Flash Swaps callback

callback.sol

function pancakeCall(address sender, uint amount0, uint amount1, bytes calldata data) {
  address token0 = IUniswapV2Pair(msg.sender).token0(); // fetch the address of token0
  address token1 = IUniswapV2Pair(msg.sender).token1(); // fetch the address of token1
  assert(msg.sender == IUniswapV2Factory(factoryV2).getPair(token0, token1)); // ensure that msg.sender is a V2 pair
  // rest of the function goes here!
  ...
  
  // transfer tokens to reimburse the required amount for swap
  IERC20(token1).transfer(msg.sender, amountRequired);
  // transfer tokens to an address who receives an arbitrage profit
  IERC20(token1).transfer(owner, amountReceived.sub(amountRequired));
}