Cap page_size in pagination urls

Currently, even with a `max_page_size` of n, we can see urls
formed in pagination with `page_size` > n. API still caps the
number of results it returns, but the URL remain invalid there.
This is a bit messy solution to make string replacement in URL
if the query param exceeds `max_page_size`

Signed-off-by: Vismay Golwala <vgolwala@redhat.com>

awx/api/pagination.py

@@ -18,7 +18,7 @@ class Pagination(pagination.PageNumberPagination):
         url = self.request and self.request.get_full_path() or ''
         url = url.encode('utf-8')
         page_number = self.page.next_page_number()
-        return replace_query_param(url, self.page_query_param, page_number)
+        return replace_query_param(self.cap_page_size(url), self.page_query_param, page_number)
 
     def get_previous_link(self):
         if not self.page.has_previous():
@@ -26,4 +26,16 @@ class Pagination(pagination.PageNumberPagination):
         url = self.request and self.request.get_full_path() or ''
         url = url.encode('utf-8')
         page_number = self.page.previous_page_number()
-        return replace_query_param(url, self.page_query_param, page_number)
+        return replace_query_param(self.cap_page_size(url), self.page_query_param, page_number)
+
+    def cap_page_size(self, url):
+        if int(self.request.query_params.get(self.page_size_query_param, 0)) > self.max_page_size:
+            url = replace_query_param(url, self.page_size_query_param, self.max_page_size)
+        return url
+
+    def get_html_context(self):
+        context = super().get_html_context()
+        context['page_links'] = [pl._replace(url=self.cap_page_size(pl.url))
+                                 for pl in context['page_links']]
+
+        return context

awx/main/tests/functional/api/test_pagination.py

@@ -1,7 +1,11 @@
 import pytest
+import json
+from unittest.mock import patch
+from urllib.parse import urlencode
 
 from awx.main.models.inventory import Group, Host
 from awx.api.pagination import Pagination
+from awx.api.versioning import reverse
 
 
 @pytest.fixture
@@ -38,3 +42,20 @@ def test_pagination_backend_output_correct_total_count(group, host):
     p = Pagination().django_paginator_class(queryset, 10)
     p.page(1)
     assert p.count == 1
+
+
+@pytest.mark.django_db
+def test_pagination_cap_page_size(get, admin, inventory):
+    for i in range(20):
+        Host(name='host-{}'.format(i), inventory=inventory).save()
+
+    def host_list_url(params):
+        request_qs = '?' + urlencode(params)
+        return reverse('api:host_list', kwargs={'version': 'v2'}) + request_qs
+
+    with patch('awx.api.pagination.Pagination.max_page_size', 5):
+        resp = get(host_list_url({'page': '2', 'page_size': '10'}), user=admin)
+        jdata = json.loads(resp.content)
+
+        assert jdata['previous'] == host_list_url({'page': '1', 'page_size': '5'})
+        assert jdata['next'] == host_list_url({'page': '3', 'page_size': '5'})