import 'dart:convert';

/// Represents an item in the shared packing list for a trip.
///
/// Each item stores a [label], completion flag [isPacked], and an optional
/// [assignee] to indicate who prend en charge l'item.
class PackingItem {
  /// Unique identifier for the packing entry.
  final String id;

  /// Text displayed in the list (ex: "Adaptateur US", "Pharmacie").
  final String label;

  /// Whether the item is already packed.
  final bool isPacked;

  /// Optional assignee (user id or name) for accountability.
  final String? assignee;

  /// Creation timestamp for ordering.
  final DateTime createdAt;

  /// Creates a packing item.
  const PackingItem({
    required this.id,
    required this.label,
    required this.isPacked,
    required this.createdAt,
    this.assignee,
  });

  /// Factory to create a new item in not-packed state.
  factory PackingItem.newItem({
    required String id,
    required String label,
    String? assignee,
  }) {
    return PackingItem(
      id: id,
      label: label,
      assignee: assignee,
      isPacked: false,
      createdAt: DateTime.now().toUtc(),
    );
  }

  /// Returns a copy with modifications.
  PackingItem copyWith({
    String? id,
    String? label,
    bool? isPacked,
    String? assignee,
    DateTime? createdAt,
  }) {
    return PackingItem(
      id: id ?? this.id,
      label: label ?? this.label,
      isPacked: isPacked ?? this.isPacked,
      assignee: assignee ?? this.assignee,
      createdAt: createdAt ?? this.createdAt,
    );
  }

  /// JSON serialization helper.
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'label': label,
      'isPacked': isPacked,
      'assignee': assignee,
      'createdAt': createdAt.toIso8601String(),
    };
  }

  /// JSON deserialization helper.
  factory PackingItem.fromJson(Map<String, dynamic> json) {
    return PackingItem(
      id: json['id'] as String,
      label: json['label'] as String,
      isPacked: json['isPacked'] as bool? ?? false,
      assignee: json['assignee'] as String?,
      createdAt: DateTime.parse(json['createdAt'] as String),
    );
  }

  /// Encodes list to JSON string.
  static String encodeList(List<PackingItem> items) {
    return json.encode(items.map((i) => i.toJson()).toList());
  }

  /// Decodes list from JSON string.
  static List<PackingItem> decodeList(String raw) {
    final decoded = json.decode(raw) as List<dynamic>;
    return decoded
        .cast<Map<String, dynamic>>()
        .map(PackingItem.fromJson)
        .toList();
  }
}