From 37458db314ab6b0bc80a78d9295da291b1cd394c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABl=20Kervella?= <kervella.mael@gmail.com>
Date: Thu, 24 May 2018 23:02:39 +0000
Subject: [PATCH] Add custom pagination for setting page_size

---
 api/pagination.py | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 api/settings.py   |  2 +-
 2 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 api/pagination.py

diff --git a/api/pagination.py b/api/pagination.py
new file mode 100644
index 00000000..a6a6adcb
--- /dev/null
+++ b/api/pagination.py
@@ -0,0 +1,47 @@
+from rest_framework import pagination
+from django.core import paginator
+from django.utils.functional import cached_property
+
+
+class AllowNegativePaginator(paginator.Paginator):
+    """
+    Paginator subclass to allow negative or null `per_page` argument,
+    meaning to show all items in one page.
+    """
+    def page(self, number):
+        """
+        Bypass the default page creation to render all items if `per_page`
+        argument is negative or null.
+        """
+        if self.per_page <= 0:
+            return self._get_page(self.object_list, 1, self)
+        return super(AllowNegativePaginator, self).page(number)
+
+    @cached_property
+    def num_pages(self):
+        """
+        Bypass the default number of page to return 1 if `per_page` argument
+        is negative or null.
+        """
+        if self.per_page <= 0:
+            return 1
+        return super(AllowNegativePaginator, self).num_pages
+
+
+class PageSizedPagination(pagination.PageNumberPagination):
+    """
+    Pagination subclass to all to control the page size
+    """
+    page_size_query_param = 'page_size'
+    all_pages_strings = ('all',)
+    django_paginator_class = AllowNegativePaginator
+
+    def get_page_size(self, request):
+        try:
+            page_size_str = request.query_params[self.page_size_query_param]
+            if page_size_str in self.all_pages_strings:
+                return -1
+        except KeyError:
+            pass
+
+        return super(PageSizedPagination, self).get_page_size(request)
diff --git a/api/settings.py b/api/settings.py
index 6bf48e33..c1ec4786 100644
--- a/api/settings.py
+++ b/api/settings.py
@@ -35,7 +35,7 @@ REST_FRAMEWORK = {
     'DEFAULT_PERMISSION_CLASSES': (
         'api.permissions.DefaultACLPermission',
     ),
-    'DEFAULT_PAGINATION_CLASS': 'rest_framework.pagination.PageNumberPagination',
+    'DEFAULT_PAGINATION_CLASS': 'api.pagination.PageSizedPagination',
     'PAGE_SIZE': 100
 }