Lightning Offline Sync

This page is for tracking the Lightning Offline Sync Feature to be completed as part of the Google Summer of Code 2011 programme.

TODOs

Item Name	Priority	Owner	Deadline	Progress	Comments
Adapt schema initialization and versioning code (calCalendarManager)		mohit		Done	Added versioning code in calStorageUpgradeHelper.jsm file. cal_events and cal_todos have an extra "offline_journal" column. and DB SCHEMA Version is 20.
Add search flags "ITEM_FILTER_OFFLINE_DELETED", "ITEM_FILTER_OFFLINE_CREATED" and "ITEM_FILTER_OFFLINE_UPDATED"		wolfgang		done
Check whether "ITEM_FILTER_ALL_ITEMS" is used in the views, if so, we need to create "ITEM_FILTER_ALL_ONLINE_ITEMS" ("ITEM_FILTER_ALL_ITEMS" & ~ITEM_FILTER_OFFLINE_DELETED)		wolfgang		cancelled	Not needed since ALL_ITEMS = 0xffff and our flags are = [29..31]
Adapt getItems in calStorageCalendar with the above and the GUI code if required		mohit
Adapt mSelectNonRecurringEventsByRange and this.mSelectNonRecurringTodosByRange queries		mohit
Write offline write method (calStorageCalendar::addOfflineItem)					To be discussed
Write offline delete method (calStorageCalendar::deleteOfflineItem)		mohit
Write offline update method (calStorageCalendar::updateOfflineItem)
Test the above		wolfgang/mohit			Testing steps should be discussed
Write replay method
Write "switch code" in calCachedCalendar					switch code = offline to online mode and back
test the above		wolfgang/mohit			Testing steps shud be discussed
Adapt code from Lightning 1.0b2 to HEAD		mohit

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Workflows

Offline operations

• addItem:

1. (entry) calCachedCalendar::addItem
2. calStorageCalendar::addOfflineItem
   1. setup calOperationListener
   2. execute calStorageCalendar::addItem with above listener
   3. listener: update flag with 'c' value (see table below)
   4. listener: invoke original listener with result code

• modifyItem

1. (entry) calCachedCalendar::modifyItem
2. calStorageCalendar::modifyOfflineItem
   1. setup calOperationListener
   2. execute calStorageCalendar::modifyItem with above listener
   3. listener: update flag with 'm' value (see table below)
   4. listener: invoke original listener with result code

• deleteItem

1. (entry) calCachedCalendar::deleteItem
2. calStorageCalendar::deleteOfflineItem
   1. update flag with 'd' value (see table below)
   2. invoke original listener with result code

Note: we cannot delete the record yet as we will need to pass the complete calItem back to the online/uncached calendar during reconcilliation

• getItem/getItems

1. code forwarded immediately to the calStorageCalendar

Note: getItems excludes results with offline column set to 'd', unless the ITEM_FILTER_OFFLINE_DELETED flag is passed via the item filter

Transition between online and offline modes

Nothing seems to be required at this stage.

Transition between offline and online modes

New code must be added to calCachedCalendar::onOfflineStatusChanged:

• manage deletions

1. setup calOperationListener "listener1"
2. invoke calStorageCalendar::getItems with ITEM_FILTER_OFFLINE_DELETE in item_filter and the above listener
3. listener1 execution:
   1. onGetResult:
      1. setup empty calOperationListener "listener2"
      2. invoke calCachedCalendar::deleteItem (this) with each resulting events and listener2
   2. onOperationComplete:
      1. perform next step ("manage additions")

• manage additions

1. setup calOperationListener "listener1"
2. invoke calStorageCalendar::getItems with ITEM_FILTER_OFFLINE_CREATED in item_filter and the above listener
3. listener1 execution:
   1. onGetResult:
      1. setup empty calOperationListener "listener2"
      2. invoke calCachedCalendar::addItem (this) with each resulting events and listener2
   2. onOperationComplete:
      1. perform next step ("manage modifications")

• manage additions

1. setup calOperationListener "listener1"
2. invoke calStorageCalendar::getItems with ITEM_FILTER_OFFLINE_MODIFIED in item_filter and the above listener
3. listener1 execution:
   1. onGetResult:
      1. setup empty calOperationListener "listener2"
      2. invoke calCachedCalendar::modifyItem (this) with each resulting events and listener2
   2. onOperationComplete:
      1. perform calCachedCalendar::refresh (this)

Note: reconciliation must occur before calIChangeLog method because "uncached calendars" (at least calDavCalendar) contain code that manages conflicts during data upload. Otherwise, the local changes would immediately be overwritten by server-side changes.

Efficient model for state updates during offline operations

From/To	Created	Modified	Deleted
(without state)	Mark as "created"	Mark as "modified"	Mark as "deleted"
Created	(none)	Keep as "created"	Delete record
Modified	(none)	Keep as "modified"	Mark as deleted
Deleted	(none)	(none)	(none)