Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.8.7+commit.e28d00a7.js&optimize=false&runs=200&gist=

contracts...Swapper.sol

//SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.7;

import "./interfaces/IUniswapV2Pair.sol";
import "./interfaces/IERC20.sol";
import "./interfaces/IWETH.sol";
import { FlashLoanReceiverBase } from "./interfaces/FlashLoanReceiverBase.sol";
import "./interfaces/ILendingPoolAddressesProvider.sol";
import "./interfaces/ILendingPool.sol";


contract Swapper is FlashLoanReceiverBase {
    uint256 MAX_INT = 2**96 - 1;

    event TransactionInputEvent(Transaction transaction);

    address owner;
    address public baseToken;
    bool useFlashLoan;
    struct TransactionSide {
        address token;
        uint256 amount;
    }

    event Log(string message);
    event LogMemoryString(string message);
    uint256 minBalance;
    struct Transaction {
        address token0;
        address token1;
        uint256 amount0In;
        uint256 amount1In;
        uint256 amount0Out;
        uint256 amount1Out;
        address pool;
        int16 dexType;
    }

    ILendingPool lendingPool;
    
    constructor(address _baseToken, ILendingPoolAddressesProvider _addressProvider, uint256 _minBalance, bool _useFlashLoan) FlashLoanReceiverBase(_addressProvider) {
        owner = msg.sender;
        baseToken = _baseToken;
        useFlashLoan = _useFlashLoan;
        if (useFlashLoan) {
            lendingPool = ILendingPool(_addressProvider.getLendingPool());
        }
        minBalance = _minBalance;
    }

    receive() external payable {
    }


    function approve(address token, address pool, uint256 amount) external {
        uint256 allowance = IERC20(token).allowance(address(this), pool);
        if (allowance == 0) {
            IERC20(token).approve(pool, MAX_INT);
        } else {
            if (allowance < amount) {
                IERC20(token).approve(pool, 0);
                IERC20(token).approve(pool, MAX_INT);
            }
        }
    }

    function approveForce(address token, address pool, uint256 amount) external {
        IERC20(token).approve(pool, amount);
    }

    function getAllowance(address token, address pool) external view returns (uint256) {
        return IERC20(token).allowance(address(this), pool);
    }

    function sendERC20(address token, address pool, uint256 amount) external {
        this.approve(token, pool, amount);
        IERC20(token).transfer(pool, amount);
    }

    function uniswapV2_executeSwap(address pool, uint256 amount0Out, uint256 amount1Out, address destination) external {
        IUniswapV2Pair(pool).swap(amount0Out, amount1Out, destination, new bytes(0));
    }

    struct LogSwapData {
        address pool;
        uint256 amount0Out;
        uint256 amount1Out;
        address destination;
    }

    function executeOperation(
        address[] calldata assets,
        uint256[] calldata amounts,
        uint256[] calldata premiums,
        address initiator,
        bytes calldata params
    )
        external
        override
        returns (bool)
    {
        require(initiator == address(this), "Swapper: II");
        (Transaction[] memory transactions, uint256 minerBribe, uint256 startBalance, uint256 transactionFee) = abi.decode(params, (Transaction[], uint256, uint256, uint256));
        this.executeArbitrage(transactions, minerBribe);
        // Approve the LendingPool contract allowance to *pull* the owed amount
        uint amountOwing = amounts[0] + premiums[0];
        IERC20(assets[0]).approve(address(LENDING_POOL), amountOwing);
        this.checkProfit(startBalance, minerBribe, transactionFee, amountOwing);
        this.sendERC20(baseToken, owner, this.getBalance() - (minBalance + amountOwing));
        return true;
    }

    function updateMinBalance(uint256 _minBalance) external {
        require(msg.sender == owner, "Swapper: NOWNR");
        minBalance = _minBalance;
    }

    function takeFlashLoan(address token, uint256 flashLoanAmount, bytes memory data) public {
        address[] memory addresses = new address[](1);
        addresses[0] = token;

        uint256[] memory amounts = new uint256[](1);
        amounts[0] = flashLoanAmount;

        uint256[] memory modes = new uint256[](1);
        modes[0] = 0;

        lendingPool.flashLoan(
            address(this),
            addresses,
            amounts,
            modes,
            address(this),
            data,
            0
        );
    }

    function arbitrage(Transaction[] memory transactions, uint256 minerBribe, uint256 transactionFee) external {
        uint256 startBalance = this.getBalance();
        bool isFlashloan = false;

        require(startBalance > 0, "Swapper: no balance");

        if (useFlashLoan && startBalance < transactions[0].amount0In + transactions[0].amount1In) {
            isFlashloan = true;
        }

        if (isFlashloan) {
            try this.takeFlashLoan(baseToken, (transactions[0].amount0In + transactions[0].amount1In) - startBalance, abi.encode(transactions, minerBribe, startBalance, transactionFee)) { 
            } catch Error(string memory reason) {
                require(false, string(abi.encodePacked("Swapper: TFLF - ", reason)));
            } catch {
                require(false, "Swapper: TFLE");
            }
        } else {
            require(startBalance >= transactions[0].amount0In + transactions[0].amount1In, "Swapper: not enough balance for first transaction");
            this.executeArbitrage(transactions, minerBribe);
            this.checkProfit(startBalance, minerBribe, transactionFee, 0);
            this.sendERC20(baseToken, owner, this.getBalance() - minBalance);
        }
    }

    function executeArbitrage(Transaction[] memory transactions, uint256 minerBribe) public {
        for (uint256 index = 0; index < transactions.length; index++) {
            if (transactions[index].dexType == 0) {
                bool zeroForOne = transactions[index].amount0In > 0 ? true : false;
                if (index == 0) {
                    try this.sendERC20(zeroForOne ? transactions[index].token0 : transactions[index].token1, transactions[index].pool, transactions[index].amount0In + transactions[index].amount1In) {
                    } catch Error(string memory reason) {
                        require(false, string(abi.encodePacked("Swapper: SEF - ", reason)));
                    } catch {
                        require(false, "Swapper: SEA");
                    }
                }

                uint256 nextPoolBalanceBeforeSending = 0;
                uint256 nextPoolBalanceAfterSending = 0;

                if (index < transactions.length -1) {
                    nextPoolBalanceBeforeSending = this.getERC20BalanceOf(transactions[index + 1].amount0In > 0 ? transactions[index + 1].token0 : transactions[index + 1].token1, transactions[index+1].pool);
                }

                try this.uniswapV2_executeSwap(
                    transactions[index].pool,
                    transactions[index].amount0Out,
                    transactions[index].amount1Out,
                    index == transactions.length - 1 ? address(this) : transactions[index+1].pool
                ) {
                } catch Error(string memory reason) {
                    require(false, string(abi.encodePacked("Swapper: EFE - ", reason)));
                } catch {
                    require(false, "Swapper: EFA");
                }

                if (index < transactions.length -1) {
                    nextPoolBalanceAfterSending = this.getERC20BalanceOf(transactions[index + 1].amount0In > 0 ? transactions[index + 1].token0 : transactions[index + 1].token1, transactions[index+1].pool);
                    if (nextPoolBalanceAfterSending - nextPoolBalanceBeforeSending != transactions[index + 1].amount0In + transactions[index + 1].amount1In) {
                        for (uint256 j=index + 1; j<transactions.length; j++) {
                            uint256 nextAmountIn = transactions[index + 1].amount0In + transactions[index + 1].amount1In;
                            transactions[j].amount0Out = this.adjustAmount(transactions[j].amount0Out, nextPoolBalanceAfterSending - nextPoolBalanceBeforeSending, nextAmountIn);
                            transactions[j].amount1Out = this.adjustAmount(transactions[j].amount1Out, nextPoolBalanceAfterSending - nextPoolBalanceBeforeSending, nextAmountIn);
                            transactions[j].amount0In = this.adjustAmount(transactions[j].amount0In, nextPoolBalanceAfterSending - nextPoolBalanceBeforeSending, nextAmountIn);
                            transactions[j].amount1In = this.adjustAmount(transactions[j].amount1In, nextPoolBalanceAfterSending - nextPoolBalanceBeforeSending, nextAmountIn);
                        }
                    }
                }
            }
        }
        if (minerBribe > 0) {
            IWETH(baseToken).withdraw(minerBribe);
            block.coinbase.transfer(minerBribe);
        }
    }

    function checkProfit(uint256 startBalance, uint256 minerBribe, uint256 transactionFee, uint256 amountOwing) view public {
        uint256 endBalance = this.getBalance();
        uint256 revenue = endBalance - startBalance;
        uint256 costOfRevenue = minerBribe + transactionFee + amountOwing;
        require(revenue >= costOfRevenue, "NP-3");
    }

    function adjustAmount(uint256 amount, uint256 numerator, uint256 denominator) external pure returns(uint256) {
        if (amount == 0) {
            return 0;
        }
        return (amount * (numerator * 1000 / denominator))/1000 - 1;
    }

    function cashoutETH(address _to, uint256 _amount) public payable {
        require(owner == _to, 'X');
        payable(_to).transfer(_amount);
    }

    function cashout() external {
        require(owner == msg.sender, 'X');
        this.cashoutETH(owner, this.getETHBalance());
        this.sendERC20(baseToken, owner, this.getBalance());
    }

    function getBalance() external view returns (uint256) {
        return IERC20(baseToken).balanceOf(address(this));
    }

    function getERC20Balance(address token) external view returns (uint256) {
        return this.getERC20BalanceOf(token, address(this));
    }

    function getERC20BalanceOf(address token, address balanceOf) external view returns (uint256) {
        return IERC20(token).balanceOf(balanceOf);
    }

    function getETHBalance() external view returns (uint256) {
        return address(this).balance;
    }
}