/**
 * Due to the fact that the Angular devkit does not support running scheduled tasks from a
 * schematic that has been launched through the TestRunner, we need to manually find the task
 * executor for the given task name and run all scheduled instances.
 *
 * Note that this means that there can be multiple tasks with the same name. The observable emits
 * only when all tasks finished executing.
 */
export function runPostScheduledTasks(runner: SchematicTestRunner, taskName: string) {

  const host = runner.engine['_host'] as EngineHost<{}, {}>;
  const tasks = runner.engine['_taskSchedulers'] as TaskScheduler[];

  return observableFrom(tasks).pipe(
    concatMap(scheduler => scheduler.finalize()),
    filter(task => task.configuration.name === taskName),
    concatMap(task => {
      return host.createTaskExecutor(task.configuration.name)
        .pipe(concatMap(executor => executor(task.configuration.options, task.context)));
    }),
    // Only emit the last emitted value because there can be multiple tasks with the same name.
    // The observable should only emit a value if all tasks completed.
    last()
  );
}