const crypto = require('crypto');

function verifyWebflowSignature(rawBody, signature, timestamp, secret) {
  // Check timestamp to prevent replay attacks (5 minute window - 300000 milliseconds)
  const currentTime = Date.now();
  if (Math.abs(currentTime - parseInt(timestamp)) > 300000) {
    return false;
  }

  // Generate HMAC signature
  const signedContent = `${timestamp}:${rawBody}`;
  const expectedSignature = crypto
    .createHmac('sha256', secret)
    .update(signedContent)
    .digest('hex');

  // Timing-safe comparison
  try {
    return crypto.timingSafeEqual(
      Buffer.from(signature),
      Buffer.from(expectedSignature)
    );
  } catch {
    return false; // Different lengths = invalid
  }
}

app.post('/webhooks/webflow', express.raw({ type: 'application/json' }), (req, res) => {
  const signature = req.headers['x-webflow-signature'];
  const timestamp = req.headers['x-webflow-timestamp'];

  if (!signature || !timestamp) {
    return res.status(400).send('Missing required headers');
  }

  // Verify signature (use OAuth client secret or webhook-specific secret)
  const isValid = verifyWebflowSignature(
    req.body.toString(),
    signature,
    timestamp,
    process.env.WEBFLOW_WEBHOOK_SECRET
  );

  if (!isValid) {
    return res.status(400).send('Invalid signature');
  }

  // Parse the verified payload
  const event = JSON.parse(req.body);

  // Handle different event types
  switch (event.triggerType) {
    case 'form_submission':
      console.log('New form submission:', event.payload.data);
      break;
    case 'ecomm_new_order':
      console.log('New order:', event.payload);
      break;
    case 'collection_item_created':
      console.log('New CMS item:', event.payload);
      break;
    // Add more event handlers as needed
  }

  // Always return 200 to acknowledge receipt
  res.status(200).send('OK');
});