/***
 *    ██████╗ ███████╗ ██████╗  ██████╗ 
 *    ██╔══██╗██╔════╝██╔════╝ ██╔═══██╗
 *    ██║  ██║█████╗  ██║  ███╗██║   ██║
 *    ██║  ██║██╔══╝  ██║   ██║██║   ██║
 *    ██████╔╝███████╗╚██████╔╝╚██████╔╝
 *    ╚═════╝ ╚══════╝ ╚═════╝  ╚═════╝ 
 *    
 * https://dego.finance
                                  
* MIT License
* ===========
*
* Copyright (c) 2020 dego
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/// File: @openzeppelin/contracts/math/Math.sol

pragma solidity ^0.5.0;

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

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

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

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

pragma solidity ^0.5.0;

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

        return c;
    }

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

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

        return c;
    }

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

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

        return c;
    }

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

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

        return c;
    }

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

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

// File: @openzeppelin/contracts/introspection/IERC165.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol

pragma solidity ^0.5.0;


/**
 * @dev Required interface of an ERC721 compliant contract.
 */
contract IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of NFTs in `owner`'s account.
     */
    function balanceOf(address owner) public view returns (uint256 balance);

    /**
     * @dev Returns the owner of the NFT specified by `tokenId`.
     */
    function ownerOf(uint256 tokenId) public view returns (address owner);

    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     *
     *
     * Requirements:
     * - `from`, `to` cannot be zero.
     * - `tokenId` must be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this
     * NFT by either {approve} or {setApprovalForAll}.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) public;
    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     * Requirements:
     * - If the caller is not `from`, it must be approved to move this NFT by
     * either {approve} or {setApprovalForAll}.
     */
    function transferFrom(address from, address to, uint256 tokenId) public;
    function approve(address to, uint256 tokenId) public;
    function getApproved(uint256 tokenId) public view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) public;
    function isApprovedForAll(address owner, address operator) public view returns (bool);


    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol

pragma solidity ^0.5.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
contract IERC721Receiver {
    /**
     * @notice Handle the receipt of an NFT
     * @dev The ERC721 smart contract calls this function on the recipient
     * after a {IERC721-safeTransferFrom}. This function MUST return the function selector,
     * otherwise the caller will revert the transaction. The selector to be
     * returned can be obtained as `this.onERC721Received.selector`. This
     * function MAY throw to revert and reject the transfer.
     * Note: the ERC721 contract address is always the message sender.
     * @param operator The address which called `safeTransferFrom` function
     * @param from The address which previously owned the token
     * @param tokenId The NFT identifier which is being transferred
     * @param data Additional data with no specified format
     * @return bytes4 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
     */
    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data)
    public returns (bytes4);
}

// File: contracts/interface/IERC20.sol

pragma solidity ^0.5.5;

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

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

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

    // add mint interface by dego
    function mint(address account, uint amount) external;
    /**
     * @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/interface/IUniswapV2Router01.sol

pragma solidity ^0.5.5;

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 swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    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/interface/IUniswapV2Pair.sol

pragma solidity >=0.5.0;

interface IUniswapV2Pair {
    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 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;
}

// File: contracts/library/UniswapV2Library.sol

pragma solidity >=0.5.0;



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'd0d4c4cd0848c93cb4fd1f498d7013ee6bfb25783ea21593d5834f5d250ece66' // 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, ) = 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(997);
        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(1000);
        uint256 denominator = reserveOut.sub(amountOut).mul(997);
        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: @openzeppelin/contracts/utils/Address.sol

pragma solidity ^0.5.5;

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

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

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

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

// File: contracts/library/SafeERC20.sol

pragma solidity ^0.5.5;





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

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

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

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

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

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

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

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

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

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

// File: contracts/library/ReentrancyGuard.sol

pragma solidity ^0.5.0;

contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }

    function initReentrancyStatus() internal {
        _status = _NOT_ENTERED;
    }
}

// File: contracts/market/NFTMarketV2.sol

pragma solidity ^0.5.5;

pragma experimental ABIEncoderV2;










contract NFTMarketV2 is IERC721Receiver,  ReentrancyGuard {

    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    // --- Data ---
    bool private initialized; // Flag of initialize data

    IERC20 public _dandy = IERC20(0x0);

    struct SalesObject {
        uint256 id;
        uint256 tokenId;
        uint256 startTime;
        uint256 durationTime;
        uint256 maxPrice;
        uint256 minPrice;
        uint256 finalPrice;
        uint8 status;
        address payable seller;
        address payable buyer;
        IERC721 nft;
    }

    uint256 public _salesAmount = 0;

    SalesObject[] _salesObjects;

    uint256 public _minDurationTime = 5 minutes;

    mapping(address => bool) public _seller;
    mapping(address => bool) public _verifySeller;
    mapping(address => bool) public _supportNft;
    bool public _isStartUserSales;

    bool public _isRewardSellerDandy = false;
    bool public _isRewardBuyerDandy = false;

    uint256 public _sellerRewardDandy = 1e15;
    uint256 public _buyerRewardDandy = 1e15;

    uint256 public _tipsFeeRate = 20;
    uint256 public _baseRate = 1000;
    address payable _tipsFeeWallet;

    event eveSales(
        uint256 indexed id, 
        uint256 tokenId,
        address buyer, 
        uint256 finalPrice, 
        uint256 tipsFee
    );

    event eveNewSales(
        uint256 indexed id,
        uint256 tokenId, 
        address seller, 
        address nft,
        address buyer, 
        uint256 startTime,
        uint256 durationTime,
        uint256 maxPrice, 
        uint256 minPrice,
        uint256 finalPrice
    );

    event eveCancelSales(
        uint256 indexed id,
        uint256 tokenId
    );

    event eveNFTReceived(address operator, address from, uint256 tokenId, bytes data);

    address public _governance;

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

    mapping(uint256 => address) public _saleOnCurrency;


    mapping(address => bool) public _supportCurrency;


    mapping(address => SupportBuyCurrency) public _supportBuyCurrency;


    mapping(uint256=>uint256) public deflationBaseRates;
    mapping(uint256=>address) public routers;
    // IUniswapV2Router01[] public routers;

    struct SupportBuyCurrency {
        bool status;
        bool isDeflation;
        uint256 deflationRate;
    }

    
    
    
    event eveSupportCurrency(
        address currency, 
        bool support
    );

    event eveSupportBuyCurrency(
        address currency, 
        bool status,
        bool isDeflation,
        uint256 deflationRate
    );

    event eveDeflationBaseRate(
        uint256 deflationBaseRate
    );

    constructor() public {
        _governance = tx.origin;
    }
    function() external payable {}
    // --- Init ---
    function initialize(
        address payable tipsFeeWallet,
        uint256 minDurationTime,
        uint256 tipsFeeRate,
        uint256 baseRate
    ) public {
        require(!initialized, "initialize: Already initialized!");
        _governance = msg.sender;
        _tipsFeeWallet = tipsFeeWallet;
        _minDurationTime = minDurationTime;
        _tipsFeeRate = tipsFeeRate;
        _baseRate = baseRate;
        initReentrancyStatus();
        initialized = true;
    }


    modifier onlyGovernance {
        require(msg.sender == _governance, "not governance");
        _;
    }

    function setGovernance(address governance)  public  onlyGovernance
    {
        require(governance != address(0), "new governance the zero address");
        emit GovernanceTransferred(_governance, governance);
        _governance = governance;
    }


    /**
     * check address
     */
    modifier validAddress( address addr ) {
        require(addr != address(0x0));
        _;
    }

    modifier checkindex(uint index) {
        require(index <= _salesObjects.length, "overflow");
        _;
    }

    modifier checkSupportBuyCurrendy(address currency) {
        SupportBuyCurrency memory supportBuyCurrency = _supportBuyCurrency[currency];
        require(supportBuyCurrency.status == true, "not support currency");
        _;
    }

    modifier checkTime(uint index) {
        require(index <= _salesObjects.length, "overflow");
        SalesObject storage obj = _salesObjects[index];
        require(obj.startTime <= now, "!open");
        _;
    }


    modifier mustNotSellingOut(uint index) {
        require(index <= _salesObjects.length, "overflow");
        SalesObject storage obj = _salesObjects[index];
        require(obj.buyer == address(0x0) && obj.status == 0, "sry, selling out");
        _;
    }

    modifier onlySalesOwner(uint index) {
        require(index <= _salesObjects.length, "overflow");
        SalesObject storage obj = _salesObjects[index];
        require(obj.seller == msg.sender || msg.sender == _governance, "author & governance");
        _;
    }

    function seize(IERC20 asset) external onlyGovernance returns (uint256 balance) {
        balance = asset.balanceOf(address(this));
        asset.safeTransfer(_governance, balance);
    }


    function setIUniswapV2Router01(address router_) public onlyGovernance {
        routers[0] = router_;
    }

    function setSellerRewardDandy(uint256 rewardDandy) public onlyGovernance {
        _sellerRewardDandy = rewardDandy;
    }

    function setBuyerRewardDandy(uint256 rewardDandy) public onlyGovernance {
        _buyerRewardDandy = rewardDandy;
    }

    function addSupportNft(address nft) public onlyGovernance validAddress(nft) {
        _supportNft[nft] = true;
    }

    function removeSupportNft(address nft) public onlyGovernance validAddress(nft) {
        _supportNft[nft] = false;
    }

    function addSeller(address seller) public onlyGovernance validAddress(seller) {
        _seller[seller] = true;
    }

    function removeSeller(address seller) public onlyGovernance validAddress(seller) {
        _seller[seller] = false;
    }
    
    function addSupportCurrency(address erc20) public onlyGovernance {
        require(_supportCurrency[erc20] == false, "the currency have support");
        _supportCurrency[erc20] = true;
        emit eveSupportCurrency(erc20, true);
    }

    function removeSupportCurrency(address erc20) public onlyGovernance {
        require(_supportCurrency[erc20], "the currency can not remove");
        _supportCurrency[erc20] = false;
        emit eveSupportCurrency(erc20, false);
    }


    function setSupportBuyCurrency(address erc20,bool status,bool isDeflation,uint256 deflationRate ) public onlyGovernance {
        if (isDeflation) {
            require(deflationRate >0, "deflationRate 0");
        }
        _supportBuyCurrency[erc20] = SupportBuyCurrency(status,isDeflation,deflationRate);
        emit eveSupportBuyCurrency(erc20,status,isDeflation,deflationRate);
    }

    function setDeflationBaseRate(uint256 deflationRate_) public onlyGovernance {
        deflationBaseRates[0] = deflationRate_;
        emit eveDeflationBaseRate(deflationRate_);
    }


    function addVerifySeller(address seller) public onlyGovernance validAddress(seller) {
        _verifySeller[seller] = true;
    }

    function removeVerifySeller(address seller) public onlyGovernance validAddress(seller) {
        _verifySeller[seller] = false;
    }

    function setIsStartUserSales(bool isStartUserSales) public onlyGovernance {
        _isStartUserSales = isStartUserSales;
    }

    function setIsRewardSellerDandy(bool isRewardSellerDandy) public onlyGovernance {
        _isRewardSellerDandy = isRewardSellerDandy;
    }

    function setIsRewardBuyerDandy(bool isRewardBuyerDandy) public onlyGovernance {
        _isRewardBuyerDandy = isRewardBuyerDandy;
    }

    function setMinDurationTime(uint256 durationTime) public onlyGovernance {
        _minDurationTime = durationTime;
    }

    function setTipsFeeWallet(address payable wallet) public onlyGovernance {
        _tipsFeeWallet = wallet;
    }

    function setDandyAddress(address addr) external onlyGovernance validAddress(addr) {
        _dandy = IERC20(addr);
    }

    function setBaseRate(uint256 rate) external onlyGovernance {
        _baseRate = rate;
    }

    function setTipsFeeRate(uint256 rate) external onlyGovernance {
        _tipsFeeRate = rate;
    }



    function getSalesEndTime(uint index) 
        external
        view
        checkindex(index)
        returns (uint256) 
    {
        SalesObject storage obj = _salesObjects[index];
        return obj.startTime.add(obj.durationTime);
    }

    function getSales(uint index) external view checkindex(index) returns(SalesObject memory) {
        return _salesObjects[index];
    }

    function getSalesPrice(uint index)
        external
        view
        checkindex(index)
        returns (uint256)
    {
        SalesObject storage obj = _salesObjects[index];
        if(obj.buyer != address(0x0) || obj.status == 1) {
            return obj.finalPrice;
        } else {
            if(obj.startTime.add(obj.durationTime) < now) {
                return obj.minPrice;
            } else if (obj.startTime >= now) {
                return obj.maxPrice;
            } else {
                uint256 per = obj.maxPrice.sub(obj.minPrice).div(obj.durationTime);
                return obj.maxPrice.sub(now.sub(obj.startTime).mul(per));
            }
        }
    }

    

    function isVerifySeller(uint index) public view checkindex(index) returns(bool) {
        SalesObject storage obj = _salesObjects[index];
        return _verifySeller[obj.seller];
    }

    function cancelSales(uint index) external checkindex(index) onlySalesOwner(index) mustNotSellingOut(index) nonReentrant {
        require(_isStartUserSales || _seller[msg.sender] == true, "cannot sales");
        SalesObject storage obj = _salesObjects[index];
        obj.status = 2;
        obj.nft.safeTransferFrom(address(this), obj.seller, obj.tokenId);

        emit eveCancelSales(index, obj.tokenId);
    }

    function startSales(uint256 tokenId,
                        uint256 maxPrice, 
                        uint256 minPrice,
                        uint256 startTime, 
                        uint256 durationTime,
                        address nft,
                        address currency)
        external 
        nonReentrant
        validAddress(nft)
        returns(uint)
    {
        require(tokenId != 0, "invalid token");
        require(startTime.add(durationTime) > now, "invalid start time");
        require(durationTime >= _minDurationTime, "invalid duration");
        require(maxPrice >= minPrice, "invalid price");
        require(_isStartUserSales || _seller[msg.sender] == true || _supportNft[nft] == true, "cannot sales");
        require(_supportCurrency[currency] == true, "not support currency");

        IERC721(nft).safeTransferFrom(msg.sender, address(this), tokenId);

        _salesAmount++;
        SalesObject memory obj;

        obj.id = _salesAmount;
        obj.tokenId = tokenId;
        obj.seller = msg.sender;
        obj.nft = IERC721(nft);
        obj.buyer = address(0x0);
        obj.startTime = startTime;
        obj.durationTime = durationTime;
        obj.maxPrice = maxPrice;
        obj.minPrice = minPrice;
        obj.finalPrice = 0;
        obj.status = 0;
        
        _saleOnCurrency[obj.id] = currency;
        
        if (_salesObjects.length == 0) {
            SalesObject memory zeroObj;
            zeroObj.tokenId = 0;
            zeroObj.seller = address(0x0);
            zeroObj.nft = IERC721(0x0);
            zeroObj.buyer = address(0x0);
            zeroObj.startTime = 0;
            zeroObj.durationTime = 0;
            zeroObj.maxPrice = 0;
            zeroObj.minPrice = 0;
            zeroObj.finalPrice = 0;
            zeroObj.status = 2;
            _salesObjects.push(zeroObj);
        }

        _salesObjects.push(obj);

        if(_isRewardSellerDandy || _verifySeller[msg.sender]) {
            _dandy.mint(msg.sender, _sellerRewardDandy);
        }
        
        uint256 tmpMaxPrice = maxPrice;
        uint256 tmpMinPrice = minPrice;
        emit eveNewSales(obj.id, tokenId, msg.sender, nft, address(0x0), startTime, durationTime, tmpMaxPrice, tmpMinPrice, 0);
        return _salesAmount;
    }

    function buy(uint index, address currency_)
        public
        nonReentrant
        mustNotSellingOut(index)
        checkTime(index)
        checkSupportBuyCurrendy(currency_)
        payable 
    {
        SalesObject storage obj = _salesObjects[index];
        require(_isStartUserSales || _seller[msg.sender] == true, "cannot sales");
        address currencyAddr = _saleOnCurrency[obj.id];
        uint256 price = this.getSalesPrice(index);
        uint256 tipsFee = price.mul(_tipsFeeRate).div(_baseRate);
        uint256 purchase = price.sub(tipsFee);
        if (address(currencyAddr) == currency_){
            if (currencyAddr == address(0x0)){
                require (msg.value >= this.getSalesPrice(index), "umm.....  your price is too low");
                uint256 returnBack = msg.value.sub(price);
                if(returnBack > 0) {
                    msg.sender.transfer(returnBack);
                }
                if(tipsFee > 0) {
                    _tipsFeeWallet.transfer(tipsFee);
                }
                obj.seller.transfer(purchase);
            }else{
                IERC20(currencyAddr).safeTransferFrom(msg.sender, _tipsFeeWallet, tipsFee);
                IERC20(currencyAddr).safeTransferFrom(msg.sender, obj.seller, purchase);
            }
        }else{
            if (currencyAddr == address(0x0)){
                uint256 ethAmount = tokenToEth(currency_, price);
                // uint256 ethAmount = 0;
                // SupportBuyCurrency memory supportBuyCurrency = _supportBuyCurrency[currency_];
                // if (supportBuyCurrency.isDeflation) {
                //     ethAmount = exactTokenToEth(currency_, price);
                // } else {
                //     ethAmount = tokenToExactEth(currency_, price);
                // }
                require (ethAmount >= price, "umm.....  your price is too low");
                uint256 returnBack = ethAmount.sub(price).add(msg.value);
                if(returnBack > 0) {
                    msg.sender.transfer(returnBack);
                }
                if(tipsFee > 0) {
                    _tipsFeeWallet.transfer(tipsFee);
                }
                obj.seller.transfer(purchase);
            }else{
                // transfer
                require(false, "not support token");
            }
        }

        if(_isRewardBuyerDandy || _verifySeller[obj.seller]) {
            _dandy.mint(msg.sender, _buyerRewardDandy);
        }

        obj.nft.safeTransferFrom(address(this), msg.sender, obj.tokenId);
        
        obj.buyer = msg.sender;
        obj.finalPrice = price;

        obj.status = 1;

        // fire event
        emit eveSales(index, obj.tokenId, msg.sender, price, tipsFee);
    }



    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data) public returns (bytes4) {
        //only receive the _nft staff
        if(address(this) != operator) {
            //invalid from nft
            return 0;
        }

        //success
        emit eveNFTReceived(operator, from, tokenId, data);
        return bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
    }
    // function exactTokenToEth(address erc20Token_, uint256 amountOutMin) internal returns (uint256) {
    //     address erc20Token = erc20Token_;
    //     SupportBuyCurrency memory supportBuyCurrency = _supportBuyCurrency[erc20Token];

    //     address[] memory path = new address[](2);
    //     path[0] = erc20Token;
    //     path[1] = getRouter().WETH();

    //     uint256[] memory amounts = UniswapV2Library.getAmountsIn(getRouter().factory(), amountOutMin, path);
    //     uint256 amountInMax = amounts[0];
        
    //     uint256 amountIn = amountInMax.mul(getDeflationBaseRate()).div(supportBuyCurrency.deflationRate).mul(getDeflationBaseRate()).div(supportBuyCurrency.deflationRate);

    //     uint256 balanceBefore = IERC20(erc20Token).balanceOf(address(this));
    //     IERC20(erc20Token).safeTransferFrom(msg.sender, address(this), amountIn);
    //     uint256 balanceAfter = IERC20(erc20Token).balanceOf(address(this));
    //     amountIn = balanceAfter.sub(balanceBefore);
    //     IERC20(erc20Token).approve(address(getRouter()), amountIn);

    //     uint256 ethBefore = address(this).balance;
     
    //     getRouter().swapExactTokensForETHSupportingFeeOnTransferTokens(amountIn, 0, path, address(this), block.timestamp);
    //     uint256 ethAfter = address(this).balance;

    //     uint256 balanceLast = IERC20(erc20Token).balanceOf(address(this));
    //     uint256 supAmount = balanceLast.sub(balanceBefore);
    //     if (supAmount>0){
    //         IERC20(erc20Token).safeTransfer(msg.sender, supAmount);
    //     }

    //     return ethAfter.sub(ethBefore);
    // }

    // function tokenToExactEth(address erc20Token, uint256 amountOut) internal returns (uint256) {
    //     address[] memory path = new address[](2);
    //     path[0] = erc20Token;
    //     path[1] = getRouter().WETH();
       
    //     uint256[] memory amounts = UniswapV2Library.getAmountsIn(getRouter().factory(), amountOut, path);
    //     uint256 amountInMax = amounts[0];
        
    //     uint256 balanceBefore = IERC20(erc20Token).balanceOf(address(this));
    //     IERC20(erc20Token).safeTransferFrom(msg.sender, address(this), amountInMax);
    //     uint256 balanceAfter = IERC20(erc20Token).balanceOf(address(this));
    //     amountInMax = balanceAfter.sub(balanceBefore);
    //     IERC20(erc20Token).approve(address(getRouter()), amountInMax);

    //     uint256 ethBefore = address(this).balance;
    //     getRouter().swapTokensForExactETH(amountOut, amountInMax, path, address(this), block.timestamp);
    //     uint256 ethAfter = address(this).balance;

    //     uint256 balanceLast = IERC20(erc20Token).balanceOf(address(this));
    //     uint256 supAmount = balanceLast.sub(balanceBefore);
    //     if (supAmount>0){
    //         IERC20(erc20Token).safeTransfer(msg.sender, supAmount);
    //     }
    //     return ethAfter.sub(ethBefore);
    // }
    function tokenToEth(address erc20Token, uint256 amountOut) private returns(uint256) {
        address[] memory path = new address[](2);
        path[0] = erc20Token;
        path[1] = getRouter().WETH();
       
        uint256[] memory amounts = UniswapV2Library.getAmountsIn(getRouter().factory(), amountOut, path);
        uint256 amountIn = amounts[0];
        
        SupportBuyCurrency memory supportBuyCurrency = _supportBuyCurrency[erc20Token];
        if (supportBuyCurrency.isDeflation) {
            amountIn = amountIn.mul(getDeflationBaseRate()).div(supportBuyCurrency.deflationRate).mul(getDeflationBaseRate()).div(supportBuyCurrency.deflationRate);
        }

        uint256 balanceBefore = IERC20(erc20Token).balanceOf(address(this));
        IERC20(erc20Token).safeTransferFrom(msg.sender, address(this), amountIn);
        uint256 balanceAfter = IERC20(erc20Token).balanceOf(address(this));
        amountIn = balanceAfter.sub(balanceBefore);
        IERC20(erc20Token).approve(address(getRouter()), amountIn);
        
        uint256 ethBefore = address(this).balance;
        if (supportBuyCurrency.isDeflation) {
            getRouter().swapExactTokensForETHSupportingFeeOnTransferTokens(amountIn, 0, path, address(this), block.timestamp);
        } else {
            getRouter().swapTokensForExactETH(amountOut, amountIn, path, address(this), block.timestamp);
        }
        uint256 ethAfter = address(this).balance;

        uint256 balanceLast = IERC20(erc20Token).balanceOf(address(this));
        uint256 supAmount = balanceLast.sub(balanceBefore);
        if (supAmount>0){
            IERC20(erc20Token).safeTransfer(msg.sender, supAmount);
        }
        return ethAfter.sub(ethBefore);
    }

    function getDeflationBaseRate() public view returns(uint256) {
        return deflationBaseRates[0];
    }
    function getRouter() public view returns(IUniswapV2Router01) {
        return IUniswapV2Router01(routers[0]);
    }
}

{
  "compilationTarget": {
    "NFTMarketV2.sol": "NFTMarketV2"
  },
  "evmVersion": "petersburg",
  "libraries": {},
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}