import 'dart:core';

class IDCardInfo {
  final String raw;
  final bool isValid;
  final String? error;
  final String? id18;
  final String? addressCode;
  final String? provinceCode;
  final String? province;
  final DateTime? birthDate;
  final String? birth;
  final int? age;
  final String? gender;
  final bool checksumValid;
  final String? constellation;
  final String? zodiac;

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

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

/// 只校验 18 位身份证号
IDCardInfo parseChineseIDCard(String? id) {
  final raw = _normalizeId(id);

  if (raw.isEmpty) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '身份证号不能为空',
      checksumValid: false,
    );
  }

  if (raw.length != 18) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '身份证号长度不正确，应为18位',
      checksumValid: false,
    );
  }

  if (!RegExp(r'^\d{17}[\dX]$').hasMatch(raw)) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '身份证号格式不正确：前17位必须是数字，最后一位必须是数字或X',
      checksumValid: false,
    );
  }

  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',
  };

  final addressCode = raw.substring(0, 6);
  final provinceCode = raw.substring(0, 2);
  final province = provinceMap[provinceCode];

  if (province == null) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '地址码不合法：省份码错误',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      checksumValid: false,
    );
  }

  final yearStr = raw.substring(6, 10);
  final monthStr = raw.substring(10, 12);
  final dayStr = raw.substring(12, 14);

  if (!RegExp(r'^(18|19|20)\d{2}$').hasMatch(yearStr)) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '年份不合法：必须以18、19或20开头',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      checksumValid: false,
    );
  }

  if (!RegExp(r'^(0[1-9]|1[0-2])$').hasMatch(monthStr)) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '月份不合法：必须在01到12之间',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      checksumValid: false,
    );
  }

  if (!RegExp(r'^(0[1-9]|[12]\d|3[01])$').hasMatch(dayStr)) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '日期不合法：必须在01到31之间',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      checksumValid: false,
    );
  }

  final year = int.parse(yearStr);
  final month = int.parse(monthStr);
  final day = int.parse(dayStr);

  DateTime? birthDate;
  try {
    final dt = DateTime(year, month, day);
    if (dt.year == year && dt.month == month && dt.day == day) {
      birthDate = dt;
    }
  } catch (_) {
    birthDate = null;
  }

  if (birthDate == null) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '出生日期无效：请检查年月日是否真实存在',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      checksumValid: false,
    );
  }

  final seqCode = raw.substring(14, 17);
  if (!RegExp(r'^\d{3}$').hasMatch(seqCode)) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '顺序码不合法：第15到17位必须全部为数字',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      birthDate: birthDate,
      birth: _formatDate(birthDate),
      checksumValid: false,
    );
  }

  final seqNum = int.parse(seqCode);
  if (seqNum == 0) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '顺序码不合法：不能为000',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      birthDate: birthDate,
      birth: _formatDate(birthDate),
      checksumValid: false,
    );
  }

  final gender = (seqNum % 2 == 1) ? '男' : '女';

  final checksumValid = _verifyCheck(raw);
  if (!checksumValid) {
    return IDCardInfo(
      raw: raw,
      isValid: false,
      error: '校验位不正确',
      id18: raw,
      addressCode: addressCode,
      provinceCode: provinceCode,
      province: province,
      birthDate: birthDate,
      birth: _formatDate(birthDate),
      age: _calcAge(birthDate),
      gender: gender,
      checksumValid: false,
      constellation: _calcConstellation(birthDate.month, birthDate.day),
      zodiac: _calcChineseZodiac(birthDate.year),
    );
  }

  return IDCardInfo(
    raw: raw,
    isValid: true,
    id18: raw,
    addressCode: addressCode,
    provinceCode: provinceCode,
    province: province,
    birthDate: birthDate,
    birth: _formatDate(birthDate),
    age: _calcAge(birthDate),
    gender: gender,
    checksumValid: true,
    constellation: _calcConstellation(birthDate.month, birthDate.day),
    zodiac: _calcChineseZodiac(birthDate.year),
  );
}

String _normalizeId(String? id) {
  return (id ?? '')
      .trim()
      .replaceAll(' ', '')
      .replaceAll('　', '')
      .replaceAll('Ｘ', 'X')
      .toUpperCase();
}

String _formatDate(DateTime d) {
  return '${d.year.toString().padLeft(4, '0')}-'
      '${d.month.toString().padLeft(2, '0')}-'
      '${d.day.toString().padLeft(2, '0')}';
}

int _calcAge(DateTime birthDate) {
  final now = DateTime.now();
  var age = now.year - birthDate.year;
  if (now.month < birthDate.month ||
      (now.month == birthDate.month && now.day < birthDate.day)) {
    age -= 1;
  }
  return age;
}

String _calcCheckChar(String id17) {
  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'];

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

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;
}

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];
  final idx = month - 1;
  if (day < startDays[idx]) {
    return names[(idx + 11) % 12];
  } else {
    return names[idx];
  }
}

String _calcChineseZodiac(int year) {
  const zodiacs = ['鼠', '牛', '虎', '兔', '龙', '蛇', '马', '羊', '猴', '鸡', '狗', '猪'];
  final idx = (year - 1900) % 12;
  final i = idx < 0 ? (idx + 12) % 12 : idx;
  return zodiacs[i];
}