feat(promo): Refactor CompanyPromoDetailView to RetrieveUpdateAPIView

Refactor CompanyPromoDetailView from a generic APIView to DRF’s
RetrieveUpdateAPIView in order to leverage built-in retrieve/update
behavior and simplify the implementation.

Key changes:
- Use `RetrieveUpdateAPIView` as the base class to get object lookup,
  serialization, validation and response handling for free
- Remove manual `get()` and `patch()` methods
- Add `business.permissions.IsPromoOwner` to `permission_classes` for
  declarative authorization
- Define `queryset = Promo.objects.with_related().only(...).for_company()`
  on the view to centralize and optimize data access
- Implement `with_related()` and `for_company(user)` on the Promo
  queryset/manager for efficient prefetching and filtering
- Drop unused imports and old helper code

This change reduces boilerplate, improves consistency with DRF
idioms, and makes permission checks and queryset logic easier to
maintain.

Author: RandomProgramm3r

promo_code/business/managers.py

@@ -22,6 +22,33 @@ def create_company(self, email, name, password=None, **extra_fields):
 
 
 class PromoManager(django.db.models.Manager):
+    def get_queryset(self):
+        return super().get_queryset()
+
+    def with_related(self):
+        return (
+            self.select_related('company')
+            .prefetch_related('unique_codes')
+            .only(
+                'id',
+                'company',
+                'description',
+                'image_url',
+                'target',
+                'max_count',
+                'active_from',
+                'active_until',
+                'mode',
+                'promo_common',
+                'created_at',
+                'company__id',
+                'company__name',
+            )
+        )
+
+    def for_company(self, user):
+        return self.with_related().filter(company=user)
+
     @django.db.transaction.atomic
     def create_promo(
         self,

promo_code/business/pagination.py

@@ -1,4 +1,3 @@
-import rest_framework.exceptions
 import rest_framework.pagination
 import rest_framework.response
 

promo_code/business/permissions.py

@@ -5,4 +5,14 @@
 
 class IsCompanyUser(rest_framework.permissions.BasePermission):
     def has_permission(self, request, view):
+        if not request.user or not request.user.is_authenticated:
+            return False
+
         return isinstance(request.user, business.models.Company)
+
+
+class IsPromoOwner(rest_framework.permissions.BasePermission):
+    message = 'The promo code does not belong to this company.'
+
+    def has_object_permission(self, request, view, obj):
+        return getattr(obj, 'company_id', None) == request.user.id

promo_code/business/views.py

@@ -1,7 +1,6 @@
 import re
 
 import django.db.models
-import django.shortcuts
 import pycountry
 import rest_framework.exceptions
 import rest_framework.generics
@@ -150,29 +149,7 @@ class CompanyPromoListView(rest_framework.generics.ListAPIView):
     pagination_class = business.pagination.CustomLimitOffsetPagination
 
     def get_queryset(self):
-        queryset = (
-            business.models.Promo.objects.filter(
-                company=self.request.user,
-            )
-            .select_related('company')
-            .prefetch_related('unique_codes')
-            .only(
-                'id',
-                'company',
-                'description',
-                'image_url',
-                'target',
-                'max_count',
-                'active_from',
-                'active_until',
-                'mode',
-                'promo_common',
-                'created_at',
-                'company__id',
-                'company__name',
-            )
-        )
-
+        queryset = business.models.Promo.objects.for_company(self.request.user)
         countries = [
             country.strip()
             for group in self.request.query_params.getlist('country', [])
@@ -298,113 +275,24 @@ def _validate_limit(self):
                 )
 
 
-class CompanyPromoDetailView(rest_framework.views.APIView):
+class CompanyPromoDetailView(rest_framework.generics.RetrieveUpdateAPIView):
+    """
+    Retrieve (GET) and partially update (PATCH) detailed information
+    about a company’s promo.
+    """
+
+    http_method_names = ['get', 'patch', 'options', 'head']
+
+    serializer_class = business.serializers.PromoDetailSerializer
+
     permission_classes = [
         rest_framework.permissions.IsAuthenticated,
         business.permissions.IsCompanyUser,
+        business.permissions.IsPromoOwner,
     ]
 
     lookup_field = 'id'
 
-    def get_queryset(self):
-        user = self.request.user
-        return (
-            business.models.Promo.objects.filter(company=user)
-            .select_related('company')
-            .prefetch_related('unique_codes')
-            .select_related('company')
-            .prefetch_related('unique_codes')
-            .only(
-                'id',
-                'company',
-                'description',
-                'image_url',
-                'target',
-                'max_count',
-                'active_from',
-                'active_until',
-                'mode',
-                'promo_common',
-                'created_at',
-                'company__id',
-                'company__name',
-            )
-        )
-
-    def get(self, request, id):
-        try:
-            promo = business.models.Promo.objects.get(
-                id=id,
-            )
-        except business.models.Promo.DoesNotExist:
-            raise rest_framework.exceptions.NotFound(
-                'Promo not found,',
-            )
-
-        if promo.company != request.user:
-            return rest_framework.response.Response(
-                {
-                    'status': 'error',
-                    'message': (
-                        'The promo code does not belong to this company.'
-                    ),
-                },
-                status=rest_framework.status.HTTP_403_FORBIDDEN,
-            )
-
-        serializer = business.serializers.PromoDetailSerializer(
-            promo,
-        )
-
-        return rest_framework.response.Response(
-            serializer.data,
-            status=rest_framework.status.HTTP_200_OK,
-        )
-
-    def patch(self, request, id, *args, **kwargs):
-        try:
-            promo = business.models.Promo.objects.get(
-                id=id,
-            )
-        except business.models.Promo.DoesNotExist:
-            return rest_framework.response.Response(
-                {
-                    'status': 'error',
-                    'message': 'Promo code not found.',
-                },
-                status=rest_framework.status.HTTP_404_NOT_FOUND,
-            )
-
-        if promo.company != request.user:
-            return rest_framework.response.Response(
-                {
-                    'status': 'error',
-                    'message': ('Promo code does not belong to this company.'),
-                },
-                status=rest_framework.status.HTTP_403_FORBIDDEN,
-            )
-
-        serializer = business.serializers.PromoDetailSerializer(
-            promo,
-            data=request.data,
-            partial=True,
-            context={
-                'request': request,
-            },
-        )
-
-        if not serializer.is_valid():
-            return rest_framework.response.Response(
-                {
-                    'status': 'error',
-                    'message': 'Request data error.',
-                },
-                status=rest_framework.status.HTTP_400_BAD_REQUEST,
-            )
-
-        serializer.save()
-
-        return rest_framework.response.Response(
-            serializer.data,
-            status=rest_framework.status.HTTP_200_OK,
-        )
+    # Use an enriched base queryset without pre-filtering by company,
+    # so that ownership mismatches raise 403 Forbidden (not 404 Not Found).
+    queryset = business.models.Promo.objects.with_related()