fix: integrity error for DUC

When receiving a payment paid from a DUC,
there isn't any card masked pan, so we
fall back to save only the payment type.
fixes #15

paygate/processors.py

@@ -500,10 +500,12 @@ def handle_processor_response(self, response, basket=None):
 
         # Payment type (VISA, MASTERCARD, PAYPAL, MBWAY, REFMB, DUC, ...)
         # We use the `card_type` to save the payment type used.
-        card_type = paygate_transaction.get("PAYMENT_TYPE_CODE", "PayGate")
+        card_type = paygate_transaction.get("PAYMENT_TYPE_CODE")
 
         # Save only a mask of the card
-        card_number = paygate_transaction.get("CARD_MASKED_PAN", card_type)
+        card_number = paygate_transaction.get("CARD_MASKED_PAN")
+        if not card_number:
+            card_number = card_type
 
         hpr = HandledProcessorResponse(
             transaction_id=transaction_id,

paygate/tests/test_views.py

@@ -366,3 +366,42 @@ def test_server_response_view_small_callback_data(self, mock__make_api_json_requ
         order = Order.objects.all().first()
         self.assertEqual(order.basket.id, basket.id)
         self.assertTrue(len(Order.objects.all()) == 1)
+
+    @mock.patch.object(PayGate, "_make_api_json_request")
+    def test_callback_server_duc(self, mock__make_api_json_request):
+        """
+        Test the server-to-server callback with a DUC payment.
+        """
+        # create data for test
+        course = CourseFactory(id='a/b/c', name='Demo Course', partner=self.partner)
+        course.save()
+        product = course.create_or_update_seat('test-certificate-type', False, 20)
+        product.save()
+        basket = create_basket(site=self.site, owner=UserFactory(), empty=True)
+        basket.add_product(product)
+        basket.save()
+
+        # mock the call to PayGate to double-check if it's being payed
+        mock__make_api_json_request.return_value = [{
+            "MERCHANT_CODE": "NAU",
+            "STATUS_CODE": "C",
+            "PAYMENT_REF": basket.order_number,
+            "PAYMENT_AMOUNT": "20.00",
+            "TRANSACTION_ID": "123415432432432",
+            "CARD_MASKED_PAN": None,
+            "PAYMENT_TYPE_CODE": "DUC",
+        }]
+
+        callback_server_data = {
+            'payment_ref': basket.order_number,
+        }
+        response = self.client.post(
+            reverse("ecommerce_plugin_paygate:callback_server"),
+            data=json.dumps(callback_server_data),
+            content_type='application/json'
+        )
+        self.assertContains(response, "Received server callback with success")
+
+        order = Order.objects.all().first()
+        self.assertEqual(order.basket.id, basket.id)
+        self.assertTrue(len(Order.objects.all()) == 1)