# All files / src/controller subtitle-stream-controller.js

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17.65% Branches 9/51
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     /*
     * Subtitle Stream Controller
    */

    import Event from '../events';
    import { logger } from '../utils/logger';
    import Decrypter from '../crypt/decrypter';
    import TaskLoop from '../task-loop';

    const State = {
      STOPPED: 'STOPPED',
      IDLE: 'IDLE',
      KEY_LOADING: 'KEY_LOADING',
      FRAG_LOADING: 'FRAG_LOADING'
    };

    class SubtitleStreamController extends TaskLoop {
      constructor (hls) {
        super(hls,
          Event.MEDIA_ATTACHED,
          Event.ERROR,
          Event.KEY_LOADED,
          Event.FRAG_LOADED,
          Event.SUBTITLE_TRACKS_UPDATED,
          Event.SUBTITLE_TRACK_SWITCH,
          Event.SUBTITLE_TRACK_LOADED,
          Event.SUBTITLE_FRAG_PROCESSED);

        this.config = hls.config;
        this.vttFragSNsProcessed = {};
        this.vttFragQueues = undefined;
        this.currentlyProcessing = null;
        this.state = State.STOPPED;
        this.currentTrackId = -1;
        this.decrypter = new Decrypter(hls.observer, hls.config);
      }

      onHandlerDestroyed () {
        this.state = State.STOPPED;
      }

      // Remove all queued items and create a new, empty queue for each track.
      clearVttFragQueues () {
        this.vttFragQueues = {};
        this.tracks.forEach(track => {
          this.vttFragQueues[track.id] = [];
        });
      }

      // If no frag is being processed and queue isn't empty, initiate processing of next frag in line.
      nextFrag () {
        if (this.currentlyProcessing === null && this.currentTrackId > -1 && this.vttFragQueues[this.currentTrackId].length) {
          let frag = this.currentlyProcessing = this.vttFragQueues[this.currentTrackId].shift();
          this.fragCurrent = frag;
          this.hls.trigger(Event.FRAG_LOADING, { frag: frag });
          this.state = State.FRAG_LOADING;
        }
      }

      // When fragment has finished processing, add sn to list of completed if successful.
      onSubtitleFragProcessed (data) {
        if (data.success) {
          this.vttFragSNsProcessed[data.frag.trackId].push(data.frag.sn);
        }

        this.currentlyProcessing = null;
        this.state = State.IDLE;
        this.nextFrag();
      }

      onMediaAttached () {
        this.state = State.IDLE;
      }

      // If something goes wrong, procede to next frag, if we were processing one.
      onError (data) {
        let frag = data.frag;
        // don't handle frag error not related to subtitle fragment
        if (frag && frag.type !== 'subtitle') {
          return;
        }

        Iif (this.currentlyProcessing) {
          this.currentlyProcessing = null;
          this.nextFrag();
        }
      }

      doTick () {
        switch (this.state) {
        case State.IDLE:
          const tracks = this.tracks;
          let trackId = this.currentTrackId;

          const processedFragSNs = this.vttFragSNsProcessed[trackId],
            fragQueue = this.vttFragQueues[trackId],
            currentFragSN = this.currentlyProcessing ? this.currentlyProcessing.sn : -1;

          const alreadyProcessed = function (frag) {
            return processedFragSNs.indexOf(frag.sn) > -1;
          };

          const alreadyInQueue = function (frag) {
            return fragQueue.some(fragInQueue => {
              return fragInQueue.sn === frag.sn;
            });
          };

            // exit if tracks don't exist
          if (!tracks) {
            break;
          }

          var trackDetails;

          if (trackId < tracks.length) {
            trackDetails = tracks[trackId].details;
          }

          if (typeof trackDetails === 'undefined') {
            break;
          }

          // Add all fragments that haven't been, aren't currently being and aren't waiting to be processed, to queue.
          trackDetails.fragments.forEach(frag => {
            if (!(alreadyProcessed(frag) || frag.sn === currentFragSN || alreadyInQueue(frag))) {
              // Load key if subtitles are encrypted
              if (frag.encrypted) {
                logger.log(`Loading key for ${frag.sn}`);
                this.state = State.KEY_LOADING;
                this.hls.trigger(Event.KEY_LOADING, { frag: frag });
              } else {
                // Frags don't know their subtitle track ID, so let's just add that...
                frag.trackId = trackId;
                fragQueue.push(frag);
                this.nextFrag();
              }
            }
          });
        }
      }

      // Got all new subtitle tracks.
      onSubtitleTracksUpdated (data) {
        logger.log('subtitle tracks updated');
        this.tracks = data.subtitleTracks;
        this.clearVttFragQueues();
        this.vttFragSNsProcessed = {};
        this.tracks.forEach(track => {
          this.vttFragSNsProcessed[track.id] = [];
        });
      }

      onSubtitleTrackSwitch (data) {
        this.currentTrackId = data.id;
        Eif (!this.tracks || this.currentTrackId === -1) {
          return;
        }

        // Check if track was already loaded and if so make sure we finish
        // downloading its frags, if not all have been downloaded yet
        const currentTrack = this.tracks[this.currentTrackId];
        if (currentTrack && currentTrack.details) {
          this.tick();
        }
      }

      // Got a new set of subtitle fragments.
      onSubtitleTrackLoaded () {
        this.tick();
      }

      onKeyLoaded () {
        if (this.state === State.KEY_LOADING) {
          this.state = State.IDLE;
          this.tick();
        }
      }

      onFragLoaded (data) {
        let fragCurrent = this.fragCurrent,
          decryptData = data.frag.decryptdata;
        let fragLoaded = data.frag,
          hls = this.hls;
        Iif (this.state === State.FRAG_LOADING &&
            fragCurrent &&
            data.frag.type === 'subtitle' &&
            fragCurrent.sn === data.frag.sn) {
          // check to see if the payload needs to be decrypted
          if ((data.payload.byteLength > 0) && (decryptData != null) && (decryptData.key != null) && (decryptData.method === 'AES-128')) {
            let startTime;
            try {
              startTime = performance.now();
            } catch (error) {
              startTime = Date.now();
            }
            // decrypt the subtitles
            this.decrypter.decrypt(data.payload, decryptData.key.buffer, decryptData.iv.buffer, function (decryptedData) {
              let endTime;
              try {
                endTime = performance.now();
              } catch (error) {
                endTime = Date.now();
              }
              hls.trigger(Event.FRAG_DECRYPTED, { frag: fragLoaded, payload: decryptedData, stats: { tstart: startTime, tdecrypt: endTime } });
            });
          }
        }
      }
    }
    export default SubtitleStreamController;