/// 账单模型
class BillModel {
  final String id;
  final String billNo;
  final String userName;
  final String userAddress;
  final String meterNo;
  final double previousReading;
  final double currentReading;
  final double usage;
  final double amount;
  final String status; // unpaid, paid, overdue
  final String period;
  final DateTime dueDate;

  BillModel({
    required this.id,
    required this.billNo,
    required this.userName,
    required this.userAddress,
    required this.meterNo,
    required this.previousReading,
    required this.currentReading,
    required this.usage,
    required this.amount,
    required this.status,
    required this.period,
    required this.dueDate,
  });

  factory BillModel.fromJson(Map<String, dynamic> json) {
    return BillModel(
      id: json['id']?.toString() ?? '',
      billNo: json['billNo'] ?? '',
      userName: json['userName'] ?? '',
      userAddress: json['userAddress'] ?? '',
      meterNo: json['meterNo'] ?? '',
      previousReading: (json['previousReading'] ?? 0).toDouble(),
      currentReading: (json['currentReading'] ?? 0).toDouble(),
      usage: (json['usage'] ?? 0).toDouble(),
      amount: (json['amount'] ?? 0).toDouble(),
      status: json['status'] ?? 'unpaid',
      period: json['period'] ?? '',
      dueDate: DateTime.tryParse(json['dueDate'] ?? '') ?? DateTime.now(),
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'billNo': billNo,
      'userName': userName,
      'userAddress': userAddress,
      'meterNo': meterNo,
      'previousReading': previousReading,
      'currentReading': currentReading,
      'usage': usage,
      'amount': amount,
      'status': status,
      'period': period,
      'dueDate': dueDate.toIso8601String(),
    };
  }
}