import { ethers } from "ethers";

const provider = new ethers.JsonRpcProvider("https://mainnet.base.org");
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY!, provider); // 推薦使用 WalletConnect
const contract = new ethers.Contract(CONTRACT_ADDRESS, ABI, provider);

async function signGaslessSwap(
  key: {
    currency0: string;
    currency1: string;
    fee: number;
    tickSpacing: number;
    hooks: string;
  },
  swapParams: {
    zeroForOne: boolean;
    amountSpecified: bigint;
    sqrtPriceLimitX96: bigint;
  },
  hookData: string = "0x",
  deadline: number = Math.floor(Date.now() / 1000) + 1200
) {
  const feeRate = await contract.gaslessFeeRate();           // 強制讀取最新值
  const chainId = (await provider.getNetwork()).chainId;

  const domain = {
    name: "SwapCoverLayer",
    version: "1",
    chainId: chainId,
    verifyingContract: contract.target as string            // 必須包含
  };

  const types = {
    PoolKey: [
      { name: "currency0", type: "address" },
      { name: "currency1", type: "address" },
      { name: "fee", type: "uint24" },
      { name: "tickSpacing", type: "int24" },
      { name: "hooks", type: "address" }
    ],
    SwapParams: [
      { name: "bool" },
      { name: "amountSpecified", type: "int256" },
      { name: "sqrtPriceLimitX96", type: "uint160" }
    ],
    Swap: [
      { name: "caller", type: "address" },
      { name: "key", type: "PoolKey" },
      { name: "params", type: "SwapParams" },
      { name: "hookData", type: "bytes" },
      { name: "feeRate", type: "uint256" },
      { name: "deadline", type: "uint256" }
    ]
  };

  const message = {
    caller: wallet.address,
    key,
    params: swapParams,
    hookData,
    feeRate,
    deadline
  };

  const signature = await wallet.signTypedData(domain, types, message);
  const { v, r, s } = ethers.Signature.from(signature);

  return { caller: wallet.address, key, swapParams, hookData, deadline, v, r, s };
}

try {
  await contract.callStatic.executeGaslessSwap(params);  // 先模擬
  await contract.executeGaslessSwap(params);             // 成功才上鏈
} catch (e) {
  if (e.message.includes("NoStablecoinInvolved")) {
    // 直接丟棄，永不虧 gas
  }
}