import 'json_util.dart';

/// 统计响应（对应后端 StatisticsResponse）
///
/// 口径说明：后端的 totalIncome / totalExpense / categoryStatistics 是按
/// **分类的 type** 判定收支的，而 /bills 列表是按 **账单的 type** 判定。
/// 两者可能不一致——前端不做交叉校验，汇总/饼图一律以此接口为准。
class StatisticsResponse {
  final double totalIncome;
  final double totalExpense;
  final double balance;
  final List<CategoryStat> categoryStatistics;
  final List<DailyStat> dailyStatistics;

  const StatisticsResponse({
    required this.totalIncome,
    required this.totalExpense,
    required this.balance,
    required this.categoryStatistics,
    required this.dailyStatistics,
  });

  bool get isEmpty => categoryStatistics.isEmpty && totalIncome == 0 && totalExpense == 0;

  factory StatisticsResponse.fromJson(Map<String, dynamic> json) {
    final income = asDouble(json['totalIncome']);
    final expense = asDouble(json['totalExpense']);
    final balanceRaw = json['balance'];
    return StatisticsResponse(
      totalIncome: income,
      totalExpense: expense,
      // 后端没给 balance 时本地兜底计算
      balance: balanceRaw == null ? income - expense : asDouble(balanceRaw),
      categoryStatistics:
          asMapList(json['categoryStatistics']).map(CategoryStat.fromJson).toList(),
      dailyStatistics:
          asMapList(json['dailyStatistics']).map(DailyStat.fromJson).toList(),
    );
  }

  static const empty = StatisticsResponse(
    totalIncome: 0,
    totalExpense: 0,
    balance: 0,
    categoryStatistics: [],
    dailyStatistics: [],
  );
}

/// 分类维度的统计项
class CategoryStat {
  final int categoryId;
  final String categoryName;
  final String categoryIcon;
  final double amount;
  final int type; // 1=支出 2=收入

  const CategoryStat({
    required this.categoryId,
    required this.categoryName,
    required this.categoryIcon,
    required this.amount,
    required this.type,
  });

  bool get isExpense => type != 2;

  factory CategoryStat.fromJson(Map<String, dynamic> json) => CategoryStat(
        categoryId: asInt(json['categoryId']),
        categoryName: asNonEmpty(json['categoryName'], '未分类'),
        categoryIcon: asNonEmpty(json['categoryIcon'], '📦'),
        amount: asDouble(json['amount']),
        type: asInt(json['type'], fallback: 1) == 2 ? 2 : 1,
      );
}

/// 按日趋势项（本期统计页不画折线图，保留以便后续扩展）
class DailyStat {
  final String date; // yyyy-MM-dd
  final double income;
  final double expense;

  const DailyStat({required this.date, required this.income, required this.expense});

  factory DailyStat.fromJson(Map<String, dynamic> json) => DailyStat(
        date: asString(json['date']),
        income: asDouble(json['income']),
        expense: asDouble(json['expense']),
      );
}