Add low-level API base class

Adds the foundation of a low-level REST API client.  This is the final prep
stage in the conversion of the object-store commands from the old restapi
interface to the keystoneclient.session-based API.

* api.api.BaseAPI holds the common operations

Change-Id: I8fba980e3eb2d787344f766507a9d0dae49dcadf

2 files changed, 349 insertions, 0 deletions

diff --git a/openstackclient/api/__init__.py b/openstackclient/api/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/openstackclient/api/__init__.py
diff --git a/openstackclient/api/api.py b/openstackclient/api/api.py
new file mode 100644
index 00000000..72a66e1c
--- /dev/null
+++ b/openstackclient/api/api.py
@@ -0,0 +1,349 @@
+#   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.
+#
+
+"""Base API Library"""
+
+import simplejson as json
+
+from keystoneclient.openstack.common.apiclient \
+    import exceptions as ksc_exceptions
+from keystoneclient import session as ksc_session
+from openstackclient.common import exceptions
+
+
+class KeystoneSession(object):
+    """Wrapper for the Keystone Session
+
+    Restore some requests.session.Session compatibility;
+    keystoneclient.session.Session.request() has the method and url
+    arguments swapped from the rest of the requests-using world.
+
+    """
+
+    def __init__(
+        self,
+        session=None,
+        endpoint=None,
+        **kwargs
+    ):
+        """Base object that contains some common API objects and methods
+
+        :param Session session:
+            The default session to be used for making the HTTP API calls.
+        :param string endpoint:
+            The URL from the Service Catalog to be used as the base for API
+            requests on this API.
+        """
+
+        super(KeystoneSession, self).__init__()
+
+        # a requests.Session-style interface
+        self.session = session
+        self.endpoint = endpoint
+
+    def _request(self, method, url, session=None, **kwargs):
+        """Perform call into session
+
+        All API calls are funneled through this method to provide a common
+        place to finalize the passed URL and other things.
+
+        :param string method:
+            The HTTP method name, i.e. ``GET``, ``PUT``, etc
+        :param string url:
+            The API-specific portion of the URL path
+        :param Session session:
+            HTTP client session
+        :param kwargs:
+            keyword arguments passed to requests.request().
+        :return: the requests.Response object
+        """
+
+        if not session:
+            session = self.session
+        if not session:
+            session = ksc_session.Session()
+
+        if self.endpoint:
+            if url:
+                url = '/'.join([self.endpoint.rstrip('/'), url.lstrip('/')])
+            else:
+                url = self.endpoint.rstrip('/')
+
+        # Why is ksc session backwards???
+        return session.request(url, method, **kwargs)
+
+
+class BaseAPI(KeystoneSession):
+    """Base API"""
+
+    def __init__(
+        self,
+        session=None,
+        service_type=None,
+        endpoint=None,
+        **kwargs
+    ):
+        """Base object that contains some common API objects and methods
+
+        :param Session session:
+            The default session to be used for making the HTTP API calls.
+        :param string service_type:
+            API name, i.e. ``identity`` or ``compute``
+        :param string endpoint:
+            The URL from the Service Catalog to be used as the base for API
+            requests on this API.
+        """
+
+        super(BaseAPI, self).__init__(session=session, endpoint=endpoint)
+
+        self.service_type = service_type
+
+    # The basic action methods all take a Session and return dict/lists
+
+    def create(
+        self,
+        url,
+        session=None,
+        method=None,
+        **params
+    ):
+        """Create a new resource
+
+        :param string url:
+            The API-specific portion of the URL path
+        :param Session session:
+            HTTP client session
+        :param string method:
+            HTTP method (default POST)
+        """
+
+        if not method:
+            method = 'POST'
+        ret = self._request(method, url, session=session, **params)
+        # Should this move into _requests()?
+        try:
+            return ret.json()
+        except json.JSONDecodeError:
+            return ret
+
+    def delete(
+        self,
+        url,
+        session=None,
+        **params
+    ):
+        """Delete a resource
+
+        :param string url:
+            The API-specific portion of the URL path
+        :param Session session:
+            HTTP client session
+        """
+
+        return self._request('DELETE', url, **params)
+
+    def list(
+        self,
+        path,
+        session=None,
+        body=None,
+        detailed=False,
+        **params
+    ):
+        """Return a list of resources
+
+        GET ${ENDPOINT}/${PATH}
+
+        path is often the object's plural resource type
+
+        :param string path:
+            The API-specific portion of the URL path
+        :param Session session:
+            HTTP client session
+        :param body: data that will be encoded as JSON and passed in POST
+            request (GET will be sent by default)
+        :param bool detailed:
+            Adds '/details' to path for some APIs to return extended attributes
+        :returns:
+            JSON-decoded response, could be a list or a dict-wrapped-list
+        """
+
+        if detailed:
+            path = '/'.join([path.rstrip('/'), 'details'])
+
+        if body:
+            ret = self._request(
+                'POST',
+                path,
+                # service=self.service_type,
+                json=body,
+                params=params,
+            )
+        else:
+            ret = self._request(
+                'GET',
+                path,
+                # service=self.service_type,
+                params=params,
+            )
+        try:
+            return ret.json()
+        except json.JSONDecodeError:
+            return ret
+
+    # Layered actions built on top of the basic action methods do not
+    # explicitly take a Session but one may still be passed in kwargs
+
+    def find_attr(
+        self,
+        path,
+        value=None,
+        attr=None,
+        resource=None,
+    ):
+        """Find a resource via attribute or ID
+
+        Most APIs return a list wrapped by a dict with the resource
+        name as key.  Some APIs (Identity) return a dict when a query
+        string is present and there is one return value.  Take steps to
+        unwrap these bodies and return a single dict without any resource
+        wrappers.
+
+        :param string path:
+            The API-specific portion of the URL path
+        :param string value:
+            value to search for
+        :param string attr:
+            attribute to use for resource search
+        :param string resource:
+            plural of the object resource name; defaults to path
+        For example:
+            n = find(netclient, 'network', 'networks', 'matrix')
+        """
+
+        # Default attr is 'name'
+        if attr is None:
+            attr = 'name'
+
+        # Default resource is path - in many APIs they are the same
+        if resource is None:
+            resource = path
+
+        def getlist(kw):
+            """Do list call, unwrap resource dict if present"""
+            ret = self.list(path, **kw)
+            if type(ret) == dict and resource in ret:
+                ret = ret[resource]
+            return ret
+
+        # Search by attribute
+        kwargs = {attr: value}
+        data = getlist(kwargs)
+        if type(data) == dict:
+            return data
+        if len(data) == 1:
+            return data[0]
+        if len(data) > 1:
+            msg = "Multiple %s exist with %s='%s'"
+            raise ksc_exceptions.CommandError(
+                msg % (resource, attr, value),
+            )
+
+        # Search by id
+        kwargs = {'id': value}
+        data = getlist(kwargs)
+        if len(data) == 1:
+            return data[0]
+        msg = "No %s with a %s or ID of '%s' found"
+        raise exceptions.CommandError(msg % (resource, attr, value))
+
+    def find_bulk(
+        self,
+        path,
+        **kwargs
+    ):
+        """Bulk load and filter locally
+
+        :param string path:
+            The API-specific portion of the URL path
+        :param kwargs:
+            A dict of AVPs to match - logical AND
+        :returns: list of resource dicts
+        """
+
+        items = self.list(path)
+        if type(items) == dict:
+            # strip off the enclosing dict
+            key = list(items.keys())[0]
+            items = items[key]
+
+        ret = []
+        for o in items:
+            try:
+                if all(o[attr] == kwargs[attr] for attr in kwargs.keys()):
+                    ret.append(o)
+            except KeyError:
+                continue
+
+        return ret
+
+    def find_one(
+        self,
+        path,
+        **kwargs
+    ):
+        """Find a resource by name or ID
+
+        :param string path:
+            The API-specific portion of the URL path
+        :returns:
+            resource dict
+        """
+
+        bulk_list = self.find_bulk(path, **kwargs)
+        num_bulk = len(bulk_list)
+        if num_bulk == 0:
+            msg = "none found"
+            raise ksc_exceptions.NotFound(msg)
+        elif num_bulk > 1:
+            msg = "many found"
+            raise RuntimeError(msg)
+        return bulk_list[0]
+
+    def find(
+        self,
+        path,
+        value=None,
+        attr=None,
+    ):
+        """Find a single resource by name or ID
+
+        :param string path:
+            The API-specific portion of the URL path
+        :param string search:
+            search expression
+        :param string attr:
+            name of attribute for secondary search
+        """
+
+        try:
+            ret = self._request('GET', "/%s/%s" % (path, value)).json()
+        except ksc_exceptions.NotFound:
+            kwargs = {attr: value}
+            try:
+                ret = self.find_one("/%s/detail" % (path), **kwargs)
+            except ksc_exceptions.NotFound:
+                msg = "%s not found" % value
+                raise ksc_exceptions.NotFound(msg)
+
+        return ret