'''
Task Coach - Your friendly task manager
Copyright (C) 2004-2009 Frank Niessink <frank@niessink.com>
Task Coach is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Task Coach is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
'''
from taskcoachlib import patterns
class ChangeTracker(patterns.Observer):
''' ChangeTracker keeps track of changes to a collection (additions,
removals) as well as changes to the items in the collection. To be used
for synchronization. '''
def __init__(self, collection):
super(ChangeTracker, self).__init__()
self.__collection = collection
self.__added = set()
self.reset()
self.registerForCollectionChanges()
self.registerForItemChanges()
def reset(self):
self.registerForItemChanges([item for item in self.__collection \
if item.id() in self.__added])
self.__added = set()
# pylint: disable-msg=W0201
self.__removed = set()
self.__modified = set()
def registerForCollectionChanges(self):
for handler, eventType in \
[(self.onAddItem, self.__collection.addItemEventType()),
(self.onRemoveItem, self.__collection.removeItemEventType())]:
self.registerObserver(handler, eventType, eventSource=self.__collection)
def registerForItemChanges(self, items=None, register=True):
items = items or self.__collection
if register:
changeObservation = self.registerObserver
else:
changeObservation = self.removeObserver
for item in items:
for eventType in item.modificationEventTypes():
changeObservation(self.onModifyItem, eventType, eventSource=item)
def onAddItem(self, event):
self.__added |= set([item.id() for item in event.values()])
def onRemoveItem(self, event):
items = event.values()
self.registerForItemChanges(items, register=False)
removedItemIds = set([item.id() for item in items])
removedItemIdsToRemember = removedItemIds - self.__added
self.__removed |= removedItemIdsToRemember
self.__added -= removedItemIds
self.__modified -= removedItemIds
def onModifyItem(self, event):
self.__modified |= set([item.id() for item in event.sources()])
def added(self):
return self.__added
def removed(self):
return self.__removed
def modified(self):
return self.__modified
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