isChineseIdNumber property

Implementation

bool get isChineseIdNumber {
  if (this == null) {
    return false;
  }
  // 1. Basic format
  if (this!.length != 18) return false;
  final digits = this!.split('');
  if (digits.sublist(0, 17).any((c) => !RegExp(r'[0-9]').hasMatch(c))) {
    return false;
  }

  // 2. Birthday (positions 7-14: YYYYMMDD)
  final year = int.parse(this!.substring(6, 10));
  final month = int.parse(this!.substring(10, 12));
  final day = int.parse(this!.substring(12, 14));

  if (month < 1 || month > 12) return false;
  if (day < 1 || day > 31) return false;

  // Validate real date (including leap year)
  final DateTime? birthDate;
  try {
    birthDate = DateTime(year, month, day);
  } on ArgumentError {
    return false;
  }
  if (birthDate.year != year ||
      birthDate.month != month ||
      birthDate.day != day) {
    return false;
  }

  // 3. Check digit (ISO 7064, MOD 11-2)
  const weights = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
  const checkMap = ['1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'];

  var sum = 0;
  for (var i = 0; i < 17; i++) {
    sum += int.parse(digits[i]) * weights[i];
  }
  final expectedCheck = checkMap[sum % 11];
  final actualCheck = digits[17].toUpperCase();

  return expectedCheck == actualCheck;
}