shaka-player/lib/text/text_utils.js

DASH/EME video player library

/*! @license
 * Shaka Player
 * Copyright 2016 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

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

goog.require('shaka.text.Cue');


shaka.text.Utils = class {
  /**
   * Flatten nested cue payloads recursively.  If a cue has nested cues,
   * their contents should be combined and replace the payload of the parent.
   *
   * @param {!shaka.text.Cue} cue
   * @return {string}
   * @private
   */
  static flattenPayload_(cue) {
    if (cue.lineBreak) {
      // This is a vertical lineBreak, so insert a newline.
      return '\n';
    }
    if (cue.nestedCues.length) {
      return cue.nestedCues.map(shaka.text.Utils.flattenPayload_).join('');
    }

    // Handle bold, italics and underline
    const openStyleTags = [];
    const bold = cue.fontWeight >= shaka.text.Cue.fontWeight.BOLD;
    const italics = cue.fontStyle == shaka.text.Cue.fontStyle.ITALIC;
    const underline = cue.textDecoration.includes(
        shaka.text.Cue.textDecoration.UNDERLINE);
    if (bold) {
      openStyleTags.push(['b']);
    }
    if (italics) {
      openStyleTags.push(['i']);
    }
    if (underline) {
      openStyleTags.push(['u']);
    }
    // Handle color classes, if the value consists of letters
    let classes = '';
    const color = shaka.text.Utils.getColorName_(cue.color);
    if (color) {
      classes += `.${color}`;
    }
    const bgColor = shaka.text.Utils.getColorName_(cue.backgroundColor);
    if (bgColor) {
      classes += `.bg_${bgColor}`;
    }
    if (classes) {
      openStyleTags.push(['c', classes]);
    }

    return openStyleTags.reduceRight((acc, [tag, classes = '']) => {
      return `<${tag}${classes}>${acc}</${tag}>`;
    }, cue.payload);
  }

  /**
   * Gets the color name from a color string.
   *
   * @param {string} string
   * @return {?string}
   * @private
   */
  static getColorName_(string) {
    switch (string.toLowerCase()) {
      case 'white':
      case '#fff':
      case '#ffffff':
        return 'white';
      case 'lime':
      case '#0f0':
      case '#00ff00':
        return 'lime';
      case 'cyan':
      case '#0ff':
      case '#00ffff':
        return 'cyan';
      case 'red':
      case '#f00':
      case '#ff0000':
        return 'red';
      case 'yellow':
      case '#ff0':
      case '#ffff00':
        return 'yellow';
      case 'magenta':
      case '#f0f':
        return 'magenta';
      case 'blue':
      case '#00f':
      case '#0000ff':
        return 'blue';
      case 'black':
      case '#000':
      case '#000000':
        return 'black';
    }
    // No color name
    return null;
  }

  /**
   * We don't want to modify the array or objects passed in, since we don't
   * technically own them.  So we build a new array and replace certain items
   * in it if they need to be flattened.
   * We also don't want to flatten the text payloads starting at a container
   * element; otherwise, for containers encapsulating multiple caption lines,
   * the lines would merge into a single cue. This is undesirable when a
   * subset of the captions are outside of the append time window. To fix
   * this, we only call flattenPayload() starting at elements marked as
   * isContainer = false.
   *
   * @param {!Array.<!shaka.text.Cue>} cues
   * @param {!Array.<!shaka.text.Cue>} result
   * @return {!Array.<!shaka.text.Cue>}
   */
  static getCuesToFlatten(cues, result) {
    for (const cue of cues) {
      if (cue.isContainer) {
        // Recurse to find the actual text payload cues.
        shaka.text.Utils.getCuesToFlatten(cue.nestedCues, result);
      } else {
        // Flatten the payload.
        const flatCue = cue.clone();
        flatCue.nestedCues = [];
        flatCue.payload = shaka.text.Utils.flattenPayload_(cue);
        result.push(flatCue);
      }
    }
    return result;
  }
};