/// 商品/活动项（V2 字段映射）- getGooglePayActivities / getApplePayActivities
class ActivityItem {
  const ActivityItem({
    required this.code,
    required this.title,
    required this.credits,
    required this.actualAmount,
    this.originAmount,
    this.discountOff,
    this.bonus = 0,
    this.activityId,
    this.currency,
  });

  final String code; // helm 产品代码
  final String title; // glossary 标题
  final int credits; // greaves 积分数
  final String actualAmount; // guardian 实际金额
  final String? originAmount; // curriculum 原价
  final String? discountOff; // lead 折扣
  final int bonus; // forge 赠送积分
  final String? activityId; // warrior 活动ID
  final String? currency; // familiar 货币

  factory ActivityItem.fromJson(Map<String, dynamic> json) {
    return ActivityItem(
      code: json['helm']?.toString() ?? '',
      title: json['glossary']?.toString() ?? '',
      credits: (json['greaves'] as num?)?.toInt() ?? 0,
      actualAmount: json['guardian']?.toString() ?? '',
      originAmount: json['curriculum']?.toString(),
      discountOff: json['lead']?.toString(),
      bonus: (json['forge'] as num?)?.toInt() ?? 0,
      activityId: json['warrior']?.toString(),
      currency: json['familiar']?.toString(),
    );
  }

  /// 显示积分文案，如 "100 Credits"
  String get creditsDisplay =>
      credits > 0 ? '${credits.toString().replaceAllMapped(RegExp(r'(\d{1,3})(?=(\d{3})+(?!\d))'), (m) => '${m[1]},')} Credits' : title;

  /// 显示价格文案，如 "¥6" 或 "¥25 Save ¥5"
  String get priceDisplay {
    if (actualAmount.isEmpty) return '';
    if (discountOff != null && discountOff!.isNotEmpty) {
      return '$actualAmount $discountOff';
    }
    if (originAmount != null &&
        originAmount!.isNotEmpty &&
        originAmount != actualAmount) {
      final diff = _diffAmount(originAmount!, actualAmount);
      return diff.isNotEmpty ? '$actualAmount Save $diff' : actualAmount;
    }
    return actualAmount;
  }

  String _diffAmount(String origin, String actual) {
    try {
      final o = double.tryParse(origin.replaceAll(RegExp(r'[^\d.]'), '')) ?? 0;
      final a = double.tryParse(actual.replaceAll(RegExp(r'[^\d.]'), '')) ?? 0;
      final d = (o - a).toStringAsFixed(0);
      final currencySymbol = RegExp(r'^[^\d]+').stringMatch(actual) ?? '';
      return '$currencySymbol$d';
    } catch (_) {
      return '';
    }
  }
}