# All files / src/utils webvtt-parser.js

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     import VTTParser from './vttparser';
    import { utf8ArrayToStr } from '../demux/id3';

    // String.prototype.startsWith is not supported in IE11
    const startsWith = function (inputString, searchString, position) {
      return inputString.substr(position || 0, searchString.length) === searchString;
    };

    const cueString2millis = function (timeString) {
      let ts = parseInt(timeString.substr(-3));
      let secs = parseInt(timeString.substr(-6, 2));
      let mins = parseInt(timeString.substr(-9, 2));
      let hours = timeString.length > 9 ? parseInt(timeString.substr(0, timeString.indexOf(':'))) : 0;

      if (!Number.isFinite(ts) || !Number.isFinite(secs) || !Number.isFinite(mins) || !Number.isFinite(hours)) {
        return -1;
      }

      ts += 1000 * secs;
      ts += 60 * 1000 * mins;
      ts += 60 * 60 * 1000 * hours;

      return ts;
    };

    // From https://github.com/darkskyapp/string-hash
    const hash = function (text) {
      let hash = 5381;
      let i = text.length;
      while (i) {
        hash = (hash * 33) ^ text.charCodeAt(--i);
      }

      return (hash >>> 0).toString();
    };

    const calculateOffset = function (vttCCs, cc, presentationTime) {
      let currCC = vttCCs[cc];
      let prevCC = vttCCs[currCC.prevCC];

      // This is the first discontinuity or cues have been processed since the last discontinuity
      // Offset = current discontinuity time
      if (!prevCC || (!prevCC.new && currCC.new)) {
        vttCCs.ccOffset = vttCCs.presentationOffset = currCC.start;
        currCC.new = false;
        return;
      }

      // There have been discontinuities since cues were last parsed.
      // Offset = time elapsed
      while (prevCC && prevCC.new) {
        vttCCs.ccOffset += currCC.start - prevCC.start;
        currCC.new = false;
        currCC = prevCC;
        prevCC = vttCCs[currCC.prevCC];
      }

      vttCCs.presentationOffset = presentationTime;
    };

    const WebVTTParser = {
      parse: function (vttByteArray, syncPTS, vttCCs, cc, callBack, errorCallBack) {
        // Convert byteArray into string, replacing any somewhat exotic linefeeds with "\n", then split on that character.
        let re = /\r\n|\n\r|\n|\r/g;
        // Uint8Array.prototype.reduce is not implemented in IE11
        let vttLines = utf8ArrayToStr(new Uint8Array(vttByteArray)).trim().replace(re, '\n').split('\n');

        let cueTime = '00:00.000';
        let mpegTs = 0;
        let localTime = 0;
        let presentationTime = 0;
        let cues = [];
        let parsingError;
        let inHeader = true;
        // let VTTCue = VTTCue || window.TextTrackCue;

        // Create parser object using VTTCue with TextTrackCue fallback on certain browsers.
        let parser = new VTTParser();

        parser.oncue = function (cue) {
          // Adjust cue timing; clamp cues to start no earlier than - and drop cues that don't end after - 0 on timeline.
          let currCC = vttCCs[cc];
          let cueOffset = vttCCs.ccOffset;

          // Update offsets for new discontinuities
          if (currCC && currCC.new) {
            if (localTime !== undefined) {
              // When local time is provided, offset = discontinuity start time - local time
              cueOffset = vttCCs.ccOffset = currCC.start;
            } else {
              calculateOffset(vttCCs, cc, presentationTime);
            }
          }

          if (presentationTime) {
            // If we have MPEGTS, offset = presentation time + discontinuity offset
            cueOffset = presentationTime - vttCCs.presentationOffset;
          }

          cue.startTime += cueOffset - localTime;
          cue.endTime += cueOffset - localTime;

          // Create a unique hash id for a cue based on start/end times and text.
          // This helps timeline-controller to avoid showing repeated captions.
          cue.id = hash(cue.startTime.toString()) + hash(cue.endTime.toString()) + hash(cue.text);

          // Fix encoding of special characters. TODO: Test with all sorts of weird characters.
          cue.text = decodeURIComponent(encodeURIComponent(cue.text));
          if (cue.endTime > 0) {
            cues.push(cue);
          }
        };

        parser.onparsingerror = function (e) {
          parsingError = e;
        };

        parser.onflush = function () {
          if (parsingError && errorCallBack) {
            errorCallBack(parsingError);
            return;
          }
          callBack(cues);
        };

        // Go through contents line by line.
        vttLines.forEach(line => {
          if (inHeader) {
            // Look for X-TIMESTAMP-MAP in header.
            if (startsWith(line, 'X-TIMESTAMP-MAP=')) {
              // Once found, no more are allowed anyway, so stop searching.
              inHeader = false;
              // Extract LOCAL and MPEGTS.
              line.substr(16).split(',').forEach(timestamp => {
                if (startsWith(timestamp, 'LOCAL:')) {
                  cueTime = timestamp.substr(6);
                } else if (startsWith(timestamp, 'MPEGTS:')) {
                  mpegTs = parseInt(timestamp.substr(7));
                }
              });
              try {
                // Calculate subtitle offset in milliseconds.
                if (syncPTS + ((vttCCs[cc].start * 90000) || 0) < 0) {
                  syncPTS += 8589934592;
                }
                // Adjust MPEGTS by sync PTS.
                mpegTs -= syncPTS;
                // Convert cue time to seconds
                localTime = cueString2millis(cueTime) / 1000;
                // Convert MPEGTS to seconds from 90kHz.
                presentationTime = mpegTs / 90000;

                if (localTime === -1) {
                  parsingError = new Error(`Malformed X-TIMESTAMP-MAP: ${line}`);
                }
              } catch (e) {
                parsingError = new Error(`Malformed X-TIMESTAMP-MAP: ${line}`);
              }
              // Return without parsing X-TIMESTAMP-MAP line.
              return;
            } else if (line === '') {
              inHeader = false;
            }
          }
          // Parse line by default.
          parser.parse(line + '\n');
        });

        parser.flush();
      }
    };

    export default WebVTTParser;