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contracts...Arbitrage.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.18;

import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
import "@balancer-labs/v2-interfaces/contracts/vault/IFlashLoanRecipient.sol";
import {ISwapRouter} from "@uniswap/v3-periphery/contracts/interfaces/ISwapRouter.sol";

contract Arbitrage is IFlashLoanRecipient {
    IVault private constant vault =
        IVault(0xBA12222222228d8Ba445958a75a0704d566BF2C8);

    address public owner;

    struct Trade {
        address[] routerPath;
        address[] tokenPath;
        uint24 fee;
    }

    constructor() {
        owner = msg.sender;
    }

    function executeTrade(
        address[] memory _routerPath,
        address[] memory _tokenPath,
        uint24 _fee,
        uint256 _flashAmount
    ) external {
        bytes memory data = abi.encode(
            Trade({routerPath: _routerPath, tokenPath: _tokenPath, fee: _fee})
        );

        // Token to flash loan, by default we are flash loaning 1 token.
        IERC20[] memory tokens = new IERC20[](1);
        tokens[0] = IERC20(_tokenPath[0]);

        // Flash loan amount.
        uint256[] memory amounts = new uint256[](1);
        amounts[0] = _flashAmount;

        vault.flashLoan(this, tokens, amounts, data);
    }

    function receiveFlashLoan(
        IERC20[] memory tokens,
        uint256[] memory amounts,
        uint256[] memory feeAmounts,
        bytes memory userData
    ) external override {
        require(msg.sender == address(vault));

        // Decode our swap data so we can use it
        Trade memory trade = abi.decode(userData, (Trade));
        uint256 flashAmount = amounts[0];

        // Since balancer called this function, we should have funds to begin swapping...

        // We perform the 1st swap.
        // We swap the flashAmount of token0 and expect to get X amount of token1
        _swapOnV3(
            trade.routerPath[0],
            trade.tokenPath[0],
            flashAmount,
            trade.tokenPath[1],
            0,
            trade.fee
        );

        // We perform the 2nd swap.
        // We swap the contract balance of token1 and
        // expect to at least get the flashAmount of token0
        _swapOnV3(
            trade.routerPath[1],
            trade.tokenPath[1],
            IERC20(trade.tokenPath[1]).balanceOf(address(this)),
            trade.tokenPath[0],
            flashAmount,
            trade.fee
        );

        // Transfer back what we flash loaned
        IERC20(trade.tokenPath[0]).transfer(address(vault), flashAmount);

        // Transfer any excess tokens [i.e. profits] to owner
        IERC20(trade.tokenPath[0]).transfer(
            owner,
            IERC20(trade.tokenPath[0]).balanceOf(address(this))
        );
    }

    // -- INTERNAL FUNCTIONS -- //

    function _swapOnV3(
        address _router,
        address _tokenIn,
        uint256 _amountIn,
        address _tokenOut,
        uint256 _amountOut,
        uint24 _fee
    ) internal {
        // Approve token to swap
        IERC20(_tokenIn).approve(_router, _amountIn);

        // Setup swap parameters
        ISwapRouter.ExactInputSingleParams memory params = ISwapRouter
            .ExactInputSingleParams({
                tokenIn: _tokenIn,
                tokenOut: _tokenOut,
                fee: _fee,
                recipient: address(this),
                deadline: block.timestamp,
                amountIn: _amountIn,
                amountOutMinimum: _amountOut,
                sqrtPriceLimitX96: 0
            });

        // Perform swap
        ISwapRouter(_router).exactInputSingle(params);
    }
}