import 'package:uuid/uuid.dart';

class Problem {
  final String id;
  final String description;
  final String location;
  final String imageUrl;
  final DateTime createdAt;
  final DateTime updatedAt;

  static final Uuid _uuid = const Uuid();

  Problem._({
    required this.id,
    required this.description,
    required this.location,
    required this.imageUrl,
    required this.createdAt,
    required this.updatedAt,
  });

  // 主工厂构造函数
  factory Problem({
    required String description,
    required String location,
    required String imageUrl,
    String? id,
    DateTime? createdAt,
    DateTime? updatedAt,
  }) {
    // 参数验证
    _validateParameters(description, location, imageUrl);

    final now = DateTime.now();
    return Problem._(
      id: id ?? _uuid.v4(),
      description: description.trim(),
      location: location.trim(),
      imageUrl: imageUrl,
      createdAt: createdAt ?? now,
      updatedAt: updatedAt ?? now,
    );
  }

  // 参数验证
  static void _validateParameters(
    String description,
    String location,
    String imageUrl,
  ) {
    if (description.isEmpty) {
      throw ArgumentError('Description cannot be empty');
    }
    if (location.isEmpty) {
      throw ArgumentError('Location cannot be empty');
    }
    if (imageUrl.isEmpty) {
      throw ArgumentError('Image URL cannot be empty');
    }

    // 验证 URL 格式（简单验证）
    if (!imageUrl.startsWith('http')) {
      throw ArgumentError('Image URL must be a valid URL');
    }
  }

  // 从 JSON 反序列化
  factory Problem.fromJson(Map<String, dynamic> json) {
    return Problem(
      id: json['id'],
      description: json['description'],
      location: json['location'],
      imageUrl: json['imageUrl'],
      createdAt: json['createdAt'] != null
          ? DateTime.parse(json['createdAt'])
          : null,
      updatedAt: json['updatedAt'] != null
          ? DateTime.parse(json['updatedAt'])
          : null,
    );
  }

  // 转换为 JSON
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'description': description,
      'location': location,
      'imageUrl': imageUrl,
      'createdAt': createdAt.toIso8601String(),
      'updatedAt': updatedAt.toIso8601String(),
    };
  }

  // 复制方法
  Problem copyWith({
    String? id,
    String? description,
    String? location,
    String? imageUrl,
    DateTime? createdAt,
    DateTime? updatedAt,
  }) {
    return Problem(
      id: id ?? this.id,
      description: description ?? this.description,
      location: location ?? this.location,
      imageUrl: imageUrl ?? this.imageUrl,
      createdAt: createdAt ?? this.createdAt,
      updatedAt: updatedAt ?? DateTime.now(), // 更新时间为当前时间
    );
  }

  // 检查是否有效
  bool get isValid => description.isNotEmpty && location.isNotEmpty;

  // 获取简短描述
  String get shortDescription {
    if (description.length <= 50) return description;
    return '${description.substring(0, 47)}...';
  }

  @override
  String toString() {
    return 'Problem(id: $id, description: $shortDescription, location: $location)';
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Problem && runtimeType == other.runtimeType && id == other.id;

  @override
  int get hashCode => id.hashCode;
}