/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {EngineHost, TaskExecutor, TaskScheduler} from '@angular-devkit/schematics';
import {SchematicTestRunner} from '@angular-devkit/schematics/testing';
import {from as observableFrom, Observable} from 'rxjs';
import {concatMap, filter, last} from 'rxjs/operators';

/**
 * 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)
    : Observable<any> {

  // Workaround until there is a public API to run scheduled tasks in the @angular-devkit.
  // See: https://github.com/angular/angular-cli/issues/11739
  const host = runner.engine['_host'] as EngineHost<{}, {}>;
  const tasks = runner.engine['_taskSchedulers'] as TaskScheduler[];
  const createTaskExecutor = (name: string) =>
      (host.createTaskExecutor(name) as any) as Observable<TaskExecutor<any>>;

  return observableFrom(tasks).pipe(
    concatMap(scheduler => scheduler.finalize()),
    filter(task => task.configuration.name === taskName),
    concatMap(task => {
      return 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()
  );
}