From 13cb4716cd0db47dd31d3ea8339ceb2c51b3a8cb Mon Sep 17 00:00:00 2001
From: Amelia Cordwell <ameliacordwell@catalyst.net.nz>
Date: Wed, 26 Apr 2017 17:12:33 +1200
Subject: [PATCH] Pagination for Task List

Number of tasks per page can be specified in the get request,
but if not specified the endpoint will return all of them.

Change-Id: I524249bf7e9f16feba8c9beaeb66267ec7da874e
---
 README.md                 | 13 ++++++++-----
 stacktask/api/v1/views.py | 35 +++++++++++++++++++++++++++++++++--
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 1bf695f..d0c0f03 100644
--- a/README.md
+++ b/README.md
@@ -41,14 +41,17 @@ Creation and management of Tasks, Tokens, and Notifications is not modular and i
 
 Endpoints for the management of tasks, tokens, and notifications. Most of these are limited by roles, and are for admin use only.
 
-* ../v1/task - GET
+* ../v1/tasks - GET
   * A json containing all tasks.
-    * This will be updated to take parameters to refine the list.
-* ../v1/task/<uuid> - GET
+    * Possible parameters are:
+    * filters (specified below)
+    * tasks_per_page, defaults to 25
+    * page, page number to access (starts at 1)
+* ../v1/tasks/<uuid> - GET
   * Get details for a specific task.
-* ../v1/task/<uuid> - PUT
+* ../v1/tasks/<uuid> - PUT
   * Update a task and retrigger pre_approve.
-* ../v1/task/<uuid> - POST
+* ../v1/tasks/<uuid> - POST
   * approve a task
 * ../v1/token - GET
   * A json containing all tokens.
diff --git a/stacktask/api/v1/views.py b/stacktask/api/v1/views.py
index d678f8e..53c2676 100644
--- a/stacktask/api/v1/views.py
+++ b/stacktask/api/v1/views.py
@@ -16,6 +16,7 @@ from logging import getLogger
 
 from django.conf import settings
 from django.utils import timezone
+from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
 
 from rest_framework.response import Response
 from rest_framework.views import APIView
@@ -160,15 +161,40 @@ class TaskList(APIViewWithLogger):
         and their related actions.
         """
 
+        page = request.GET.get('page', 1)
+        tasks_per_page = request.GET.get('tasks_per_page', None)
+
         if 'admin' in request.keystone_user['roles']:
             if filters:
                 tasks = Task.objects.filter(**filters).order_by("-created_on")
             else:
                 tasks = Task.objects.all().order_by("-created_on")
+
+            if tasks_per_page:
+                paginator = Paginator(tasks, tasks_per_page)
+                try:
+                    tasks = paginator.page(page)
+                except EmptyPage:
+                    return Response({'tasks': [],
+                                     'pages': paginator.num_pages,
+                                     'has_more': False,
+                                     'has_prev': False}, status=200)
+                    # NOTE(amelia): 'has_more'and 'has_prev' names are
+                    # based on the horizon pagination table pagination names
+                except PageNotAnInteger:
+                    return Response({'error': 'Page not an integer'},
+                                    status=400)
+
             task_list = []
             for task in tasks:
                 task_list.append(task._to_dict())
-            return Response({'tasks': task_list}, status=200)
+            if tasks_per_page:
+                return Response({'tasks': task_list,
+                                 'pages': paginator.num_pages,
+                                 'has_more': tasks.has_next(),
+                                 'has_prev': tasks.has_previous()}, status=200)
+            else:
+                return Response({'tasks': task_list})
         else:
             if filters:
                 # Ignore any filters with project_id in them
@@ -183,10 +209,15 @@ class TaskList(APIViewWithLogger):
                 tasks = Task.objects.filter(
                     project_id__exact=request.keystone_user['project_id']
                 ).order_by("-created_on")
+
+            paginator = Paginator(tasks, tasks_per_page)
+            tasks = paginator.page(page)
+
             task_list = []
             for task in tasks:
                 task_list.append(task.to_dict())
-            return Response({'tasks': task_list}, status=200)
+            return Response({'tasks': task_list,
+                             'pages': paginator.num_pages}, status=200)
 
 
 class TaskDetail(APIViewWithLogger):