Add API Discovery to Ironic Inspector

This patch allows for API discovery via the root API endpoint and
version endpoints. These endpoints will return a json blob containing
all the information required to talk to the different API versions and
resources.

Change-Id: Id427f1ca542523afb3513b047e32b5aad39bf743
Closes-Bug: #1477959

HTTP-API.rst

@@ -228,6 +228,43 @@ major version and is always ``1`` for now, ``Y`` is a minor version.
   ``X-OpenStack-Ironic-Inspector-API-Maximum-Version`` headers with minimum
   and maximum API versions supported by the server.
 
+API Discovery
+~~~~~~~~~~~~~
+
+The API supports API discovery. You can query different parts of the API to
+discover what other endpoints are avaliable.
+
+* ``GET /`` List API Versions
+
+  Response:
+
+  * 200 - OK
+
+  Response body: JSON dictionary containing a list of ``versions``, each
+  version contains:
+
+  * ``status`` Either CURRENT or SUPPORTED
+  * ``id`` The version identifier
+  * ``links`` A list of links to this version endpoint containing:
+
+    * ``href`` The URL
+    * ``rel`` The relationship between the version and the href
+
+* ``GET /v1`` List API v1 resources
+
+  Response:
+
+  * 200 - OK
+
+  Response body: JSON dictionary containing a list of ``resources``, each
+  resource contains:
+
+  * ``name`` The name of this resources
+  * ``links`` A list of link to this resource containing:
+
+    * ``href`` The URL
+    * ``rel`` The relationship between the resource and the href
+
 Version History
 ^^^^^^^^^^^^^^^
 

ironic_inspector/main.py

@@ -15,6 +15,8 @@ import eventlet
 eventlet.monkey_patch()
 
 import functools
+import os
+import re
 import ssl
 import sys
 
@@ -108,13 +110,55 @@ def add_version_headers(res):
     return res
 
 
+def create_link_object(urls):
+    links = []
+    for url in urls:
+        links.append({"rel": "self",
+                      "href": os.path.join(flask.request.url_root, url)})
+    return links
+
+
+def generate_resource_data(resources):
+    data = []
+    for resource in resources:
+        item = {}
+        item['name'] = str(resource).split('/')[-1]
+        item['links'] = create_link_object([str(resource)[1:]])
+        data.append(item)
+    return data
+
+
 @app.route('/', methods=['GET'])
-@app.route('/v1', methods=['GET'])
 @convert_exceptions
 def api_root():
-    # TODO(dtantsur): this endpoint only returns API version now, it's possible
-    # we'll return something meaningful in addition later
-    return flask.jsonify({})
+    versions = [
+        {
+            "status": "CURRENT",
+            "id": '%s.%s' % CURRENT_API_VERSION,
+        },
+    ]
+
+    for version in versions:
+        version['links'] = create_link_object(
+            ["v%s" % version['id'].split('.')[0]])
+
+    return flask.jsonify(versions=versions)
+
+
+@app.route('/<version>', methods=['GET'])
+@convert_exceptions
+def version_root(version):
+    pat = re.compile("^\/%s\/[^\/]*?$" % version)
+
+    resources = []
+    for url in app.url_map.iter_rules():
+        if pat.match(str(url)):
+            resources.append(url)
+
+    if not resources:
+        raise utils.Error(_('Version not found.'), code=404)
+
+    return flask.jsonify(resources=generate_resource_data(resources))
 
 
 @app.route('/v1/continue', methods=['POST'])
@@ -126,6 +170,7 @@ def api_continue():
     return flask.jsonify(process.process(data))
 
 
+# TODO(sambetts) Add API discovery for this endpoint
 @app.route('/v1/introspection/<uuid>', methods=['GET', 'POST'])
 @convert_exceptions
 def api_introspection(uuid):

ironic_inspector/test/test_main.py

@@ -305,11 +305,53 @@ class TestApiVersions(BaseAPITest):
         self.assertEqual('%d.%d' % main.CURRENT_API_VERSION,
                          res.headers.get(main._MAX_VERSION_HEADER))
 
-    def test_root_endpoints(self):
-        for endpoint in '/', '/v1':
-            res = self.app.get(endpoint)
-            self.assertEqual(200, res.status_code)
-            self._check_version_present(res)
+    def test_root_endpoint(self):
+        res = self.app.get("/")
+        self.assertEqual(200, res.status_code)
+        self._check_version_present(res)
+        data = res.data.decode('utf-8')
+        json_data = json.loads(data)
+        expected = {"versions": [{
+            "status": "CURRENT", "id": '%s.%s' % main.CURRENT_API_VERSION,
+            "links": [{
+                "rel": "self",
+                "href": ("http://localhost/v%s" %
+                         main.CURRENT_API_VERSION[0])
+            }]
+        }]}
+        self.assertEqual(expected, json_data)
+
+    @mock.patch.object(main.app.url_map, "iter_rules", autospec=True)
+    def test_version_endpoint(self, mock_rules):
+        mock_rules.return_value = ["/v1/endpoint1", "/v1/endpoint2/<uuid>",
+                                   "/v1/endpoint1/<name>",
+                                   "/v2/endpoint1", "/v1/endpoint3",
+                                   "/v1/endpoint2/<uuid>/subpoint"]
+        endpoint = "/v1"
+        res = self.app.get(endpoint)
+        self.assertEqual(200, res.status_code)
+        self._check_version_present(res)
+        json_data = json.loads(res.data.decode('utf-8'))
+        expected = {u'resources': [
+            {
+                u'name': u'endpoint1',
+                u'links': [{
+                    u'rel': u'self',
+                    u'href': u'http://localhost/v1/endpoint1'}]
+            },
+            {
+                u'name': u'endpoint3',
+                u'links': [{
+                    u'rel': u'self',
+                    u'href': u'http://localhost/v1/endpoint3'}]
+            },
+        ]}
+        self.assertDictEqual(expected, json_data)
+
+    def test_version_endpoint_invalid(self):
+        endpoint = "/v-1"
+        res = self.app.get(endpoint)
+        self.assertEqual(404, res.status_code)
 
     def test_404_unexpected(self):
         # API version on unknown pages