// File: /contracts/UniswapV2Router02.sol



pragma solidity =0.6.6;

// import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
import './interfaces/IUniswapV2Pair.sol';
import './interfaces/IUniswapV2Factory.sol';
import '@uniswap/lib/contracts/libraries/TransferHelper.sol';

import './interfaces/IUniswapV2Router02.sol';
import './libraries/UniswapV2Library.sol';
import './libraries/SafeMath.sol';
import './interfaces/IERC20.sol';
import './interfaces/IWETH.sol';

contract UniswapV2Router02 is IUniswapV2Router02 {
    using SafeMath for uint256;
    // string public name = 'PolkaBridgeAMM: Router';
    address public immutable override factory;
    address public immutable override WETH;
    // address public owner;
    // string public debugStr;

    modifier ensure(uint256 deadline) {
        require(deadline >= block.timestamp, 'UniswapV2Router: EXPIRED');
        _;
    }

    // modifier onlyOwner() {
    //     require(msg.sender == owner, 'Only Owner');
    //     _;
    // }
    constructor(address _factory, address _WETH) public {
        factory = _factory;
        WETH = _WETH;
        // owner = msg.sender;
    }

    receive() external payable {
        require(msg.sender == WETH, 'transfer ETH from unexpected sender'); // only accept ETH via fallback from the WETH contract
    }

    // function transferOwnership(address _new_owner) public onlyOwner {
    //     owner = _new_owner;
    // }

    // **** ADD LIQUIDITY ****
    function _addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin
    ) internal virtual returns (uint256 amountA, uint256 amountB) {
        // create the pair if it doesn't exist yet
        if (IUniswapV2Factory(factory).getPair(tokenA, tokenB) == address(0)) {
            IUniswapV2Factory(factory).createPair(tokenA, tokenB);
        }
        (uint256 reserveA, uint256 reserveB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
        if (reserveA == 0 && reserveB == 0) {
            (amountA, amountB) = (amountADesired, amountBDesired);
        } else {
            uint256 amountBOptimal = UniswapV2Library.quote(amountADesired, reserveA, reserveB);
            if (amountBOptimal <= amountBDesired) {
                require(amountBOptimal >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
                (amountA, amountB) = (amountADesired, amountBOptimal);
            } else {
                uint256 amountAOptimal = UniswapV2Library.quote(amountBDesired, reserveB, reserveA);
                require(amountAOptimal <= amountADesired, 'amountA should less or equal than amountB'); // assert(amountAOptimal <= amountADesired);
                require(amountAOptimal >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
                (amountA, amountB) = (amountAOptimal, amountBDesired);
            }
        }
    }

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        virtual
        override
        ensure(deadline)
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        (amountA, amountB) = _addLiquidity(tokenA, tokenB, amountADesired, amountBDesired, amountAMin, amountBMin);
        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);

        TransferHelper.safeTransferFrom(tokenA, msg.sender, pair, amountA);
        TransferHelper.safeTransferFrom(tokenB, msg.sender, pair, amountB);
        liquidity = IUniswapV2Pair(pair).mint(to);
    }

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        virtual
        override
        ensure(deadline)
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        )
    {
        (amountToken, amountETH) = _addLiquidity(
            token,
            WETH,
            amountTokenDesired,
            msg.value,
            amountTokenMin,
            amountETHMin
        );
        address pair = UniswapV2Library.pairFor(factory, token, WETH);
        TransferHelper.safeTransferFrom(token, msg.sender, pair, amountToken);
        IWETH(WETH).deposit{value: amountETH}();
        require(IWETH(WETH).transfer(pair, amountETH), 'WETH transfer failed in addLiquidityETH'); // assert(IWETH(WETH).transfer(pair, amountETH));
        liquidity = IUniswapV2Pair(pair).mint(to);
        // refund dust eth, if any
        if (msg.value > amountETH) TransferHelper.safeTransferETH(msg.sender, msg.value - amountETH);
    }

    // **** REMOVE LIQUIDITY ****
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) public virtual override ensure(deadline) returns (uint256 amountA, uint256 amountB) {
        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
        bool bTransfered = IUniswapV2Pair(pair).transferFrom(msg.sender, pair, liquidity);
        require(bTransfered, 'Failed in sending liquidity to pair'); // send liquidity to pair
        (uint256 amount0, uint256 amount1) = IUniswapV2Pair(pair).burn(to);
        (address token0, ) = UniswapV2Library.sortTokens(tokenA, tokenB);
        (amountA, amountB) = tokenA == token0 ? (amount0, amount1) : (amount1, amount0);
        require(amountA >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
        require(amountB >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
    }

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external virtual override ensure(deadline) returns (uint256 amountToken, uint256 amountETH) {
        (amountToken, amountETH) = removeLiquidity(
            token,
            WETH,
            liquidity,
            amountTokenMin,
            amountETHMin,
            address(this),
            deadline
        );
        TransferHelper.safeTransfer(token, to, IERC20(token).balanceOf(address(this)));
        IWETH(WETH).withdraw(amountETH);
        TransferHelper.safeTransferETH(to, amountETH);
    }

    // function removeLiquidityWithPermit(
    //     address tokenA,
    //     address tokenB,
    //     uint256 liquidity,
    //     uint256 amountAMin,
    //     uint256 amountBMin,
    //     address to,
    //     uint256 deadline,
    //     bool approveMax,
    //     uint8 v,
    //     bytes32 r,
    //     bytes32 s
    // ) external virtual override returns (uint256 amountA, uint256 amountB) {
    //     address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
    //     uint256 value = approveMax ? uint256(-1) : liquidity;
    //     IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
    //     (amountA, amountB) = removeLiquidity(tokenA, tokenB, liquidity, amountAMin, amountBMin, to, deadline);
    // }

    // function removeLiquidityETHWithPermit(
    //     address token,
    //     uint256 liquidity,
    //     uint256 amountTokenMin,
    //     uint256 amountETHMin,
    //     address to,
    //     uint256 deadline,
    //     bool approveMax,
    //     uint8 v,
    //     bytes32 r,
    //     bytes32 s
    // ) external virtual override returns (uint256 amountToken, uint256 amountETH) {
    //     address pair = UniswapV2Library.pairFor(factory, token, WETH);
    //     uint256 value = approveMax ? uint256(-1) : liquidity;
    //     IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
    //     (amountToken, amountETH) = removeLiquidityETH(token, liquidity, amountTokenMin, amountETHMin, to, deadline);
    // }

    // **** REMOVE LIQUIDITY (supporting fee-on-transfer tokens) ****
    // function removeLiquidityETHSupportingFeeOnTransferTokens(
    //     address token,
    //     uint256 liquidity,
    //     uint256 amountTokenMin,
    //     uint256 amountETHMin,
    //     address to,
    //     uint256 deadline
    // ) public virtual override ensure(deadline) returns (uint256 amountETH) {
    //     // (, amountETH) = removeLiquidity(token, WETH, liquidity, amountTokenMin, amountETHMin, address(this), deadline);
    //     // TransferHelper.safeTransfer(token, to, IERC20(token).balanceOf(address(this)));
    //     // IWETH(WETH).withdraw(amountETH);
    //     // TransferHelper.safeTransferETH(to, amountETH);
    //     (, amountETH) = removeLiquidityETH(token, liquidity, amountTokenMin, amountETHMin, to, deadline);
    // }

    // function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
    //     address token,
    //     uint256 liquidity,
    //     uint256 amountTokenMin,
    //     uint256 amountETHMin,
    //     address to,
    //     uint256 deadline,
    //     bool approveMax,
    //     uint8 v,
    //     bytes32 r,
    //     bytes32 s
    // ) external virtual override returns (uint256 amountETH) {
    //     address pair = UniswapV2Library.pairFor(factory, token, WETH);
    //     uint256 value = approveMax ? uint256(-1) : liquidity;
    //     IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
    //     amountETH = removeLiquidityETHSupportingFeeOnTransferTokens(
    //         token,
    //         liquidity,
    //         amountTokenMin,
    //         amountETHMin,
    //         to,
    //         deadline
    //     );
    // }

    // **** SWAP ****
    // requires the initial amount to have already been sent to the first pair
    function _swap(
        uint256[] memory amounts,
        address[] memory path,
        address _to
    ) internal virtual {
        for (uint256 i; i < path.length - 1; i++) {
            (address input, address output) = (path[i], path[i + 1]);
            (address token0, ) = UniswapV2Library.sortTokens(input, output);
            uint256 amountOut = amounts[i + 1];
            (uint256 amount0Out, uint256 amount1Out) = input == token0
                ? (uint256(0), amountOut)
                : (amountOut, uint256(0));
            address to = i < path.length - 2 ? UniswapV2Library.pairFor(factory, output, path[i + 2]) : _to;
            IUniswapV2Pair(UniswapV2Library.pairFor(factory, input, output)).swap(amount0Out, amount1Out, to);
        }
    }

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external virtual override ensure(deadline) { //returns (uint256[] memory amounts) {
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            UniswapV2Library.pairFor(factory, path[0], path[1]),
            amountIn
        );
        uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
        _swapSupportingFeeOnTransferTokens(path, to);
        require(
            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
            'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
        );
        // amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
        // require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
        // TransferHelper.safeTransferFrom(
        //     path[0],
        //     msg.sender,
        //     UniswapV2Library.pairFor(factory, path[0], path[1]),
        //     // amounts[0]
        //     amountIn
        // );
        // _swap(amounts, path, to);
    }

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            UniswapV2Library.pairFor(factory, path[0], path[1]),
            amounts[0]
        );
        _swap(amounts, path, to);
    }

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable virtual override ensure(deadline) { //returns (uint256[] memory amounts) {
        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
        uint256 amountIn = msg.value;
        IWETH(WETH).deposit{value: amountIn}();
        require(
            IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn),
            'UniswapV2Router: WETH transfer failed in swapExactETHForTokens'
        ); // assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn));
        uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
        _swapSupportingFeeOnTransferTokens(path, to);
        require(
            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
            'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
        );
        // require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
        // amounts = UniswapV2Library.getAmountsOut(factory, msg.value, path);
        // require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
        // // IWETH(WETH).deposit{value: amounts[0]}();
        // IWETH(WETH).deposit{value: msg.value}();
        // require(
        //     // IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]),
        //     IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), msg.value),
        //     'UniswapV2Router: WETH transfer failed in swapExactETHForTokens'
        // ); // assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
        // _swap(amounts, path, to);
    }

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            UniswapV2Library.pairFor(factory, path[0], path[1]),
            amounts[0]
        );
        _swap(amounts, path, address(this));
        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
    }

    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external virtual override ensure(deadline) { //returns (uint256[] memory amounts) {
        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            UniswapV2Library.pairFor(factory, path[0], path[1]),
            amountIn
        );
        _swapSupportingFeeOnTransferTokens(path, address(this));
        uint256 amountOut = IERC20(WETH).balanceOf(address(this));
        require(amountOut >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
        IWETH(WETH).withdraw(amountOut);
        TransferHelper.safeTransferETH(to, amountOut);
        // require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
        // amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
        // require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
        // TransferHelper.safeTransferFrom(
        //     path[0],
        //     msg.sender,
        //     UniswapV2Library.pairFor(factory, path[0], path[1]),
        //     // amounts[0]
        //     amountIn
        // );
        // _swap(amounts, path, address(this));
        // IWETH(WETH).withdraw(amounts[amounts.length - 1]);
        // TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
    }

    function swapETHForExactTokens(
        uint256 amountOut,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable virtual override ensure(deadline) returns (uint256[] memory amounts) {
        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
        require(amounts[0] <= msg.value, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
        IWETH(WETH).deposit{value: amounts[0]}();
        require(
            IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]),
            'UniswapV2Router: WETH transfer failed in swapETHForExactTokens'
        ); // assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
        _swap(amounts, path, to);
        // refund dust eth, if any
        if (msg.value > amounts[0]) TransferHelper.safeTransferETH(msg.sender, msg.value - amounts[0]);
    }

    // **** SWAP (supporting fee-on-transfer tokens) ****
    // requires the initial amount to have already been sent to the first pair
    function _swapSupportingFeeOnTransferTokens(address[] memory path, address _to) internal virtual {
        for (uint256 i; i < path.length - 1; i++) {
            (address input, address output) = (path[i], path[i + 1]);
            (address token0, ) = UniswapV2Library.sortTokens(input, output);
            IUniswapV2Pair pair = IUniswapV2Pair(UniswapV2Library.pairFor(factory, input, output));
            uint256 amountInput;
            uint256 amountOutput;
            {
                // scope to avoid stack too deep errors
                (uint256 reserve0, uint256 reserve1, ) = pair.getReserves();
                (uint256 reserveInput, uint256 reserveOutput) = input == token0
                    ? (reserve0, reserve1)
                    : (reserve1, reserve0);
                amountInput = IERC20(input).balanceOf(address(pair)).sub(reserveInput);
                amountOutput = UniswapV2Library.getAmountOut(amountInput, reserveInput, reserveOutput);
            }
            (uint256 amount0Out, uint256 amount1Out) = input == token0
                ? (uint256(0), amountOutput)
                : (amountOutput, uint256(0));
            address to = i < path.length - 2 ? UniswapV2Library.pairFor(factory, output, path[i + 2]) : _to;
            pair.swap(amount0Out, amount1Out, to);
        }
    }

    // function swapExactTokensForTokensSupportingFeeOnTransferTokens(
    //     uint256 amountIn,
    //     uint256 amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint256 deadline
    // ) external virtual override ensure(deadline) {
    //     TransferHelper.safeTransferFrom(
    //         path[0],
    //         msg.sender,
    //         UniswapV2Library.pairFor(factory, path[0], path[1]),
    //         amountIn
    //     );
    //     uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
    //     _swapSupportingFeeOnTransferTokens(path, to);
    //     require(
    //         IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
    //         'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
    //     );
    // }

    // function swapExactETHForTokensSupportingFeeOnTransferTokens(
    //     uint256 amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint256 deadline
    // ) external payable virtual override ensure(deadline) {
    //     require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
    //     uint256 amountIn = msg.value;
    //     IWETH(WETH).deposit{value: amountIn}();
    //     require(
    //         IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn),
    //         'UniswapV2Router: WETH transfer failed in swapExactETHForTokensSupportingFeeOnTransferTokens'
    //     ); // assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn));
    //     uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
    //     _swapSupportingFeeOnTransferTokens(path, to);
    //     require(
    //         IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
    //         'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
    //     );
    // }

    // function swapExactTokensForETHSupportingFeeOnTransferTokens(
    //     uint256 amountIn,
    //     uint256 amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint256 deadline
    // ) external virtual override ensure(deadline) {
    //     require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
    //     TransferHelper.safeTransferFrom(
    //         path[0],
    //         msg.sender,
    //         UniswapV2Library.pairFor(factory, path[0], path[1]),
    //         amountIn
    //     );
    //     _swapSupportingFeeOnTransferTokens(path, address(this));
    //     uint256 amountOut = IERC20(WETH).balanceOf(address(this));
    //     require(amountOut >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
    //     IWETH(WETH).withdraw(amountOut);
    //     TransferHelper.safeTransferETH(to, amountOut);
    // }

    // **** LIBRARY FUNCTIONS ****
    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure virtual override returns (uint256 amountB) {
        return UniswapV2Library.quote(amountA, reserveA, reserveB);
    }

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure virtual override returns (uint256 amountOut) {
        return UniswapV2Library.getAmountOut(amountIn, reserveIn, reserveOut);
    }

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure virtual override returns (uint256 amountIn) {
        return UniswapV2Library.getAmountIn(amountOut, reserveIn, reserveOut);
    }

    function getAmountsOut(uint256 amountIn, address[] calldata path)
        external
        view
        virtual
        override
        returns (uint256[] memory amounts)
    {
        return UniswapV2Library.getAmountsOut(factory, amountIn, path);
    }

    function getAmountsIn(uint256 amountOut, address[] calldata path)
        external
        view
        virtual
        override
        returns (uint256[] memory amounts)
    {
        return UniswapV2Library.getAmountsIn(factory, amountOut, path);
    }
}

// File: /contracts/libraries/UniswapV2Library.sol



pragma solidity 0.6.6;

// import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
import '../interfaces/IUniswapV2Pair.sol';

import './SafeMath.sol';

library UniswapV2Library {
    using SafeMath for uint256;

    // returns sorted token addresses, used to handle return values from pairs sorted in this order
    function sortTokens(address tokenA, address tokenB) internal pure returns (address token0, address token1) {
        require(tokenA != tokenB, 'UniswapV2Library: IDENTICAL_ADDRESSES');
        (token0, token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        require(token0 != address(0), 'UniswapV2Library: ZERO_ADDRESS');
    }

    // calculates the CREATE2 address for a pair without making any external calls
    function pairFor(
        address factory,
        address tokenA,
        address tokenB
    ) internal pure returns (address pair) {
        (address token0, address token1) = sortTokens(tokenA, tokenB);
        pair = address(
            uint256(
                keccak256(
                    abi.encodePacked(
                        hex'ff',
                        factory,
                        keccak256(abi.encodePacked(token0, token1)),
                        hex'8b59d0fbd3a2da5e26f61e1d4b91f355d2c382ec32c993635b0d80dce6e1ef1c' // init code hash of factory
                    )
                )
            )
        );
    }

    // fetches and sorts the reserves for a pair
    function getReserves(
        address factory,
        address tokenA,
        address tokenB
    ) internal view returns (uint256 reserveA, uint256 reserveB) {
        (address token0, ) = sortTokens(tokenA, tokenB);
        (uint256 reserve0, uint256 reserve1, ) = IUniswapV2Pair(pairFor(factory, tokenA, tokenB)).getReserves();
        (reserveA, reserveB) = tokenA == token0 ? (reserve0, reserve1) : (reserve1, reserve0);
    }

    // given some amount of an asset and pair reserves, returns an equivalent amount of the other asset
    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) internal pure returns (uint256 amountB) {
        require(amountA > 0, 'UniswapV2Library: INSUFFICIENT_AMOUNT');
        require(reserveA > 0 && reserveB > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
        amountB = amountA.mul(reserveB) / reserveA;
    }

    // given an input amount of an asset and pair reserves, returns the maximum output amount of the other asset
    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) internal pure returns (uint256 amountOut) {
        require(amountIn > 0, 'UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
        uint256 amountInWithFee = amountIn.mul(998);
        // uint256 amountInWithFee = amountIn.mul(9984);
        uint256 numerator = amountInWithFee.mul(reserveOut);
        uint256 denominator = reserveIn.mul(1000).add(amountInWithFee);
        amountOut = numerator / denominator;
    }

    // given an output amount of an asset and pair reserves, returns a required input amount of the other asset
    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) internal pure returns (uint256 amountIn) {
        require(amountOut > 0, 'UniswapV2Library: INSUFFICIENT_OUTPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
        // uint256 numerator = reserveIn.mul(amountOut).mul(10000);
        uint256 numerator = reserveIn.mul(amountOut).mul(1000);
        // uint256 denominator = reserveOut.sub(amountOut).mul(9984);
        uint256 denominator = reserveOut.sub(amountOut).mul(998);

        amountIn = (numerator / denominator).add(1);
    }

    // performs chained getAmountOut calculations on any number of pairs
    function getAmountsOut(
        address factory,
        uint256 amountIn,
        address[] memory path
    ) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
        amounts = new uint256[](path.length);
        amounts[0] = amountIn;
        for (uint256 i; i < path.length - 1; i++) {
            (uint256 reserveIn, uint256 reserveOut) = getReserves(factory, path[i], path[i + 1]);
            amounts[i + 1] = getAmountOut(amounts[i], reserveIn, reserveOut);
        }
    }

    // performs chained getAmountIn calculations on any number of pairs
    function getAmountsIn(
        address factory,
        uint256 amountOut,
        address[] memory path
    ) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
        amounts = new uint256[](path.length);
        amounts[amounts.length - 1] = amountOut;
        for (uint256 i = path.length - 1; i > 0; i--) {
            (uint256 reserveIn, uint256 reserveOut) = getReserves(factory, path[i - 1], path[i]);
            amounts[i - 1] = getAmountIn(amounts[i], reserveIn, reserveOut);
        }
    }
}

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



pragma solidity =0.6.6;

// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)

library SafeMath {
    function add(uint x, uint y) internal pure returns (uint z) {
        require((z = x + y) >= x, 'ds-math-add-overflow');
    }

    function sub(uint x, uint y) internal pure returns (uint z) {
        require((z = x - y) <= x, 'ds-math-sub-underflow');
    }

    function mul(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x, 'ds-math-mul-overflow');
    }
    function div(uint x, uint y) internal pure returns (uint z) {
        z = x / y;
    }
}

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



pragma solidity >=0.5.0;

interface IWETH {
    function deposit() external payable;
    function transfer(address to, uint value) external returns (bool);
    function withdraw(uint) external;
}

// File: /contracts/interfaces/IUniswapV2Router02.sol



pragma solidity >=0.6.2;

import './IUniswapV2Router01.sol';

interface IUniswapV2Router02 is IUniswapV2Router01 {
    // function removeLiquidityETHSupportingFeeOnTransferTokens(
    //     address token,
    //     uint liquidity,
    //     uint amountTokenMin,
    //     uint amountETHMin,
    //     address to,
    //     uint deadline
    // ) external returns (uint amountETH);
    // function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
    //     address token,
    //     uint liquidity,
    //     uint amountTokenMin,
    //     uint amountETHMin,
    //     address to,
    //     uint deadline,
    //     bool approveMax, uint8 v, bytes32 r, bytes32 s
    // ) external returns (uint amountETH);

    // function swapExactTokensForTokensSupportingFeeOnTransferTokens(
    //     uint amountIn,
    //     uint amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint deadline
    // ) external;
    // function swapExactETHForTokensSupportingFeeOnTransferTokens(
    //     uint amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint deadline
    // ) external payable;
    // function swapExactTokensForETHSupportingFeeOnTransferTokens(
    //     uint amountIn,
    //     uint amountOutMin,
    //     address[] calldata path,
    //     address to,
    //     uint deadline
    // ) external;
}

// File: /contracts/interfaces/IUniswapV2Router01.sol



pragma solidity >=0.6.2;

interface IUniswapV2Router01 {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    // function removeLiquidityWithPermit(
    //     address tokenA,
    //     address tokenB,
    //     uint liquidity,
    //     uint amountAMin,
    //     uint amountBMin,
    //     address to,
    //     uint deadline,
    //     bool approveMax, uint8 v, bytes32 r, bytes32 s
    // ) external returns (uint amountA, uint amountB);
    // function removeLiquidityETHWithPermit(
    //     address token,
    //     uint liquidity,
    //     uint amountTokenMin,
    //     uint amountETHMin,
    //     address to,
    //     uint deadline,
    //     bool approveMax, uint8 v, bytes32 r, bytes32 s
    // ) external returns (uint amountToken, uint amountETH);
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;// returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        payable;
        // returns (uint[] memory amounts);
    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
        external;
        // returns (uint[] memory amounts);
    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);

    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}

// File: /contracts/interfaces/IUniswapV2Pair.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.6;

import './IUniswapV2ERC20.sol';

interface IUniswapV2Pair is IUniswapV2ERC20 {
    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);
    // event TreasurySet(address _address);

    // function setTreasuryAddress(address _address) external;

    // function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    // function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    // function burnETH(address to, address to1) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to) external;
    // function skim(address to) external;
    function sync() external;    
    function initialize(address, address, address) external;
}

// File: /contracts/interfaces/IUniswapV2Factory.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.6;

interface IUniswapV2Factory {

    event PairCreated(address indexed token0, address indexed token1, address pair, uint);
    event TreasurySet(address _address);
    

    function setTreasuryAddress(address _address) external;
    
    function getPair(address tokenA, address tokenB) external view returns (address pair);
    function allPairs() external view returns (uint);
    // function allPairsLength() external view returns (uint);

    function createPair(address tokenA, address tokenB) external returns (address pair);

}

// File: /contracts/interfaces/IUniswapV2ERC20.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.6;

interface IUniswapV2ERC20 {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
}

// File: /contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.6;

interface IERC20 {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);
}

// File: @uniswap/lib/contracts/libraries/TransferHelper.sol



// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity >=0.6.0;

// helper methods for interacting with ERC20 tokens and sending ETH that do not consistently return true/false
library TransferHelper {
    function safeApprove(
        address token,
        address to,
        uint256 value
    ) internal {
        // bytes4(keccak256(bytes('approve(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x095ea7b3, to, value));
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            'TransferHelper::safeApprove: approve failed'
        );
    }

    function safeTransfer(
        address token,
        address to,
        uint256 value
    ) internal {
        // bytes4(keccak256(bytes('transfer(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            'TransferHelper::safeTransfer: transfer failed'
        );
    }

    function safeTransferFrom(
        address token,
        address from,
        address to,
        uint256 value
    ) internal {
        // bytes4(keccak256(bytes('transferFrom(address,address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd, from, to, value));
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            'TransferHelper::transferFrom: transferFrom failed'
        );
    }

    function safeTransferETH(address to, uint256 value) internal {
        (bool success, ) = to.call{value: value}(new bytes(0));
        require(success, 'TransferHelper::safeTransferETH: ETH transfer failed');
    }
}