// Express.js webhook handler
const crypto = require('crypto');

// Capture raw body for signature verification (avoid re-serializing JSON).
app.use(require('express').json({
  verify: (req, _res, buf) => { req.rawBody = buf; }
}));

app.post('/webhook', (req, res) => {
  // Verify webhook signature
  const signature = req.headers['x-zm-signature'];
  const timestamp = req.headers['x-zm-request-timestamp'];
  const body = req.rawBody ? req.rawBody.toString('utf8') : JSON.stringify(req.body);
  const payload = `v0:${timestamp}:${body}`;
  const hash = crypto.createHmac('sha256', WEBHOOK_SECRET)
    .update(payload).digest('hex');
  
  if (signature !== `v0=${hash}`) {
    return res.status(401).send('Invalid signature');
  }

  // Handle event
  const { event, payload } = req.body;
  console.log(`Received: ${event}`);
  
  res.status(200).send();
});