webvtt-parser/parser.js

WebVTT parser and validator

// Any copyright is dedicated to the Public Domain.
// http://creativecommons.org/publicdomain/zero/1.0/

// Not intended to be fast, but if you can make it faster, please help out!

(function () {
  var defaultCueSettings = {
    direction:"horizontal",
    snapToLines:true,
    linePosition:"auto",
    lineAlign:"start",
    textPosition:"auto",
    positionAlign:"auto",
    size:100,
    alignment:"center",
  };

  var WebVTTParser = function(entities) {
    if (!entities) {
      entities = {
        "&amp": "&",
        "&lt": "<",
        "&gt": ">",
        "&lrm": "\u200e",
        "&rlm": "\u200f",
        "&nbsp": "\u00A0"
      }
    }
    this.entities = entities
    this.parse = function(input, mode) {
      // global search and replace for \0
      input = input.replace(/\0/g, '\uFFFD');
      var NEWLINE = /\r\n|\r|\n/,
          startTime = Date.now(),
          linePos = 0,
          lines = input.split(NEWLINE),
          alreadyCollected = false,
          styles = [],
          cues = [],
          errors = []
      function err(message, col) {
        errors.push({message:message, line:linePos+1, col:col})
      }

      var line = lines[linePos],
          lineLength = line.length,
          signature = "WEBVTT",
          bom = 0,
          signature_length = signature.length

      /* Byte order mark */
      if (line[0] === "\ufeff") {
        bom = 1
        signature_length += 1
      }
      /* SIGNATURE */
      if (
        lineLength < signature_length ||
        line.indexOf(signature) !== 0+bom ||
        lineLength > signature_length &&
        line[signature_length] !== " " &&
        line[signature_length] !== "\t"
      ) {
        err("No valid signature. (File needs to start with \"WEBVTT\".)")
      }

      linePos++

      /* HEADER */
      while(lines[linePos] != "" && lines[linePos] != undefined) {
        err("No blank line after the signature.")
        if(lines[linePos].indexOf("-->") != -1) {
          alreadyCollected = true
          break
        }
        linePos++
      }

      /* CUE LOOP */
      while(lines[linePos] != undefined) {
        var cue
        while(!alreadyCollected && lines[linePos] == "") {
          linePos++
        }
        if(!alreadyCollected && lines[linePos] == undefined)
          break

        /* CUE CREATION */
        cue = Object.assign({}, defaultCueSettings, {
          id:"",
          startTime:0,
          endTime:0,
          pauseOnExit:false,
          direction:"horizontal",
          snapToLines:true,
          linePosition:"auto",
          lineAlign:"start",
          textPosition:"auto",
          positionAlign:"auto",
          size:100,
          alignment:"center",
          text:"",
          tree:null
        })

        var parseTimings = true

        if(lines[linePos].indexOf("-->") == -1) {
          cue.id = lines[linePos]

          /* COMMENTS
             Not part of the specification's parser as these would just be ignored. However,
             we want them to be conforming and not get "Cue identifier cannot be standalone".
           */
          if(/^NOTE($|[ \t])/.test(cue.id)) { // .startsWith fails in Chrome
            linePos++
            while(lines[linePos] != "" && lines[linePos] != undefined) {
              if(lines[linePos].indexOf("-->") != -1)
                err("Cannot have timestamp in a comment.")
              linePos++
            }
            continue
          }

          /* STYLES */
          if(/^STYLE($|[ \t])/.test(cue.id)) {
            var style = []
            var invalid = false
            linePos++
            while(lines[linePos] != "" && lines[linePos] != undefined) {
              if(lines[linePos].indexOf("-->") != -1) {
                err("Cannot have timestamp in a style block.")
                invalid = true
              }
              style.push(lines[linePos])
              linePos++
            }
            if(cues.length) {
              err("Style blocks cannot appear after the first cue.")
              continue
            }
            if (!invalid) {
              styles.push(style.join('\n'))
            }
            continue
          }

          linePos++

          if(lines[linePos] == "" || lines[linePos] == undefined) {
            err("Cue identifier cannot be standalone.")
            continue
          }

          if(lines[linePos].indexOf("-->") == -1) {
            parseTimings = false
            err("Cue identifier needs to be followed by timestamp.")
            continue
          }
        }

        /* TIMINGS */
        alreadyCollected = false
        var timings = new WebVTTCueTimingsAndSettingsParser(lines[linePos], err)
        var previousCueStart = 0
        if(cues.length > 0) {
          previousCueStart = cues[cues.length-1].startTime
        }
        if(parseTimings && !timings.parse(cue, previousCueStart)) {
          /* BAD CUE */

          cue = null
          linePos++

          /* BAD CUE LOOP */
          while(lines[linePos] != "" && lines[linePos] != undefined) {
            if(lines[linePos].indexOf("-->") != -1) {
              alreadyCollected = true
              break
            }
            linePos++
          }
          continue
        }
        linePos++

        /* CUE TEXT LOOP */
        while(lines[linePos] != "" && lines[linePos] != undefined) {
          if(lines[linePos].indexOf("-->") != -1) {
            err("Blank line missing before cue.")
            alreadyCollected = true
            break
          }
          if(cue.text != "")
            cue.text += "\n"
          cue.text += lines[linePos]
          linePos++
        }

        /* CUE TEXT PROCESSING */
        var cuetextparser = new WebVTTCueTextParser(cue.text, err, mode, entities)
        cue.tree = cuetextparser.parse(cue.startTime, cue.endTime)
        cues.push(cue)
      }
      cues.sort(function(a, b) {
        if (a.startTime < b.startTime)
          return -1
        if (a.startTime > b.startTime)
          return 1
        if (a.endTime > b.endTime)
          return -1
        if (a.endTime < b.endTime)
          return 1
        return 0
      })
      /* END */
      return {cues:cues, errors:errors, time:Date.now()-startTime, styles: styles}
    }
  }

  var WebVTTCueTimingsAndSettingsParser = function(line, errorHandler) {
    var SPACE = /[\u0020\t\f]/,
        NOSPACE = /[^\u0020\t\f]/,
        line = line,
        pos = 0,
        err = function(message) {
          errorHandler(message, pos+1)
        },
        spaceBeforeSetting = true
    function skip(pattern) {
      while(
        line[pos] != undefined &&
        pattern.test(line[pos])
      ) {
        pos++
      }
    }
    function collect(pattern) {
      var str = ""
      while(
        line[pos] != undefined &&
        pattern.test(line[pos])
      ) {
        str += line[pos]
        pos++
      }
      return str
    }
    /* http://dev.w3.org/html5/webvtt/#collect-a-webvtt-timestamp */
    function timestamp() {
      var units = "minutes",
          val1,
          val2,
          val3,
          val4
      // 3
      if(line[pos] == undefined) {
        err("No timestamp found.")
        return
      }
      // 4
      if(!/\d/.test(line[pos])) {
        err("Timestamp must start with a character in the range 0-9.")
        return
      }
      // 5-7
      val1 = collect(/\d/)
      if(val1.length > 2 || parseInt(val1, 10) > 59) {
        units = "hours"
      }
      // 8
      if(line[pos] != ":") {
        err("No time unit separator found.")
        return
      }
      pos++
      // 9-11
      val2 = collect(/\d/)
      if(val2.length != 2) {
        err("Must be exactly two digits.")
        return
      }
      // 12
      if(units == "hours" || line[pos] == ":") {
        if(line[pos] != ":") {
          err("No seconds found or minutes is greater than 59.")
          return
        }
        pos++
        val3 = collect(/\d/)
        if(val3.length != 2) {
          err("Must be exactly two digits.")
          return
        }
      } else {
        if (val1.length != 2) {
          err("Must be exactly two digits.")
          return
        }
        val3 = val2
        val2 = val1
        val1 = "0"
      }
      // 13
      if(line[pos] != ".") {
        err("No decimal separator (\".\") found.")
        return
      }
      pos++
      // 14-16
      val4 = collect(/\d/)
      if(val4.length != 3) {
        err("Milliseconds must be given in three digits.")
        return
      }
      // 17
      if(parseInt(val2, 10) > 59) {
        err("You cannot have more than 59 minutes.")
        return
      }
      if(parseInt(val3, 10) > 59) {
        err("You cannot have more than 59 seconds.")
        return
      }
      return parseInt(val1, 10) * 60 * 60 + parseInt(val2, 10) * 60 + parseInt(val3, 10) + parseInt(val4, 10) / 1000
    }

    /* http://dev.w3.org/html5/webvtt/#parse-the-webvtt-settings */
    function parseSettings(input, cue) {
      var settings = input.split(SPACE),
          seen = []
      for(var i=0; i < settings.length; i++) {
        if(settings[i] == "")
          continue

        var index = settings[i].indexOf(':'),
            setting = settings[i].slice(0, index),
            value = settings[i].slice(index + 1)

        if(seen.indexOf(setting) != -1) {
          err("Duplicate setting.")
        }
        seen.push(setting)

        if(value == "") {
          err("No value for setting defined.")
          return
        }

        if(setting == "vertical") { // writing direction
          if(value != "rl" && value != "lr") {
            err("Writing direction can only be set to 'rl' or 'rl'.")
            continue
          }
          cue.direction = value
        } else if(setting == "line") { // line position and optionally line alignment
          if (/,/.test(value)) {
            var comp = value.split(',')
            value = comp[0]
            var lineAlign = comp[1]
          }
          if(!/^[-\d](\d*)(\.\d+)?%?$/.test(value)) {
            err("Line position takes a number or percentage.")
            continue
          }
          if(value.indexOf("-", 1) != -1) {
            err("Line position can only have '-' at the start.")
            continue
          }
          if(value.indexOf("%") != -1 && value.indexOf("%") != value.length-1) {
            err("Line position can only have '%' at the end.")
            continue
          }
          if(value[0] == "-" && value[value.length-1] == "%") {
            err("Line position cannot be a negative percentage.")
            continue
          }
          var numVal = value;
          var isPercent = false;
          if(value[value.length-1] == "%") {
            isPercent = true;
            numVal = value.slice(0, value.length-1)
            if(parseInt(value, 10) > 100) {
              err("Line position cannot be >100%.")
              continue
            }
          }
          if (numVal === '' || isNaN(numVal) || !isFinite(numVal)) {
            err("Line position needs to be a number")
            continue
          }
          if (lineAlign !== undefined) {
            if (!["start", "center", "end"].includes(lineAlign)) {
              err("Line alignment needs to be one of start, center or end")
              continue
            }
            cue.lineAlign = lineAlign
          }
          cue.snapToLines = !isPercent;
          cue.linePosition = parseFloat(numVal)
          if (parseFloat(numVal).toString() !== numVal) {
            cue.nonSerializable = true;
          }
        } else if(setting == "position") { // text position and optional positionAlign
          if (/,/.test(value)) {
            var comp = value.split(',')
            value = comp[0]
            var positionAlign = comp[1]
          }
          if(value[value.length-1] != "%") {
            err("Text position must be a percentage.")
            continue
          }
          if(parseInt(value, 10) > 100 || parseInt(value, 10) < 0) {
            err("Text position needs to be between 0 and 100%.")
            continue
          }
          numVal = value.slice(0, value.length-1)
          if (numVal === '' || isNaN(numVal) || !isFinite(numVal)) {
            err("Line position needs to be a number")
            continue
          }
          if (positionAlign !== undefined) {
            if (!["line-left", "center", "line-right"].includes(positionAlign)) {
              err("Position alignment needs to be one of line-left, center or line-right")
              continue
            }
            cue.positionAlign = positionAlign
          }
          cue.textPosition = parseFloat(numVal)
        } else if(setting == "size") { // size
          if(value[value.length-1] != "%") {
            err("Size must be a percentage.")
            continue
          }
          if(parseInt(value, 10) > 100) {
            err("Size cannot be >100%.")
            continue
          }
          var size = value.slice(0, value.length -1)
          if (size === undefined || size === "" || isNaN(size)) {
            err("Size needs to be a number")
            size = 100
            continue
          } else {
            size = parseFloat(size)
            if (size < 0 || size > 100) {
              err("Size needs to be between 0 and 100%.")
              continue;
            }
          }
          cue.size = size
        } else if(setting == "align") { // alignment
          var alignValues = ["start", "center", "end", "left", "right"]
          if(alignValues.indexOf(value) == -1) {
            err("Alignment can only be set to one of " + alignValues.join(", ") + ".")
            continue
          }
          cue.alignment = value
        } else {
          err("Invalid setting.")
        }
      }
    }

    this.parse = function(cue, previousCueStart) {
      skip(SPACE)
      cue.startTime = timestamp()
      if(cue.startTime == undefined) {
        return
      }
      if(cue.startTime < previousCueStart) {
        err("Start timestamp is not greater than or equal to start timestamp of previous cue.")
      }
      if(NOSPACE.test(line[pos])) {
        err("Timestamp not separated from '-->' by whitespace.")
      }
      skip(SPACE)
      // 6-8
      if(line[pos] != "-") {
        err("No valid timestamp separator found.")
        return
      }
      pos++
      if(line[pos] != "-") {
        err("No valid timestamp separator found.")
        return
      }
      pos++
      if(line[pos] != ">") {
        err("No valid timestamp separator found.")
        return
      }
      pos++
      if(NOSPACE.test(line[pos])) {
        err("'-->' not separated from timestamp by whitespace.")
      }
      skip(SPACE)
      cue.endTime = timestamp()
      if(cue.endTime == undefined) {
        return
      }
      if(cue.endTime <= cue.startTime) {
        err("End timestamp is not greater than start timestamp.")
      }

      if(NOSPACE.test(line[pos])) {
        spaceBeforeSetting = false
      }
      skip(SPACE)
      parseSettings(line.substring(pos), cue)
      return true
    }
    this.parseTimestamp = function() {
      var ts = timestamp()
      if(line[pos] != undefined) {
        err("Timestamp must not have trailing characters.")
        return
      }
      return ts
    }
  }

  var WebVTTCueTextParser = function(line, errorHandler, mode, entities) {
    this.entities = entities
    var self = this
    var line = line,
        pos = 0,
        err = function(message) {
          if(mode == "metadata")
            return
          errorHandler(message, pos+1)
        }

    this.parse = function(cueStart, cueEnd) {
      function removeCycles(tree) {
        const cyclelessTree = {...tree};
        if (tree.children) {
          cyclelessTree.children = tree.children.map(removeCycles);
        }
        if (cyclelessTree.parent) {
          delete cyclelessTree.parent;
        }
        return cyclelessTree;
      }

      var result = {children:[]},
          current = result,
          timestamps = []

      function attach(token) {
        current.children.push({type:"object", name:token[1], classes:token[2], children:[], parent:current})
        current = current.children[current.children.length-1]
      }
      function inScope(name) {
        var node = current
        while(node) {
          if(node.name == name)
            return true
          node = node.parent
        }
        return
      }

      while(line[pos] != undefined) {
        var token = nextToken()
        if(token[0] == "text") {
          current.children.push({type:"text", value:token[1], parent:current})
        } else if(token[0] == "start tag") {
          if(mode == "chapters")
            err("Start tags not allowed in chapter title text.")
          var name = token[1]
          if(name != "v" && name != "lang" && token[3] != "") {
            err("Only <v> and <lang> can have an annotation.")
          }
          if(
            name == "c" ||
            name == "i" ||
            name == "b" ||
            name == "u" ||
            name == "ruby"
          ) {
            attach(token)
          } else if(name == "rt" && current.name == "ruby") {
            attach(token)
          } else if(name == "v") {
            if(inScope("v")) {
              err("<v> cannot be nested inside itself.")
            }
            attach(token)
            current.value = token[3] // annotation
            if(!token[3]) {
              err("<v> requires an annotation.")
            }
          } else if(name == "lang") {
            attach(token)
            current.value = token[3] // language
          } else {
            err("Incorrect start tag.")
          }
        } else if(token[0] == "end tag") {
          if(mode == "chapters")
            err("End tags not allowed in chapter title text.")
          // XXX check <ruby> content
          if(token[1] == current.name) {
            current = current.parent
          } else if(token[1] == "ruby" && current.name == "rt") {
            current = current.parent.parent
          } else {
            err("Incorrect end tag.")
          }
        } else if(token[0] == "timestamp") {
          if(mode == "chapters")
            err("Timestamp not allowed in chapter title text.")
          var timings = new WebVTTCueTimingsAndSettingsParser(token[1], err),
              timestamp = timings.parseTimestamp()
          if(timestamp != undefined) {
            if(timestamp <= cueStart || timestamp >= cueEnd) {
              err("Timestamp must be between start timestamp and end timestamp.")
            }
            if(timestamps.length > 0 && timestamps[timestamps.length-1] >= timestamp) {
              err("Timestamp must be greater than any previous timestamp.")
            }
            current.children.push({type:"timestamp", value:timestamp, parent:current})
            timestamps.push(timestamp)
          }
        }
      }
      while(current.parent) {
        if(current.name != "v") {
          err("Required end tag missing.")
        }
        current = current.parent
      }
      return removeCycles(result)
    }

    function nextToken() {
      var state = "data",
          result = "",
          buffer = "",
          classes = []
      while(line[pos-1] != undefined || pos == 0) {
        var c = line[pos]
        if(state == "data") {
          if(c == "&") {
            buffer = c
            state = "escape"
          } else if(c == "<" && result == "") {
            state = "tag"
          } else if(c == "<" || c == undefined) {
            return ["text", result]
          } else {
            result += c
          }
        } else if(state == "escape") {
          if(c == "<" || c == undefined) {
            err("Incorrect escape.")
            let m;
            if (m = buffer.match(/^&#([0-9]+)$/)) {
              result += String.fromCharCode(m[1])
            } else {
              if(self.entities[buffer]) {
                result += self.entities[buffer]
              } else {
                result += buffer
              }
            }
            return ["text", result]
          } else if(c == "&") {
            err("Incorrect escape.")
            result += buffer
            buffer = c
          } else if(/[a-z#0-9]/i.test(c)) {
            buffer += c
          } else if(c == ";") {
            let m;
            if (m = buffer.match(/^&#(x?[0-9]+)$/)) {
              // we prepend "0" so that x20 be interpreted as hexadecim (0x20)
              result += String.fromCharCode("0" + m[1])
            } else if(self.entities[buffer + c]) {
              result += self.entities[buffer + c]
            } else if (m = Object.keys(entities).find(n => buffer.startsWith(n))) { // partial match
              result += self.entities[m] + buffer.slice(m.length) + c
            } else {
              err("Incorrect escape.")
              result += buffer + ";"
            }
            state = "data"
          } else {
            err("Incorrect escape.")
            result += buffer + c
            state = "data"
          }
        } else if(state == "tag") {
          if(c == "\t" || c == "\n" || c == "\f" || c == " ") {
            state = "start tag annotation"
          } else if(c == ".") {
            state = "start tag class"
          } else if(c == "/") {
            state = "end tag"
          } else if(/\d/.test(c)) {
            result = c
            state = "timestamp tag"
          } else if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            return ["start tag", "", [], ""]
          } else {
            result = c
            state = "start tag"
          }
        } else if(state == "start tag") {
          if(c == "\t" || c == "\f" || c == " ") {
            state = "start tag annotation"
          } else if(c == "\n") {
            buffer = c
            state = "start tag annotation"
          } else if(c == ".") {
            state = "start tag class"
          } else if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            return ["start tag", result, [], ""]
          } else {
            result += c
          }
        } else if(state == "start tag class") {
          if(c == "\t" || c == "\f" || c == " ") {
            if (buffer) {
              classes.push(buffer)
            }
            buffer = ""
            state = "start tag annotation"
          } else if(c == "\n") {
            if (buffer) {
              classes.push(buffer)
            }
            buffer = c
            state = "start tag annotation"
          } else if(c == ".") {
            if (buffer) {
              classes.push(buffer)
            }
            buffer = ""
          } else if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            if (buffer) {
              classes.push(buffer)
            }
            return ["start tag", result, classes, ""]
          } else {
            buffer += c
          }
        } else if(state == "start tag annotation") {
          if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            buffer = buffer.split(/[\u0020\t\f\r\n]+/).filter(function(item) { if(item) return true }).join(" ")
            return ["start tag", result, classes, buffer]
          } else {
            buffer +=c
          }
        } else if(state == "end tag") {
          if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            return ["end tag", result]
          } else {
            result += c
          }
        } else if(state == "timestamp tag") {
          if(c == ">" || c == undefined) {
            if(c == ">") {
              pos++
            }
            return ["timestamp", result]
          } else {
            result += c
          }
        } else {
          err("Never happens.") // The joke is it might.
        }
        // 8
        pos++
      }
    }
  }

  var WebVTTSerializer = function() {
    function serializeTimestamp(seconds) {
      const ms = ("00" + (seconds - Math.floor(seconds)).toFixed(3)*1000).slice(-3);
      let h = 0, m = 0, s = 0;
      if (seconds >= 3600) {
        h = Math.floor(seconds/3600);
      }
      m = Math.floor((seconds - 3600*h) / 60);
      s = Math.floor(seconds - 3600*h - 60*m);
      return (h ? h + ":" : "") + ("" + m).padStart(2, "0") + ":" + ("" + s).padStart(2, "0") + "." + ms;
    }
    function serializeCueSettings(cue) {
      var result = ""
      const nonDefaultSettings = Object.keys(defaultCueSettings).filter(s => cue[s] !== defaultCueSettings[s]);
      if (nonDefaultSettings.includes("direction")) {
        result+= " vertical:" + cue.direction
      }
      if (nonDefaultSettings.includes("alignment")) {
        result+= " align:" + cue.alignment
      }
      if (nonDefaultSettings.includes("size")) {
        result+= " size:" + cue.size + "%"
      }
      if (nonDefaultSettings.includes("lineAlign") || nonDefaultSettings.includes("linePosition")) {
        result += " line:" + cue.linePosition +  (cue.snapToLines ? "" : "%") + (cue.lineAlign && cue.lineAlign != defaultCueSettings.lineAlign ? "," + cue.lineAlign : "")
      }
      if (nonDefaultSettings.includes("textPosition") || nonDefaultSettings.includes("positionAlign")) {
        result += " position:" + cue.textPosition + "%" + (cue.positionAlign && cue.positionAlign !== defaultCueSettings.positionAlign ? "," + cue.positionAlign : "")
      }
      return result
    }
    function serializeTree(tree) {
      var result = ""
      for (var i = 0; i < tree.length; i++) {
        var node = tree[i]
        if(node.type == "text") {
          result += node.value.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
        } else if(node.type == "object") {
          result += "<" + node.name
          if(node.classes) {
            for(var y = 0; y < node.classes.length; y++) {
              result += "." + node.classes[y]
            }
          }
          if(node.value) {
            result += " " + node.value
          }
          result += ">"
          if(node.children)
            result += serializeTree(node.children)
          result += "</" + node.name + ">"
        } else if(node.type == "timestamp") {
          result += "<" + serializeTimestamp(node.value) + ">"
        } else {
          result += "<" + node.value + ">"
        }
      }
      return result
    }
    function serializeCue(cue) {
      return (cue.id !== undefined ? cue.id + "\n" : "")
        + serializeTimestamp(cue.startTime)
        + " --> "
        + serializeTimestamp(cue.endTime)
        + serializeCueSettings(cue)
        + "\n" + serializeTree(cue.tree.children) + "\n\n"
    }
    function serializeStyle(style) {
      return "STYLE\n" + style + "\n\n"
    }
    this.serialize = function(cues, styles) {
      var result = "WEBVTT\n\n"
      if (styles) {
        for(var i=0;i<styles.length;i++) {
          result += serializeStyle(styles[i])
        }
      }
      for(var i=0;i<cues.length;i++) {
        result += serializeCue(cues[i])
      }
      return result
    }
  }

  function exportify(object) {
    object.WebVTTParser = WebVTTParser
    object.WebVTTCueTimingsAndSettingsParser = WebVTTCueTimingsAndSettingsParser
    object.WebVTTCueTextParser = WebVTTCueTextParser
    object.WebVTTSerializer = WebVTTSerializer
  }
  if (typeof window !== 'undefined') exportify(window);
  if (typeof exports !== 'undefined') exportify(exports);
})()