update validation logic and address comments

backend/clubs/migrations/0091_applicationextension.py

@@ -1,4 +1,4 @@
-# Generated by Django 3.2.18 on 2023-11-23 00:07
+# Generated by Django 3.2.18 on 2023-11-25 03:58
 
 import django.db.models.deletion
 from django.conf import settings
@@ -42,5 +42,6 @@ class Migration(migrations.Migration):
                     ),
                 ),
             ],
+            options={"unique_together": {("user", "application")}},
         ),
     ]

backend/clubs/models.py

@@ -1603,6 +1603,9 @@ class ApplicationExtension(models.Model):
     )
     end_time = models.DateTimeField()
 
+    class Meta:
+        unique_together = (("user", "application"),)
+
 
 class ApplicationCommittee(models.Model):
     """

backend/clubs/serializers.py

@@ -2444,12 +2444,6 @@ class Meta:
             "end_time",
         )
 
-    def validate_username(self, value):
-        user = get_user_model().objects.filter(username=value).first()
-        if not user:
-            raise serializers.ValidationError("Please provide a valid username!")
-        return value
-
     def create(self, validated_data):
         username = validated_data.get("user").pop("username")
         validated_data["user"] = get_user_model().objects.get(username=username)
@@ -2462,13 +2456,50 @@ def create(self, validated_data):
         return super().create(validated_data)
 
     def update(self, instance, validated_data):
-        user_field = validated_data.pop("user", None)
-        if user_field:
+        if user_field := validated_data.pop("user", None):
             username = user_field.pop("username")
             user = get_user_model().objects.get(username=username)
             instance.user = user
         return super().update(instance, validated_data)
 
+    def validate(self, data):
+        username = None
+        if user_field := data.get("user") or not self.instance:
+            username = user_field.get("username")
+            user = get_user_model().objects.filter(username=username).first()
+            if not user:
+                raise serializers.ValidationError("Please provide a valid username!")
+
+        application_pk = self.context["view"].kwargs.get("application_pk")
+        application = ClubApplication.objects.filter(pk=application_pk).first()
+
+        if not application:
+            raise serializers.ValidationError("Invalid application id!")
+
+        if (
+            (
+                not self.instance
+                or (username and self.instance.user.username != username)
+            )
+            and ApplicationExtension.objects.filter(
+                user=user, application=application
+            ).exists()
+        ):
+            raise serializers.ValidationError(
+                "An extension for this user and application already exists!"
+            )
+
+        extension_end_time = data.get("end_time")
+        if (
+            extension_end_time
+            and extension_end_time <= application.application_end_time
+        ):
+            raise serializers.ValidationError(
+                "Extension end time must be greater than the application end time!"
+            )
+
+        return data
+
 
 class ApplicationSubmissionSerializer(serializers.ModelSerializer):
     committee = ApplicationCommitteeSerializer(required=False, read_only=True)

backend/clubs/views.py

@@ -4458,11 +4458,7 @@ def question_response(self, *args, **kwargs):
 
         # prevent submissions outside of the open duration
         now = timezone.now()
-        extension = (
-            application.extensions.filter(user=self.request.user)
-            .order_by("-end_time")
-            .first()
-        )
+        extension = application.extensions.filter(user=self.request.user).first()
         end_time = (
             max(extension.end_time, application.application_end_time)
             if extension
@@ -4814,7 +4810,7 @@ def current(self, *args, **kwargs):
                                 - $ref: "#/components/schemas/ClubApplication"
         ---
         """
-        qs = self.get_queryset()
+        qs = self.get_queryset().prefetch_related("extensions")
         now = timezone.now()
         user = self.request.user
         q = Q(application_end_time__gte=now)