index.js

const axios = require('axios').default;
const { Keypair, PublicKey, Connection, Transaction, sendAndConfirmRawTransaction, LAMPORTS_PER_SOL } = require('@solana/web3.js');
const {
    createMint, getOrCreateAssociatedTokenAccount, Account,
    mintTo, createTransferInstruction, createAccount, getAccount, getAssociatedTokenAddress,
} = require('@solana/spl-token');
const base58 = require('bs58');

const baseURL = 'https://octane-mainnet-beta.breakroom.show/api';

async function main() {
  const connection = new Connection('https://api.mainnet-beta.solana.com', 'confirmed');

  // (1) Preparation

  // Let's now connect to Octane instance and get some needed params:
  // 1) how much we should pay for transaction in tokens
  // 2) which account will pay for transaction in SOL (feePayer)
  // Normally, you should also learn which kind of tokens supported and
  // get price in each of them, but devnet endpoint accepts any token through
  // config overrides. 
  const response = (await axios.get(baseURL, {
    headers: {'Accept': 'application/json'}
  })).data;
  const feePayer = new PublicKey(response.feePayer);
  const mint = new PublicKey(response.endpoints.transfer.tokens[0].mint);
  const feeAccount = new PublicKey(response.endpoints.transfer.tokens[0].account);
  const simpleTransactionFee = response.endpoints.transfer.tokens[0].fee;


  // (2) Prepare the hypothetical end user account
  const endUserKeypair = Keypair.fromSecretKey(base58.decode(process.env.SECRET_KEY));
  const endUserTokenAccount = await getAssociatedTokenAddress(mint, endUserKeypair.publicKey);

  // (3) Create the transaction — we'll transfer some tokens to targetOwner as our first gasless transaction. 

  const targetOwner = new PublicKey('EmMC1F6X25qsnXVzNzKUyqFWfLF2GsVJW55fGJRm9feY');
  const targetAccount = await getAssociatedTokenAddress(mint, targetOwner);

  // The transaction would consist of two instructions:
  // 1) token transfer to octane's token account as payment for running transaction gasless
  // 2) the payload, actual instruction we want to execute. in this case, it's also a token transfer to targetKeypair, but it could be anything.
  const transaction = new Transaction();
  transaction.add(createTransferInstruction(endUserTokenAccount, feeAccount, endUserKeypair.publicKey, simpleTransactionFee));
  transaction.add(createTransferInstruction(endUserTokenAccount, targetAccount, endUserKeypair.publicKey, 100));
  transaction.feePayer = feePayer;
  transaction.recentBlockhash = (await connection.getLatestBlockhash()).blockhash;
  
  transaction.partialSign(endUserKeypair); // in client code, you should use wallet adapter instead

  // (4) Send the transaction to octane to sign and attach signature to transaction

  const octaneResponse = (await axios.post(baseURL + '/transfer', {
    transaction: base58.encode(transaction.serialize({requireAllSignatures: false})),
  })).data;
  transaction.addSignature(feePayer, base58.decode(octaneResponse.signature));

  // (5) Send transaction to network

  await sendAndConfirmRawTransaction(connection, transaction.serialize(), { commitment: 'confirmed' });
  console.log('Find on mainnet explorer ///', octaneResponse.signature);
}

main();