Create a Simple Webhook Listener with Node.js and Express

const express = require('express');
const bodyParser = require('body-parser'); // For parsing incoming request bodies
const crypto = require('crypto'); // For verifying webhook signatures

const app = express();
const PORT = process.env.PORT || 3000;
const WEBHOOK_SECRET = process.env.WEBHOOK_SECRET || 'your-super-secret-key'; // Shared secret for signature verification

// Use body-parser to parse JSON bodies. IMPORTANT: raw body is needed for signature verification
app.use(bodyParser.json({
  verify: (req, res, buf) => {
    req.rawBody = buf; // Make the raw body available for signature verification
  }
}));

// Webhook endpoint
app.post('/webhook', (req, res) => {
  // --- Optional: Verify webhook signature (highly recommended for production) ---
  // Example for GitHub-like HMAC-SHA256 signature
  const signature = req.headers['x-hub-signature-256'] || req.headers['x-webhook-signature'];
  if (signature) {
    const hmac = crypto.createHmac('sha256', WEBHOOK_SECRET);
    const digest = 'sha256=' + hmac.update(req.rawBody).digest('hex');
    if (signature !== digest) {
      console.warn('Webhook signature mismatch! Request potentially unauthorized.');
      return res.status(401).send('Signature mismatch');
    }
    console.log('Webhook signature verified successfully.');
  } else {
    console.warn('No webhook signature provided. Proceeding without verification (NOT recommended for sensitive data).');
  }

  // --- Process the webhook payload ---
  const eventType = req.headers['x-github-event'] || 'unknown_event'; // Example for GitHub
  const payload = req.body;

  console.log(`Received ${eventType} event:`, payload);

  // In a real application, you would typically:
  // - Save the event to a database
  // - Queue a job for asynchronous processing (e.g., using a message queue like RabbitMQ or Kafka)
  // - Trigger other internal services or notifications

  res.status(200).send('Webhook received and processed');
});

// Basic health check
app.get('/', (req, res) => {
  res.send('Webhook listener is running.');
});

app.listen(PORT, () => {
  console.log(`Webhook listener running on http://localhost:${PORT}`);
});