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The usageDirect event log wrapper receives data from UsageStatsManager's event log API. The data format is a "list" of events which are worked through in order. The process is tricky and requires assumptions and workarounds, which are documented here.

• Query time is the time interval that the event log wrapper is queried for.
• It is currently at most spanning across one day (not across midnight) in the user's timezone (see #25).
• Now is the point in time at which the query is happening. Now may be inside query time. Ago is relative to now.
• A dashed out scenario should not happen, but has to be expected anyway (faulty data).
• Current behavior normally describes how the event log wrapper interprets data. A behavior in italics is not implemented in the event log wrapper, but performed by the usageDirect process that copies the data to database.
• Rules apply top to bottom.

Scenario	Technical name	Handled	Current behavior
App opens and closes within query time	Open and close events in order	Yes	Count from open event until close event
–––	Duplicate close event	Yes	Drop second close event
–––	Duplicate open event	Yes	Drop first open event
Device is powered off	Shutdown event	Yes	Treat shutdown event as close event for all previous unmatched open events (per Android docs)
Device is booted	Startup event	Yes	Drop all previous unmatched open events (per Android docs)
App opens before query time	True unmatched close event	Yes	If open event is contained in logs of the preceeding 24 hours, count from start of query time until close event, drop otherwise (UnmatchedCloseEventGuardian)
–––	Faulty unmatched close event	Yes	Drop event
App closes after query time	True unmatched open event	Partially	If query time ends in the future and if app contained in ActivityManager.getRunningAppProcesses()¹, count from open event until now, drop otherwise (can cause #25)
–––	Faulty unmatched open event	Yes	Drop event
App open for whole query time	No event	Partially	If query time ends in the future and if app contained in ActivityManager.getRunningAppProcesses()¹, count from start of query time until now, undetected otherwise
Event log is emptied	Data gone	Yes	Don't overwrite existing data, add new data incrementally
Switch timezone	Midnight moves in time	Yes	Add time that was not counted yet to the day it belongs assuming the timezone at query time

¹Documented as not inteded for this purpose and does not work with the app set as launcher app.