Know the moment money moves

// Express receiver for Localpayment webhooks (Node.js 18+).
import crypto from 'node:crypto';
import express from 'express';
import { jobQueue } from './queue.js'; // your own async job queue

const app = express();

// Load the webhook secret from your secrets manager at boot. Never hardcode it.
const WEBHOOK_SECRET = process.env.LP_WEBHOOK_SECRET;
if (!WEBHOOK_SECRET) throw new Error('LP_WEBHOOK_SECRET is not configured');

function hasValidSignature(rawBody, header) {
  if (typeof rawBody !== 'string') return false;
  // Header format: "x-Signature: HMAC-SHA256 <hex>". Strip the prefix first.
  const received = String(header ?? '').replace(/^HMAC-SHA256\s+/i, '').trim();
  if (!/^[0-9a-f]{64}$/i.test(received)) return false;

  const expected = crypto.createHmac('sha256', WEBHOOK_SECRET).update(rawBody, 'utf8').digest();
  return crypto.timingSafeEqual(Buffer.from(received, 'hex'), expected);
}

// The body is JSON sent as Content-Type text/plain: keep the raw text for the HMAC.
app.post('/webhooks/localpayment', express.text({ type: '*/*', limit: '1mb' }), (req, res) => {
  if (!hasValidSignature(req.body, req.get('x-signature'))) return res.sendStatus(401);

  let event;
  try {
    event = JSON.parse(req.body);
  } catch {
    return res.sendStatus(400);
  }

  res.sendStatus(200); // acknowledge fast, before any heavy work
  // Process asynchronously. Deduplicate on internalId/externalId + status
  // so a retried delivery is applied only once. Never log the full payload.
  jobQueue.enqueue(event);
});