// utils/id_card_util.dart
import 'dart:core';

class IDCardInfo {
  final String raw;
  final bool isValid;
  final String? error;
  final String? id18; // 标准化到18位（若输入15位则自动转换）
  final String? provinceCode;
  final String? province;
  final DateTime? birthDate;
  final String? birth; // YYYY-MM-DD
  final int? age;
  final String? gender; // '男' / '女'
  final bool checksumValid;
  final String? constellation; // 星座
  final String? zodiac; // 生肖

  IDCardInfo({
    required this.raw,
    required this.isValid,
    this.error,
    this.id18,
    this.provinceCode,
    this.province,
    this.birthDate,
    this.birth,
    this.age,
    this.gender,
    required this.checksumValid,
    this.constellation,
    this.zodiac,
  });

  Map<String, dynamic> toJson() => {
    'raw': raw,
    'isValid': isValid,
    'error': error,
    'id18': id18,
    'provinceCode': provinceCode,
    'province': province,
    'birth': birth,
    'age': age,
    'gender': gender,
    'checksumValid': checksumValid,
    'constellation': constellation,
    'zodiac': zodiac,
  };

  @override
  String toString() => toJson().toString();
}

/// 主要调用函数：传入身份证号字符串，返回 IDCardInfo
IDCardInfo parseChineseIDCard(String id) {
  final raw = (id ?? '').toString().trim().toUpperCase();
  if (raw.isEmpty) {
    return IDCardInfo(raw: raw, isValid: false, error: '空字符串', checksumValid: false);
  }

  // 省份码映射（常见）
  const provinceMap = <String, String>{
    '11': '北京市',
    '12': '天津市',
    '13': '河北省',
    '14': '山西省',
    '15': '内蒙古自治区',
    '21': '辽宁省',
    '22': '吉林省',
    '23': '黑龙江省',
    '31': '上海市',
    '32': '江苏省',
    '33': '浙江省',
    '34': '安徽省',
    '35': '福建省',
    '36': '江西省',
    '37': '山东省',
    '41': '河南省',
    '42': '湖北省',
    '43': '湖南省',
    '44': '广东省',
    '45': '广西壮族自治区',
    '46': '海南省',
    '50': '重庆市',
    '51': '四川省',
    '52': '贵州省',
    '53': '云南省',
    '54': '西藏自治区',
    '61': '陕西省',
    '62': '甘肃省',
    '63': '青海省',
    '64': '宁夏回族自治区',
    '65': '新疆维吾尔自治区',
    '71': '台湾省',
    '81': '香港特别行政区',
    '82': '澳门特别行政区',
    '91': '国外'
  };

  // 校验正则：15 位全数字；18 位前17 数字 + 最后一位数字或 X
  final reg15 = RegExp(r'^\d{15}$');
  final reg18 = RegExp(r'^\d{17}[\dX]$');

  String standardized = raw;
  bool convertedFrom15 = false;
  if (reg15.hasMatch(raw)) {
    // 15 位 -> 转 18 位（在第6位后插入 "19"），然后计算校验位
    final prefix17 = raw.substring(0, 6) + '19' + raw.substring(6);
    final checkChar = _calcCheckChar(prefix17);
    standardized = prefix17 + checkChar;
    convertedFrom15 = true;
  } else if (reg18.hasMatch(raw)) {
    standardized = raw;
  } else {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '身份证格式不正确（不是15位或18位）',
      checksumValid: false,
    );
  }

  // 取出生日期
  final birthStr = standardized.substring(6, 14); // YYYYMMDD
  final year = int.tryParse(birthStr.substring(0, 4));
  final month = int.tryParse(birthStr.substring(4, 6));
  final day = int.tryParse(birthStr.substring(6, 8));

  if (year == null || month == null || day == null) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '无法解析出生日期',
      id18: standardized,
      checksumValid: _verifyCheck(standardized),
    );
  }

  // 校验日期是否真实存在（例如闰年等）
  DateTime? birthDate;
  try {
    birthDate = DateTime(year, month, day);
    // 额外检查同一天
    if (birthDate.year != year || birthDate.month != month || birthDate.day != day) {
      birthDate = null;
    }
  } catch (e) {
    birthDate = null;
  }

  if (birthDate == null) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '出生日期无效',
      id18: standardized,
      checksumValid: _verifyCheck(standardized),
    );
  }

  // 年龄计算（按生日是否已过来算）
  final now = DateTime.now();
  int age = now.year - birthDate.year;
  if (now.month < birthDate.month || (now.month == birthDate.month && now.day < birthDate.day)) {
    age -= 1;
  }

  // 性别：第 17 位（索引 16）为序列码的最后一位，奇数男 偶数女
  final seq = standardized.substring(14, 17); // 3 位序列号
  final seqNum = int.tryParse(seq);
  final gender = (seqNum != null && seqNum % 2 == 1) ? '男' : '女';

  // 省份
  final provinceCode = standardized.substring(0, 2);
  final province = provinceMap[provinceCode] ?? '未知';

  // 校验位验证
  final checksumValid = _verifyCheck(standardized);

  // 星座与生肖
  final constellation = _calcConstellation(birthDate.month, birthDate.day);
  final zodiac = _calcChineseZodiac(birthDate.year);

  return IDCardInfo(
    raw: raw,
    isValid: true,
    id18: standardized,
    provinceCode: provinceCode,
    province: province,
    birthDate: birthDate,
    birth: '${birthDate.year.toString().padLeft(4, '0')}-${birthDate.month.toString().padLeft(2, '0')}-${birthDate.day.toString().padLeft(2, '0')}',
    age: age,
    gender: gender,
    checksumValid: checksumValid,
    constellation: constellation,
    zodiac: zodiac,
  );
}

// ---- 辅助函数 ----

// 计算 17 位前缀的校验码（返回 '0'-'9' 或 'X'）
String _calcCheckChar(String id17) {
  // 权重
  const weights = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
  // 校验码映射 remainder -> char
  const checkMap = ['1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'];

  int sum = 0;
  for (var i = 0; i < 17; i++) {
    final ch = id17[i];
    final n = int.tryParse(ch) ?? 0;
    sum += n * weights[i];
  }
  final mod = sum % 11;
  return checkMap[mod];
}

// 验证完整 18 位身份证的校验位是否正确
bool _verifyCheck(String id18) {
  if (id18.length != 18) return false;
  final id17 = id18.substring(0, 17);
  final expected = _calcCheckChar(id17);
  final actual = id18[17].toUpperCase();
  return expected == actual;
}

// 计算星座（西方）
String _calcConstellation(int month, int day) {
  const names = [
    '摩羯座', '水瓶座', '双鱼座', '白羊座', '金牛座', '双子座',
    '巨蟹座', '狮子座', '处女座', '天秤座', '天蝎座', '射手座'
  ];
  const startDays = [20, 19, 21, 21, 21, 22, 23, 23, 23, 23, 22, 22];
  // 月份从1开始
  final idx = (month - 1);
  if (day < startDays[idx]) {
    return names[(idx + 11) % 12];
  } else {
    return names[idx];
  }
}

// 计算生肖（中国农历生肖按公历年对照，简化算法）
String _calcChineseZodiac(int year) {
  const zodiacs = [
    '鼠', '牛', '虎', '兔', '龙', '蛇', '马', '羊', '猴', '鸡', '狗', '猪'
  ];
  // 1900 是鼠年（可以用任意基准）
  final idx = (year - 1900) % 12;
  final i = idx < 0 ? (idx + 12) % 12 : idx;
  return zodiacs[i];
}