Add Version Endpoints

* At root URL will list all versions with respect to these [1]
  guidelines.
* v1/ path will list it's own version information

[1] https://wiki.openstack.org/wiki/VersionDiscovery

Change-Id: I9162408ab0cea03ba1cbf3326d0af80188385501

README.md

@@ -37,6 +37,10 @@ The points that are modular, or will be made more modular in future, are the Tas
 
 Creation and management of Tasks, Tokens, and Notifications is not modular and is the framework around the defined Actions and TaskViews that handles how they are executed. This helps keep the way Actions are executed consistent and simpler to maintain, but does also allow Actions to run almost any logic within those consistent steps.
 
+#### Version Endpoints:
+* ../ - GET
+    * JSON containing details of the currently available versions (just v1 for now)
+
 #### Admin Endpoints:
 
 Endpoints for the management of tasks, tokens, and notifications. Most of these are limited by roles, or are for admin use only.

adjutant/api/urls.py

@@ -18,11 +18,17 @@ from django.conf import settings
 
 from rest_framework_swagger.views import get_swagger_view
 
-urlpatterns = []
+from adjutant.api import views
+from adjutant.api.v1 import views as views_v1
+
+urlpatterns = [
+    url(r'^$', views.VersionView.as_view()),
+]
 
 # NOTE(adriant): This may not be the best approach, but it does work. Will
 # gladly accept a cleaner alternative if it presents itself.
 if apps.is_installed('adjutant.api.v1'):
+    urlpatterns.append(url(r'^v1/?$', views_v1.V1VersionEndpoint.as_view()))
     urlpatterns.append(url(r'^v1/', include('adjutant.api.v1.urls')))
 
 

adjutant/api/v1/app.py

@@ -1,6 +1,10 @@
 from django.apps import AppConfig
+from adjutant.api.views import build_version_details
 
 
 class APIV1Config(AppConfig):
     name = "adjutant.api.v1"
     label = 'api_v1'
+
+    def ready(self):
+        build_version_details('1.0', 'CURRENT', relative_endpoint='v1/')

adjutant/api/v1/views.py

@@ -23,11 +23,16 @@ from rest_framework.response import Response
 from rest_framework.views import APIView
 
 from adjutant.api import utils
+from adjutant.api.views import SingleVersionView
 from adjutant.api.models import Notification, Task, Token
 from adjutant.api.v1.utils import (
     create_notification, create_token, parse_filters, send_stage_email)
 
 
+class V1VersionEndpoint(SingleVersionView):
+    version = '1.0'
+
+
 class APIViewWithLogger(APIView):
     """
     APIView with a logger.

adjutant/api/views.py

@@ -0,0 +1,68 @@
+from rest_framework.views import APIView
+from rest_framework.response import Response
+
+
+_VERSIONS = {}
+
+
+def build_version_details(id, status, links=None, relative_endpoint=None):
+    """
+    Build a standard version dictionary
+    """
+    int_id = int(float(id))
+    if not relative_endpoint:
+        relative_endpoint = "v%s/" % int_id
+    mime_type = "application/vnd.openstack.adjutant-v%s+json" % int_id
+    version_details = {
+        'status': status,
+        'id': id,
+        'media-types': [
+            {
+                'base': 'application/json',
+                'type': mime_type
+            }
+        ],
+        'links': []
+    }
+
+    if links:
+        version_details['links'] = links
+
+    version_details['relative_endpoint'] = relative_endpoint
+    _VERSIONS[id] = version_details
+    return version_details
+
+
+class VersionView(APIView):
+
+    def get(self, request):
+        versions = []
+        for version in _VERSIONS.values():
+            version = version.copy()
+            rel_endpoint = version.pop('relative_endpoint')
+            url = request.build_absolute_uri() + rel_endpoint
+            version['links'] = version['links'] + [{'href': url,
+                                                    'rel': 'self'}]
+            versions.append(version)
+
+        return Response({'versions': versions}, status=200)
+
+
+class SingleVersionView(APIView):
+    """
+    A view to be added to the root of each API version detailing it's
+    own version details. Should be subclassed and have a version set.
+    """
+
+    def get(self, request):
+
+        version = _VERSIONS.get(self.version, {}).copy()
+        if not version:
+            return Response({'error': 'Not Found'}, status=404)
+
+        version.pop('relative_endpoint')
+
+        version['links'] = version['links'] + [
+            {'href': request.build_absolute_uri(),
+             'rel': 'self'}]
+        return Response({'version': version}, status=200)