Pay gas in USDC.
Zero native tokens.

import { createClient, encodeFunctionData, http, maxUint256, parseAbi } from "viem";
import { taikoAlethia } from "viem/chains";

const client = createClient({
  chain: taikoAlethia,
  transport: http("https://servo.taiko.xyz/rpc"),
});

const accountAbi = parseAbi([
  "function execute(address,uint256,bytes)",
  "function executeBatch(address[] targets, uint256[] values, bytes[] calldatas)",
]);
const usdcAbi = parseAbi([
  "function allowance(address owner, address spender) view returns (uint256)",
  "function nonces(address owner) view returns (uint256)",
  "function permit(address owner, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s)",
]);

const action = encodeFunctionData({
  abi: targetAbi,
  functionName: "doThing",
  args: [123n],
});

let userOp = {
  sender,
  nonce: "0x0",
  initCode,
  callData: encodeFunctionData({
    abi: accountAbi,
    functionName: "execute",
    args: [target, 0n, action],
  }),
  callGasLimit: "0x0",
  verificationGasLimit: "0x0",
  preVerificationGas: "0x0",
  maxFeePerGas,
  maxPriorityFeePerGas,
  signature: DUMMY_SIG,
};

// 1. Stub quote for the real action. This reveals the paymaster + token + maxTokenCost.
const stub = await client.request({
  method: "pm_getPaymasterStubData",
  params: [userOp, entryPoint, "taikoMainnet"],
});

// 2. If the undeployed account has no allowance yet, prepend permit() in the same UserOp.
const allowance = await publicClient.readContract({
  address: stub.tokenAddress,
  abi: usdcAbi,
  functionName: "allowance",
  args: [sender, stub.paymaster],
});

if (allowance < BigInt(stub.maxTokenCostMicros)) {
  const permit = await signPermitWithViem({
    owner,
    token: stub.tokenAddress,
    spender: stub.paymaster,
    value: maxUint256,
    nonce: await publicClient.readContract({
      address: stub.tokenAddress,
      abi: usdcAbi,
      functionName: "nonces",
      args: [sender],
    }),
  });

  userOp = {
    ...userOp,
    callData: encodeFunctionData({
      abi: accountAbi,
      functionName: "executeBatch",
      args: [
        [stub.tokenAddress, target],
        [0n, 0n],
        [permit.calldata, action],
      ],
    }),
  };
}

// 3. Final quote for the exact UserOp you will submit.
const quote = await client.request({
  method: "pm_getPaymasterData",
  params: [userOp, entryPoint, "taikoMainnet"],
});

// 4. Sign the final UserOp hash and send it.
await bundlerClient.sendUserOperation({
  ...userOp,
  ...quote,
});