GiftsNGifts

// Step 2: Webhook verify - idempotent, runs exactly once per payment
export const paymentVerification = async (req, res) => {
  const { razorpay_order_id, razorpay_payment_id, razorpay_signature } = req.body;

  // Acquire lock - second call on same ID returns 409 immediately
  const lock = await acquireIdempotencyLock(razorpay_order_id);
  if (!lock) return res.status(409).json({ error: "Payment already processing" });

  try {
    if (await isAlreadyProcessed(razorpay_order_id))
      return res.json({ success: true, alreadyProcessed: true });

    // HMAC signature check - rejects tampered webhooks
    const hmac = crypto.createHmac("sha256", process.env.RAZORPAY_KEY_SECRET);
    hmac.update(`${razorpay_order_id}|${razorpay_payment_id}`);
    if (hmac.digest("hex") !== razorpay_signature)
      return res.status(400).json({ error: "Signature mismatch" });

    // Atomic stock confirmation + order state transition
    await confirmStockPurchase(pendingOrder.reservations);
    await transitionOrder(order, ORDER_STATES.CONFIRMED);
    await markProcessed(razorpay_order_id);
    completeIdempotencyLock(razorpay_order_id);
  } catch (err) {
    await releaseReservation(pendingOrder.reservations); // rollback on failure
    throw err;
  }
};