/*
 * FPS Controller
*/

import Event from '../events';
import EventHandler from '../event-handler';
import {logger} from '../utils/logger';

class FPSController extends EventHandler{

  constructor(hls) {
    super(hls, Event.MEDIA_ATTACHING);
  }

  destroy() {
    if (this.timer) {
      clearInterval(this.timer);
    }
    this.isVideoPlaybackQualityAvailable = false;
  }
  
  onMediaAttaching(data) {
    if (this.hls.config.capLevelOnFPSDrop) {
      this.video = data.media instanceof HTMLVideoElement ? data.media : null;
      if (typeof this.video.getVideoPlaybackQuality === 'function') {
        this.isVideoPlaybackQualityAvailable = true;
      }
      clearInterval(this.timer);
      this.timer = setInterval(this.checkFPSInterval.bind(this), this.hls.config.fpsDroppedMonitoringPeriod);
    } 
  }
  
  checkFPS(video, decodedFrames, droppedFrames) {
    let currentTime = performance.now();
    if (decodedFrames) {
      if (this.lastTime) {
        let currentPeriod = currentTime - this.lastTime,
            currentDropped = droppedFrames - this.lastDroppedFrames,
            currentDecoded = decodedFrames - this.lastDecodedFrames,
            droppedFPS = 1000 * currentDropped / currentPeriod;
        this.hls.trigger(Event.FPS_DROP, {currentDropped: currentDropped, currentDecoded: currentDecoded, totalDroppedFrames: droppedFrames});
        if (droppedFPS > 0) {
          //logger.log('checkFPS : droppedFPS/decodedFPS:' + droppedFPS/(1000 * currentDecoded / currentPeriod));
          if (currentDropped > this.hls.config.fpsDroppedMonitoringThreshold * currentDecoded) {
            let currentLevel = this.hls.currentLevel;
            logger.warn('drop FPS ratio greater than max allowed value for currentLevel: ' + currentLevel);
            if (currentLevel > 0 && (this.hls.autoLevelCapping === -1 || this.hls.autoLevelCapping >= currentLevel)) {
              currentLevel = currentLevel - 1;
              this.hls.trigger(Event.FPS_DROP_LEVEL_CAPPING, {level: currentLevel, droppedLevel: this.hls.currentLevel});
              this.hls.autoLevelCapping = currentLevel;
              this.hls.streamController.nextLevelSwitch();
            }
          }
        }
      }
      this.lastTime = currentTime;
      this.lastDroppedFrames = droppedFrames;
      this.lastDecodedFrames = decodedFrames;
    }
  }
  
  checkFPSInterval() {
    if (this.video) {
      if (this.isVideoPlaybackQualityAvailable) {
        let videoPlaybackQuality = this.video.getVideoPlaybackQuality();
        this.checkFPS(this.video, videoPlaybackQuality.totalVideoFrames, videoPlaybackQuality.droppedVideoFrames);
      } else {
        this.checkFPS(this.video, this.video.webkitDecodedFrameCount, this.video.webkitDroppedFrameCount);  
      }
    }
  } 
}

export default FPSController;