Add pagination. Thanks @devioustree!

djangorestframework/mixins.py

@@ -4,20 +4,17 @@ classes that can be added to a `View`.
 """
 
 from django.contrib.auth.models import AnonymousUser
-from django.db.models.query import QuerySet
+from django.core.paginator import Paginator
 from django.db.models.fields.related import ForeignKey
 from django.http import HttpResponse
 
 from djangorestframework import status
-from djangorestframework.parsers import FormParser, MultiPartParser
 from djangorestframework.renderers import BaseRenderer
 from djangorestframework.resources import Resource, FormResource, ModelResource
 from djangorestframework.response import Response, ErrorResponse
 from djangorestframework.utils import as_tuple, MSIE_USER_AGENT_REGEX
 from djangorestframework.utils.mediatypes import is_form_media_type, order_by_precedence
 
-from decimal import Decimal
-import re
 from StringIO import StringIO
 
 
@@ -640,3 +637,93 @@ class ListModelMixin(object):
         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:
+            raise ErrorResponse(status.HTTP_404_NOT_FOUND,
+                                {'detail': 'That page contains no results'})
+
+        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

djangorestframework/tests/mixins.py

@@ -1,11 +1,14 @@
-"""Tests for the status module"""
+"""Tests for the mixin module"""
 from django.test import TestCase
+from django.utils import simplejson as json
 from djangorestframework import status
 from djangorestframework.compat import RequestFactory
 from django.contrib.auth.models import Group, User
-from djangorestframework.mixins import CreateModelMixin
+from djangorestframework.mixins import CreateModelMixin, PaginatorMixin
 from djangorestframework.resources import ModelResource
+from djangorestframework.response import Response
 from djangorestframework.tests.models import CustomUser
+from djangorestframework.views import View
 
 
 class TestModelCreation(TestCase):
@@ -30,7 +33,6 @@ class TestModelCreation(TestCase):
         self.assertEquals(1, Group.objects.count())
         self.assertEquals('foo', response.cleaned_content.name)
 
-
     def test_creation_with_m2m_relation(self):
         class UserResource(ModelResource):
             model = User
@@ -41,7 +43,11 @@ class TestModelCreation(TestCase):
         group = Group(name='foo')
         group.save()
 
-        form_data = {'username': 'bar', 'password': 'baz', 'groups': [group.id]}        
+        form_data = {
+            'username': 'bar',
+            'password': 'baz',
+            'groups': [group.id]
+        }
         request = self.req.post('/groups', data=form_data)
         cleaned_data = dict(form_data)
         cleaned_data['groups'] = [group]
@@ -92,7 +98,6 @@ class TestModelCreation(TestCase):
         self.assertEquals(1, response.cleaned_content.groups.count())
         self.assertEquals('foo1', response.cleaned_content.groups.all()[0].name)
 
-        
         group2 = Group(name='foo2')
         group2.save()
 
@@ -111,3 +116,122 @@ class TestModelCreation(TestCase):
         self.assertEquals('foo2', response.cleaned_content.groups.all()[1].name)
 
 
+class MockPaginatorView(PaginatorMixin, View):
+    total = 60
+
+    def get(self, request):
+        return range(0, self.total)
+
+    def post(self, request):
+        return Response(status.CREATED, {'status': 'OK'})
+
+
+class TestPagination(TestCase):
+    def setUp(self):
+        self.req = RequestFactory()
+
+    def test_default_limit(self):
+        """ Tests if pagination works without overwriting the limit """
+        request = self.req.get('/paginator')
+        response = MockPaginatorView.as_view()(request)
+
+        content = json.loads(response.content)
+
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(MockPaginatorView.total, content['total'])
+        self.assertEqual(MockPaginatorView.limit, content['per_page'])
+
+        self.assertEqual(range(0, MockPaginatorView.limit), content['results'])
+
+    def test_overwriting_limit(self):
+        """ Tests if the limit can be overwritten """
+        limit = 10
+
+        request = self.req.get('/paginator')
+        response = MockPaginatorView.as_view(limit=limit)(request)
+
+        content = json.loads(response.content)
+
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(content['per_page'], limit)
+
+        self.assertEqual(range(0, limit), content['results'])
+
+    def test_limit_param(self):
+        """ Tests if the client can set the limit """
+        from math import ceil
+
+        limit = 5
+        num_pages = int(ceil(MockPaginatorView.total / float(limit)))
+
+        request = self.req.get('/paginator/?limit=%d' % limit)
+        response = MockPaginatorView.as_view()(request)
+
+        content = json.loads(response.content)
+
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(MockPaginatorView.total, content['total'])
+        self.assertEqual(limit, content['per_page'])
+        self.assertEqual(num_pages, content['pages'])
+
+    def test_exceeding_limit(self):
+        """ Makes sure the client cannot exceed the default limit """
+        from math import ceil
+
+        limit = MockPaginatorView.limit + 10
+        num_pages = int(ceil(MockPaginatorView.total / float(limit)))
+
+        request = self.req.get('/paginator/?limit=%d' % limit)
+        response = MockPaginatorView.as_view()(request)
+
+        content = json.loads(response.content)
+
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(MockPaginatorView.total, content['total'])
+        self.assertNotEqual(limit, content['per_page'])
+        self.assertNotEqual(num_pages, content['pages'])
+        self.assertEqual(MockPaginatorView.limit, content['per_page'])
+
+    def test_only_works_for_get(self):
+        """ Pagination should only work for GET requests """
+        request = self.req.post('/paginator', data={'content': 'spam'})
+        response = MockPaginatorView.as_view()(request)
+
+        content = json.loads(response.content)
+
+        self.assertEqual(response.status_code, status.CREATED)
+        self.assertEqual(None, content.get('per_page'))
+        self.assertEqual('OK', content['status'])
+
+    def test_non_int_page(self):
+        """ Tests that it can handle invalid values """
+        request = self.req.get('/paginator/?page=spam')
+        response = MockPaginatorView.as_view()(request)
+
+        self.assertEqual(response.status_code, status.NOT_FOUND)
+
+    def test_page_range(self):
+        """ Tests that the page range is handle correctly """
+        request = self.req.get('/paginator/?page=0')
+        response = MockPaginatorView.as_view()(request)
+        content = json.loads(response.content)
+        self.assertEqual(response.status_code, status.NOT_FOUND)
+
+        request = self.req.get('/paginator/')
+        response = MockPaginatorView.as_view()(request)
+        content = json.loads(response.content)
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(range(0, MockPaginatorView.limit), content['results'])
+
+        num_pages = content['pages']
+
+        request = self.req.get('/paginator/?page=%d' % num_pages)
+        response = MockPaginatorView.as_view()(request)
+        content = json.loads(response.content)
+        self.assertEqual(response.status_code, status.OK)
+        self.assertEqual(range(MockPaginatorView.limit*(num_pages-1), MockPaginatorView.total), content['results'])
+
+        request = self.req.get('/paginator/?page=%d' % (num_pages + 1,))
+        response = MockPaginatorView.as_view()(request)
+        content = json.loads(response.content)
+        self.assertEqual(response.status_code, status.NOT_FOUND)