapV2Exchange.sol";
import "./IOneSplit.sol";
import "./UniversalERC20.sol";


contract IFreeFromUpTo is IERC20 {
    function freeFromUpTo(address from, uint256 value) external returns(uint256 freed);
}

interface IReferralGasSponsor {
    function makeGasDiscount(
        uint256 gasSpent,
        uint256 returnAmount,
        bytes calldata msgSenderCalldata
    ) external;
}


library Array {
    function first(IERC20[] memory arr) internal pure returns(IERC20) {
        return arr[0];
    }

    function last(IERC20[] memory arr) internal pure returns(IERC20) {
        return arr[arr.length - 1];
    }
}


//
// Security assumptions:
// 1. It is safe to have infinite approves of any tokens to this smart contract,
//    since it could only call `transferFrom()` with first argument equal to msg.sender
// 2. It is safe to call `swap()` with reliable `minReturn` argument,
//    if returning amount will not reach `minReturn` value whole swap will be reverted.
// 3. Additionally CHI tokens could be burned from caller in case of FLAG_ENABLE_CHI_BURN (0x10000000000)
//    presented in `flags` or from transaction origin in case of FLAG_ENABLE_CHI_BURN_BY_ORIGIN (0x4000000000000000)
//    presented in `flags`. Burned amount would refund up to 43% of gas fees.
//
contract OneSplitAudit is IOneSplit, Ownable {
    using SafeMath for uint256;
    using UniversalERC20 for IERC20;
    using Array for IERC20[];

    IWETH constant internal weth = IWETH(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
    IFreeFromUpTo public constant chi = IFreeFromUpTo(0x0000000000004946c0e9F43F4Dee607b0eF1fA1c);

    IOneSplitMulti public oneSplitImpl;

    event ImplementationUpdated(address indexed newImpl);

    event Swapped(
        IERC20 indexed fromToken,
        IERC20 indexed destToken,
        uint256 fromTokenAmount,
        uint256 destTokenAmount,
        uint256 minReturn,
        uint256[] distribution,
        uint256[] flags,
        address referral,
        uint256 feePercent
    );

    constructor(IOneSplitMulti impl) public {
        setNewImpl(impl);
    }

    function() external payable {
        // solium-disable-next-line security/no-tx-origin
        require(msg.sender != tx.origin, "OneSplit: do not send ETH directly");
    }

    function setNewImpl(IOneSplitMulti impl) public onlyOwner {
        oneSplitImpl = impl;
        emit ImplementationUpdated(address(impl));
    }

    /// @notice Calculate expected returning amount of `destToken`
    /// @param fromToken (IERC20) Address of token or `address(0)` for Ether
    /// @param destToken (IERC20) Address of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param parts (uint256) Number of pieces source volume could be splitted,
    /// works like granularity, higly affects gas usage. Should be called offchain,
    /// but could be called onchain if user swaps not his own funds, but this is still considered as not safe.
    /// @param flags (uint256) Flags for enabling and disabling some features, default 0
    function getExpectedReturn(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 parts,
        uint256 flags // See contants in IOneSplit.sol
    )
        public
        view
        returns(
            uint256 returnAmount,
            uint256[] memory distribution
        )
    {
        (returnAmount, , distribution) = getExpectedReturnWithGas(
            fromToken,
            destToken,
            amount,
            parts,
            flags,
            0
        );
    }

    /// @notice Calculate expected returning amount of `destToken`
    /// @param fromToken (IERC20) Address of token or `address(0)` for Ether
    /// @param destToken (IERC20) Address of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param parts (uint256) Number of pieces source volume could be splitted,
    /// works like granularity, higly affects gas usage. Should be called offchain,
    /// but could be called onchain if user swaps not his own funds, but this is still considered as not safe.
    /// @param flags (uint256) Flags for enabling and disabling some features, default 0
    /// @param destTokenEthPriceTimesGasPrice (uint256) destToken price to ETH multiplied by gas price
    function getExpectedReturnWithGas(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 parts,
        uint256 flags, // See constants in IOneSplit.sol
        uint256 destTokenEthPriceTimesGasPrice
    )
        public
        view
        returns(
            uint256 returnAmount,
            uint256 estimateGasAmount,
            uint256[] memory distribution
        )
    {
        return oneSplitImpl.getExpectedReturnWithGas(
            fromToken,
            destToken,
            amount,
            parts,
            flags,
            destTokenEthPriceTimesGasPrice
        );
    }

    /// @notice Calculate expected returning amount of first `tokens` element to
    /// last `tokens` element through ann the middle tokens with corresponding
    /// `parts`, `flags` and `destTokenEthPriceTimesGasPrices` array values of each step
    /// @param tokens (IERC20[]) Address of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param parts (uint256[]) Number of pieces source volume could be splitted
    /// @param flags (uint256[]) Flags for enabling and disabling some features, default 0
    /// @param destTokenEthPriceTimesGasPrices (uint256[]) destToken price to ETH multiplied by gas price
    function getExpectedReturnWithGasMulti(
        IERC20[] memory tokens,
        uint256 amount,
        uint256[] memory parts,
        uint256[] memory flags,
        uint256[] memory destTokenEthPriceTimesGasPrices
    )
        public
        view
        returns(
            uint256[] memory returnAmounts,
            uint256 estimateGasAmount,
            uint256[] memory distribution
        )
    {
        return oneSplitImpl.getExpectedReturnWithGasMulti(
            tokens,
            amount,
            parts,
            flags,
            destTokenEthPriceTimesGasPrices
        );
    }

    /// @notice Swap `amount` of `fromToken` to `destToken`
    /// @param fromToken (IERC20) Address of token or `address(0)` for Ether
    /// @param destToken (IERC20) Address of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param minReturn (uint256) Minimum expected return, else revert
    /// @param distribution (uint256[]) Array of weights for volume distribution returned by `getExpectedReturn`
    /// @param flags (uint256) Flags for enabling and disabling some features, default 0
    function swap(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256 flags // See contants in IOneSplit.sol
    ) public payable returns(uint256) {
        return swapWithReferral(
            fromToken,
            destToken,
            amount,
            minReturn,
            distribution,
            flags,
            address(0),
            0
        );
    }

    /// @notice Swap `amount` of `fromToken` to `destToken`
    /// param fromToken (IERC20) Address of token or `address(0)` for Ether
    /// param destToken (IERC20) Address of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param minReturn (uint256) Minimum expected return, else revert
    /// @param distribution (uint256[]) Array of weights for volume distribution returned by `getExpectedReturn`
    /// @param flags (uint256) Flags for enabling and disabling some features, default 0
    /// @param referral (address) Address of referral
    /// @param feePercent (uint256) Fees percents normalized to 1e18, limited to 0.03e18 (3%)
    function swapWithReferral(
        IERC20 fromToken,
        IERC20 destToken,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256 flags, // See contants in IOneSplit.sol
        address referral,
        uint256 feePercent
    ) public payable returns(uint256) {
        IERC20[] memory tokens = new IERC20[](2);
        tokens[0] = fromToken;
        tokens[1] = destToken;

        uint256[] memory flagsArray = new uint256[](1);
        flagsArray[0] = flags;

        swapWithReferralMulti(
            tokens,
            amount,
            minReturn,
            distribution,
            flagsArray,
            referral,
            feePercent
        );
    }

    /// @notice Swap `amount` of first element of `tokens` to the latest element of `destToken`
    /// @param tokens (IERC20[]) Addresses of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param minReturn (uint256) Minimum expected return, else revert
    /// @param distribution (uint256[]) Array of weights for volume distribution returned by `getExpectedReturn`
    /// @param flags (uint256[]) Flags for enabling and disabling some features, default 0
    function swapMulti(
        IERC20[] memory tokens,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256[] memory flags
    ) public payable returns(uint256) {
        swapWithReferralMulti(
            tokens,
            amount,
            minReturn,
            distribution,
            flags,
            address(0),
            0
        );
    }

    /// @notice Swap `amount` of first element of `tokens` to the latest element of `destToken`
    /// @param tokens (IERC20[]) Addresses of token or `address(0)` for Ether
    /// @param amount (uint256) Amount for `fromToken`
    /// @param minReturn (uint256) Minimum expected return, else revert
    /// @param distribution (uint256[]) Array of weights for volume distribution returned by `getExpectedReturn`
    /// @param flags (uint256[]) Flags for enabling and disabling some features, default 0
    /// @param referral (address) Address of referral
    /// @param feePercent (uint256) Fees percents normalized to 1e18, limited to 0.03e18 (3%)
    function swapWithReferralMulti(
        IERC20[] memory tokens,
        uint256 amount,
        uint256 minReturn,
        uint256[] memory distribution,
        uint256[] memory flags,
        address referral,
        uint256 feePercent
    ) public payable returns(uint256 returnAmount) {
        require(tokens.length >= 2 && amount > 0, "OneSplit: swap makes no sense");
        require(flags.length == tokens.length - 1, "OneSplit: flags array length is invalid");
        require((msg.value != 0) == tokens.first().isETH(), "OneSplit: msg.value should be used only for ETH swap");
        require(feePercent <= 0.03e18, "OneSplit: feePercent out of range");

        uint256 gasStart = gasleft();

        Balances memory beforeBalances = _getFirstAndLastBalances(tokens, true);

        // Transfer From
        if (amount == uint256(-1)) {
            amount = Math.min(
                tokens.first().balanceOf(msg.sender),
                tokens.first().allowance(msg.sender, address(this))
            );
        }
        tokens.first().universalTransferFromSenderToThis(amount);
        uint256 confirmed = tokens.first().universalBalanceOf(address(this)).sub(beforeBalances.ofFromToken);

        // Swap
        tokens.first().universalApprove(address(oneSplitImpl), confirmed);
        oneSplitImpl.swapMulti.value(tokens.first().isETH() ? confirmed : 0)(
            tokens,
            confirmed,
            minReturn,
            distribution,
            flags
        );

        Balances memory afterBalances = _getFirstAndLastBalances(tokens, false);

        // Return
        returnAmount = afterBalances.ofDestToken.sub(beforeBalances.ofDestToken);
        require(returnAmount >= minReturn, "OneSplit: actual return amount is less than minReturn");
        tokens.last().universalTransfer(referral, returnAmount.mul(feePercent).div(1e18));
        tokens.last().universalTransfer(msg.sender, returnAmount.sub(returnAmount.mul(feePercent).div(1e18)));

        emit Swapped(
            tokens.first(),
            tokens.last(),
            amount,
            returnAmount,
            minReturn,
            distribution,
            flags,
            referral,
            feePercent
        );

        // Return remainder
        if (afterBalances.ofFromToken > beforeBalances.ofFromToken) {
            tokens.first().universalTransfer(msg.sender, afterBalances.ofFromToken.sub(beforeBalances.ofFromToken));
        }

        if ((flags[0] & (FLAG_ENABLE_CHI_BURN | FLAG_ENABLE_CHI_BURN_BY_ORIGIN)) > 0) {
            uint256 gasSpent = 21000 + gasStart - gasleft() + 16 * msg.data.length;
            _chiBurnOrSell(
                ((flags[0] & FLAG_ENABLE_CHI_BURN_BY_ORIGIN) > 0) ? tx.origin : msg.sender,
                (gasSpent + 14154) / 41947
            );
        }
        else if ((flags[0] & FLAG_ENABLE_REFERRAL_GAS_SPONSORSHIP) > 0) {
            uint256 gasSpent = 21000 + gasStart - gasleft() + 16 * msg.data.length;
            IReferralGasSponsor(referral).makeGasDiscount(gasSpent, returnAmount, msg.data);
        }
    }

    function claimAsset(IERC20 asset, uint256 amount) public onlyOwner {
        asset.universalTransfer(msg.sender, amount);
    }

    function _chiBurnOrSell(address payable sponsor, uint256 amount) internal {
        IUniswapV2Exchange exchange = IUniswapV2Exchange(0xa6f3ef841d371a82ca757FaD08efc0DeE2F1f5e2);
        (uint256 sellRefund,,) = UniswapV2ExchangeLib.getReturn(exchange, chi, weth, amount);
        uint256 burnRefund = amount.mul(18_000).mul(tx.gasprice);

        if (sellRefund < burnRefund.add(tx.gasprice.mul(36_000))) {
            chi.freeFromUpTo(sponsor, amount);
        }
        else {
            chi.transferFrom(sponsor, address(exchange), amount);
            exchange.swap(0, sellRefund, address(this), "");
            weth.withdraw(weth.balanceOf(address(this)));
            sponsor.transfer(address(this).balance);
        }
    }

    struct Balances {
        uint256 ofFromToken;
        uint256 ofDestToken;
    }

    function _getFirstAndLastBalances(IERC20[] memory tokens, bool subValue) internal view returns(Balances memory) {
        return Balances({
            ofFromToken: tokens.first().universalBalanceOf(address(this)).sub(subValue ? msg.value : 0),
            ofDestToken: tokens.last().universalBalanceOf(address(this))
        });
    }
}
// File: /home/travis/Documents/Ubuntu_Shared/misc-frax-contracts/contracts/UniversalERC20.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";


library UniversalERC20 {

    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    IERC20 private constant ZERO_ADDRESS = IERC20(0x0000000000000000000000000000000000000000);
    IERC20 private constant ETH_ADDRESS = IERC20(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);

    function universalTransfer(IERC20 token, address to, uint256 amount) internal returns(bool) {
        if (amount == 0) {
            return true;
        }

        if (isETH(token)) {
            address(uint160(to)).transfer(amount);
        } else {
            token.safeTransfer(to, amount);
            return true;
        }
    }

    function universalTransferFrom(IERC20 token, address from, address to, uint256 amount) internal {
        if (amount == 0) {
            return;
        }

        if (isETH(token)) {
            require(from == msg.sender && msg.value >= amount, "Wrong useage of ETH.universalTransferFrom()");
            if (to != address(this)) {
                address(uint160(to)).transfer(amount);
            }
            if (msg.value > amount) {
                msg.sender.transfer(msg.value.sub(amount));
            }
        } else {
            token.safeTransferFrom(from, to, amount);
        }
    }

    function universalTransferFromSenderToThis(IERC20 token, uint256 amount) internal {
        if (amount == 0) {
            return;
        }

        if (isETH(token)) {
            if (msg.value > amount) {
                // Return remainder if exist
                msg.sender.transfer(msg.value.sub(amount));
            }
        } else {
            token.safeTransferFrom(msg.sender, address(this), amount);
        }
    }

    function universalApprove(IERC20 token, address to, uint256 amount) internal {
        if (!isETH(token)) {
            if (amount == 0) {
                token.safeApprove(to, 0);
                return;
            }

            uint256 allowance = token.allowance(address(this), to);
            if (allowance < amount) {
                if (allowance > 0) {
                    token.safeApprove(to, 0);
                }
                token.safeApprove(to, amount);
            }
        }
    }

    function universalBalanceOf(IERC20 token, address who) internal view returns (uint256) {
        if (isETH(token)) {
            return who.balance;
        } else {
            return token.balanceOf(who);
        }
    }

    function universalDecimals(IERC20 token) internal view returns (uint256) {

        if (isETH(token)) {
            return 18;
        }

        (bool success, bytes memory data) = address(token).staticcall.gas(10000)(
            abi.encodeWithSignature("decimals()")
        );
        if (!success || data.length == 0) {
            (success, data) = address(token).staticcall.gas(10000)(
                abi.encodeWithSignature("DECIMALS()")
            );
        }

        return (success && data.length > 0) ? abi.decode(data, (uint256)) : 18;
    }

    function isETH(IERC20 token) internal pure returns(bool) {
        return (address(token) == address(ZERO_ADDRESS) || address(token) == address(ETH_ADDRESS));
    }

    function eq(IERC20 a, IERC20 b) internal pure returns(bool) {
        return a == b || (isETH(a) && isETH(b));
    }

    function notExist(IERC20 token) internal pure returns(bool) {
        return (address(token) == address(-1));
    }
}
// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.5.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

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

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



pragma solidity ^0.5.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

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



pragma solidity ^0.5.0;

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

        return c;
    }

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

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

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

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

        return c;
    }

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

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

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

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/ownership/Ownable.sol



pragma solidity ^0.5.0;

import "../GSN/Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;

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

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

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

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

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

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

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

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



pragma solidity ^0.5.0;

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

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

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

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

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



pragma solidity ^0.5.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for 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, "SafeERC20: decreased allowance below zero");
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

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

        // 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");
        }
    }
}

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



pragma solidity ^0.5.5;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following 
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

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