// File: contracts/core/interfaces/IRouter.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IRouter {
    function addPlugin(address _plugin) external;
    function pluginTransfer(address _token, address _account, address _receiver, uint256 _amount) external;
    function pluginIncreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external;
    function pluginDecreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external returns (uint256);
    function swap(address[] memory _path, uint256 _amountIn, uint256 _minOut, address _receiver) external;
}

// File: contracts/core/interfaces/IVault.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "./IVaultUtils.sol";

interface IVault {
    function isInitialized() external view returns (bool);
    function isSwapEnabled() external view returns (bool);
    function isLeverageEnabled() external view returns (bool);

    function setVaultUtils(IVaultUtils _vaultUtils) external;
    function setError(uint256 _errorCode, string calldata _error) external;

    function router() external view returns (address);
    function usdg() external view returns (address);
    function gov() external view returns (address);

    function whitelistedTokenCount() external view returns (uint256);
    function maxLeverage() external view returns (uint256);

    function minProfitTime() external view returns (uint256);
    function hasDynamicFees() external view returns (bool);
    function fundingInterval() external view returns (uint256);
    function totalTokenWeights() external view returns (uint256);
    function getTargetUsdgAmount(address _token) external view returns (uint256);

    function inManagerMode() external view returns (bool);
    function inPrivateLiquidationMode() external view returns (bool);

    function maxGasPrice() external view returns (uint256);

    function approvedRouters(address _account, address _router) external view returns (bool);
    function isLiquidator(address _account) external view returns (bool);
    function isManager(address _account) external view returns (bool);

    function minProfitBasisPoints(address _token) external view returns (uint256);
    function tokenBalances(address _token) external view returns (uint256);
    function lastFundingTimes(address _token) external view returns (uint256);

    function setMaxLeverage(uint256 _maxLeverage) external;
    function setInManagerMode(bool _inManagerMode) external;
    function setManager(address _manager, bool _isManager) external;
    function setIsSwapEnabled(bool _isSwapEnabled) external;
    function setIsLeverageEnabled(bool _isLeverageEnabled) external;
    function setMaxGasPrice(uint256 _maxGasPrice) external;
    function setUsdgAmount(address _token, uint256 _amount) external;
    function setBufferAmount(address _token, uint256 _amount) external;
    function setMaxGlobalShortSize(address _token, uint256 _amount) external;
    function setInPrivateLiquidationMode(bool _inPrivateLiquidationMode) external;
    function setLiquidator(address _liquidator, bool _isActive) external;

    function setFundingRate(uint256 _fundingInterval, uint256 _fundingRateFactor, uint256 _stableFundingRateFactor) external;

    function setFees(
        uint256 _taxBasisPoints,
        uint256 _stableTaxBasisPoints,
        uint256 _mintBurnFeeBasisPoints,
        uint256 _swapFeeBasisPoints,
        uint256 _stableSwapFeeBasisPoints,
        uint256 _marginFeeBasisPoints,
        uint256 _liquidationFeeUsd,
        uint256 _minProfitTime,
        bool _hasDynamicFees
    ) external;

    function setTokenConfig(
        address _token,
        uint256 _tokenDecimals,
        uint256 _redemptionBps,
        uint256 _minProfitBps,
        uint256 _maxUsdgAmount,
        bool _isStable,
        bool _isShortable
    ) external;

    function setPriceFeed(address _priceFeed) external;
    function withdrawFees(address _token, address _receiver) external returns (uint256);

    function directPoolDeposit(address _token) external;
    function buyUSDG(address _token, address _receiver) external returns (uint256);
    function sellUSDG(address _token, address _receiver) external returns (uint256);
    function swap(address _tokenIn, address _tokenOut, address _receiver) external returns (uint256);
    function increasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external;
    function decreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external returns (uint256);
    function validateLiquidation(address _account, address _collateralToken, address _indexToken, bool _isLong, bool _raise) external view returns (uint256, uint256);
    function liquidatePosition(address _account, address _collateralToken, address _indexToken, bool _isLong, address _feeReceiver) external;
    function tokenToUsdMin(address _token, uint256 _tokenAmount) external view returns (uint256);

    function priceFeed() external view returns (address);
    function fundingRateFactor() external view returns (uint256);
    function stableFundingRateFactor() external view returns (uint256);
    function cumulativeFundingRates(address _token) external view returns (uint256);
    function getNextFundingRate(address _token) external view returns (uint256);
    function getFeeBasisPoints(address _token, uint256 _usdgDelta, uint256 _feeBasisPoints, uint256 _taxBasisPoints, bool _increment) external view returns (uint256);

    function liquidationFeeUsd() external view returns (uint256);
    function taxBasisPoints() external view returns (uint256);
    function stableTaxBasisPoints() external view returns (uint256);
    function mintBurnFeeBasisPoints() external view returns (uint256);
    function swapFeeBasisPoints() external view returns (uint256);
    function stableSwapFeeBasisPoints() external view returns (uint256);
    function marginFeeBasisPoints() external view returns (uint256);

    function allWhitelistedTokensLength() external view returns (uint256);
    function allWhitelistedTokens(uint256) external view returns (address);
    function whitelistedTokens(address _token) external view returns (bool);
    function stableTokens(address _token) external view returns (bool);
    function shortableTokens(address _token) external view returns (bool);
    function feeReserves(address _token) external view returns (uint256);
    function globalShortSizes(address _token) external view returns (uint256);
    function globalShortAveragePrices(address _token) external view returns (uint256);
    function maxGlobalShortSizes(address _token) external view returns (uint256);
    function tokenDecimals(address _token) external view returns (uint256);
    function tokenWeights(address _token) external view returns (uint256);
    function guaranteedUsd(address _token) external view returns (uint256);
    function poolAmounts(address _token) external view returns (uint256);
    function bufferAmounts(address _token) external view returns (uint256);
    function reservedAmounts(address _token) external view returns (uint256);
    function usdgAmounts(address _token) external view returns (uint256);
    function maxUsdgAmounts(address _token) external view returns (uint256);
    function getRedemptionAmount(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getMaxPrice(address _token) external view returns (uint256);
    function getMinPrice(address _token) external view returns (uint256);

    function getDelta(address _indexToken, uint256 _size, uint256 _averagePrice, bool _isLong, uint256 _lastIncreasedTime) external view returns (bool, uint256);
    function getPosition(address _account, address _collateralToken, address _indexToken, bool _isLong) external view returns (uint256, uint256, uint256, uint256, uint256, uint256, bool, uint256);
}

// File: contracts/core/interfaces/IVaultUtils.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IVaultUtils {
    function updateCumulativeFundingRate(address _collateralToken, address _indexToken) external returns (bool);
    function validateIncreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external view;
    function validateDecreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external view;
    function validateLiquidation(address _account, address _collateralToken, address _indexToken, bool _isLong, bool _raise) external view returns (uint256, uint256);
    function getEntryFundingRate(address _collateralToken, address _indexToken, bool _isLong) external view returns (uint256);
    function getPositionFee(address _account, address _collateralToken, address _indexToken, bool _isLong, uint256 _sizeDelta) external view returns (uint256);
    function getFundingFee(address _account, address _collateralToken, address _indexToken, bool _isLong, uint256 _size, uint256 _entryFundingRate) external view returns (uint256);
    function getBuyUsdgFeeBasisPoints(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getSellUsdgFeeBasisPoints(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getSwapFeeBasisPoints(address _tokenIn, address _tokenOut, uint256 _usdgAmount) external view returns (uint256);
    function getFeeBasisPoints(address _token, uint256 _usdgDelta, uint256 _feeBasisPoints, uint256 _taxBasisPoints, bool _increment) external view returns (uint256);
}

// File: contracts/core/Router.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "../libraries/math/SafeMath.sol";
import "../libraries/token/IERC20.sol";
import "../libraries/token/SafeERC20.sol";
import "../libraries/utils/Address.sol";

import "../tokens/interfaces/IWETH.sol";
import "./interfaces/IVault.sol";
import "./interfaces/IRouter.sol";

contract Router is IRouter {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    using Address for address payable;

    address public gov;

    // wrapped BNB / ETH
    address public weth;
    address public usdg;
    address public vault;

    mapping (address => bool) public plugins;
    mapping (address => mapping (address => bool)) public approvedPlugins;

    event Swap(address account, address tokenIn, address tokenOut, uint256 amountIn, uint256 amountOut);

    modifier onlyGov() {
        require(msg.sender == gov, "Router: forbidden");
        _;
    }

    constructor(address _vault, address _usdg, address _weth) public {
        vault = _vault;
        usdg = _usdg;
        weth = _weth;

        gov = msg.sender;
    }

    receive() external payable {
        require(msg.sender == weth, "Router: invalid sender");
    }

    function setGov(address _gov) external onlyGov {
        gov = _gov;
    }

    function addPlugin(address _plugin) external override onlyGov {
        plugins[_plugin] = true;
    }

    function removePlugin(address _plugin) external onlyGov {
        plugins[_plugin] = false;
    }

    function approvePlugin(address _plugin) external {
        approvedPlugins[msg.sender][_plugin] = true;
    }

    function denyPlugin(address _plugin) external {
        approvedPlugins[msg.sender][_plugin] = false;
    }

    function pluginTransfer(address _token, address _account, address _receiver, uint256 _amount) external override {
        _validatePlugin(_account);
        IERC20(_token).safeTransferFrom(_account, _receiver, _amount);
    }

    function pluginIncreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external override {
        _validatePlugin(_account);
        IVault(vault).increasePosition(_account, _collateralToken, _indexToken, _sizeDelta, _isLong);
    }

    function pluginDecreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external override returns (uint256) {
        _validatePlugin(_account);
        return IVault(vault).decreasePosition(_account, _collateralToken, _indexToken, _collateralDelta, _sizeDelta, _isLong, _receiver);
    }

    function directPoolDeposit(address _token, uint256 _amount) external {
        IERC20(_token).safeTransferFrom(_sender(), vault, _amount);
        IVault(vault).directPoolDeposit(_token);
    }

    function swap(address[] memory _path, uint256 _amountIn, uint256 _minOut, address _receiver) public override {
        IERC20(_path[0]).safeTransferFrom(_sender(), vault, _amountIn);
        uint256 amountOut = _swap(_path, _minOut, _receiver);
        emit Swap(msg.sender, _path[0], _path[_path.length - 1], _amountIn, amountOut);
    }

    function swapETHToTokens(address[] memory _path, uint256 _minOut, address _receiver) external payable {
        require(_path[0] == weth, "Router: invalid _path");
        _transferETHToVault();
        uint256 amountOut = _swap(_path, _minOut, _receiver);
        emit Swap(msg.sender, _path[0], _path[_path.length - 1], msg.value, amountOut);
    }

    function swapTokensToETH(address[] memory _path, uint256 _amountIn, uint256 _minOut, address payable _receiver) external {
        require(_path[_path.length - 1] == weth, "Router: invalid _path");
        IERC20(_path[0]).safeTransferFrom(_sender(), vault, _amountIn);
        uint256 amountOut = _swap(_path, _minOut, address(this));
        _transferOutETH(amountOut, _receiver);
        emit Swap(msg.sender, _path[0], _path[_path.length - 1], _amountIn, amountOut);
    }

    function increasePosition(address[] memory _path, address _indexToken, uint256 _amountIn, uint256 _minOut, uint256 _sizeDelta, bool _isLong, uint256 _price) external {
        if (_amountIn > 0) {
            IERC20(_path[0]).safeTransferFrom(_sender(), vault, _amountIn);
        }
        if (_path.length > 1 && _amountIn > 0) {
            uint256 amountOut = _swap(_path, _minOut, address(this));
            IERC20(_path[_path.length - 1]).safeTransfer(vault, amountOut);
        }
        _increasePosition(_path[_path.length - 1], _indexToken, _sizeDelta, _isLong, _price);
    }

    function increasePositionETH(address[] memory _path, address _indexToken, uint256 _minOut, uint256 _sizeDelta, bool _isLong, uint256 _price) external payable {
        require(_path[0] == weth, "Router: invalid _path");
        if (msg.value > 0) {
            _transferETHToVault();
        }
        if (_path.length > 1 && msg.value > 0) {
            uint256 amountOut = _swap(_path, _minOut, address(this));
            IERC20(_path[_path.length - 1]).safeTransfer(vault, amountOut);
        }
        _increasePosition(_path[_path.length - 1], _indexToken, _sizeDelta, _isLong, _price);
    }

    function decreasePosition(address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver, uint256 _price) external {
        _decreasePosition(_collateralToken, _indexToken, _collateralDelta, _sizeDelta, _isLong, _receiver, _price);
    }

    function decreasePositionETH(address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address payable _receiver, uint256 _price) external {
        uint256 amountOut = _decreasePosition(_collateralToken, _indexToken, _collateralDelta, _sizeDelta, _isLong, address(this), _price);
        _transferOutETH(amountOut, _receiver);
    }

    function decreasePositionAndSwap(address[] memory _path, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver, uint256 _price, uint256 _minOut) external {
        uint256 amount = _decreasePosition(_path[0], _indexToken, _collateralDelta, _sizeDelta, _isLong, address(this), _price);
        IERC20(_path[0]).safeTransfer(vault, amount);
        _swap(_path, _minOut, _receiver);
    }

    function decreasePositionAndSwapETH(address[] memory _path, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address payable _receiver, uint256 _price, uint256 _minOut) external {
        require(_path[_path.length - 1] == weth, "Router: invalid _path");
        uint256 amount = _decreasePosition(_path[0], _indexToken, _collateralDelta, _sizeDelta, _isLong, address(this), _price);
        IERC20(_path[0]).safeTransfer(vault, amount);
        uint256 amountOut = _swap(_path, _minOut, address(this));
        _transferOutETH(amountOut, _receiver);
    }

    function _increasePosition(address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong, uint256 _price) private {
        if (_isLong) {
            require(IVault(vault).getMaxPrice(_indexToken) <= _price, "Router: mark price higher than limit");
        } else {
            require(IVault(vault).getMinPrice(_indexToken) >= _price, "Router: mark price lower than limit");
        }

        IVault(vault).increasePosition(_sender(), _collateralToken, _indexToken, _sizeDelta, _isLong);
    }

    function _decreasePosition(address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver, uint256 _price) private returns (uint256) {
        if (_isLong) {
            require(IVault(vault).getMinPrice(_indexToken) >= _price, "Router: mark price lower than limit");
        } else {
            require(IVault(vault).getMaxPrice(_indexToken) <= _price, "Router: mark price higher than limit");
        }

        return IVault(vault).decreasePosition(_sender(), _collateralToken, _indexToken, _collateralDelta, _sizeDelta, _isLong, _receiver);
    }

    function _transferETHToVault() private {
        IWETH(weth).deposit{value: msg.value}();
        IERC20(weth).safeTransfer(vault, msg.value);
    }

    function _transferOutETH(uint256 _amountOut, address payable _receiver) private {
        IWETH(weth).withdraw(_amountOut);
        _receiver.sendValue(_amountOut);
    }

    function _swap(address[] memory _path, uint256 _minOut, address _receiver) private returns (uint256) {
        if (_path.length == 2) {
            return _vaultSwap(_path[0], _path[1], _minOut, _receiver);
        }
        if (_path.length == 3) {
            uint256 midOut = _vaultSwap(_path[0], _path[1], 0, address(this));
            IERC20(_path[1]).safeTransfer(vault, midOut);
            return _vaultSwap(_path[1], _path[2], _minOut, _receiver);
        }

        revert("Router: invalid _path.length");
    }

    function _vaultSwap(address _tokenIn, address _tokenOut, uint256 _minOut, address _receiver) private returns (uint256) {
        uint256 amountOut;

        if (_tokenOut == usdg) { // buyUSDG
            amountOut = IVault(vault).buyUSDG(_tokenIn, _receiver);
        } else if (_tokenIn == usdg) { // sellUSDG
            amountOut = IVault(vault).sellUSDG(_tokenOut, _receiver);
        } else { // swap
            amountOut = IVault(vault).swap(_tokenIn, _tokenOut, _receiver);
        }

        require(amountOut >= _minOut, "Router: insufficient amountOut");
        return amountOut;
    }

    function _sender() private view returns (address) {
        return msg.sender;
    }

    function _validatePlugin(address _account) private view {
        require(plugins[msg.sender], "Router: invalid plugin");
        require(approvedPlugins[_account][msg.sender], "Router: plugin not approved");
    }
}

// File: contracts/libraries/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

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

        return c;
    }

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

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

        return c;
    }

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

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

        return c;
    }

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

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

        return c;
    }

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

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

// File: contracts/libraries/token/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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: contracts/libraries/token/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

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 IERC20;` 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));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

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

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: contracts/libraries/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.2;

/**
 * @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) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

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

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

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

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/tokens/interfaces/IWETH.sol



//SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IWETH {
    function deposit() external payable;
    function transfer(address to, uint value) external returns (bool);
    function withdraw(uint) external;
}