clapper/src/assets/node-ytdl-core/sig.js

/* Copyright (C) 2012-present by fent
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

const jsVarStr = '[a-zA-Z_\\$][a-zA-Z_0-9]*';
const jsSingleQuoteStr = `'[^'\\\\]*(:?\\\\[\\s\\S][^'\\\\]*)*'`;
const jsDoubleQuoteStr = `"[^"\\\\]*(:?\\\\[\\s\\S][^"\\\\]*)*"`;
const jsQuoteStr = `(?:${jsSingleQuoteStr}|${jsDoubleQuoteStr})`;
const jsKeyStr = `(?:${jsVarStr}|${jsQuoteStr})`;
const jsPropStr = `(?:\\.${jsVarStr}|\\[${jsQuoteStr}\\])`;
const jsEmptyStr = `(?:''|"")`;
const reverseStr = ':function\\(a\\)\\{' +
  '(?:return )?a\\.reverse\\(\\)' +
'\\}';
const sliceStr = ':function\\(a,b\\)\\{' +
  'return a\\.slice\\(b\\)' +
'\\}';
const spliceStr = ':function\\(a,b\\)\\{' +
  'a\\.splice\\(0,b\\)' +
'\\}';
const swapStr = ':function\\(a,b\\)\\{' +
  'var c=a\\[0\\];a\\[0\\]=a\\[b(?:%a\\.length)?\\];a\\[b(?:%a\\.length)?\\]=c(?:;return a)?' +
'\\}';
const actionsObjRegexp = new RegExp(
  `var (${jsVarStr})=\\{((?:(?:${
    jsKeyStr}${reverseStr}|${
    jsKeyStr}${sliceStr}|${
    jsKeyStr}${spliceStr}|${
    jsKeyStr}${swapStr
  }),?\\r?\\n?)+)\\};`);
const actionsFuncRegexp = new RegExp(`${`function(?: ${jsVarStr})?\\(a\\)\\{` +
    `a=a\\.split\\(${jsEmptyStr}\\);\\s*` +
    `((?:(?:a=)?${jsVarStr}`}${
  jsPropStr
}\\(a,\\d+\\);)+)` +
    `return a\\.join\\(${jsEmptyStr}\\)` +
  `\\}`);
const reverseRegexp = new RegExp(`(?:^|,)(${jsKeyStr})${reverseStr}`, 'm');
const sliceRegexp = new RegExp(`(?:^|,)(${jsKeyStr})${sliceStr}`, 'm');
const spliceRegexp = new RegExp(`(?:^|,)(${jsKeyStr})${spliceStr}`, 'm');
const swapRegexp = new RegExp(`(?:^|,)(${jsKeyStr})${swapStr}`, 'm');

const swapHeadAndPosition = (arr, position) => {
  const first = arr[0];
  arr[0] = arr[position % arr.length];
  arr[position] = first;

  return arr;
}

function decipher(sig, tokens) {
  sig = sig.split('');
  tokens = tokens.split(',');

  for(let i = 0, len = tokens.length; i < len; i++) {
    let token = tokens[i], pos;
    switch (token[0]) {
      case 'r':
        sig = sig.reverse();
        break;
      case 'w':
        pos = ~~token.slice(1);
        sig = swapHeadAndPosition(sig, pos);
        break;
      case 's':
        pos = ~~token.slice(1);
        sig = sig.slice(pos);
        break;
      case 'p':
        pos = ~~token.slice(1);
        sig.splice(0, pos);
        break;
    }
  }

  return sig.join('');
};

function extractActions(body) {
  const objResult = actionsObjRegexp.exec(body);
  const funcResult = actionsFuncRegexp.exec(body);

  if(!objResult || !funcResult)
    return null;

  const obj = objResult[1].replace(/\$/g, '\\$');
  const objBody = objResult[2].replace(/\$/g, '\\$');
  const funcBody = funcResult[1].replace(/\$/g, '\\$');

  let result = reverseRegexp.exec(objBody);
  const reverseKey = result && result[1]
    .replace(/\$/g, '\\$')
    .replace(/\$|^'|^"|'$|"$/g, '');
  result = sliceRegexp.exec(objBody);
  const sliceKey = result && result[1]
    .replace(/\$/g, '\\$')
    .replace(/\$|^'|^"|'$|"$/g, '');
  result = spliceRegexp.exec(objBody);
  const spliceKey = result && result[1]
    .replace(/\$/g, '\\$')
    .replace(/\$|^'|^"|'$|"$/g, '');
  result = swapRegexp.exec(objBody);
  const swapKey = result && result[1]
    .replace(/\$/g, '\\$')
    .replace(/\$|^'|^"|'$|"$/g, '');

  const keys = `(${[reverseKey, sliceKey, spliceKey, swapKey].join('|')})`;
  const myreg = `(?:a=)?${obj
  }(?:\\.${keys}|\\['${keys}'\\]|\\["${keys}"\\])` +
    `\\(a,(\\d+)\\)`;
  const tokenizeRegexp = new RegExp(myreg, 'g');
  const tokens = [];

  while((result = tokenizeRegexp.exec(funcBody)) !== null) {
    const key = result[1] || result[2] || result[3];
    const pos = result[4];
    switch (key) {
      case swapKey:
        tokens.push(`w${result[4]}`);
        break;
      case reverseKey:
        tokens.push('r');
        break;
      case sliceKey:
        tokens.push(`s${result[4]}`);
        break;
      case spliceKey:
        tokens.push(`p${result[4]}`);
        break;
    }
  }

  return tokens.join(',');
}