Flashloan_swap.sol

Flashloan_swap.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.6.12;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

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

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

interface IMySwapRouter {
    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        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 getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
}

contract Flashloan {
    
    IMySwapRouter immutable public mySwapRouter;
    IERC20 public busd;
    IERC20 public wbnb;
    // address[]  public swapPath;
    
    constructor(IERC20 _busd, IERC20 _wbnb, IMySwapRouter _swapRouter) public {
        busd = _busd;
        wbnb = _wbnb;
        mySwapRouter = _swapRouter;
        // swapPath = [address(_wbnb), address(_busd)];
    }
    
    function swapWithoutFee(uint256 amount) external {
        
        // busd.approve(address(this), amount);
        // busd.transfer(address(this), amount);
        
        address[] memory path = new address[](2);
        
        path[0] = address(busd);
        path[1] = address(wbnb);
        
        uint amountOutMin = mySwapRouter.getAmountsOut(
            amount,
            path
        )[1];

        busd.approve(address(mySwapRouter), amount);
        mySwapRouter.swapExactTokensForTokens(
            amount,
            amountOutMin,
            path,
            address(this),
            block.timestamp
        );
        
    }
    
    function swap(uint256 amount) external {
        
        address[] memory path = new address[](2);
        
        path[0] = address(busd);
        path[1] = address(wbnb);
        
        uint amountOutMin = mySwapRouter.getAmountsOut(
            amount,
            path
        )[1];
        
        busd.approve(address(mySwapRouter), amount);
        mySwapRouter.swapExactTokensForTokensSupportingFeeOnTransferTokens(
            amount,
            amountOutMin,
            path,
            address(this),
            block.timestamp
        );
        
    }
    
}