/** Used to compose unicode character classes. */
const rsAstralRange = '\\ud800-\\udfff';
const rsComboMarksRange = '\\u0300-\\u036f';
const reComboHalfMarksRange = '\\ufe20-\\ufe2f';
const rsComboSymbolsRange = '\\u20d0-\\u20ff';
const rsComboRange = rsComboMarksRange + reComboHalfMarksRange + rsComboSymbolsRange;
const rsVarRange = '\\ufe0e\\ufe0f';

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

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

/** Used to match [string symbols](https://mathiasbynens.be/notes/javascript-unicode). */
const reUnicode = RegExp(`${ rsFitz }(?=${ rsFitz })|${ rsSymbol + rsSeq }`, 'g');

/**
 * Gets the size of a Unicode `string`.
 *
 * @private
 * @param {string} string The string inspect.
 * @returns {number} Returns the string size.
 */
function unicodeSize(string) {
  let result = reUnicode.lastIndex = 0;
  while (reUnicode.test(string)) {
    ++result;
  }
  return result;
}

export default unicodeSize;