import { ElementRef, Injectable } from '@angular/core';

@Injectable()
export class TalyStickyService {
  private stickyElements = new Set<ElementRef<HTMLElement>>();

  public addStickyElement(element: ElementRef<HTMLElement> | unknown) {
    // Since the element is a result of a runtime query, we cannot guarantee that it will be of the ElementRef<HTMLElement> type.
    // Therefore, a runtime type check is required
    if (
      !(element instanceof ElementRef) ||
      typeof element?.nativeElement?.offsetHeight !== 'number'
    ) {
      console.warn(
        'Unable to register element in TalyStickyService: Missing "offsetHeight" property. Please provide a DOM element of type ElementRef<HTMLElement>.'
      );
      return;
    }
    this.stickyElements.add(element);
  }

  public getStickyElementHeights() {
    const totalHeight = Array.from(this.stickyElements)
      .map((element) => element.nativeElement.offsetHeight ?? 0)
      .reduce((height, acc) => acc + height, 0);
    return totalHeight;
  }
}