�¡ FLASH SWAPS: Préstamos sin Colateral en 1 Bloque

Simulador de Flash Swap Arbitraje

Flash Swap ” Solidity

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";

contract FlashArbBot {
  IUniswapV2Router02 immutable uniRouter;
  IUniswapV2Router02 immutable sushiRouter;
  address immutable owner;

  constructor(address _uni, address _sushi) {
    uniRouter = IUniswapV2Router02(_uni);
    sushiRouter = IUniswapV2Router02(_sushi);
    owner = msg.sender;
  }

  // Paso 1: Iniciar el flash swap
  function initiateFlashSwap(
    address pair,
    uint256 wethAmount
  ) external {
    // amount0Out=0, amount1Out=wethAmount (WETH es token1)
    IUniswapV2Pair(pair).swap(
      0, wethAmount, address(this),
      abi.encode(wethAmount) // data != "" activa flash swap
    );
  }

  // Paso 2: Callback ” Uniswap llama este función
  function uniswapV2Call(
    address,    // sender
    uint256,    // amount0
    uint256 amount1, // WETH recibido
    bytes calldata data
  ) external {
    // Vender WETH en SushiSwap (precio más alto)
    address[] memory path = new address[](2);
    path[0] = WETH; path[1] = USDC;
    uint256[] memory amounts = sushiRouter.swapExactTokensForTokens(
      amount1, 0, path, address(this), block.timestamp
    );
    // Devolver WETH + 0.3% fee a Uniswap
    uint256 repay = amount1 * 1000 / 997 + 1;
    IWETH(WETH).transfer(msg.sender, repay);
    // Profit = USDC recibido - costo del repay
    uint256 profit = amounts[1] - (repay * uniPrice / 1e18);
    IERC20(USDC).transfer(owner, profit);
  }
}