EOA paymaster

import { createPublicClient, encodeFunctionData, http, numberToHex, parseAbi } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { botChainTestnet } from "@uzolabs/sdk/chains";

// No public paymaster is confirmed for BOT Chain. Set this to an endpoint your provider gives you.
const PAYMASTER_URL = process.env.PAYMASTER_URL as string;
const GUEST_BOOK = "0x7962412A92E5553E66C794c3a352422DEB7BAc27";

const account = privateKeyToAccount(process.env.BOT_PRIVATE_KEY as `0x${string}`);
const chainClient = createPublicClient({ chain: botChainTestnet, transport: http() });
const paymaster = createPublicClient({ chain: botChainTestnet, transport: http(PAYMASTER_URL) });

const data = encodeFunctionData({
  abi: parseAbi(["function sign(string message) returns (uint256 id)"]),
  functionName: "sign",
  args: ["Sponsored by a paymaster"],
});
const gas = await chainClient.estimateGas({ account, to: GUEST_BOOK, data });

// 1. Ask whether the paymaster will pay for this transaction. Every value is hex.
const result = await paymaster.request<{
  Method: "pm_isSponsorable";
  Parameters: [{ to: `0x${string}`; from: `0x${string}`; value: `0x${string}`; data: `0x${string}`; gas: `0x${string}` }];
  ReturnType: { Sponsorable?: boolean; sponsorable?: boolean; SponsorPolicy?: string; sponsorPolicy?: string };
}>({
  method: "pm_isSponsorable",
  params: [{ to: GUEST_BOOK, from: account.address, value: "0x0", data, gas: numberToHex(gas) }],
});
// BOT Chain's docs capitalize the fields. Read both spellings until a live endpoint confirms one.
const sponsorable = result.Sponsorable ?? result.sponsorable ?? false;
console.log("Sponsorable:", sponsorable, "Policy:", result.SponsorPolicy ?? result.sponsorPolicy);
if (!sponsorable) process.exit(0);

// 2. Sign a legacy transaction with a gas price of 0 and send it to the paymaster, not the public RPC.
const nonce = await chainClient.getTransactionCount({ address: account.address });
const signed = await account.signTransaction({
  type: "legacy",
  chainId: botChainTestnet.id,
  to: GUEST_BOOK,
  data,
  gas,
  gasPrice: 0n,
  nonce,
});
const hash = await paymaster.request({ method: "eth_sendRawTransaction", params: [signed] });
console.log(`Sent: ${botChainTestnet.blockExplorers.default.url}/tx/${hash}`);