class PhoneHelper {
  static String normalizePhone(String phone) {
    final raw = phone.trim();
    if (raw.isEmpty) return '';

    final digits = raw.replaceAll(RegExp(r'\D'), '');
    if (digits.isEmpty) return raw;

    if (raw.startsWith('+')) {
      return '+$digits';
    }

    if (raw.startsWith('00') && digits.length > 2) {
      return '+${digits.substring(2)}';
    }

    // Iranian local formats
    if (digits.length == 11 && digits.startsWith('0')) {
      return '+98${digits.substring(1)}';
    }
    if (digits.length == 10) {
      return '+98$digits';
    }
    if (digits.startsWith('98') && digits.length >= 12 && digits.length <= 15) {
      return '+$digits';
    }

    // Preserve full international numbers instead of collapsing them to
    // the last 10 digits, which can merge different identities together.
    if (digits.length >= 11 && digits.length <= 15) {
      return '+$digits';
    }

    return raw;
  }
}