/** Used to compose unicode character classes. */
var rsAstralRange = '\\ud800-\\udfff',
    rsComboRange = '\\u0300-\\u036f\\ufe20-\\ufe23',
    rsVarRange = '\\ufe0e\\ufe0f';

/** Used to compose unicode capture groups. */
var rsAstral = '[' + rsAstralRange + ']',
    rsCombo = '[' + rsComboRange + ']',
    rsModifier = '(?:\\ud83c[\\udffb-\\udfff])',
    rsNonAstral = '[^' + rsAstralRange + ']',
    rsRegional = '(?:\\ud83c[\\udde6-\\uddff]){2}',
    rsSurrPair = '[\\ud800-\\udbff][\\udc00-\\udfff]',
    rsZWJ = '\\u200d';

/** Used to compose unicode regexes. */
var reOptMod = rsModifier + '?',
    rsOptVar = '[' + rsVarRange + ']?',
    rsOptJoin = '(?:' + rsZWJ + '(?:' + [rsNonAstral, rsRegional, rsSurrPair].join('|') + ')' + rsOptVar + reOptMod + ')*',
    rsSeq = rsOptVar + reOptMod + rsOptJoin,
    rsSymbol = '(?:' + [rsNonAstral + rsCombo + '?', rsCombo, rsRegional, rsSurrPair, rsAstral].join('|') + ')';

/** Used to match [string symbols](https://mathiasbynens.be/notes/javascript-unicode). */
var reComplexSymbol = RegExp(rsSymbol + rsSeq, 'g');

/** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
var reHasComplexSymbol = RegExp('[' + rsZWJ + rsAstralRange + rsComboRange + rsVarRange + ']');

/**
 * Gets the number of symbols in `string`.
 *
 * @param {string} string The string to inspect.
 * @returns {number} Returns the string size.
 */
function stringSize(string) {
  if (!(string && reHasComplexSymbol.test(string))) {
    return string.length;
  }
  var result = reComplexSymbol.lastIndex = 0;
  while (reComplexSymbol.test(string)) {
    result++;
  }
  return result;
}

export default stringSize;