import { Injectable } from '@angular/core';
import { Observable, Subject, Subscriber } from 'rxjs';

/**
 * Layout dimensions type
 */
export interface NbLayoutDimensions {

  /**
   * clientWidth
   * @type {number}
   */
  clientWidth: number;

  /**
   * clientHeight
   * @type {number}
   */
  clientHeight: number;

  /**
   * scrollWidth
   * @type {number}
   */
  scrollWidth: number;

  /**
   * scrollHeight
   * @type {number}
   */
  scrollHeight: number;
}

/**
 * Simple helper service to return Layout dimensions
 * Depending of current Layout scroll mode (default or `withScroll` when scroll is moved to an element
 * inside of the layout) corresponding dimensions will be returns  - of `documentElement` in first case and
 * `.scrollable-container` in the second.
 */
@Injectable()
export class NbLayoutRulerService {

  private contentDimensionsReq$ = new Subject();

  /**
   * Content dimensions
   * @returns {Observable<NbLayoutDimensions>}
   */
  getDimensions(): Observable<NbLayoutDimensions> {
    return new Observable((observer: Subscriber<NbLayoutDimensions>) => {
      const listener = new Subject<NbLayoutDimensions>();
      listener.subscribe(observer);
      this.contentDimensionsReq$.next({ listener });

      return () => listener.complete();
    });
  }

  /**
   * @private
   * @returns {Subject<any>}
   */
  onGetDimensions(): Subject<any> {
    return this.contentDimensionsReq$;
  }
}