Validador DNI en dart / NIF validator dart

nif_validator.dart

bool validateNIF(String value){

  var validChars = 'TRWAGMYFPDXBNJZSQVHLCKET';
  RegExp nifRegex = new RegExp(r'^[0-9]{8}[TRWAGMYFPDXBNJZSQVHLCKET]$');

  var str = value.toString().toUpperCase();
  if (!nifRegex.hasMatch(str)) return false;

  String nie = str
      .replaceAll(new RegExp(r"/^[X]/"), '0')
      .replaceAll(new RegExp(r"/^[Y]/"), '1')
      .replaceAll(new RegExp(r"/^[Z]/"), '2');


  var letter = str.substring(str.length-1);
  var charIndex = int.parse(nie.substring(0, 8)) % 23;
  return validChars[charIndex] == letter;



}