import 'package:flutter/foundation.dart';

@immutable // 标记为不可变类
class ChallengeModel {
  final int? id;
  final String title;
  final String description;
  final DateTime startDate;
  final DateTime endDate;
  final int participants;
  final bool completed;
  final String difficulty;
  final int? remainingDays; // 改为可选字段

  const ChallengeModel({
    required this.id,
    required this.title,
    required this.description,
    required this.startDate,
    required this.endDate,
    required this.participants,
    required this.completed,
    required this.difficulty,
    this.remainingDays, // 可选计算字段
  });

  int get calculatedRemainingDays => endDate.difference(DateTime.now()).inDays;

  factory ChallengeModel.fromJson(Map<String, dynamic> json) {
    return ChallengeModel(
      id: json['id'] as int?,
      title: json['title'] as String,
      description: json['description'] as String,
      startDate: DateTime.parse(json['startDate'] as String),
      endDate: DateTime.parse(json['endDate'] as String),
      participants: json['participants'] as int,
      completed: json['completed'] as bool,
      difficulty: json['difficulty'] as String,
    );
  }

  /// 转换为JSON
  Map<String, dynamic> toJson() => {
    if (id != null) 'id': id,
    'title': title,
    'description': description,
    'startDate': startDate.toIso8601String(),
    'endDate': endDate.toIso8601String(),
    'participants': participants,
    'completed': completed,
    'difficulty': difficulty,
  };

  ChallengeModel copyWith({
    int? id,
    String? title,
    String? description,
    DateTime? startDate,
    DateTime? endDate,
    int? participants,
    bool? completed,
    String? difficulty,
  }) {
    return ChallengeModel(
      id: id ?? this.id,
      title: title ?? this.title,
      description: description ?? this.description,
      startDate: startDate ?? this.startDate,
      endDate: endDate ?? this.endDate,
      participants: participants ?? this.participants,
      completed: completed ?? this.completed,
      difficulty: difficulty ?? this.difficulty,
    );
  }
}