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

/**
 * This service is used to store the state of the view boxes when are inside a data grid.
 *
 * @export
 * @class ViewBoxesStateService
 */
@Injectable()
export class ViewBoxesStateService {
  /**
   * keeps track of the view boxes completed
   *
   * @private
   * @type {any[]}
   * @memberof ViewBoxesStateService
   */
  private _viewBoxes: any[] = [];

  /**
   * This is the number of view boxes that have been completed.
   *
   * @private
   * @memberof ViewBoxesStateService
   */
  private _viewBoxesCompleted = 0;

  /**
   * This is the subject that is used to notify the view boxes that they are ready.
   *
   * @private
   * @memberof ViewBoxesStateService
   */
  private subject = new Subject<any>();

  /**
   * It returns an observable that can be subscribed to
   * @returns An observable
   * @memberof ViewBoxesStateService
   */
  getObserver(): Observable<any> {
    return this.subject.asObservable();
  }

  /**
   * This function returns the number of view boxes in the view box array.
   *
   * @returns The number of view boxes in the view box array.
   * @memberof ViewBoxesStateService
   */
  getTotalViewBoxes(): number {
    return this._viewBoxes.length;
  }

  /**
   * This function takes a ViewBoxComponent as an argument and pushes it into the _viewBoxes array.
   *
   * @param viewBox ViewBoxComponent - this is the viewBox that is being registered.
   * @memberof ViewBoxesStateService
   */
  registerViewBox(viewBox: any): void {
    this._viewBoxes.push(viewBox);
  }

  /**
   * When the viewBoxReady() function is called, the _viewBoxesCompleted variable is incremented by one
   *
   * @memberof ViewBoxesStateService
   */
  viewBoxReady(): void {
    this._viewBoxesCompleted++;
    if (this._viewBoxesCompleted === this._viewBoxes.length) {
      this.subject.next(this._viewBoxesCompleted);
    }
  }

  /**
   * It clears the view boxes array and resets the view boxes completed counter
   *
   * @memberof ViewBoxesStateService
   */
  clear(): void {
    this._viewBoxes = [];
    this._viewBoxesCompleted = 0;
  }
}