// Webhook endpoint to receive payment notifications
app.post('/webhooks/rebell', express.json(), (req, res) => {
  // 1. Verify the signature (see Authentication docs)
  if (!verifySignature(req)) {
    return res.status(401).json({ result: { resultStatus: 'F' } });
  }

  const { paymentId, paymentRequestId, paymentStatus, paymentAmount } = req.body;

  // 2. Process the payment result
  if (paymentStatus === 'SUCCESS') {
    // Update order status, trigger fulfillment, etc.
    updateOrderStatus(paymentRequestId, 'paid');
  } else if (paymentStatus === 'FAIL') {
    updateOrderStatus(paymentRequestId, 'failed');
  }

  // 3. Acknowledge receipt
  res.json({ result: { resultStatus: 'S' } });
});

{
  "result": {
    "resultStatus": "S",
    "resultCode": "<string>",
    "resultMessage": "<string>"
  }
}