/**
 * @license
 * Copyright Google Inc. 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
 */
/* tslint:disable:array-type member-access variable-name typedef
 only-arrow-functions directive-class-suffix component-class-suffix
 component-selector*/
import {Directive, ElementRef, NgZone, OnDestroy, OnInit, Renderer2} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import {Subject} from 'rxjs/Subject';

import {ScrollDispatcher} from './scroll-dispatcher';


/**
 * Sends an event when the directive's element is scrolled. Registers itself
 * with the ScrollDispatcher service to include itself as part of its collection
 * of scrolling events that it can be listened to through the service.
 */
@Directive({selector: '[cdk-scrollable], [cdkScrollable]'})
export class Scrollable implements OnInit, OnDestroy {
  private _elementScrolled: Subject<Event> = new Subject();
  private _scrollListener: Function|null;

  constructor(
		private _elementRef: ElementRef, private _scroll: ScrollDispatcher,
		private _ngZone: NgZone, private _renderer: Renderer2) {}

  ngOnInit() {
	this._scrollListener = this._ngZone.runOutsideAngular(() => {
		return this._renderer.listen(
			this.getElementRef().nativeElement, 'scroll', (event: Event) => {
			this._elementScrolled.next(event);
			});
	});

	this._scroll.register(this);
  }

  ngOnDestroy() {
	this._scroll.deregister(this);

	if (this._scrollListener) {
		this._scrollListener();
		this._scrollListener = null;
	}
  }

  /**
   * Returns observable that emits when a scroll event is fired on the host
   * element.
   */
  elementScrolled(): Observable<any> {
	return this._elementScrolled.asObservable();
  }

  getElementRef(): ElementRef {
	return this._elementRef;
  }
}