Function GetAuthChain

roomserver/internal/query/query.go:532–577

GetAuthChain fetches the auth chain for the given auth events. An auth chain is the list of all events that are referenced in the auth_events section, and all their auth_events, recursively. The returned set of events contain the given events. Will *not* error if we don't have all auth events.

(
	ctx context.Context, fn eventsFromIDs, authEventIDs []string,
)

// all their auth_events, recursively. The returned set of events contain the
// given events. Will *not* error if we don't have all auth events.
func GetAuthChain(
	ctx context.Context, fn eventsFromIDs, authEventIDs []string,
) ([]*gomatrixserverlib.Event, error) {
	// List of event IDs to fetch. On each pass, these events will be requested
	// from the database and the `eventsToFetch` will be updated with any new
	// events that we have learned about and need to find. When `eventsToFetch`
	// is eventually empty, we should have reached the end of the chain.
	eventsToFetch := authEventIDs
	authEventsMap := make(map[string]*gomatrixserverlib.Event)

	for len(eventsToFetch) > 0 {
		// Try to retrieve the events from the database.
		events, err := fn(ctx, eventsToFetch)
		if err != nil {
			return nil, err
		}

		// We've now fetched these events so clear out `eventsToFetch`. Soon we may
		// add newly discovered events to this for the next pass.
		eventsToFetch = eventsToFetch[:0]

		for _, event := range events {
			// Store the event in the event map - this prevents us from requesting it
			// from the database again.
			authEventsMap[event.EventID()] = event.Event

			// Extract all of the auth events from the newly obtained event. If we
			// don't already have a record of the event, record it in the list of
			// events we want to request for the next pass.
			for _, authEvent := range event.AuthEvents() {
				if _, ok := authEventsMap[authEvent.EventID]; !ok {
					eventsToFetch = append(eventsToFetch, authEvent.EventID)
				}
			}
		}
	}

	// We've now retrieved all of the events we can. Flatten them down into an
	// array and return them.
	var authEvents []*gomatrixserverlib.Event
	for _, event := range authEventsMap {
		authEvents = append(authEvents, event)
	}

	return authEvents, nil
}

// QueryRoomVersionCapabilities implements api.RoomserverInternalAPI
func (r *Queryer) QueryRoomVersionCapabilities(