2017-02-21 14:50:30 +00:00
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package input
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import (
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"bytes"
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"github.com/matrix-org/dendrite/roomserver/types"
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"github.com/matrix-org/gomatrixserverlib"
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)
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// updateLatestEvents updates the list of latest events for this room.
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// The latest events are the events that aren't referenced by another event in the database:
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//
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// Time goes down the page. 1 is the m.room.create event (root).
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//
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// 1 After storing 1 the latest events are {1}
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// | After storing 2 the latest events are {2}
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// 2 After storing 3 the latest events are {3}
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// / \ After storing 4 the latest events are {3,4}
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// 3 4 After storing 5 the latest events are {5,4}
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// | | After storing 6 the latest events are {5,6}
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// 5 6 <--- latest After storing 7 the latest events are {6,7}
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// |
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// 7 <----- latest
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//
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func updateLatestEvents(
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db RoomEventDatabase, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
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) (err error) {
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oldLatest, updater, err := db.GetLatestEventsForUpdate(roomNID)
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if err != nil {
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return
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}
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defer func() {
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if err == nil {
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// Commit if there wasn't an error.
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// Set the returned err value if we encounter an error committing.
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// This only works because err is a named return.
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err = updater.Commit()
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} else {
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// Ignore any error we get rolling back since we don't want to
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// clobber the current error
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// TODO: log the error here.
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updater.Rollback()
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}
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}()
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err = doUpdateLatestEvents(updater, oldLatest, roomNID, stateAtEvent, event)
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return
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}
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func doUpdateLatestEvents(
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updater types.RoomRecentEventsUpdater, oldLatest []types.StateAtEventAndReference, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
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) error {
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var err error
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var prevEvents []gomatrixserverlib.EventReference
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prevEvents = event.PrevEvents()
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if err = updater.StorePreviousEvents(stateAtEvent.EventNID, prevEvents); err != nil {
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return err
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}
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// Check if this event references any of the latest events in the room.
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2017-02-22 16:51:10 +00:00
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var alreadyInLatest bool
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2017-02-21 14:50:30 +00:00
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var newLatest []types.StateAtEventAndReference
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for _, l := range oldLatest {
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2017-02-22 16:51:10 +00:00
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keep := true
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2017-02-21 14:50:30 +00:00
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for _, prevEvent := range prevEvents {
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if l.EventID == prevEvent.EventID && bytes.Compare(l.EventSHA256, prevEvent.EventSHA256) == 0 {
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// This event can be removed from the latest events cause we've found an event that references it.
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// (If an event is referenced by another event then it can't be one of the latest events in the room
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// because we have an event that comes after it)
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2017-02-22 16:51:10 +00:00
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keep = false
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break
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2017-02-21 14:50:30 +00:00
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}
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2017-02-22 16:51:10 +00:00
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}
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if l.EventNID == stateAtEvent.EventNID {
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alreadyInLatest = true
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}
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if keep {
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2017-02-21 14:50:30 +00:00
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// Keep the event in the latest events.
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newLatest = append(newLatest, l)
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}
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}
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eventReference := event.EventReference()
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// Check if this event is already referenced by another event in the room.
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var alreadyReferenced bool
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if alreadyReferenced, err = updater.IsReferenced(eventReference); err != nil {
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return err
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}
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2017-02-22 16:51:10 +00:00
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if !alreadyReferenced && !alreadyInLatest {
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// This event is not referenced by any of the events in the room
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// and the event is not already in the latest events.
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2017-02-21 14:50:30 +00:00
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// Add it to the latest events
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newLatest = append(newLatest, types.StateAtEventAndReference{
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StateAtEvent: stateAtEvent,
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EventReference: eventReference,
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})
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}
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if err = updater.SetLatestEvents(roomNID, newLatest); err != nil {
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return err
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}
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return nil
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}
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