DexSwapArbitrage.sol

pragma solidity ^0.6.6  ;

import './libraries/DexSwapLibrary.sol';
import './interfaces/IDexSwapRouter.sol';
import './interfaces/IDexSwapPair.sol';
import './interfaces/IDexSwapFactory.sol';
import './interfaces/IERC20.sol';

contract DexSwapArbitrage {
  address public factory;
  uint constant deadline = 10 days;
  IDexSwapRouter public dexSwapRoute;

  constructor(address _factory, address _dexSwapRoute) public {
    factory = _factory;  
    dexSwapRoute = IDexSwapRouter(_dexSwapRoute);
  }

  function startDexSwapArbitrage(
    address token0, 
    address token1, 
    uint amount0, 
    uint amount1
  ) external {
    address pairAddress = IDexSwapFactory(factory).getPair(token0, token1);
    require(pairAddress != address(0), 'This pool does not exist');
    IDexSwapPair(pairAddress).swap(
      amount0, 
      amount1, 
      address(this), 
      bytes('not empty')
    );
  }

  function uniswapV2Call(
    address _sender, 
    uint _amount0, 
    uint _amount1, 
    bytes calldata _data
  ) external {
    address[] memory path = new address[](2);
    uint amountToken = _amount0 == 0 ? _amount1 : _amount0;
    address token0 = IDexSwapPair(msg.sender).token0();
    address token1 = IDexSwapPair(msg.sender).token1();

    require(
      msg.sender == DexSwapLibrary.pairFor(factory, token0, token1), 
      'Unauthorized'
    ); 
    require(_amount0 == 0 || _amount1 == 0);

    path[0] = _amount0 == 0 ? token1 : token0;
    path[1] = _amount0 == 0 ? token0 : token1;

    IERC20 token = IERC20(_amount0 == 0 ? token1 : token0);
    
    token.approve(address(dexSwapRoute), amountToken);

    uint amountRequired = DexSwapLibrary.getAmountsIn(
      factory, 
      amountToken, 
      path
    )[0];
    uint amountReceived = dexSwapRoute.swapExactTokensForTokens(
      amountToken, 
      amountRequired, 
      path, 
      msg.sender, 
      deadline
    )[1];

    IERC20 otherToken = IERC20(_amount0 == 0 ? token0 : token1);
    otherToken.transfer(msg.sender, amountRequired);
    otherToken.transfer(tx.origin, amountReceived - amountRequired);
  }
}