// File: contracts/interfaces/IKingSwapFactory.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0;

interface IKingSwapFactory {
    event PairCreated(address indexed token0, address indexed token1, address pair, uint);

    function feeTo() external view returns (address);
    function feeToSetter() external view returns (address);
    function migrator() external view returns (address);

    function getPair(address tokenA, address tokenB) external view returns (address pair);
    function allPairs(uint) external view returns (address pair);
    function allPairsLength() external view returns (uint);

    function createPair(address tokenA, address tokenB) external returns (address pair);

    function setFeeTo(address) external;
    function setFeeToSetter(address) external;
    function setMigrator(address) external;
}

// File: contracts/interfaces/IKingSwapPair.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0;

interface IKingSwapPair {
    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;

    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);

    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 stoken() 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 swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
    function dealSlippageWithIn(address[] calldata path, uint amountIn, address to, bool ifmint) external returns (uint amountOut);
    function dealSlippageWithOut(address[] calldata path, uint amountOut, address to, bool ifmint) external returns (uint extra);
    function getAmountOutMarket(address token, uint amountIn) external view returns (uint _out, uint t0Price);
    function getAmountInMarket(address token, uint amountOut) external view returns (uint _in, uint t0Price);
    function getAmountOutFinal(address token, uint256 amountIn) external view returns (uint256 amountOut, uint256 stokenAmount);
    function getAmountInFinal(address token, uint256 amountOut) external view returns (uint256 amountIn, uint256 stokenAmount);
    function getTokenMarketPrice(address token) external view returns (uint price);
}

// File: contracts/interfaces/IKingSwapRouter.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.2;

interface IKingSwapRouter {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB
        );

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountToken,
            uint256 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
        returns (
            uint256 amountA,
            uint256 amountB
        );

    function removeLiquidityETHWithPermit(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
        returns (
            uint256 amountToken,
            uint256 amountETH
        );

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external returns (uint256[] memory amounts);

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external returns (uint256[] memory amounts);

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external payable returns (uint256[] memory amounts);

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external returns (uint256[] memory amounts);

    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external returns (uint256[] memory amounts);

    function swapETHForExactTokens(
        uint256 amountOut,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external payable returns (uint256[] memory amounts);

    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure returns (uint256 amountB);

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountOut);

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountIn);

    function getAmountsOut(uint256 amountIn, address[] calldata path) external view returns (uint256[] memory amounts);

    function getAmountsIn(uint256 amountOut, address[] calldata path) external view returns (uint256[] memory amounts);

    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountETH);

    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountETH);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external;

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external payable;

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external;
}

// File: contracts/interfaces/IWETH.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0;

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

// File: contracts/kingswap/KingSwapRouter.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity =0.6.12;

import "../interfaces/IKingSwapFactory.sol";
import "./libraries/TransferHelper.sol";
import "../interfaces/IKingSwapRouter.sol";
import "./libraries/KingSwapLibrary.sol";
import "./libraries/SafeMath.sol";
import "./interfaces/IERC20.sol";
import "../interfaces/IWETH.sol";

contract KingSwapRouter is IKingSwapRouter {
    using SafeMath for uint256;

    address public immutable override factory;
    address public immutable override WETH;

    modifier ensure(uint256 deadline) {
        require(deadline >= block.timestamp, "KingSwapRouter: EXPIRED");
        _;
    }

    constructor(address _factory, address _WETH) public {
        factory = _factory;
        WETH = _WETH;
    }

    receive() external payable {
        assert(msg.sender == WETH); // only accept ETH via fallback from the WETH contract
    }

    // **** 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 (IKingSwapFactory(factory).getPair(tokenA, tokenB) == address(0)) {
            IKingSwapFactory(factory).createPair(tokenA, tokenB);
        }
        (uint256 reserveA, uint256 reserveB) = KingSwapLibrary.getReserves(factory, tokenA, tokenB);
        if (reserveA == 0 && reserveB == 0) {
            (amountA, amountB) = (amountADesired, amountBDesired);
        } else {
            uint256 amountBOptimal = KingSwapLibrary.quote(amountADesired, reserveA, reserveB);
            if (amountBOptimal <= amountBDesired) {
                require(amountBOptimal >= amountBMin, "KingSwapRouter: INSUFFICIENT_B_AMOUNT");
                (amountA, amountB) = (amountADesired, amountBOptimal);
            } else {
                uint256 amountAOptimal = KingSwapLibrary.quote(amountBDesired, reserveB, reserveA);
                assert(amountAOptimal <= amountADesired);
                require(amountAOptimal >= amountAMin, "KingSwapRouter: 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 = KingSwapLibrary.pairFor(factory, tokenA, tokenB);
        TransferHelper.safeTransferFrom(tokenA, msg.sender, pair, amountA);
        TransferHelper.safeTransferFrom(tokenB, msg.sender, pair, amountB);
        liquidity = IKingSwapPair(pair).mint(to);
    }

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        virtual
        override
        payable
        ensure(deadline)
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        )
    {
        (amountToken, amountETH) = _addLiquidity(
            token,
            WETH,
            amountTokenDesired,
            msg.value,
            amountTokenMin,
            amountETHMin
        );
        address pair = KingSwapLibrary.pairFor(factory, token, WETH);
        TransferHelper.safeTransferFrom(token, msg.sender, pair, amountToken);
        IWETH(WETH).deposit{value: amountETH}();
        assert(IWETH(WETH).transfer(pair, amountETH));
        liquidity = IKingSwapPair(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 = KingSwapLibrary.pairFor(factory, tokenA, tokenB);
        IKingSwapPair(pair).transferFrom(msg.sender, pair, liquidity); // send liquidity to pair
        (address token0, ) = KingSwapLibrary.sortTokens(tokenA, tokenB);
        if (tokenA == token0) {
            (amountA, amountB) = IKingSwapPair(pair).burn(to);
        } else {
            (amountB, amountA) = IKingSwapPair(pair).burn(to);
        }
        require(amountA >= amountAMin, "KingSwappRouter: INSUFFICIENT_A_AMOUNT");
        require(amountB >= amountBMin, "KingSwapRouter: INSUFFICIENT_B_AMOUNT");
    }

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        public
        virtual
        override
        ensure(deadline)
        returns (
            uint256 amountToken,
            uint256 amountETH
        )
    {
        (amountToken, amountETH) = removeLiquidity(
            token,
            WETH,
            liquidity,
            amountTokenMin,
            amountETHMin,
            address(this),
            deadline
        );
        TransferHelper.safeTransfer(token, to, amountToken);
        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
        )
    {
        IKingSwapPair(KingSwapLibrary.pairFor(factory, tokenA, tokenB)).permit(
            msg.sender,
            address(this),
            approveMax ? uint256(-1) : liquidity,
            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 = KingSwapLibrary.pairFor(factory, token, WETH);
        uint256 value = approveMax ? uint256(-1) : liquidity;
        IKingSwapPair(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);
    }

    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 = KingSwapLibrary.pairFor(factory, token, WETH);
        uint256 value = approveMax ? uint256(-1) : liquidity;
        IKingSwapPair(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, ) = KingSwapLibrary.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 ? KingSwapLibrary.pairFor(factory, output, path[i + 2]) : _to;
            IKingSwapPair(KingSwapLibrary.pairFor(factory, input, output)).swap(
                amount0Out,
                amount1Out,
                to,
                new bytes(0)
            );
        }
    }

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        amounts = KingSwapLibrary.getAmountsOut(factory, amountIn, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        TransferHelper.safeTransferFrom(path[0], msg.sender, pair, amounts[0]);
        if (path.length == 2) {
            amounts[1] = IKingSwapPair(pair).dealSlippageWithIn(path, amounts[0], to, ifmint);
        }
        require(amounts[amounts.length - 1] >= amountOutMin, "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT");
        _swap(amounts, path, to);
    }

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        amounts = KingSwapLibrary.getAmountsIn(factory, amountOut, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        if (path.length == 2) {
            uint256 extra = IKingSwapPair(pair).dealSlippageWithOut(path, amountOut, to, ifmint);
            amounts[0] = amounts[0].add(extra);
        }
        require(amounts[0] <= amountInMax, "KingSwapRouter: EXCESSIVE_INPUT_AMOUNT");
        TransferHelper.safeTransferFrom(path[0], msg.sender, pair, amounts[0]);
        _swap(amounts, path, to);
    }

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override payable ensure(deadline) returns (uint256[] memory amounts) {
        require(path[0] == WETH, "KingSwapRouter: INVALID_PATH");
        amounts = KingSwapLibrary.getAmountsOut(factory, msg.value, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        IWETH(WETH).deposit{value: amounts[0]}();
        assert(IWETH(WETH).transfer(pair, amounts[0]));
        if (path.length == 2) {
            amounts[1] = IKingSwapPair(pair).dealSlippageWithIn(path, amounts[0], to, ifmint);
        }
        require(amounts[amounts.length - 1] >= amountOutMin, "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT");
        _swap(amounts, path, to);
    }

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        require(path[path.length - 1] == WETH, "KingSwapRouter: INVALID_PATH");
        amounts = KingSwapLibrary.getAmountsIn(factory, amountOut, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        if (path.length == 2) {
            uint256 extra = IKingSwapPair(pair).dealSlippageWithOut(path, amountOut, to, ifmint);
            amounts[0] = amounts[0].add(extra);
        }
        require(amounts[0] <= amountInMax, "KingSwapRouter: EXCESSIVE_INPUT_AMOUNT");
        TransferHelper.safeTransferFrom(path[0], msg.sender, pair, 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,
        bool ifmint
    ) external virtual override ensure(deadline) returns (uint256[] memory amounts) {
        require(path[path.length - 1] == WETH, "KingSwapRouter: INVALID_PATH");
        amounts = KingSwapLibrary.getAmountsOut(factory, amountIn, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        TransferHelper.safeTransferFrom(path[0], msg.sender, pair, amounts[0]);
        if (path.length == 2) {
            amounts[1] = IKingSwapPair(pair).dealSlippageWithIn(path, amounts[0], to, ifmint);
        }
        require(amounts[amounts.length - 1] >= amountOutMin, "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT");
        _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,
        bool ifmint
    ) external virtual override payable ensure(deadline) returns (uint256[] memory amounts) {
        require(path[0] == WETH, "KingSwapRouter: INVALID_PATH");
        amounts = KingSwapLibrary.getAmountsIn(factory, amountOut, path);
        address pair = KingSwapLibrary.pairFor(factory, path[0], path[1]);
        if (path.length == 2) {
            uint256 extra = IKingSwapPair(pair).dealSlippageWithOut(path, amountOut, to, ifmint);
            amounts[0] = amounts[0].add(extra);
        }
        IWETH(WETH).deposit{value: amounts[0]}();
        assert(IWETH(WETH).transfer(pair, 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,
        bool ifmint
    ) internal virtual {
        for (uint256 i; i < path.length - 1; i++) {
            (address token0, ) = KingSwapLibrary.sortTokens(path[i], path[i + 1]);
            IKingSwapPair pair = IKingSwapPair(KingSwapLibrary.pairFor(factory, path[i], path[i + 1]));
            uint256 amountOutput;
            {
                // scope to avoid stack too deep errors
                (uint256 reserve0, uint256 reserve1, ) = pair.getReserves();
                (uint256 reserveInput, uint256 reserveOutput) = path[i] == token0
                    ? (reserve0, reserve1)
                    : (reserve1, reserve0);
                uint256 amountInput = IERC20(path[i]).balanceOf(address(pair)).sub(reserveInput);
                if (path.length == 2) {
                    amountOutput = pair.dealSlippageWithIn(path, amountInput, _to, ifmint);
                } else {
                    amountOutput = KingSwapLibrary.getAmountOut(amountInput, reserveInput, reserveOutput);
                }
            }
            (uint256 amount0Out, uint256 amount1Out) = path[i] == token0
                ? (uint256(0), amountOutput)
                : (amountOutput, uint256(0));
            address to = i < path.length - 2 ? KingSwapLibrary.pairFor(factory, path[i + 1], path[i + 2]) : _to;
            pair.swap(amount0Out, amount1Out, to, new bytes(0));
        }
    }

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override ensure(deadline) {
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            KingSwapLibrary.pairFor(factory, path[0], path[1]),
            amountIn
        );
        uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
        _swapSupportingFeeOnTransferTokens(path, to, ifmint);
        require(
            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
            "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT"
        );
    }

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override payable ensure(deadline) {
        require(path[0] == WETH, "KingSwapRouter: INVALID_PATH");
        uint256 amountIn = msg.value;
        IWETH(WETH).deposit{value: amountIn}();
        assert(IWETH(WETH).transfer(KingSwapLibrary.pairFor(factory, path[0], path[1]), amountIn));
        uint256 balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
        _swapSupportingFeeOnTransferTokens(path, to, ifmint);
        require(
            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
            "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT"
        );
    }

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline,
        bool ifmint
    ) external virtual override ensure(deadline) {
        require(path[path.length - 1] == WETH, "KingSwapRouter: INVALID_PATH");
        TransferHelper.safeTransferFrom(
            path[0],
            msg.sender,
            KingSwapLibrary.pairFor(factory, path[0], path[1]),
            amountIn
        );
        _swapSupportingFeeOnTransferTokens(path, address(this), ifmint);
        uint256 amountOut = IERC20(WETH).balanceOf(address(this));
        require(amountOut >= amountOutMin, "KingSwapRouter: INSUFFICIENT_OUTPUT_AMOUNT");
        IWETH(WETH).withdraw(amountOut);
        TransferHelper.safeTransferETH(to, amountOut);
    }

    // **** LIBRARY FUNCTIONS ****
    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) public virtual override pure returns (uint256 amountB) {
        return KingSwapLibrary.quote(amountA, reserveA, reserveB);
    }

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) public virtual override pure returns (uint256 amountOut) {
        return KingSwapLibrary.getAmountOut(amountIn, reserveIn, reserveOut);
    }

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) public virtual override pure returns (uint256 amountIn) {
        return KingSwapLibrary.getAmountIn(amountOut, reserveIn, reserveOut);
    }

    function getAmountsOut(uint256 amountIn, address[] memory path)
        public
        virtual
        override
        view
        returns (uint256[] memory amounts)
    {
        return KingSwapLibrary.getAmountsOut(factory, amountIn, path);
    }

    function getAmountsIn(uint256 amountOut, address[] memory path)
        public
        virtual
        override
        view
        returns (uint256[] memory amounts)
    {
        return KingSwapLibrary.getAmountsIn(factory, amountOut, path);
    }
}

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



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0;

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);
    function mint(address to, uint value) external returns (bool);
    function burn(address from, uint value) external returns (bool);
}

// File: contracts/kingswap/libraries/KingSwapLibrary.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0;

import '../../interfaces/IKingSwapPair.sol';
import './SafeMath.sol';

library KingSwapLibrary {
    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, 'KingSwapLibrary: IDENTICAL_ADDRESSES');
        (token0, token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        require(token0 != address(0), 'KingSwapLibrary: 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'b766a1c755935658001853a78ea8c0fff7929f287e3a93a2d64bbf31efe48ba2' // init code hash
                    )
                )
            )
        );
    }

    // 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, ) = IKingSwapPair(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, 'KingSwapLibrary: INSUFFICIENT_AMOUNT');
        require(reserveA > 0 && reserveB > 0, 'KingSwapLibrary: 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, 'KingSwapLibrary: INSUFFICIENT_INPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'KingSwapLibrary: INSUFFICIENT_LIQUIDITY');
        uint256 amountInWithFee = amountIn.mul(9975);
        uint256 numerator = amountInWithFee.mul(reserveOut);
        uint256 denominator = reserveIn.mul(10000).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, 'KingSwapLibrary: INSUFFICIENT_OUTPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'KingSwapLibrary: INSUFFICIENT_LIQUIDITY');
        uint256 numerator = reserveIn.mul(amountOut).mul(10000);
        uint256 denominator = reserveOut.sub(amountOut).mul(9975);
        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, 'KingSwapLibrary: 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, 'KingSwapLibrary: 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/kingswap/libraries/SafeMath.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity =0.6.12;

// 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');
    }
}

// File: contracts/kingswap/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, uint 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: APPROVE_FAILED');
    }

    function safeTransfer(address token, address to, uint 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: TRANSFER_FAILED');
    }

    function safeTransferFrom(address token, address from, address to, uint 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: TRANSFER_FROM_FAILED');
    }

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