--- /dev/null
+#
+# This module allows us to parse a machine placement directive into a
+# Placement object suitable for passing through the websocket API.
+#
+# Once https://bugs.launchpad.net/juju/+bug/1645480 is addressed, this
+# module should be deprecated.
+#
+
+from .client import client
+
+MACHINE_SCOPE = "#"
+
+
+def parse(directive):
+ """
+ Given a string in the format `scope:directive`, or simply `scope`
+ or `directive`, return a Placement object suitable for passing
+ back over the websocket API.
+
+ """
+ if not directive:
+ # Handle null case
+ return None
+
+ if isinstance(directive, (list, tuple)):
+ results = []
+ for d in directive:
+ results.extend(parse(d))
+ return results
+
+ if isinstance(directive, (dict, client.Placement)):
+ # We've been handed something that we can simply hand back to
+ # the api. (Forwards compatibility)
+ return [directive]
+
+ # Juju 2.0 can't handle lxc containers.
+ directive = directive.replace('lxc', 'lxd')
+
+ if ":" in directive:
+ # Planner has given us a scope and directive in string form
+ scope, directive = directive.split(":")
+ return [client.Placement(scope=scope, directive=directive)]
+
+ if directive.isdigit():
+ # Planner has given us a machine id (we rely on juju core to
+ # verify its validity.)
+ return [client.Placement(scope=MACHINE_SCOPE, directive=directive)]
+
+ if "/" in directive:
+ # e.g. "0/lxd/0"
+ # https://github.com/juju/juju/blob/master/instance/placement_test.go#L29
+ return [
+ client.Placement(scope=MACHINE_SCOPE, directive=directive),
+ ]
+
+ # Planner has probably given us a container type. Leave it up to
+ # juju core to verify that it is valid.
+ return [client.Placement(scope=directive)]