interface AttachableVideoView<Engine> {
  attachEngine(engine: Engine): void;
  detachEngine(): void;
}

interface VideoViewAttachmentState<Engine> {
  view: AttachableVideoView<Engine> | null;
  engine: Engine | null;
}

export function createVideoViewAttachmentState<
  Engine
>(): VideoViewAttachmentState<Engine> {
  return {
    view: null,
    engine: null,
  };
}

export function detachVideoView<Engine>(
  state: VideoViewAttachmentState<Engine>
): void {
  if (state.view != null && state.engine != null) {
    state.view.detachEngine();
  }
  state.view = null;
  state.engine = null;
}

export function syncVideoViewAttachment<Engine>(
  state: VideoViewAttachmentState<Engine>,
  nextView: AttachableVideoView<Engine> | null,
  nextEngine: Engine | undefined
): void {
  if (
    state.view != null &&
    (state.view !== nextView || state.engine !== nextEngine)
  ) {
    detachVideoView(state);
  }

  if (
    nextView != null &&
    nextEngine != null &&
    (state.view !== nextView || state.engine !== nextEngine)
  ) {
    nextView.attachEngine(nextEngine);
    state.view = nextView;
    state.engine = nextEngine;
  }
}