// SPDX-License-Identifier: MIT


pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}


// File @openzeppelin/contracts/access/Ownable.sol@v4.8.3


// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


// File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.8.3


// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` 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 from,
        address to,
        uint256 amount
    ) external returns (bool);
}


// File @openzeppelin/contracts/utils/math/SafeMath.sol@v4.8.3


// OpenZeppelin Contracts (last updated v4.6.0) (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // 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 (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @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) {
        return a + b;
    }

    /**
     * @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 a - b;
    }

    /**
     * @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) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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 a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}


// File contracts/BlindBackrun.sol

pragma solidity ^0.8.0;



interface IWETH is IERC20 {
    function deposit() external payable;
    function withdraw(uint) external;
}

interface IUniswapV2Pair {
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function token0() external view returns (address);
    function token1() external view returns (address);
}

interface IPairReserves{
     struct PairReserves {
        uint256 reserve0;
        uint256 reserve1;
        uint256 price;
        bool isWETHZero;
    }
}

contract BlindBackrun is Ownable {
    using SafeMath for uint256;
    uint256 uniswappyFee = 997;

    address public immutable WETH_ADDRESS;

    constructor() {
        WETH_ADDRESS = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    }

    /// @notice Executes an arbitrage transaction between two Uniswap V2 pairs.
    /// @notice Pair addresses need to be computed off-chain.
    /// @dev Only the contract owner can call this function.
    /// @param firstPairAddress Address of the first Uniswap V2 pair.
    /// @param secondPairAddress Address of the second Uniswap V2 pair.
    function executeArbitrage(
        address firstPairAddress,
        address secondPairAddress,
        uint percentageToPayToCoinbase
    ) external onlyOwner {
        uint256 balanceBefore = IERC20(WETH_ADDRESS).balanceOf(address(this));
        IUniswapV2Pair firstPair = IUniswapV2Pair(firstPairAddress);
        IUniswapV2Pair secondPair = IUniswapV2Pair(secondPairAddress);

        IPairReserves.PairReserves memory firstPairData = getPairData(firstPair);
        IPairReserves.PairReserves memory secondPairData = getPairData(secondPair);


        uint256 amountIn = getAmountIn(firstPairData, secondPairData);
        IERC20(WETH_ADDRESS).transfer(firstPairAddress, amountIn);
        
        uint256 firstPairAmountOut;
        uint256 finalAmountOut;
        if (firstPairData.isWETHZero == true){
            firstPairAmountOut = getAmountOut(amountIn, firstPairData.reserve0, firstPairData.reserve1);
            finalAmountOut = getAmountOut(firstPairAmountOut, secondPairData.reserve1, secondPairData.reserve0);

            firstPair.swap(0, firstPairAmountOut, secondPairAddress, "");
            secondPair.swap(finalAmountOut, 0, address(this), "");
        } else {
            firstPairAmountOut = getAmountOut(amountIn, firstPairData.reserve1, firstPairData.reserve0);
            finalAmountOut = getAmountOut(firstPairAmountOut, secondPairData.reserve0, secondPairData.reserve1);

            firstPair.swap(firstPairAmountOut, 0, secondPairAddress, "");          
            secondPair.swap(0, finalAmountOut, address(this), "");
        }
        
        uint256 balanceAfter = IERC20(WETH_ADDRESS).balanceOf(address(this));
        require(balanceAfter > balanceBefore, "Arbitrage failed");
        uint profit = balanceAfter.sub(balanceBefore);
        uint profitToCoinbase = profit.mul(percentageToPayToCoinbase).div(100);
        IWETH(WETH_ADDRESS).withdraw(profitToCoinbase);
        block.coinbase.transfer(profitToCoinbase);
    }

    /// @notice Calculates the required input amount for the arbitrage transaction.
    /// @param firstPairData Struct containing data about the first Uniswap V2 pair.
    /// @param secondPairData Struct containing data about the second Uniswap V2 pair.
    /// @return amountIn, the optimal amount to trade to arbitrage two v2 pairs.
    function getAmountIn(
        IPairReserves.PairReserves memory firstPairData, 
        IPairReserves.PairReserves memory secondPairData
    ) public returns (uint256) {
        uint256 numerator = getNumerator(firstPairData, secondPairData);
        uint256 denominator = getDenominator(firstPairData, secondPairData);
        
        uint256 amountIn = 
            numerator
            .mul(1000)
            .div(denominator);

        return amountIn;
    }

    function getNumerator(
        IPairReserves.PairReserves memory firstPairData, 
        IPairReserves.PairReserves memory secondPairData
    ) public view returns (uint256) {
        if (firstPairData.isWETHZero == true) {
            uint presqrt = 
                uniswappyFee
                    .mul(uniswappyFee)
                    .mul(firstPairData.reserve1)
                    .mul(secondPairData.reserve0)
                    .div(secondPairData.reserve1)
                    .div(firstPairData.reserve0);
            
            uint256 numerator = 
            (
                sqrt(presqrt)
                .sub(1e3)
            )            
            .mul(secondPairData.reserve1)
            .mul(firstPairData.reserve0);

            return numerator;
        } else {
            uint presqrt = 
                uniswappyFee
                    .mul(uniswappyFee)
                    .mul(firstPairData.reserve0)
                    .mul(secondPairData.reserve1)
                    .div(secondPairData.reserve0)
                    .div(firstPairData.reserve1);
            
            uint256 numerator = 
            (
                sqrt(presqrt)
                .sub(1e3)
            )            
            .mul(secondPairData.reserve0)
            .mul(firstPairData.reserve1);

            return numerator;
        }
    }

    function getDenominator(
            IPairReserves.PairReserves memory firstPairData, 
            IPairReserves.PairReserves memory secondPairData
        ) public returns (uint256){
        if (firstPairData.isWETHZero == true) {
            uint256 denominator = 
                (
                    uniswappyFee
                    .mul(secondPairData.reserve1)
                    .mul(1000)
                )
                .add(
                    uniswappyFee
                    .mul(uniswappyFee)
                    .mul(firstPairData.reserve1)
                );
            return denominator;
        } else {
            uint256 denominator = 
                (
                    uniswappyFee
                    .mul(secondPairData.reserve0)
                    .mul(1000)
                )
                .add(
                    uniswappyFee
                    .mul(uniswappyFee)
                    .mul(firstPairData.reserve0)
                );
            return denominator;
        }
    }

    /// @notice Retrieves price and reserve data for a given Uniswap V2 pair. Also checks which token is WETH.
    /// @param pair The Uniswap V2 pair to retrieve data for.
    /// @return A PairReserves struct containing price and reserve data for the given pair.
    function getPairData(IUniswapV2Pair pair) private view returns (IPairReserves.PairReserves memory) {
        (uint256 reserve0, uint256 reserve1, ) = pair.getReserves();
        uint256 price;

        bool isWETHZero = false;
        if (pair.token0() == WETH_ADDRESS) {
            price = reserve1.mul(1e18).div(reserve0);
            isWETHZero = true;
        } else {
            price = reserve0.mul(1e18).div(reserve1);
        }

        return IPairReserves.PairReserves(reserve0, reserve1, price, isWETHZero);
    }

    /// @notice Calculates the square root of a given number.
    /// @param x: The number to calculate the square root of.
    /// @return y: The square root of the given number.
    function sqrt(uint256 x) private pure returns (uint256) {
        if (x == 0) return 0;
        uint256 z = x.add(1).div(2);
        uint256 y = x;
        while (z < y) {
            y = z;
            z = ((x.div(z)).add(z)).div(2);
        }
        return y;
    }

    /// @notice Calculates the output amount for a given input amount and reserves.
    /// @param amountIn The input amount.
    /// @param reserveIn The reserve of the input token.
    /// @param reserveOut The reserve of the output token.
    /// @return amountOut The output amount.
    function getAmountOut(uint amountIn,
        uint reserveIn,
        uint reserveOut
    ) internal pure returns (uint amountOut) {
        uint amountInWithFee = amountIn.mul(997);
        uint numerator = amountInWithFee.mul(reserveOut);
        uint denominator = reserveIn.mul(1000).add(amountInWithFee);
        amountOut = numerator / denominator;
        return amountOut;
    }

    /// @notice Transfers all WETH held by the contract to the contract owner.
    /// @dev Only the contract owner can call this function.
    function withdrawWETHToOwner() external onlyOwner {
        uint256 balance = IERC20(WETH_ADDRESS).balanceOf(address(this));
        IERC20(WETH_ADDRESS).transfer(msg.sender, balance);
    }

    /// @notice Transfers all ETH held by the contract to the contract owner.
    /// @dev Only the contract owner can call this function.
    function withdrawETHToOwner() external onlyOwner {
        uint256 balance = address(this).balance;
        payable(msg.sender).transfer(balance);
    }

    /// @notice Executes a call to another contract with the provided data and value.
    /// @dev Only the contract owner can call this function.
    /// @dev Reverted calls will result in a revert. 
    /// @param _to The address of the contract to call.
    /// @param _value The amount of Ether to send with the call.
    /// @param _data The calldata to send with the call.
    function call(address payable _to, uint256 _value, bytes memory _data) external onlyOwner {
        (bool success, ) = _to.call{value: _value}(_data);
        require(success, "External call failed");
    }

    /// @notice Fallback function that allows the contract to receive Ether.
    receive() external payable {}
}