import {
  Injectable,
  Renderer2,
  RendererFactory2,
} from '@angular/core';
import { ReplaySubject } from 'rxjs/internal/ReplaySubject';

// Сенсор
import { ResizeSensor } from 'css-element-queries';

// Интерфейсы
import { ISize } from '../interfaces';

// Сервис скролла
@Injectable({ providedIn: 'root' })
export class HitScrollService {

  constructor(rendererFactory: RendererFactory2) {
    this.renderer = rendererFactory.createRenderer(null, null);
    this.size$ = new ReplaySubject<ISize>(1);
    this.addSensor();
  }

  // ID области со скролом
  private readonly ID = 'hit-scroll-sensor';

  // Ссылка на renderer
  private readonly renderer: Renderer2;

  // Размер слайдера
  public readonly size$: ReplaySubject<ISize>;

  // Добавить сенсор размера скрола
  private addSensor(): void {
    if (!document.getElementById(this.ID)) {
      const SIZE_VIEW = 200;
      const view = this.renderer.createElement('div');
      const canvas = this.renderer.createElement('div');

      // tslint:disable-next-line:no-unused-expression
      new ResizeSensor(canvas, (): void => {
        const size = {
          width: SIZE_VIEW - canvas.offsetWidth,
          height: SIZE_VIEW - canvas.offsetHeight,
        };
        this.size$.next(size);
      });

      this.renderer.setAttribute(view, 'id', this.ID);
      this.renderer.setStyle(view, 'overflow', 'scroll');
      this.renderer.setStyle(view, 'position', 'absolute');
      this.renderer.setStyle(view, 'margin', '0');
      this.renderer.setStyle(view, 'padding', '0');
      this.renderer.setStyle(view, 'left', '-10000px');
      this.renderer.setStyle(view, 'top', '-10000px');
      this.renderer.setStyle(view, 'visibility', 'hidden');
      this.renderer.setStyle(view, 'opacity', '0');
      this.renderer.setStyle(view, 'box-sizing', 'border-box');
      this.renderer.setStyle(view, 'width', `${SIZE_VIEW}px`);
      this.renderer.setStyle(view, 'height', `${SIZE_VIEW}px`);
      this.renderer.setStyle(canvas, 'position', 'absolute');
      this.renderer.setStyle(canvas, 'top', '0');
      this.renderer.setStyle(canvas, 'right', '0');
      this.renderer.setStyle(canvas, 'bottom', '0');
      this.renderer.setStyle(canvas, 'left', '0');
      this.renderer.setStyle(canvas, 'padding', '0');
      this.renderer.setStyle(canvas, 'margin', '0');
      this.renderer.setStyle(canvas, 'box-sizing', 'border-box');
      this.renderer.appendChild(view, canvas);
      this.renderer.appendChild(document.body, view);
    }
  }
}