import {ChangeDetector} from './interfaces';
import {CHECK_ONCE, DETACHED, CHECK_ALWAYS} from './constants';

/**
 * Controls change detection.
 *
 * {@link ChangeDetectorRef} allows requesting checks for detectors that rely on observables. It also allows detaching and
 * attaching change detector subtrees.
 *
 * @exportedAs angular2/change_detection
 */
export class ChangeDetectorRef {
  _cd:ChangeDetector;

  constructor(cd:ChangeDetector) {
    this._cd = cd;
  }

  /**
   * Request to check all ON_PUSH ancestors.
   */
  requestCheck() {
    this._cd.markPathToRootAsCheckOnce();
  }

  /**
   * Detaches the change detector from the change detector tree.
   *
   * The detached change detector will not be checked until it is reattached.
   */
  detach() {
    this._cd.mode = DETACHED;
  }

  /**
   * Reattach the change detector to the change detector tree.
   *
   * This also requests a check of this change detector. This reattached change detector will be checked during the
   * next change detection run.
   */
  reattach() {
    this._cd.mode = CHECK_ALWAYS;
    this.requestCheck();
  }
}