Related pagination mixin

adit_radis_shared/common/mixins.py

@@ -1,6 +1,7 @@
 from typing import Any, Protocol
 
 from django.core.exceptions import SuspiciousOperation
+from django.core.paginator import EmptyPage, PageNotAnInteger, Paginator
 from django.db.models import QuerySet
 from django.http import HttpRequest, HttpResponse
 from django.views.generic import TemplateView
@@ -16,14 +17,11 @@
 class ViewProtocol(Protocol):
     request: HttpRequest
 
-    def dispatch(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse:
-        ...
+    def dispatch(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse: ...
 
-    def get(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse:
-        ...
+    def get(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse: ...
 
-    def get_context_data(self, **kwargs: Any) -> dict[str, Any]:
-        ...
+    def get_context_data(self, **kwargs: Any) -> dict[str, Any]: ...
 
 
 class LockedMixinProtocol(ViewProtocol, Protocol):
@@ -63,14 +61,11 @@ class RelatedFilterMixinProtocol(ViewProtocol, Protocol):
     filterset: FilterSet
     object_list: QuerySet
 
-    def get_strict(self) -> bool:
-        ...
+    def get_strict(self) -> bool: ...
 
-    def get_filterset_class(self) -> type[FilterSet]:
-        ...
+    def get_filterset_class(self) -> type[FilterSet]: ...
 
-    def get_filterset(self, filterset_class: type[FilterSet]) -> FilterSet:
-        ...
+    def get_filterset(self, filterset_class: type[FilterSet]) -> FilterSet: ...
 
 
 class RelatedFilterMixin(FilterMixin):
@@ -147,3 +142,55 @@ def get_context_data(self: PageSizeSelectMixinProtocol, **kwargs):
         context["page_size_select"] = PageSizeSelectForm(self.request.GET, self.page_sizes)
 
         return context
+
+
+class RelatedPaginationMixinProtocol(ViewProtocol, Protocol):
+    object_list: QuerySet
+    paginate_by: int
+
+    def get_object(self) -> Any: ...
+
+    def get_context_data(self, **kwargs) -> dict[str, Any]: ...
+
+    def get_related_queryset(self) -> QuerySet: ...
+
+
+class RelatedPaginationMixin:
+    """This mixin provides pagination for a related queryset. This makes it possible to
+    paginate a related queryset in a DetailView. The related queryset is obtained by
+    the `get_related_queryset()` method that must be implemented by the subclass.
+    If used in combination with `RelatedFilterMixin`, the `RelatedPaginationMixin` must be
+    inherited first."""
+
+    request: HttpRequest
+
+    def get_related_queryset(self: RelatedPaginationMixinProtocol) -> QuerySet:
+        raise NotImplementedError("You must implement this method")
+
+    def get_context_data(self: RelatedPaginationMixinProtocol, **kwargs):
+        context = super().get_context_data(**kwargs)
+
+        if "object_list" in context:
+            queryset = context["object_list"]
+        else:
+            queryset = self.get_related_queryset()
+
+        paginator = Paginator(queryset, self.paginate_by)
+        page = self.request.GET.get("page")
+
+        if page is None:
+            page = 1
+
+        try:
+            paginated_queryset = paginator.page(page)
+        except PageNotAnInteger:
+            paginated_queryset = paginator.page(1)
+        except EmptyPage:
+            paginated_queryset = paginator.page(paginator.num_pages)
+
+        context["object_list"] = paginated_queryset
+        context["paginator"] = paginator
+        context["is_paginated"] = paginated_queryset.has_other_pages()
+        context["page_obj"] = paginated_queryset
+
+        return context