feat(upgrade):pagination support for articles

- add function in list all views to paginate articles
- import paginator from django framework

[DELIVERS #160617682]

authors/apps/articles/views.py

@@ -14,6 +14,11 @@
 
 class ArticleAPIView(generics.ListCreateAPIView):
     """create an article, list all articles """
+from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
+from rest_framework import serializers
+from django.core.exceptions import ObjectDoesNotExist
+class ArticleAPIView(generics.ListCreateAPIView):
+    """create an article, list all articles paginated to 5 per page"""
     queryset = Article.objects.all()
     permission_classes = (IsAuthenticatedOrReadOnly,)
     renderer_classes = (ArticleJSONRenderer,)
@@ -28,9 +33,26 @@ def create(self, request, *args, **kwargs):
         return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)
 
     def perform_create(self, serializer):
-        serializer.save(author=self.request.user)
+        serializer.save(author=self.request.user)   
+
+    def get(self, request):
+        paginator = Paginator(self.queryset, 5)  # show 5 articles at a time.
+        page = request.GET.get('page')
+        try:
+            self.queryset = paginator.page(page)
+        except PageNotAnInteger:
+            # If page is not an integer, deliver first page
+            self.queryset = paginator.page(1)
+        except EmptyPage:
+            # if page is out of range, deliver last page of results
+            self.queryset = paginator.page(paginator.num_pages)
+
+        serializer = self.serializer_class(self.queryset, many=True)
+        return Response({"articles": serializer.data,
+                         "number_of_pages": paginator.num_pages,
+                         "number_of_articles": paginator.count}, status=status.HTTP_200_OK)
+
 
-
 class ArticleAPIDetailsView(generics.RetrieveUpdateDestroyAPIView):
     """retreive, update and delete an article """
     permission_classes = (IsAuthenticatedOrReadOnly,)