Coco in NodeJS

In this example we will setup a coco wallet in a long-running NodeJS process (like a web server).

Dependencies

After setting up your node project we need to install the required dependencies.

• @cashu/coco-core: Our core module
• @cashu/coco-sqlite: Our Node storage adapter
• better-sqlite3: A SQLite driver / client for Node
• ws & @types/ws: A websocket implementation for node
• @scure/bip39: A set of utilities to work with BIP39 mnemonics

Setup

Once all dependencies are installed we need to prepare our project so that we can use coco.

Seed Getter

Coco requires a BIP39 conforming seed to work. In our example we will read a BIP39 mnemonic from a local file and convert it into the Uint8Array for coco to read.

// seedgetter.ts
import { readFile } from 'node:fs/promises';
import { mnemonicToSeed } from '@scure/bip39';

export function cachedSeedGetter() {
  let seed: Uint8Array | undefined = undefined;
  async function seedGetter() {
    if (seed) {
      return seed;
    }
    const file = await readFile('./mnemonic.txt', 'utf8');
    seed = await mnemonicToSeed(file);
    return seed;
  }
  return seedGetter;
}

Persistence

We are going to use better-sqlite3 to persist our wallet data. Coco expects a repository implementation when instantiating. The @cashu/coco-sqlite package helps us bridge better-sqlite3 to Coco.

// repo.ts
import { SqliteRepositories } from '@cashu/coco-sqlite';
import Database from 'better-sqlite3';

const db = new Database('./coco.db');
export const repo = new SqliteRepositories({ database: db });

Websockets

As node does not offer a native Websocket implementation we will provide one to Coco using the ws package

// websocket.ts
import { WebSocket } from 'ws';
import { WebSocketFactory } from '@cashu/coco-core';

export const websocketFactory: WebSocketFactory = (url: string) => new WebSocket(url);

Initialize Coco

Now that we have all the parts prepared we can bring them together and instantiate coco

import { initializeCoco } from '@cashu/coco-core';
import { repo } from './repo.ts';
import { websocketFactory } from './websocket.ts';
import { cachedSeedGetter } from './seedgetter.ts';

export const coco = await initializeCoco({
  repo: repo,
  seedGetter: cachedSeedGetter(),
  websocketFactory: websocketFactory,
});

Use Coco

Now that we have instantiated and exported an active coco manager class, we can use it in our modules

import { coco } from './coco.ts';

async function apiBalanceController(res, req, next) {
  const balances = await coco.wallet.balances.byMint();
  const total = await coco.wallet.balances.total();
  res.json({ balances, total });
}