Function waitForLoaded

src/compat/database/list/audit-trail.ts:40–62

(query: DatabaseQuery, action$: Observable<SnapshotAction<T>[]>, scheduler?: SchedulerLike)

}

function waitForLoaded<T>(query: DatabaseQuery, action$: Observable<SnapshotAction<T>[]>, scheduler?: SchedulerLike) {
  const loaded$ = loadedData<T>(query, scheduler);
  return loaded$
    .pipe(
      withLatestFrom(action$),
      // Get the latest values from the "loaded" and "child" datasets
      // We can use both datasets to form an array of the latest values.
      map(([loaded, actions]) => {
        // Store the last key in the data set
        const lastKeyToLoad = loaded.lastKeyToLoad;
        // Store all child keys loaded at this point
        const loadedKeys = actions.map(snap => snap.key);
        return { actions, lastKeyToLoad, loadedKeys };
      }),
      // This is the magical part, only emit when the last load key
      // in the dataset has been loaded by a child event. At this point
      // we can assume the dataset is "whole".
      skipWhile(meta => meta.loadedKeys.indexOf(meta.lastKeyToLoad) === -1),
      // Pluck off the meta data because the user only cares
      // to iterate through the snapshots
      map(meta => meta.actions)
    );
}