api_core: Add routing header

api_core/google/api_core/gapic_v1/__init__.py

@@ -14,8 +14,10 @@
 
 from google.api_core.gapic_v1 import config
 from google.api_core.gapic_v1 import method
+from google.api_core.gapic_v1 import routing_header
 
 __all__ = [
     'config',
     'method',
+    'routing_header',
 ]

api_core/google/api_core/gapic_v1/routing_header.py

@@ -0,0 +1,27 @@
+# Copyright 2017 Google LLC
+#
+# 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.
+
+"""Helpers for handling routing header params."""
+
+METADATA_KEY = 'x-goog-header-params'
+
+
+def to_routing_header(params):
+    """Returns the routing header string that the params form"""
+    return "&".join(["{}={}".format(*pair) for pair in params])
+
+
+def to_grpc_metadata(params):
+    """Returns the gRPC metadata that the routing header params form"""
+    return (METADATA_KEY, to_routing_header(params))

api_core/tests/unit/gapic/test_routing_header.py

@@ -0,0 +1,29 @@
+# Copyright 2017 Google LLC
+#
+# 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 google.api_core.gapic_v1 import routing_header
+
+
+def test_to_routing_header():
+    params = [('name', 'meep'), ('book.read', True)]
+    value = routing_header.to_routing_header(params)
+    assert value == "name=meep&book.read=True"
+
+
+def test_to_grpc_metadata():
+    params = [('name', 'meep'), ('book.read', True)]
+    metadata = routing_header.to_grpc_metadata(params)
+    assert metadata == (
+        routing_header.METADATA_KEY, "name=meep&book.read=True")