# All files / src/controller level-controller.js

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     /*
     * Level Controller
    */

    import Event from '../events';
    import EventHandler from '../event-handler';
    import {logger} from '../utils/logger';
    import {ErrorTypes, ErrorDetails} from '../errors';
    import {isCodecSupportedInMp4} from '../utils/codecs';

    class LevelController extends EventHandler {

      constructor(hls) {
        super(hls,
          Event.MANIFEST_LOADED,
          Event.LEVEL_LOADED,
          Event.FRAG_LOADED,
          Event.ERROR);
        this._manualLevel = -1;
        this.timer = null;
      }

      destroy() {
        this.cleanTimer();
        this._manualLevel = -1;
      }

      cleanTimer() {
        if (this.timer !== null) {
          clearTimeout(this.timer);
          this.timer = null;
        }
      }

      startLoad() {
        let levels = this._levels;

        this.canload = true;
        this.levelRetryCount = 0;

        // clean up live level details to force reload them, and reset load errors
        if(levels) {
          levels.forEach(level => {
            level.loadError = 0;
            const levelDetails = level.details;
            if (levelDetails && levelDetails.live) {
              level.details = undefined;
            }
          });
        }
        // speed up live playlist refresh if timer exists
        if (this.timer) {
          this.tick();
        }
      }

      stopLoad() {
        this.canload = false;
      }

      onManifestLoaded(data) {
        let levels          = [],
            bitrateStart,
            levelSet        = {},
            levelFromSet    = null,
            videoCodecFound = false,
            audioCodecFound = false,
            chromeOrFirefox = /chrome|firefox/.test(navigator.userAgent.toLowerCase());

        // regroup redundant levels together
        data.levels.forEach(level => {
          level.loadError = 0;
          level.fragmentError = false;

          videoCodecFound = videoCodecFound || !!level.videoCodec;
          audioCodecFound = audioCodecFound || !!level.audioCodec || !!(level.attrs && level.attrs.AUDIO);

          // erase audio codec info if browser does not support mp4a.40.34.
          // demuxer will autodetect codec and fallback to mpeg/audio
          if (chromeOrFirefox === true && level.audioCodec && level.audioCodec.indexOf('mp4a.40.34') !== -1) {
            level.audioCodec = undefined;
          }

          levelFromSet = levelSet[level.bitrate];

          if (levelFromSet === undefined) {
            level.url = [level.url];
            level.urlId = 0;
            levelSet[level.bitrate] = level;
            levels.push(level);
          } else {
            levelFromSet.url.push(level.url);
          }
        });

        // remove audio-only level if we also have levels with audio+video codecs signalled
        if (videoCodecFound === true && audioCodecFound === true) {
          levels = levels.filter(({videoCodec}) => !!videoCodec);
        }

        // only keep levels with supported audio/video codecs
        levels = levels.filter(({audioCodec, videoCodec}) => {
          return (!audioCodec || isCodecSupportedInMp4(audioCodec)) && (!videoCodec || isCodecSupportedInMp4(videoCodec));
        });

        if (levels.length > 0) {
          // start bitrate is the first bitrate of the manifest
          bitrateStart = levels[0].bitrate;
          // sort level on bitrate
          levels.sort(function (a, b) {
            return a.bitrate - b.bitrate;
          });
          this._levels = levels;
          // find index of first level in sorted levels
          for (let i = 0; i < levels.length; i++) {
            if (levels[i].bitrate === bitrateStart) {
              this._firstLevel = i;
              logger.log(`manifest loaded,${levels.length} level(s) found, first bitrate:${bitrateStart}`);
              break;
            }
          }
          this.hls.trigger(Event.MANIFEST_PARSED, {
            levels    : levels,
            firstLevel: this._firstLevel,
            stats     : data.stats,
            audio     : audioCodecFound,
            video     : videoCodecFound,
            altAudio  : data.audioTracks.length > 0
          });
        } else {
          this.hls.trigger(Event.ERROR, {
            type   : ErrorTypes.MEDIA_ERROR,
            details: ErrorDetails.MANIFEST_INCOMPATIBLE_CODECS_ERROR,
            fatal  : true,
            url    : this.hls.url,
            reason : 'no level with compatible codecs found in manifest'
          });
        }
      }

      get levels() {
        return this._levels;
      }

      get level() {
        return this._level;
      }

      set level(newLevel) {
        let levels = this._levels;
        if (levels) {
          newLevel = Math.min(newLevel, levels.length-1);
          if (this._level !== newLevel || levels[newLevel].details === undefined) {
            this.setLevelInternal(newLevel);
          }
        }
      }

     setLevelInternal(newLevel) {
        const levels = this._levels;
        const hls = this.hls;
        // check if level idx is valid
        if (newLevel >= 0 && newLevel < levels.length) {
          // stopping live reloading timer if any
          this.cleanTimer();
          if (this._level !== newLevel) {
            logger.log(`switching to level ${newLevel}`);
            this._level = newLevel;
            var levelProperties = levels[newLevel];
            levelProperties.level = newLevel;
            // LEVEL_SWITCH to be deprecated in next major release
            hls.trigger(Event.LEVEL_SWITCH, levelProperties);
            hls.trigger(Event.LEVEL_SWITCHING, levelProperties);
          }
          var level = levels[newLevel], levelDetails = level.details;
           // check if we need to load playlist for this level
          if (!levelDetails || levelDetails.live === true) {
            // level not retrieved yet, or live playlist we need to (re)load it
            var urlId = level.urlId;
            hls.trigger(Event.LEVEL_LOADING, {url: level.url[urlId], level: newLevel, id: urlId});
          }
        } else {
          // invalid level id given, trigger error
          hls.trigger(Event.ERROR, {type : ErrorTypes.OTHER_ERROR, details: ErrorDetails.LEVEL_SWITCH_ERROR, level: newLevel, fatal: false, reason: 'invalid level idx'});
        }
     }

      get manualLevel() {
        return this._manualLevel;
      }

      set manualLevel(newLevel) {
        this._manualLevel = newLevel;
        if (this._startLevel === undefined) {
          this._startLevel = newLevel;
        }
        if (newLevel !== -1) {
          this.level = newLevel;
        }
      }

      get firstLevel() {
        return this._firstLevel;
      }

      set firstLevel(newLevel) {
        this._firstLevel = newLevel;
      }

      get startLevel() {
        // hls.startLevel takes precedence over config.startLevel
        // if none of these values are defined, fallback on this._firstLevel (first quality level appearing in variant manifest)
        if (this._startLevel === undefined) {
          let configStartLevel = this.hls.config.startLevel;
          if (configStartLevel !== undefined) {
            return configStartLevel;
          } else {
            return this._firstLevel;
          }
        } else {
          return this._startLevel;
        }
      }

      set startLevel(newLevel) {
        this._startLevel = newLevel;
      }

      onError(data) {
        if (data.fatal === true) {
          if (data.type === ErrorTypes.NETWORK_ERROR) {
            this.cleanTimer();
          }
          return;
        }

        let details = data.details, levelError = false, fragmentError = false;
        let levelIndex, level;
        let {config} = this.hls;

        // try to recover not fatal errors
        switch (details) {
          case ErrorDetails.FRAG_LOAD_ERROR:
          case ErrorDetails.FRAG_LOAD_TIMEOUT:
          case ErrorDetails.FRAG_LOOP_LOADING_ERROR:
          case ErrorDetails.KEY_LOAD_ERROR:
          case ErrorDetails.KEY_LOAD_TIMEOUT:
            levelIndex = data.frag.level;
            fragmentError = true;
            break;
          case ErrorDetails.LEVEL_LOAD_ERROR:
          case ErrorDetails.LEVEL_LOAD_TIMEOUT:
            levelIndex = data.context.level;
            levelError = true;
            break;
          case ErrorDetails.REMUX_ALLOC_ERROR:
            levelIndex = data.level;
            break;
        }
        /* try to switch to a redundant stream if any available.
         * if no redundant stream available, emergency switch down (if in auto mode and current level not 0)
         * otherwise, we cannot recover this network error ...
         */
        if (levelIndex !== undefined) {
          level = this._levels[levelIndex];
          level.loadError++;
          level.fragmentError = fragmentError;

          // Allow fragment retry as long as configuration allows.
          // Since fragment retry logic could depend on the levels, we should not enforce retry limits when there is an issue with fragments
          // FIXME Find a better abstraction where fragment/level retry management is well decoupled
          if (fragmentError === true){
            // if any redundant streams available and if we haven't try them all (level.loadError is reseted on successful frag/level load.
            // if level.loadError reaches redundantLevels it means that we tried them all, no hope  => let's switch down
            const redundantLevels = level.url.length;

            if (redundantLevels > 1 && level.loadError < redundantLevels) {
              level.urlId = (level.urlId + 1) % redundantLevels;
              level.details = undefined;
              logger.warn(`level controller,${details} for level ${levelIndex}: switching to redundant stream id ${level.urlId}`);
            } else {
              // we could try to recover if in auto mode and current level not lowest level (0)
              if ((this._manualLevel === -1) && levelIndex !== 0) {
                logger.warn(`level controller,${details}: switch-down for next fragment`);
                this.hls.nextAutoLevel = levelIndex - 1;
              } else  {
                logger.warn(`level controller, ${details}: reload a fragment`);
                // reset this._level so that another call to set level() will trigger again a frag load
                this._level = undefined;
              }
            }
          } else if (levelError === true){
            if ((this.levelRetryCount + 1) <= config.levelLoadingMaxRetry) {
              // exponential backoff capped to max retry timeout
              const delay = Math.min(Math.pow(2, this.levelRetryCount) * config.levelLoadingRetryDelay, config.levelLoadingMaxRetryTimeout);
              // reset load counter to avoid frag loop loading error
              this.timer = setTimeout(() => this.tick(), delay);
              // boolean used to inform stream controller not to switch back to IDLE on non fatal error
              data.levelRetry = true;
              this.levelRetryCount++;
              logger.warn(`level controller,${details}, retry in ${delay} ms, current retry count is ${this.levelRetryCount}`);
            } else {
              logger.error(`cannot recover ${details} error`);
              this._level = undefined;
              // stopping live reloading timer if any
              this.cleanTimer();
              // switch error to fatal
              data.fatal = true;
            }
          }
        }
      }

      // reset errors on the successful load of a fragment
      onFragLoaded({frag}) {
        if (frag !== undefined && frag.type === 'main') {
          const level = this._levels[frag.level];
          if (level !== undefined) {
            level.fragmentError = false;
            level.loadError = 0;
            this.levelRetryCount = 0;
          }
        }
      }

      onLevelLoaded(data) {
        const levelId = data.level;
        // only process level loaded events matching with expected level
        if (levelId === this._level) {
          let curLevel = this._levels[levelId];
          // reset level load error counter on successful level loaded only if there is no issues with fragments
          if(curLevel.fragmentError === false){
            curLevel.loadError = 0;
            this.levelRetryCount = 0;
          }
          let newDetails = data.details;
          // if current playlist is a live playlist, arm a timer to reload it
          if (newDetails.live) {
            let reloadInterval = 1000 * ( newDetails.averagetargetduration ? newDetails.averagetargetduration : newDetails.targetduration),
                curDetails     = curLevel.details;
            if (curDetails && newDetails.endSN === curDetails.endSN) {
              // follow HLS Spec, If the client reloads a Playlist file and finds that it has not
              // changed then it MUST wait for a period of one-half the target
              // duration before retrying.
              reloadInterval /= 2;
              logger.log(`same live playlist, reload twice faster`);
            }
            // decrement reloadInterval with level loading delay
            reloadInterval -= performance.now() - data.stats.trequest;
            // in any case, don't reload more than every second
            reloadInterval = Math.max(1000, Math.round(reloadInterval));
            logger.log(`live playlist, reload in ${reloadInterval} ms`);
            this.timer = setTimeout(() => this.tick(), reloadInterval);
          } else {
            this.cleanTimer();
          }
        }
      }

      tick() {
        var levelId = this._level;
        if (levelId !== undefined && this.canload) {
          var level = this._levels[levelId];
          if (level && level.url) {
            var urlId = level.urlId;
            this.hls.trigger(Event.LEVEL_LOADING, {url: level.url[urlId], level: levelId, id: urlId});
          }
        }
      }

      get nextLoadLevel() {
        if (this._manualLevel !== -1) {
          return this._manualLevel;
        } else {
         return this.hls.nextAutoLevel;
        }
      }

      set nextLoadLevel(nextLevel) {
        this.level = nextLevel;
        if (this._manualLevel === -1) {
          this.hls.nextAutoLevel = nextLevel;
        }
      }
    }

    export default LevelController;