1 files changed, 54 insertions, 0 deletions
diff --git a/deprecated/automation/common/state_machine.py b/deprecated/automation/common/state_machine.py
new file mode 100644
index 00000000..d1cf42c8
--- /dev/null
+++ b/deprecated/automation/common/state_machine.py
@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2011 Google Inc. All Rights Reserved.
+#
+
+__author__ = 'kbaclawski@google.com (Krystian Baclawski)'
+
+from automation.common import events
+
+
+class BasicStateMachine(object):
+  """Generic class for constructing state machines.
+  
+  Keeps all states and possible transition of a state machine. Ensures that
+  transition between two states is always valid. Also stores transition events
+  in a timeline object.
+  """
+  state_machine = {}
+  final_states = []
+
+  def __init__(self, initial_state):
+    assert initial_state in self.state_machine,\
+           'Initial state does not belong to this state machine'
+
+    self._state = initial_state
+
+    self.timeline = events.EventHistory()
+    self.timeline.AddEvent(self._state)
+
+  def __str__(self):
+    return self._state
+
+  def __eq__(self, value):
+    if isinstance(value, BasicStateMachine):
+      value = str(value)
+
+    return self._state == value
+
+  def __ne__(self, value):
+    return not self == value
+
+  def _TransitionAllowed(self, to_state):
+    return to_state in self.state_machine.get(self._state, [])
+
+  def Change(self, new_state):
+    assert self._TransitionAllowed(new_state),\
+           'Transition from %s to %s not possible' % (self._state, new_state)
+
+    self._state = new_state
+
+    self.timeline.AddEvent(self._state)
+
+    if self._state in self.final_states:
+      self.timeline.last.Finish()