Method CalculateAndStoreStateBeforeEvent

roomserver/state/state.go:593–609

CalculateAndStoreStateBeforeEvent calculates a snapshot of the state of a room before an event. Stores the snapshot of the state in the database. Returns a numeric ID for the snapshot of the state before the event.

(
	ctx context.Context,
	event *gomatrixserverlib.Event,
	isRejected bool,
)

// Stores the snapshot of the state in the database.
// Returns a numeric ID for the snapshot of the state before the event.
func (v *StateResolution) CalculateAndStoreStateBeforeEvent(
	ctx context.Context,
	event *gomatrixserverlib.Event,
	isRejected bool,
) (types.StateSnapshotNID, error) {
	span, ctx := opentracing.StartSpanFromContext(ctx, "StateResolution.CalculateAndStoreStateBeforeEvent")
	defer span.Finish()

	// Load the state at the prev events.
	prevStates, err := v.db.StateAtEventIDs(ctx, event.PrevEventIDs())
	if err != nil {
		return 0, err
	}

	// The state before this event will be the state after the events that came before it.
	return v.CalculateAndStoreStateAfterEvents(ctx, prevStates)
}

// CalculateAndStoreStateAfterEvents finds the room state after the given events.
// Stores the resulting state in the database and returns a numeric ID for that snapshot.