..
      All Rights Reserved.

      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      License for the specific language governing permissions and limitations
      under the License.

============================
API Discovery with JSON Home
============================

What is JSON Home?
==================

JSON Home describes a method of API discovery for non-browser HTTP clients. The
`draft`_ is still in review, but keystone supplies an implementation accessible
to end-users. The result of calling keystone's JSON Home API is a JSON document
that informs the user about API endpoints, where to find them, and even
information about the API's status (e.g. experimental, supported, deprecated).
More information keystone's implementation of JSON Home can be found in the
`specification`_.

.. _`draft`: https://mnot.github.io/I-D/json-home/
.. _`specification`: http://specs.openstack.org/openstack/keystone-specs/specs/keystone/juno/json-home.html

Requesting JSON Home Documents
==============================

Requesting keystone's JSON Home document is easy. The API does not require a
token, but future implementations might expand in it's protection with token
validation and enforcement. To get a JSON Home document, just query a keystone
endpoint with ``application/json-home`` specified in the ``Accept`` header:

.. code-block:: bash

   curl -X GET -H "Accept: application/json-home" http://example.com/identity/

The result will be a JSON document containing a list of ``resources``:

.. code-block:: console

   {
       "resources": [
           "https://docs.openstack.org/api/openstack-identity/3/ext/OS-TRUST/1.0/rel/trusts": {
               "href": "/v3/OS-TRUST/trusts"
           },
           "https://docs.openstack.org/api/openstack-identity/3/ext/s3tokens/1.0/rel/s3tokens": {
               "href": "/v3/s3tokens"
           },
           "https://docs.openstack.org/api/openstack-identity/3/rel/application_credential": {
               "href-template": "/v3/users/{user_id}/application_credentials/{application_credential_id}",
               "href-vars": {
                   "application_credential_id": "https://docs.openstack.org/api/openstack-identity/3/param/application_credential_id",
                   "user_id": "https://docs.openstack.org/api/openstack-identity/3/param/user_id"
               }
           },
           "https://docs.openstack.org/api/openstack-identity/3/rel/auth_catalog": {
               "href": "/v3/auth/catalog"
           },
           "https://docs.openstack.org/api/openstack-identity/3/rel/auth_domains": {
               "href": "/v3/auth/domains"
           },
           "https://docs.openstack.org/api/openstack-identity/3/rel/auth_projects": {
               "href": "/v3/auth/projects"
           },
           "https://docs.openstack.org/api/openstack-identity/3/rel/auth_system": {
               "href": "/v3/auth/system"
           },
           ...
       ]
   }

The list of resources can then be parsed based on the relationship key for a
dictionary of data about that endpoint. This includes a path where users can
find interact with the endpoint for that specific resources. API status
information will also be present.