rx-player/src/parsers/texttracks/webvtt/utils.ts

Canal+ HTML5 Video Player

/**
 * Copyright 2015 CANAL+ Group
 *
 * 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.
 */

import isNonEmptyString from "../../../utils/is_non_empty_string";

/**
 * Returns first line after the WEBVTT header.
 * That is, the line after the first blank line after the first line!
 * @param {Array.<string>} linified
 * @returns {Number}
 */
function getFirstLineAfterHeader(linified: string[]): number {
  let i = 0;
  while (i < linified.length) {
    if (linified[i] === "") {
      return i + 1;
    }
    i++;
  }
  return i;
}

/**
 * Returns true if the given line looks like the beginning of a Style block.
 * @param {Array.<string>} lines
 * @param {number} index
 * @returns {Boolean}
 */
function isStartOfStyleBlock(lines: string[], index: number): boolean {
  return (
    typeof lines[index] === "string" &&
    /^STYLE( .*)?$/g.test(lines[index]) &&
    // A cue identifer can also contain "STYLE". Check that we have no timings
    // on the second line
    (lines[index + 1] === undefined || lines[index + 1].indexOf("-->") < 0)
  );
}

/**
 * Returns true if the given line looks like the beginning of a comment block.
 * @param {string} text
 * @returns {Boolean}
 */
function isStartOfNoteBlock(lines: string[], index: number): boolean {
  return (
    typeof lines[index] === "string" &&
    /^NOTE( .*)?$/g.test(lines[index]) &&
    // A cue identifer can also contain "NOTE". Check that we have no timings
    // on the second line
    (lines[index + 1] === undefined || lines[index + 1].indexOf("-->") < 0)
  );
}

/**
 * Returns true if the given line looks like the beginning of a region block.
 * @param {string} text
 * @returns {Boolean}
 */
function isStartOfRegionBlock(lines: string[], index: number): boolean {
  return (
    typeof lines[index] === "string" &&
    /^REGION( .*)?$/g.test(lines[index]) &&
    // A cue identifer can also contain "REGION". Check that we have no timings
    // on the second line
    (lines[index + 1] === undefined || lines[index + 1].indexOf("-->") < 0)
  );
}

/**
 * Returns true if the line given looks like the beginning of a cue.
 * You should provide to this function only lines following "empty" lines.
 * @param {Array.<string>} lines
 * @param {number} index
 * @returns {Boolean}
 */
function isStartOfCueBlock(lines: string[], index: number): boolean {
  // checked cases:
  //   - empty lines
  //   - start of a comment
  //   - start of a region
  //   - start of a style
  // Anything else whose first or second line is a timestamp line is a cue.
  const firstLine = lines[index];
  if (
    firstLine === undefined ||
    firstLine === "" ||
    isStartOfStyleBlock(lines, index) ||
    isStartOfRegionBlock(lines, index) ||
    isStartOfNoteBlock(lines, index)
  ) {
    return false;
  }

  if (firstLine.indexOf("-->") >= 0) {
    return true;
  }

  const secondLine = lines[index + 1];
  return secondLine !== undefined && secondLine.indexOf("-->") >= 0;
}

/**
 * Find end of current WebVTT cue block.
 * @param {Array<string>} linified
 * @param {number} startOfCueBlock
 * @returns {number}
 */
function findEndOfCueBlock(linified: string[], startOfCueBlock: number): number {
  let firstEmptyLineIndex = startOfCueBlock + 1;

  // continue incrementing i until either:
  //   - empty line
  //   - end
  while (isNonEmptyString(linified[firstEmptyLineIndex])) {
    firstEmptyLineIndex++;
  }
  return firstEmptyLineIndex;
}

export {
  getFirstLineAfterHeader,
  isStartOfCueBlock,
  isStartOfNoteBlock,
  isStartOfRegionBlock,
  isStartOfStyleBlock,
  findEndOfCueBlock,
};