+# Copyright 2020 Canonical Ltd.
+#
+# 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 charms.reactive import RelationBase
+from charms.reactive import hook
+from charms.reactive import scopes
+
+
+class OsmRORequires(RelationBase):
+ scope = scopes.GLOBAL
+
+ @hook("{requires:osm-ro}-relation-joined")
+ def joined(self):
+ conv = self.conversation()
+ conv.set_state("{relation_name}.joined")
+
+ @hook("{requires:osm-ro}-relation-changed")
+ def changed(self):
+ conv = self.conversation()
+ if self.ros():
+ conv.set_state("{relation_name}.ready")
+ else:
+ conv.remove_state("{relation_name}.ready")
+
+ @hook("{requires:osm-ro}-relation-departed")
+ def departed(self):
+ conv = self.conversation()
+ conv.remove_state("{relation_name}.ready")
+ conv.remove_state("{relation_name}.joined")
+
+ def ros(self):
+ """Return the NBI's host and port.
+
+ [{
+ 'host': <host>,
+ 'port': <port>,
+ }]
+ """
+ ros = []
+ for conv in self.conversations():
+ port = conv.get_remote("port")
+ host = conv.get_remote("host") or conv.get_remote("private-address")
+ if host and port:
+ ros.append({"host": host, "port": port})
+ return ros