function PlayControl(data) {
  this.data = data;
  this.stop_play_flag = true;
  this.pause_play_flag = false;

  this.pause_resume_play = function () {
    this.pause_play_flag = !this.pause_play_flag;

    if (!this.pause_play_flag && !this.stop_play_flag) {
      this.play(this.on_load_world_finished);
    }
  };

  this.stop_play = function () {
    this.stop_play_flag = true;
    this.pause_play_flag = false;
  };

  this.on_load_world_finished = null;
  this.play = function (on_load_world_finished, fps = 2) {
    this.on_load_world_finished = on_load_world_finished;

    if (!this.data.meta) {
      console.log("no meta data! cannot play");
      return;
    }

    // if (this.stop_play_flag == false && !resume){
    //     return;
    // }

    this.stop_play_flag = false;
    this.pause_play_flag = false;

    var scene_meta = data.world.sceneMeta;

    var scope = this;

    let start_frame = data.world.frameInfo.frame;

    let current_frame_index = scene_meta.frames.findIndex(function (x) {
      return x == data.world.frameInfo.frame;
    });
    if (current_frame_index == scene_meta.frames.length - 1) {
      //this is the last frmae
      // we go to first frame.
      start_frame = scene_meta.frames[0];
    }

    play_frame(scene_meta, start_frame, on_load_world_finished);

    async function play_frame(scene_meta, frame, on_load_world_finished) {
      if (!scope.stop_play_flag && !scope.pause_play_flag) {
        var world = await scope.data.getWorld(scene_meta.scene, frame);

        if (world.preloaded()) {
          //found, data ready
          scope.data.activate_world(world, function () {
            //on load finished
            //views[0].detach_control();
            on_load_world_finished(world);

            // play next frame
            let frame_index = world.frameInfo.frame_index;
            if (frame_index + 1 < scene_meta.frames.length) {
              var next_frame = scene_meta.frames[frame_index + 1];
              setTimeout(function () {
                play_frame(scene_meta, next_frame, on_load_world_finished);
              }, 1000 / fps);
            } else {
              scope.stop_play();
            }
          });
        } else {
          //not ready.
          console.log("wait buffer!", frame);

          setTimeout(function () {
            play_frame(scene_meta, frame, on_load_world_finished);
          }, 10);
        }
      }
    }
  };

  // function play_current_scene_without_buffer(){

  //     if (!data.meta){
  //         console.log("no meta data! cannot play");
  //         return;
  //     }

  //     if (stop_play_flag== false){
  //         return;
  //     }

  //     stop_play_flag = false;

  //     var scene_meta = data.get_current_world_scene_meta();
  //     var sceneName= scene_meta.scene;

  //     play_frame(scene_meta, data.world.frameInfo.frame);

  //     function play_frame(scene_meta, frame){
  //         load_world(sceneName, frame);

  //         if (!stop_play_flag)
  //         {
  //             var frame_index = scene_meta.frames.findIndex(function(x){return x == frame;});
  //             if (frame_index+1 < scene_meta.frames.length)
  //             {
  //                 next_frame = scene_meta.frames[frame_index+1];
  //                 setTimeout(
  //                     function(){
  //                         play_frame(scene_meta, next_frame);
  //                     },
  //                     100);
  //             }
  //             else{
  //                 stop_play_flag = true;
  //             }

  //         }
  //     };
  // }
}

export { PlayControl };