cc-4105: added mechanism to remove duplicate events

python_apps/media-monitor2/media/monitor/eventcontractor.py

@@ -0,0 +1,30 @@
+from media.monitor.log import Loggable
+from media.monitor.events import DeleteFile
+
+class EventContractor(Loggable):
+    def __init__(self):
+        self.store = {}
+
+    def event_registered(self, evt):
+        return evt.path in self.store
+
+    def get_old_event(self, evt):
+        return evt.store[ evt.path ]
+
+    def register(self, evt):
+        if self.event_registered(evt):
+            old_e = self.get_old_event(evt)
+            # If two events are of the same type we can safely discard the old
+            # one
+            if evt.__class__ == old_e.__class__:
+                old_e.morph_into(evt)
+            # delete overrides any other event
+            elif isinstance(evt, DeleteFile):
+                old_e.morph_into(evt)
+        else:
+            evt.add_safe_pack_hook( lambda : self.__unregister(evt) )
+            self.store[ evt.path ] = evt
+
+    # events are unregistered automatically no need to screw around with them
+    def __unregister(self, evt):
+        del self.store[evt.path]