Implement tag and ingredient filtering

app/recipe/views.py

@@ -114,6 +114,17 @@ def upload_image(self, request, pk=None):
         return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
 
 
+@extend_schema_view(
+    list=extend_schema(
+        parameters=[
+            OpenApiParameter(
+                'assigned_only',
+                OpenApiTypes.INT, enum=[0, 1],
+                description='Filter by items assigned to recipes.',
+            )
+        ]
+    )
+)
 class BaserecipeAttrViewSet(mixins.DestroyModelMixin,
                             mixins.UpdateModelMixin,
                             mixins.ListModelMixin,
@@ -124,7 +135,15 @@ class BaserecipeAttrViewSet(mixins.DestroyModelMixin,
 
     def get_queryset(self):
         """Filter queryset to authenticated user."""
-        return self.queryset.filter(user=self.request.user).order_by('-name')
+        assigned_only = bool(
+            int(self.request.query_params.get('assigned_only', 0))
+        )
+        queryset = self.queryset
+        if assigned_only:
+            queryset = queryset.filter(recipe__isnull=False)
+        return queryset.filter(
+                user=self.request.user
+            ).order_by('-name').distinct()
 
 
 class TagViewSet(BaserecipeAttrViewSet):