Add number_of_months field to UpdatePaymentSerializer and implement validation in UpdatePaymentAPIView

billing/serializers.py

@@ -14,12 +14,9 @@ class PaymentSerializer(serializers.ModelSerializer):
 class UpdatePaymentSerializer(serializers.ModelSerializer):
     class Meta:
         model = Payment
-        fields = [
+        fields = ["paid", "paid_at", "method", "number_of_months"]
-            "paid",
-            "paid_at",
-            "method",
-        ]
 
     paid = serializers.BooleanField(required=True, allow_null=True)
     paid_at = serializers.DateTimeField(required=True, allow_null=True)
     method = serializers.ChoiceField(choices=Payment.PAYMENT_TYPES, required=True)
+    number_of_months = serializers.IntegerField(required=True, allow_null=True)

billing/views.py

@@ -1,6 +1,7 @@
 # Create your views here.
 # billing/views.py
 from datetime import datetime, timedelta
+from django.utils import timezone
 
 import requests
 from decouple import config
@@ -81,12 +82,25 @@ class UpdatePaymentAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
     lookup_field = "pk"
 
     def update(self, request, *args, **kwargs):
+        number_of_months = request.data.get("number_of_months")
+
+        if not number_of_months:
+            return Response(
+                {"message": "number_of_months is required."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+        if not isinstance(number_of_months, int):
+            return Response(
+                {"message": "number_of_months must be an integer."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+        device_expire_date = timezone.now() + timedelta(days=30 * number_of_months)
         instance = self.get_object()
         devices = instance.devices.all()
         serializer = self.get_serializer(instance, data=request.data, partial=False)
         serializer.is_valid(raise_exception=True)
         self.perform_update(serializer)
-        devices.update(is_active=True, expiry_date=instance.expires_at)
+        devices.update(is_active=True, expiry_date=device_expire_date)
         return Response(serializer.data)