source: node_modules/ret/lib/util.js

const types = require('./types');
const sets  = require('./sets');


const CTRL = '@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^ ?';
const SLSH = { '0': 0, 't': 9, 'n': 10, 'v': 11, 'f': 12, 'r': 13 };

/**
 * Finds character representations in str and convert all to
 * their respective characters
 *
 * @param {String} str
 * @return {String}
 */
exports.strToChars = function(str) {
  /* jshint maxlen: false */
  var chars_regex = /(\[\\b\])|(\\)?\\(?:u([A-F0-9]{4})|x([A-F0-9]{2})|(0?[0-7]{2})|c([@A-Z[\\\]^?])|([0tnvfr]))/g;
  str = str.replace(chars_regex, function(s, b, lbs, a16, b16, c8, dctrl, eslsh) {
    if (lbs) {
      return s;
    }

    var code = b ? 8 :
      a16   ? parseInt(a16, 16) :
      b16   ? parseInt(b16, 16) :
      c8    ? parseInt(c8,   8) :
      dctrl ? CTRL.indexOf(dctrl) :
      SLSH[eslsh];

    var c = String.fromCharCode(code);

    // Escape special regex characters.
    if (/[[\]{}^$.|?*+()]/.test(c)) {
      c = '\\' + c;
    }

    return c;
  });

  return str;
};


/**
 * turns class into tokens
 * reads str until it encounters a ] not preceeded by a \
 *
 * @param {String} str
 * @param {String} regexpStr
 * @return {Array.<Array.<Object>, Number>}
 */
exports.tokenizeClass = (str, regexpStr) => {
  /* jshint maxlen: false */
  var tokens = [];
  var regexp = /\\(?:(w)|(d)|(s)|(W)|(D)|(S))|((?:(?:\\)(.)|([^\]\\]))-(?:\\)?([^\]]))|(\])|(?:\\)?([^])/g;
  var rs, c;


  while ((rs = regexp.exec(str)) != null) {
    if (rs[1]) {
      tokens.push(sets.words());

    } else if (rs[2]) {
      tokens.push(sets.ints());

    } else if (rs[3]) {
      tokens.push(sets.whitespace());

    } else if (rs[4]) {
      tokens.push(sets.notWords());

    } else if (rs[5]) {
      tokens.push(sets.notInts());

    } else if (rs[6]) {
      tokens.push(sets.notWhitespace());

    } else if (rs[7]) {
      tokens.push({
        type: types.RANGE,
        from: (rs[8] || rs[9]).charCodeAt(0),
        to: rs[10].charCodeAt(0),
      });

    } else if ((c = rs[12])) {
      tokens.push({
        type: types.CHAR,
        value: c.charCodeAt(0),
      });

    } else {
      return [tokens, regexp.lastIndex];
    }
  }

  exports.error(regexpStr, 'Unterminated character class');
};


/**
 * Shortcut to throw errors.
 *
 * @param {String} regexp
 * @param {String} msg
 */
exports.error = (regexp, msg) => {
  throw new SyntaxError('Invalid regular expression: /' + regexp + '/: ' + msg);
};