From 1eb2dfcc3a84deb21aeae5a427cc8b11f578c00c Mon Sep 17 00:00:00 2001
From: Tom Drummond <tom@devioustree.co.uk>
Date: Tue, 19 Jul 2011 17:06:56 +0100
Subject: [PATCH] Added pagination mixin. Need to write tests

---
 djangorestframework/mixins.py | 89 +++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/djangorestframework/mixins.py b/djangorestframework/mixins.py
index bb26ad963..56f173935 100644
--- a/djangorestframework/mixins.py
+++ b/djangorestframework/mixins.py
@@ -4,6 +4,7 @@ classes that can be added to a `View`.
 """
 
 from django.contrib.auth.models import AnonymousUser
+from django.core.paginator import Paginator
 from django.db.models.query import QuerySet
 from django.db.models.fields.related import ForeignKey
 from django.http import HttpResponse
@@ -637,4 +638,92 @@ class ListModelMixin(object):
             queryset = queryset.order_by(*args)
         return queryset.filter(**kwargs)
 
+########## Pagination Mixins ##########
+
+class PaginatorMixin(object):
+    """
+    Adds pagination support to GET requests
+    Obviously should only be used on lists :)
+    
+    A default limit can be set by setting `limit` on the object. This will also
+    be used as the maximum if the client sets the `limit` GET param
+    """
+    limit = 20
+
+    def get_limit(self):
+        """ Helper method to determine what the `limit` should be """
+        try:
+            limit = int(self.request.GET.get('limit', self.limit))
+            return min(limit, self.limit)
+        except ValueError:
+            return self.limit
+
+    def url_with_page_number(self, page_number):
+        """ Constructs a url used for getting the next/previous urls """
+        url = "%s?page=%d" % (self.request.path, page_number)
+
+        limit = self.get_limit()
+        if limit != self.limit:
+            url = "%s&limit=%d" % (url, limit)
+
+        return url
+
+    def next(self, page):
+        """ Returns a url to the next page of results (if any) """
+        if not page.has_next():
+            return None
+
+        return self.url_with_page_number(page.next_page_number())
+
+    def previous(self, page):
+        """ Returns a url to the previous page of results (if any) """
+        if not page.has_previous():
+            return None
+
+        return self.url_with_page_number(page.previous_page_number())
+
+    def serialize_page_info(self, page):
+        """ This is some useful information that is added to the response """
+        return {
+            'next': self.next(page),
+            'page': page.number,
+            'pages': page.paginator.num_pages,
+            'per_page': self.get_limit(),
+            'previous': self.previous(page),
+            'total': page.paginator.count,
+        }
+
+    def filter_response(self, obj):
+        """
+        Given the response content, paginate and then serialize.
+        
+        The response is modified to include to useful data relating to the number
+        of objects, number of pages, next/previous urls etc. etc.
+        
+        The serialised objects are put into `results` on this new, modified
+        response
+        """
+        
+        # We don't want to paginate responses for anything other than GET requests
+        if self.method.upper() != 'GET':
+            return self._resource.filter_response(obj)
+
+        paginator = Paginator(obj, self.get_limit())
+
+        try:
+            page_num = int(self.request.GET.get('page', '1'))
+        except ValueError:
+            page_num = 1
+
+        if page_num not in paginator.page_range:
+            raise ErrorResponse(status.HTTP_404_NOT_FOUND, {'detail': 'That page contains no results'})
+
+        page = paginator.page(page_num)
+
+        serialized_object_list = self._resource.filter_response(page.object_list)
+        serialized_page_info = self.serialize_page_info(page)
+
+        serialized_page_info['results'] = serialized_object_list
+
+        return serialized_page_info