import { Immediate } from '../util/Immediate';
import { AsyncAction } from './AsyncAction';
import { AsapScheduler } from './AsapScheduler';

/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
export class AsapAction<T> extends AsyncAction<T> {

  constructor(protected scheduler: AsapScheduler,
              protected work: (this: AsapAction<T>, state?: T) => void) {
    super(scheduler, work);
  }

  protected requestAsyncId(scheduler: AsapScheduler, id?: any, delay: number = 0): any {
    // If delay is greater than 0, request as an async action.
    if (delay !== null && delay > 0) {
      return super.requestAsyncId(scheduler, id, delay);
    }
    // Push the action to the end of the scheduler queue.
    scheduler.actions.push(this);
    // If a microtask has already been scheduled, don't schedule another
    // one. If a microtask hasn't been scheduled yet, schedule one now. Return
    // the current scheduled microtask id.
    return scheduler.scheduled || (scheduler.scheduled = Immediate.setImmediate(
      scheduler.flush.bind(scheduler, null)
    ));
  }
  protected recycleAsyncId(scheduler: AsapScheduler, id?: any, delay: number = 0): any {
    // If delay exists and is greater than 0, or if the delay is null (the
    // action wasn't rescheduled) but was originally scheduled as an async
    // action, then recycle as an async action.
    if ((delay !== null && delay > 0) || (delay === null && this.delay > 0)) {
      return super.recycleAsyncId(scheduler, id, delay);
    }
    // If the scheduler queue is empty, cancel the requested microtask and
    // set the scheduled flag to undefined so the next AsapAction will schedule
    // its own.
    if (scheduler.actions.length === 0) {
      Immediate.clearImmediate(id);
      scheduler.scheduled = undefined;
    }
    // Return undefined so the action knows to request a new async id if it's rescheduled.
    return undefined;
  }
}