server.ts

import express, { Express, Request, Response } from 'express';
import cors from 'cors';
import { deserialize } from 'borsh';
import { Account } from 'near-api-js';
import { SCHEMA, SignedDelegate, actionCreators } from '@near-js/transactions';
import { getAccount } from './util';

const app: Express = express();
app.use(cors());
app.use(express.json());

const RELAYER_ID = 'the-relayer.testnet';
const RELAYER_PRIVATE_KEY =
  'ed25519:2fpNWkegHqdeJNYCzaT1rhjJSsXASjeTvfzpz5xWRQavvap8CkU2ri7mjFMrFmsL3EvTtgWfy8RNY6y66aPy7Pt6';
const NETWORK_ID = 'testnet';

app.post('/', async (req: Request, res: Response) => {
  const serializedTxs: Buffer[] = req.body;
  const relayerAccount: Account = await getAccount(
    NETWORK_ID,
    RELAYER_ID,
    RELAYER_PRIVATE_KEY,
  );

  const outcomes = await Promise.all(
    serializedTxs.map(async (serializedTx) => {
      const deserializedTx: SignedDelegate = deserialize(
        SCHEMA.SignedDelegate,
        Buffer.from(serializedTx),
      ) as SignedDelegate;

      return await relayerAccount.signAndSendTransaction({
        actions: [actionCreators.signedDelegate(deserializedTx)],
        receiverId: deserializedTx.delegateAction.senderId,
      });
    }),
  );

  res.json({ message: 'Relayed', data: outcomes });
});

app.listen(5000, () => {
  console.log(`Relayer is running on port 5000`);
});