Source: lib/text/ttml_text_parser.js

/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

goog.provide('shaka.text.TtmlTextParser');

goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.text.Cue');
goog.require('shaka.text.CueRegion');
goog.require('shaka.text.TextEngine');
goog.require('shaka.util.ArrayUtils');
goog.require('shaka.util.Error');
goog.require('shaka.util.StringUtils');
goog.require('shaka.util.XmlUtils');



/**
 * @constructor
 * @implements {shakaExtern.TextParser}
 */
shaka.text.TtmlTextParser = function() {};


/**
 * @const {string}
 * @private
 */
shaka.text.TtmlTextParser.parameterNs_ = 'http://www.w3.org/ns/ttml#parameter';


/**
 * @const {string}
 * @private
 */
shaka.text.TtmlTextParser.styleNs_ = 'http://www.w3.org/ns/ttml#styling';


/** @override */
shaka.text.TtmlTextParser.prototype.parseInit = function(data) {
  goog.asserts.assert(false, 'TTML does not have init segments');
};


/** @override */
shaka.text.TtmlTextParser.prototype.parseMedia = function(data, time) {
  const TtmlTextParser = shaka.text.TtmlTextParser;
  const XmlUtils = shaka.util.XmlUtils;
  const ttpNs = TtmlTextParser.parameterNs_;
  let str = shaka.util.StringUtils.fromUTF8(data);
  let ret = [];
  let parser = new DOMParser();
  let xml = null;

  try {
    xml = parser.parseFromString(str, 'text/xml');
  } catch (exception) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.TEXT,
        shaka.util.Error.Code.INVALID_XML);
  }

  if (xml) {
    // Try to get the framerate, subFrameRate and frameRateMultiplier
    // if applicable
    let frameRate = null;
    let subFrameRate = null;
    let frameRateMultiplier = null;
    let tickRate = null;
    let spaceStyle = null;
    let tts = xml.getElementsByTagName('tt');
    let tt = tts[0];
    // TTML should always have tt element.
    if (!tt) {
      throw new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.TEXT,
          shaka.util.Error.Code.INVALID_XML);
    } else {
      frameRate = XmlUtils.getAttributeNS(tt, ttpNs, 'frameRate');
      subFrameRate = XmlUtils.getAttributeNS(tt, ttpNs, 'subFrameRate');
      frameRateMultiplier =
          XmlUtils.getAttributeNS(tt, ttpNs, 'frameRateMultiplier');
      tickRate = XmlUtils.getAttributeNS(tt, ttpNs, 'tickRate');
      spaceStyle = tt.getAttribute('xml:space') || 'default';
    }

    if (spaceStyle != 'default' && spaceStyle != 'preserve') {
      throw new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.TEXT,
          shaka.util.Error.Code.INVALID_XML);
    }
    let whitespaceTrim = spaceStyle == 'default';

    let rateInfo = new TtmlTextParser.RateInfo_(
        frameRate, subFrameRate, frameRateMultiplier, tickRate);

    let styles = TtmlTextParser.getLeafNodes_(
        tt.getElementsByTagName('styling')[0]);
    let regionElements = TtmlTextParser.getLeafNodes_(
        tt.getElementsByTagName('layout')[0]);
    let cueRegions = [];
    for (let i = 0; i < regionElements.length; i++) {
      let cueRegion = TtmlTextParser.parseCueRegion_(
          regionElements[i], styles);
      if (cueRegion) {
        cueRegions.push(cueRegion);
      }
    }

    let textNodes = TtmlTextParser.getLeafNodes_(
        tt.getElementsByTagName('body')[0]);

    for (let i = 0; i < textNodes.length; i++) {
      let cue = TtmlTextParser.parseCue_(textNodes[i],
                                         time.periodStart,
                                         rateInfo,
                                         styles,
                                         regionElements,
                                         cueRegions,
                                         whitespaceTrim);
      if (cue) {
        ret.push(cue);
      }
    }
  }

  return ret;
};


/**
 * @const
 * @private {!RegExp}
 * @example 50% 10%
 */
shaka.text.TtmlTextParser.percentValues_ = /^(\d{1,2}|100)% (\d{1,2}|100)%$/;


/**
 * @const
 * @private {!RegExp}
 * @example 100px
 */
shaka.text.TtmlTextParser.unitValues_ = /^(\d+px|\d+em)$/;


/**
 * @const
 * @private {!RegExp}
 * @example 100px
 */
shaka.text.TtmlTextParser.pixelValues_ = /^(\d+)px (\d+)px$/;

/**
 * @const
 * @private {!RegExp}
 * @example 00:00:40:07 (7 frames) or 00:00:40:07.1 (7 frames, 1 subframe)
 */
shaka.text.TtmlTextParser.timeColonFormatFrames_ =
    /^(\d{2,}):(\d{2}):(\d{2}):(\d{2})\.?(\d+)?$/;


/**
 * @const
 * @private {!RegExp}
 * @example 00:00:40 or 00:40
 */
shaka.text.TtmlTextParser.timeColonFormat_ = /^(?:(\d{2,}):)?(\d{2}):(\d{2})$/;


/**
 * @const
 * @private {!RegExp}
 * @example 01:02:43.0345555 or 02:43.03
 */
shaka.text.TtmlTextParser.timeColonFormatMilliseconds_ =
    /^(?:(\d{2,}):)?(\d{2}):(\d{2}\.\d{2,})$/;


/**
 * @const
 * @private {!RegExp}
 * @example 75f or 75.5f
 */
shaka.text.TtmlTextParser.timeFramesFormat_ = /^(\d*(?:\.\d*)?)f$/;


/**
 * @const
 * @private {!RegExp}
 * @example 50t or 50.5t
 */
shaka.text.TtmlTextParser.timeTickFormat_ = /^(\d*(?:\.\d*)?)t$/;


/**
 * @const
 * @private {!RegExp}
 * @example 3.45h, 3m or 4.20s
 */
shaka.text.TtmlTextParser.timeHMSFormat_ =
    new RegExp(['^(?:(\\d*(?:\\.\\d*)?)h)?',
                '(?:(\\d*(?:\\.\\d*)?)m)?',
                '(?:(\\d*(?:\\.\\d*)?)s)?',
                '(?:(\\d*(?:\\.\\d*)?)ms)?$'].join(''));



/**
 * @const
 * @private {!Object.<string, shaka.text.Cue.lineAlign>}
 */
shaka.text.TtmlTextParser.textAlignToLineAlign_ = {
  'left': shaka.text.Cue.lineAlign.START,
  'center': shaka.text.Cue.lineAlign.CENTER,
  'right': shaka.text.Cue.lineAlign.END,
  'start': shaka.text.Cue.lineAlign.START,
  'end': shaka.text.Cue.lineAlign.END,
};


/**
 * @const
 * @private {!Object.<string, shaka.text.Cue.positionAlign>}
 */
shaka.text.TtmlTextParser.textAlignToPositionAlign_ = {
  'left': shaka.text.Cue.positionAlign.LEFT,
  'center': shaka.text.Cue.positionAlign.CENTER,
  'right': shaka.text.Cue.positionAlign.RIGHT,
};


/**
 * Gets the leaf nodes of the xml node tree. Ignores the text, br elements
 * and the spans positioned inside paragraphs
 *
 * @param {Element} element
 * @return {!Array.<!Element>}
 * @private
 */
shaka.text.TtmlTextParser.getLeafNodes_ = function(element) {
  let result = [];
  if (!element) {
    return result;
  }

  let childNodes = element.childNodes;
  for (let i = 0; i < childNodes.length; i++) {
    // Currently we don't support styles applicable to span
    // elements, so they are ignored.
    let isSpanChildOfP = childNodes[i].nodeName == 'span' &&
        element.nodeName == 'p';
    if (childNodes[i].nodeType == Node.ELEMENT_NODE &&
        childNodes[i].nodeName != 'br' && !isSpanChildOfP) {
      // Get the leaves the child might contain.
      goog.asserts.assert(childNodes[i] instanceof Element,
                          'Node should be Element!');
      let leafChildren = shaka.text.TtmlTextParser.getLeafNodes_(
          /** @type {Element} */(childNodes[i]));
      goog.asserts.assert(leafChildren.length > 0,
                          'Only a null Element should return no leaves!');
      result = result.concat(leafChildren);
    }
  }

  // if no result at this point, the element itself must be a leaf.
  if (!result.length) {
    result.push(element);
  }
  return result;
};


/**
 * Inserts \n where <br> tags are found.
 *
 * @param {!Node} element
 * @param {boolean} whitespaceTrim
 * @private
 */
shaka.text.TtmlTextParser.addNewLines_ = function(element, whitespaceTrim) {
  let childNodes = element.childNodes;

  for (let i = 0; i < childNodes.length; i++) {
    if (childNodes[i].nodeName == 'br' && i > 0) {
      childNodes[i - 1].textContent += '\n';
    } else if (childNodes[i].childNodes.length > 0) {
      shaka.text.TtmlTextParser.addNewLines_(childNodes[i], whitespaceTrim);
    } else if (whitespaceTrim) {
      // Trim leading and trailing whitespace.
      let trimmed = childNodes[i].textContent.trim();
      // Collapse multiple spaces into one.
      trimmed = trimmed.replace(/\s+/g, ' ');

      childNodes[i].textContent = trimmed;
    }
  }
};


/**
 * Parses an Element into a TextTrackCue or VTTCue.
 *
 * @param {!Element} cueElement
 * @param {number} offset
 * @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
 * @param {!Array.<!Element>} styles
 * @param {!Array.<!Element>} regionElements
 * @param {!Array.<!shaka.text.CueRegion>} cueRegions
 * @param {boolean} whitespaceTrim
 * @return {shaka.text.Cue}
 * @private
 */
shaka.text.TtmlTextParser.parseCue_ = function(
    cueElement, offset, rateInfo, styles, regionElements,
    cueRegions, whitespaceTrim) {

  // Disregard empty elements:
  // TTML allows for empty elements like <div></div>.
  // If cueElement has neither time attributes, nor
  // non-whitespace text, don't try to make a cue out of it.
  if (!cueElement.hasAttribute('begin') &&
      !cueElement.hasAttribute('end') &&
      /^\s*$/.test(cueElement.textContent)) {
    return null;
  }

  shaka.text.TtmlTextParser.addNewLines_(cueElement, whitespaceTrim);

  // Get time.
  let start = shaka.text.TtmlTextParser.parseTime_(
      cueElement.getAttribute('begin'), rateInfo);
  let end = shaka.text.TtmlTextParser.parseTime_(
      cueElement.getAttribute('end'), rateInfo);
  let duration = shaka.text.TtmlTextParser.parseTime_(
      cueElement.getAttribute('dur'), rateInfo);
  let payload = cueElement.textContent;

  if (end == null && duration != null) {
    end = start + duration;
  }

  if (start == null || end == null) {
    throw new shaka.util.Error(
        shaka.util.Error.Severity.CRITICAL,
        shaka.util.Error.Category.TEXT,
        shaka.util.Error.Code.INVALID_TEXT_CUE);
  }

  start += offset;
  end += offset;

  let cue = new shaka.text.Cue(start, end, payload);

  // Get other properties if available.
  let regionElement = shaka.text.TtmlTextParser.getElementFromCollection_(
      cueElement, 'region', regionElements);
  if (regionElement && regionElement.getAttribute('xml:id')) {
    let regionId = regionElement.getAttribute('xml:id');
    let regionsWithId = cueRegions.filter(function(region) {
      return region.id == regionId;
    });
    cue.region = regionsWithId[0];
  }
  shaka.text.TtmlTextParser.addStyle_(cue, cueElement, regionElement, styles);

  return cue;
};


/**
 * Parses an Element into a TextTrackCue or VTTCue.
 *
 * @param {!Element} regionElement
 * @param {!Array.<!Element>} styles
 * @return {shaka.text.CueRegion}
 * @private
 */
shaka.text.TtmlTextParser.parseCueRegion_ = function(regionElement, styles) {
  const TtmlTextParser = shaka.text.TtmlTextParser;
  let region = new shaka.text.CueRegion();
  let id = regionElement.getAttribute('xml:id');
  if (!id) {
    shaka.log.warning('TtmlTextParser parser encountered a region with ' +
                      'no id. Region will be ignored.');
    return null;
  }
  region.id = id;

  let results = null;
  let percentage = null;
  let extent = TtmlTextParser.getStyleAttributeFromRegion_(
      regionElement, styles, 'extent');
  if (extent) {
    percentage = TtmlTextParser.percentValues_.exec(extent);
    results = percentage || TtmlTextParser.pixelValues_.exec(extent);
    if (results != null) {
      region.width = Number(results[1]);
      region.height = Number(results[2]);
      region.widthUnits = percentage ?
                         shaka.text.CueRegion.units.PERCENTAGE :
                         shaka.text.CueRegion.units.PX;

      region.heightUnits = percentage ?
                         shaka.text.CueRegion.units.PERCENTAGE :
                         shaka.text.CueRegion.units.PX;
    }
  }

  let origin = TtmlTextParser.getStyleAttributeFromRegion_(
      regionElement, styles, 'origin');
  if (origin) {
    percentage = TtmlTextParser.percentValues_.exec(origin);
    results = percentage || TtmlTextParser.pixelValues_.exec(origin);
    if (results != null) {
      region.viewportAnchorX = Number(results[1]);
      region.viewportAnchorY = Number(results[2]);
      region.viewportAnchorUnits = percentage ?
                shaka.text.CueRegion.units.PERCENTAGE :
                shaka.text.CueRegion.units.PX;
    }
  }

  return region;
};

/**
 * Adds applicable style properties to a cue.
 *
 * @param {!shaka.text.Cue} cue
 * @param {!Element} cueElement
 * @param {Element} region
 * @param {!Array.<!Element>} styles
 * @private
 */
shaka.text.TtmlTextParser.addStyle_ = function(
    cue, cueElement, region, styles) {
  const TtmlTextParser = shaka.text.TtmlTextParser;
  const Cue = shaka.text.Cue;

  let direction = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'direction');
  if (direction == 'rtl') {
    cue.writingDirection = Cue.writingDirection.HORIZONTAL_RIGHT_TO_LEFT;
  }

  // Direction attribute specifies one-dimentional writing direction
  // (left to right or right to left). Writing mode specifies that
  // plus whether text is vertical or horizontal.
  // They should not contradict each other. If they do, we give
  // preference to writing mode.
  let writingMode = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'writingMode');
  if (writingMode == 'tb' || writingMode == 'tblr') {
    cue.writingDirection = Cue.writingDirection.VERTICAL_LEFT_TO_RIGHT;
  } else if (writingMode == 'tbrl') {
    cue.writingDirection = Cue.writingDirection.VERTICAL_RIGHT_TO_LEFT;
  } else if (writingMode == 'rltb' || writingMode == 'rl') {
    cue.writingDirection = Cue.writingDirection.HORIZONTAL_RIGHT_TO_LEFT;
  } else if (writingMode) {
    cue.writingDirection = Cue.writingDirection.HORIZONTAL_LEFT_TO_RIGHT;
  }

  let align = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'textAlign');
  if (align) {
    cue.positionAlign = TtmlTextParser.textAlignToPositionAlign_[align];
    cue.lineAlign = TtmlTextParser.textAlignToLineAlign_[align];

    goog.asserts.assert(align.toUpperCase() in Cue.textAlign,
                        align.toUpperCase() +
                        ' Should be in Cue.textAlign values!');

    cue.textAlign = Cue.textAlign[align.toUpperCase()];
  }

  let displayAlign = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'displayAlign');
  if (displayAlign) {
    goog.asserts.assert(displayAlign.toUpperCase() in Cue.displayAlign,
                        displayAlign.toUpperCase() +
                        ' Should be in Cue.displayAlign values!');
    cue.displayAlign = Cue.displayAlign[displayAlign.toUpperCase()];
  }

  let color = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'color');
  if (color) {
    cue.color = color;
  }

  let backgroundColor = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'backgroundColor');
  if (backgroundColor) {
    cue.backgroundColor = backgroundColor;
  }

  let fontFamily = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'fontFamily');
  if (fontFamily) {
    cue.fontFamily = fontFamily;
  }

  let fontWeight = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'fontWeight');
  if (fontWeight && fontWeight == 'bold') {
    cue.fontWeight = Cue.fontWeight.BOLD;
  }

  let wrapOption = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'wrapOption');
  if (wrapOption && wrapOption == 'noWrap') {
    cue.wrapLine = false;
  }

  let lineHeight = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'lineHeight');
  if (lineHeight && lineHeight.match(TtmlTextParser.unitValues_)) {
    cue.lineHeight = lineHeight;
  }

  let fontSize = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'fontSize');
  if (fontSize && fontSize.match(TtmlTextParser.unitValues_)) {
    cue.fontSize = fontSize;
  }

  let fontStyle = TtmlTextParser.getStyleAttribute_(
      cueElement, region, styles, 'fontStyle');
  if (fontStyle) {
    goog.asserts.assert(fontStyle.toUpperCase() in Cue.fontStyle,
                        fontStyle.toUpperCase() +
                        ' Should be in Cue.fontStyle values!');
    cue.fontStyle = Cue.fontStyle[fontStyle.toUpperCase()];
  }

  // Text decoration is an array of values which can come both from the
  // element's style or be inherited from elements' parent nodes. All of those
  // values should be applied as long as they don't contradict each other. If
  // they do, elements' own style gets preference.
  let textDecorationRegion = TtmlTextParser.getStyleAttributeFromRegion_(
      region, styles, 'textDecoration');
  if (textDecorationRegion) {
    TtmlTextParser.addTextDecoration_(cue, textDecorationRegion);
  }

  let textDecorationElement = TtmlTextParser.getStyleAttributeFromElement_(
      cueElement, styles, 'textDecoration');
  if (textDecorationElement) {
    TtmlTextParser.addTextDecoration_(cue, textDecorationElement);
  }
};


/**
 * Parses text decoration values and adds/removes them to/from the cue.
 *
 * @param {!shaka.text.Cue} cue
 * @param {string} decoration
 * @private
 */
shaka.text.TtmlTextParser.addTextDecoration_ = function(cue, decoration) {
  const Cue = shaka.text.Cue;
  let values = decoration.split(' ');
  for (let i = 0; i < values.length; i++) {
    switch (values[i]) {
      case 'underline':
        if (cue.textDecoration.indexOf(Cue.textDecoration.UNDERLINE) < 0) {
          cue.textDecoration.push(Cue.textDecoration.UNDERLINE);
        }
        break;
      case 'noUnderline':
        if (cue.textDecoration.indexOf(Cue.textDecoration.UNDERLINE) >= 0) {
          shaka.util.ArrayUtils.remove(cue.textDecoration,
                                       Cue.textDecoration.UNDERLINE);
        }
        break;
      case 'lineThrough':
        if (cue.textDecoration.indexOf(Cue.textDecoration.LINE_THROUGH) < 0) {
          cue.textDecoration.push(Cue.textDecoration.LINE_THROUGH);
        }
        break;
      case 'noLineThrough':
        if (cue.textDecoration.indexOf(Cue.textDecoration.LINE_THROUGH) >= 0) {
          shaka.util.ArrayUtils.remove(cue.textDecoration,
                                       Cue.textDecoration.LINE_THROUGH);
        }
        break;
      case 'overline':
        if (cue.textDecoration.indexOf(Cue.textDecoration.OVERLINE) < 0) {
          cue.textDecoration.push(Cue.textDecoration.OVERLINE);
        }
        break;
      case 'noOverline':
        if (cue.textDecoration.indexOf(Cue.textDecoration.OVERLINE) >= 0) {
          shaka.util.ArrayUtils.remove(cue.textDecoration,
                                       Cue.textDecoration.OVERLINE);
        }
        break;
    }
  }
};


/**
 * Finds a specified attribute on either the original cue element or its
 * associated region and returns the value if the attribute was found.
 *
 * @param {!Element} cueElement
 * @param {Element} region
 * @param {!Array.<!Element>} styles
 * @param {string} attribute
 * @return {?string}
 * @private
 */
shaka.text.TtmlTextParser.getStyleAttribute_ = function(
    cueElement, region, styles, attribute) {
  // An attribute can be specified on region level or in a styling block
  // associated with the region or original element.
  const TtmlTextParser = shaka.text.TtmlTextParser;
  let attr = TtmlTextParser.getStyleAttributeFromElement_(
      cueElement, styles, attribute);
  if (attr) {
    return attr;
  }

  return TtmlTextParser.getStyleAttributeFromRegion_(
      region, styles, attribute);
};


/**
 * Finds a specified attribute on the element's associated region
 * and returns the value if the attribute was found.
 *
 * @param {Element} region
 * @param {!Array.<!Element>} styles
 * @param {string} attribute
 * @return {?string}
 * @private
 */
shaka.text.TtmlTextParser.getStyleAttributeFromRegion_ = function(
    region, styles, attribute) {
  const XmlUtils = shaka.util.XmlUtils;
  const ttsNs = shaka.text.TtmlTextParser.styleNs_;

  let regionChildren = shaka.text.TtmlTextParser.getLeafNodes_(region);
  for (let i = 0; i < regionChildren.length; i++) {
    let attr = XmlUtils.getAttributeNS(regionChildren[i], ttsNs, attribute);
    if (attr) {
      return attr;
    }
  }

  let style = shaka.text.TtmlTextParser.getElementFromCollection_(
      region, 'style', styles);
  if (style) {
    return XmlUtils.getAttributeNS(style, ttsNs, attribute);
  }
  return null;
};


/**
 * Finds a specified attribute on the cue element and returns the value
 * if the attribute was found.
 *
 * @param {!Element} cueElement
 * @param {!Array.<!Element>} styles
 * @param {string} attribute
 * @return {?string}
 * @private
 */
shaka.text.TtmlTextParser.getStyleAttributeFromElement_ = function(
    cueElement, styles, attribute) {
  const XmlUtils = shaka.util.XmlUtils;
  const ttsNs = shaka.text.TtmlTextParser.styleNs_;

  let getElementFromCollection_ =
      shaka.text.TtmlTextParser.getElementFromCollection_;
  let style = getElementFromCollection_(cueElement, 'style', styles);
  if (style) {
    return XmlUtils.getAttributeNS(style, ttsNs, attribute);
  }
  return null;
};


/**
 * Selects an item from |collection| whose id matches |attributeName|
 * from |element|.
 *
 * @param {Element} element
 * @param {string} attributeName
 * @param {!Array.<Element>} collection
 * @return {Element}
 * @private
 */
shaka.text.TtmlTextParser.getElementFromCollection_ = function(
    element, attributeName, collection) {
  if (!element || collection.length < 1) {
    return null;
  }
  let item = null;
  let itemName = shaka.text.TtmlTextParser.getInheritedAttribute_(
      element, attributeName);
  if (itemName) {
    for (let i = 0; i < collection.length; i++) {
      if (collection[i].getAttribute('xml:id') == itemName) {
        item = collection[i];
        break;
      }
    }
  }

  return item;
};


/**
 * Traverses upwards from a given node until a given attribute is found.
 *
 * @param {!Element} element
 * @param {string} attributeName
 * @return {?string}
 * @private
 */
shaka.text.TtmlTextParser.getInheritedAttribute_ = function(
    element, attributeName) {
  let ret = null;
  while (element) {
    ret = element.getAttribute(attributeName);
    if (ret) {
      break;
    }

    // Element.parentNode can lead to XMLDocument, which is not an Element and
    // has no getAttribute().
    let parentNode = element.parentNode;
    if (parentNode instanceof Element) {
      element = parentNode;
    } else {
      break;
    }
  }
  return ret;
};


/**
 * Parses a TTML time from the given word.
 *
 * @param {string} text
 * @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
 * @return {?number}
 * @private
 */
shaka.text.TtmlTextParser.parseTime_ = function(text, rateInfo) {
  let ret = null;
  const TtmlTextParser = shaka.text.TtmlTextParser;

  if (TtmlTextParser.timeColonFormatFrames_.test(text)) {
    ret = TtmlTextParser.parseColonTimeWithFrames_(rateInfo, text);
  } else if (TtmlTextParser.timeColonFormat_.test(text)) {
    ret = TtmlTextParser.parseTimeFromRegex_(
        TtmlTextParser.timeColonFormat_, text);
  } else if (TtmlTextParser.timeColonFormatMilliseconds_.test(text)) {
    ret = TtmlTextParser.parseTimeFromRegex_(
        TtmlTextParser.timeColonFormatMilliseconds_, text);
  } else if (TtmlTextParser.timeFramesFormat_.test(text)) {
    ret = TtmlTextParser.parseFramesTime_(rateInfo, text);
  } else if (TtmlTextParser.timeTickFormat_.test(text)) {
    ret = TtmlTextParser.parseTickTime_(rateInfo, text);
  } else if (TtmlTextParser.timeHMSFormat_.test(text)) {
    ret = TtmlTextParser.parseTimeFromRegex_(
        TtmlTextParser.timeHMSFormat_, text);
  }

  return ret;
};


/**
 * Parses a TTML time in frame format.
 *
 * @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
 * @param {string} text
 * @return {?number}
 * @private
 */
shaka.text.TtmlTextParser.parseFramesTime_ = function(rateInfo, text) {

  // 75f or 75.5f
  let results = shaka.text.TtmlTextParser.timeFramesFormat_.exec(text);
  let frames = Number(results[1]);

  return frames / rateInfo.frameRate;
};


/**
 * Parses a TTML time in tick format.
 *
 * @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
 * @param {string} text
 * @return {?number}
 * @private
 */
shaka.text.TtmlTextParser.parseTickTime_ = function(rateInfo, text) {

  // 50t or 50.5t
  let results = shaka.text.TtmlTextParser.timeTickFormat_.exec(text);
  let ticks = Number(results[1]);

  return ticks / rateInfo.tickRate;
};


/**
 * Parses a TTML colon formatted time containing frames.
 *
 * @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
 * @param {string} text
 * @return {?number}
 * @private
 */
shaka.text.TtmlTextParser.parseColonTimeWithFrames_ = function(
    rateInfo, text) {

  // 01:02:43:07 ('07' is frames) or 01:02:43:07.1 (subframes)
  let results = shaka.text.TtmlTextParser.timeColonFormatFrames_.exec(text);

  let hours = Number(results[1]);
  let minutes = Number(results[2]);
  let seconds = Number(results[3]);
  let frames = Number(results[4]);
  let subframes = Number(results[5]) || 0;

  frames += subframes / rateInfo.subFrameRate;
  seconds += frames / rateInfo.frameRate;

  return seconds + (minutes * 60) + (hours * 3600);
};


/**
 * Parses a TTML time with a given regex. Expects regex to be some
 * sort of a time-matcher to match hours, minutes, seconds and milliseconds
 *
 * @param {!RegExp} regex
 * @param {string} text
 * @return {?number}
 * @private
 */
shaka.text.TtmlTextParser.parseTimeFromRegex_ = function(regex, text) {
  let results = regex.exec(text);
  if (results == null || results[0] == '') {
    return null;
  }
  // This capture is optional, but will still be in the array as undefined,
  // in which case it is 0.
  let hours = Number(results[1]) || 0;
  let minutes = Number(results[2]) || 0;
  let seconds = Number(results[3]) || 0;
  let miliseconds = Number(results[4]) || 0;

  return (miliseconds / 1000) + seconds + (minutes * 60) + (hours * 3600);
};



/**
 * Contains information about frame/subframe rate
 * and frame rate multiplier for time in frame format.
 *
 * @example 01:02:03:04(4 frames) or 01:02:03:04.1(4 frames, 1 subframe)
 * @param {?string} frameRate
 * @param {?string} subFrameRate
 * @param {?string} frameRateMultiplier
 * @param {?string} tickRate
 * @constructor
 * @struct
 * @private
 */
shaka.text.TtmlTextParser.RateInfo_ = function(
    frameRate, subFrameRate, frameRateMultiplier, tickRate) {

  /**
   * @type {number}
   */
  this.frameRate = Number(frameRate) || 30;

  /**
   * @type {number}
   */
  this.subFrameRate = Number(subFrameRate) || 1;

  /**
   * @type {number}
   */
  this.tickRate = Number(tickRate);
  if (this.tickRate == 0) {
    if (frameRate) {
      this.tickRate = this.frameRate * this.subFrameRate;
    } else {
      this.tickRate = 1;
    }
  }

  if (frameRateMultiplier) {
    let multiplierResults = /^(\d+) (\d+)$/g.exec(frameRateMultiplier);
    if (multiplierResults) {
      let numerator = multiplierResults[1];
      let denominator = multiplierResults[2];
      let multiplierNum = numerator / denominator;
      this.frameRate *= multiplierNum;
    }
  }
};


shaka.text.TextEngine.registerParser(
    'application/ttml+xml',
    shaka.text.TtmlTextParser);