Refactoring Database Code (#66)

* Extracted the HTTP client logic into a separate internal module; Changed return order of set_if_unchanged(); Updated test cases

* Disabling a test case temporarily

* Updated documentation and tests

* Using the readonly accessor to patch the session

Author: hiranya911

firebase_admin/_http_client.py

@@ -0,0 +1,112 @@
+# Copyright 2017 Google Inc.
+#
+# 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.
+
+"""Internal HTTP client module.
+
+ This module provides utilities for making HTTP calls using the requests library.
+ """
+
+from google.auth import transport
+import requests
+
+
+class HttpClient(object):
+    """Base HTTP client used to make HTTP calls.
+
+    HttpClient maintains an HTTP session, and handles request authentication if necessary.
+    """
+
+    def __init__(self, credential=None, session=None, base_url='', headers=None):
+        """Cretes a new HttpClient instance from the provided arguments.
+
+        If a credential is provided, initializes a new HTTP session authorized with it. If neither
+        a credential nor a session is provided, initializes a new unauthorized session.
+
+        Args:
+          credential: A Google credential that can be used to authenticate requests (optional).
+          session: A custom HTTP session (optional).
+          base_url: A URL prefix to be added to all outgoing requests (optional).
+          headers: A map of headers to be added to all outgoing requests (optional).
+        """
+        if credential:
+            self._session = transport.requests.AuthorizedSession(credential)
+        elif session:
+            self._session = session
+        else:
+            self._session = requests.Session() # pylint: disable=redefined-variable-type
+
+        if headers:
+            self._session.headers.update(headers)
+        self._base_url = base_url
+
+    @property
+    def session(self):
+        return self._session
+
+    @property
+    def base_url(self):
+        return self._base_url
+
+    def parse_body(self, resp):
+        raise NotImplementedError
+
+    def request(self, method, url, **kwargs):
+        """Makes an HTTP call using the Python requests library.
+
+        This is the sole entry point to the requests library. All other helper methods in this
+        class call this method to send HTTP requests out. Refer to
+        http://docs.python-requests.org/en/master/api/ for more information on supported options
+        and features.
+
+        Args:
+          method: HTTP method name as a string (e.g. get, post).
+          url: URL of the remote endpoint.
+          kwargs: An additional set of keyword arguments to be passed into the requests API
+              (e.g. json, params).
+
+        Returns:
+          Response: An HTTP response object.
+
+        Raises:
+          RequestException: Any requests exceptions encountered while making the HTTP call.
+        """
+        resp = self._session.request(method, self._base_url + url, **kwargs)
+        resp.raise_for_status()
+        return resp
+
+    def headers(self, method, url, **kwargs):
+        resp = self.request(method, url, **kwargs)
+        return resp.headers
+
+    def body(self, method, url, **kwargs):
+        resp = self.request(method, url, **kwargs)
+        return self.parse_body(resp)
+
+    def headers_and_body(self, method, url, **kwargs):
+        resp = self.request(method, url, **kwargs)
+        return resp.headers, self.parse_body(resp)
+
+    def close(self):
+        self._session.close()
+        self._session = None
+
+
+class JsonHttpClient(HttpClient):
+    """An HTTP client that parses response messages as JSON."""
+
+    def __init__(self, **kwargs):
+        HttpClient.__init__(self, **kwargs)
+
+    def parse_body(self, resp):
+        return resp.json()