Add a Client 'instantiator'

This function mocks a class constructor but returns a client instance
for the specified version. This reduces the number of imports needed to
use the API and makes it easier to migrate from one version to the
other.

Change-Id: I20bb9adef4fa4f6bb87c53020454c791d765c389
Partially-Implements: python-marconiclient-v1

marconiclient/queues/client.py

@@ -0,0 +1,26 @@
+# Copyright (c) 2013 Red Hat, 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.
+
+from marconiclient import errors
+from marconiclient.queues.v1 import client as cv1
+
+_CLIENTS = {1: cv1.Client}
+
+
+def Client(url=None, version=None, conf=None):
+    try:
+        return _CLIENTS[version](url, version, conf)
+    except KeyError:
+        raise errors.MarconiError('Unknown client version')

tests/unit/queues/test_client.py

@@ -0,0 +1,34 @@
+# Copyright (c) 2013 Red Hat, 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.
+
+from marconiclient import errors
+from marconiclient.queues import client
+from marconiclient.tests import base
+
+
+class TestClient(base.TestBase):
+
+    def test_get_instance(self):
+        version = list(client._CLIENTS.keys())[0]
+        cli = client.Client('http://example.com',
+                            version, {})
+        self.assertTrue(isinstance(cli,
+                                   client._CLIENTS[version]))
+
+    def test_version_failure(self):
+        self.assertRaises(errors.MarconiError,
+                          client.Client,
+                          'http://example.org',
+                          -1, {})