/**
 * @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 {Subscription} from 'rxjs/Subscription';

import {OverlayRef} from '../overlay-ref';

import {ScrollDispatcher} from './scroll-dispatcher';
import {getMdScrollStrategyAlreadyAttachedError, ScrollStrategy} from './scroll-strategy';

/**
 * Config options for the RepositionScrollStrategy.
 */
export interface RepositionScrollStrategyConfig { scrollThrottle?: number; }

/**
 * Strategy that will update the element position as the user is scrolling.
 */
export class RepositionScrollStrategy implements ScrollStrategy {
  private _scrollSubscription: Subscription|null = null;
  private _overlayRef: OverlayRef;

  constructor(
		private _scrollDispatcher: ScrollDispatcher,
		private _config?: RepositionScrollStrategyConfig) {}

  attach(overlayRef: OverlayRef) {
	if (this._overlayRef) {
		throw getMdScrollStrategyAlreadyAttachedError();
	}

	this._overlayRef = overlayRef;
  }

  enable() {
	if (!this._scrollSubscription) {
		const throttle = this._config ? this._config.scrollThrottle : 0;

		this._scrollSubscription =
			this._scrollDispatcher.scrolled(throttle, () => {
			this._overlayRef.updatePosition();
			});
	}
  }

  disable() {
	if (this._scrollSubscription) {
		this._scrollSubscription.unsubscribe();
		this._scrollSubscription = null;
	}
  }
}