angular/angular

@Injectable({
  providedIn: 'root',
  useFactory: (document, window, handler: ErrorHandler) => new ShopScrollerService(
    document, 
    document.querySelector('.mat-sidenav-content'), 
    handler
  ),
  deps: [DOCUMENT, ErrorHandler]
})
export class ShopScrollerService implements ViewportScroller {

  private offset: () => [number, number] = () => [0, 0];

  constructor(private document: Document, private window: any, private errorHandler: ErrorHandler) {
    setTimeout(() => {
      this.window = document.querySelector('.mat-sidenav-content');
    }, 1000)
  }

  /**
   * Configures the top offset used when scrolling to an anchor.
   * @param offset A position in screen coordinates (a tuple with x and y values)
   * or a function that returns the top offset position.
   *
   */
  setOffset(offset: [number, number]|(() => [number, number])): void {
    if (Array.isArray(offset)) {
      this.offset = () => offset;
    } else {
      this.offset = offset;
    }
  }

  /**
   * Retrieves the current scroll position.
   * @returns The position in screen coordinates.
   */
  getScrollPosition(): [number, number] {
    if (this.supportScrollRestoration() && this.window instanceof Window) {
      return [this.window.scrollX, this.window.scrollY];
    } 
    else if(this.supportScrollRestoration() && this.window instanceof HTMLElement){
      return [this.window.scrollLeft, this.window.scrollTop]
    }
    else {
      return [0, 0];
    }
  }

  /**
   * Sets the scroll position.
   * @param position The new position in screen coordinates.
   */
  scrollToPosition(position: [number, number]): void {
    if (this.supportScrollRestoration()) {
      this.window.scrollTo(position[0], position[1]);
    }
  }

  /**
   * Scrolls to an anchor element.
   * @param anchor The ID of the anchor element.
   */
  scrollToAnchor(anchor: string): void {
    if (this.supportScrollRestoration()) {
      // Escape anything passed to `querySelector` as it can throw errors and stop the application
      // from working if invalid values are passed.
      if (this.window.CSS && this.window.CSS.escape) {
        anchor = this.window.CSS.escape(anchor);
      } else {
        anchor = anchor.replace(/(\"|\'\ |:|\.|\[|\]|,|=)/g, '\\$1');
      }
      try {
        const elSelectedById = this.document.querySelector(`#${anchor}`);
        if (elSelectedById) {
          this.scrollToElement(elSelectedById);
          return;
        }
        const elSelectedByName = this.document.querySelector(`[name='${anchor}']`);
        if (elSelectedByName) {
          this.scrollToElement(elSelectedByName);
          return;
        }
      } catch (e) {
        this.errorHandler.handleError(e);
      }
    }
  }

  /**
   * Disables automatic scroll restoration provided by the browser.
   */
  setHistoryScrollRestoration(scrollRestoration: 'auto'|'manual'): void {
    if (this.supportScrollRestoration()) {
      const history = this.window.history;
      if (history && history.scrollRestoration) {
        history.scrollRestoration = scrollRestoration;
      }
    }
  }

  private scrollToElement(el: any): void {
    const rect = el.getBoundingClientRect();
    const left = rect.left + this.window.pageXOffset;
    const top = rect.top + this.window.pageYOffset;
    const offset = this.offset();
    this.window.scrollTo(left - offset[0], top - offset[1]);
  }

  /**
   * We only support scroll restoration when we can get a hold of window.
   * This means that we do not support this behavior when running in a web worker.
   *
   * Lifting this restriction right now would require more changes in the dom adapter.
   * Since webworkers aren't widely used, we will lift it once RouterScroller is
   * battle-tested.
   */
  private supportScrollRestoration(): boolean {
    try {
      return !!this.window && !!this.window.scrollTo;
    } catch {
      return false;
    }
  }
}