/**
 * Counter to register pending tile headers for the particular frameNumber
 * Until all tiles are loaded we won't call `onTraversalEnd` callback
 */
export class I3SPendingTilesRegister {
  private frameNumberMap: Map<string, Map<number, number>> = new Map();

  /**
   * Register a new pending tile header for the particular frameNumber
   * @param viewportId
   * @param frameNumber
   */
  register(viewportId: string, frameNumber: number) {
    const viewportMap = this.frameNumberMap.get(viewportId) || new Map();
    const oldCount = viewportMap.get(frameNumber) || 0;
    viewportMap.set(frameNumber, oldCount + 1);
    this.frameNumberMap.set(viewportId, viewportMap);
  }

  /**
   * Deregister a pending tile header for the particular frameNumber
   * @param viewportId
   * @param frameNumber
   */
  deregister(viewportId: string, frameNumber: number) {
    const viewportMap = this.frameNumberMap.get(viewportId);
    if (!viewportMap) {
      return;
    }
    const oldCount = viewportMap.get(frameNumber) || 1;
    viewportMap.set(frameNumber, oldCount - 1);
  }

  /**
   * Check is there are no pending tile headers registered for the particular frameNumber
   * @param viewportId
   * @param frameNumber
   * @returns
   */
  isZero(viewportId: string, frameNumber: number) {
    const count = this.frameNumberMap.get(viewportId)?.get(frameNumber) || 0;
    return count === 0;
  }
}