import 'package:intl/intl.dart';

class DateTimeUtils {
  static final DateFormat _dateFormat = DateFormat('yyyy-MM-dd');
  static final DateFormat _timeFormat = DateFormat('HH:mm');
  static final DateFormat _dateTimeFormat = DateFormat('yyyy-MM-dd HH:mm');
  static final DateFormat _monthFormat = DateFormat('yyyy-MM');

  static String formatDate(DateTime date) {
    return _dateFormat.format(date);
  }

  static String formatTime(DateTime date) {
    return _timeFormat.format(date);
  }

  static String formatDateTime(DateTime date) {
    return _dateTimeFormat.format(date);
  }

  static String formatMonth(DateTime date) {
    return _monthFormat.format(date);
  }

  static String formatRelative(DateTime date) {
    final now = DateTime.now();
    final diff = now.difference(date);

    if (diff.inMinutes < 1) {
      return '刚刚';
    } else if (diff.inMinutes < 60) {
      return '${diff.inMinutes}分钟前';
    } else if (diff.inHours < 24) {
      return '${diff.inHours}小时前';
    } else if (diff.inDays < 7) {
      return '${diff.inDays}天前';
    } else if (diff.inDays < 30) {
      return '${(diff.inDays / 7).floor()}周前';
    } else if (diff.inDays < 365) {
      return '${(diff.inDays / 30).floor()}个月前';
    } else {
      return formatDate(date);
    }
  }

  static String formatSmart(DateTime date) {
    final now = DateTime.now();
    final today = DateTime(now.year, now.month, now.day);
    final yesterday = today.subtract(const Duration(days: 1));
    final dateDay = DateTime(date.year, date.month, date.day);

    if (dateDay == today) {
      return '今天 ${formatTime(date)}';
    } else if (dateDay == yesterday) {
      return '昨天 ${formatTime(date)}';
    } else if (now.difference(date).inDays < 7) {
      return formatRelative(date);
    } else {
      return formatDateTime(date);
    }
  }
}

class NumberUtils {
  static String formatCompact(int number) {
    if (number >= 100000000) {
      return '${(number / 100000000).toStringAsFixed(1)}亿';
    } else if (number >= 10000) {
      return '${(number / 10000).toStringAsFixed(1)}万';
    } else if (number >= 1000) {
      return '${(number / 1000).toStringAsFixed(1)}k';
    }
    return number.toString();
  }

  static String formatPercent(double value, {int decimals = 1}) {
    return '${(value * 100).toStringAsFixed(decimals)}%';
  }

  static String formatCurrency(double value, {String symbol = '¥'}) {
    return '$symbol${value.toStringAsFixed(2)}';
  }
}

class Validators {
  static String? required(String? value, [String? fieldName]) {
    if (value == null || value.trim().isEmpty) {
      return '请输入${fieldName ?? '内容'}';
    }
    return null;
  }

  static String? phone(String? value) {
    if (value == null || value.isEmpty) {
      return '请输入手机号';
    }
    if (!RegExp(r'^1[3-9]\d{9}$').hasMatch(value)) {
      return '请输入有效的手机号';
    }
    return null;
  }

  static String? email(String? value) {
    if (value == null || value.isEmpty) {
      return '请输入邮箱';
    }
    if (!RegExp(r'^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$').hasMatch(value)) {
      return '请输入有效的邮箱';
    }
    return null;
  }

  static String? password(String? value) {
    if (value == null || value.isEmpty) {
      return '请输入密码';
    }
    if (value.length < 6) {
      return '密码至少6位';
    }
    if (value.length > 20) {
      return '密码最多20位';
    }
    return null;
  }

  static String? minLength(String? value, int length, [String? fieldName]) {
    if (value == null || value.length < length) {
      return '${fieldName ?? '内容'}至少$length个字符';
    }
    return null;
  }

  static String? maxLength(String? value, int length, [String? fieldName]) {
    if (value != null && value.length > length) {
      return '${fieldName ?? '内容'}最多$length个字符';
    }
    return null;
  }
}