import 'dart:convert';

/// Represents a dated reminder or to-do for the trip.
class ReminderItem {
  /// Unique identifier.
  final String id;

  /// Text to display.
  final String title;

  /// Optional detailed note.
  final String? note;

  /// Due date/time (UTC) for the reminder.
  final DateTime dueAt;

  /// Completion flag.
  final bool isDone;

  /// Creation timestamp.
  final DateTime createdAt;

  /// Creates a reminder item.
  const ReminderItem({
    required this.id,
    required this.title,
    required this.dueAt,
    required this.isDone,
    required this.createdAt,
    this.note,
  });

  /// Convenience builder for new pending reminder.
  factory ReminderItem.newItem({
    required String id,
    required String title,
    required DateTime dueAt,
    String? note,
  }) {
    return ReminderItem(
      id: id,
      title: title,
      note: note,
      dueAt: dueAt,
      isDone: false,
      createdAt: DateTime.now().toUtc(),
    );
  }

  /// Copy with changes.
  ReminderItem copyWith({
    String? id,
    String? title,
    String? note,
    DateTime? dueAt,
    bool? isDone,
    DateTime? createdAt,
  }) {
    return ReminderItem(
      id: id ?? this.id,
      title: title ?? this.title,
      note: note ?? this.note,
      dueAt: dueAt ?? this.dueAt,
      isDone: isDone ?? this.isDone,
      createdAt: createdAt ?? this.createdAt,
    );
  }

  /// JSON serialization.
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'title': title,
      'note': note,
      'dueAt': dueAt.toIso8601String(),
      'isDone': isDone,
      'createdAt': createdAt.toIso8601String(),
    };
  }

  /// JSON deserialization.
  factory ReminderItem.fromJson(Map<String, dynamic> json) {
    return ReminderItem(
      id: json['id'] as String,
      title: json['title'] as String,
      note: json['note'] as String?,
      dueAt: DateTime.parse(json['dueAt'] as String),
      isDone: json['isDone'] as bool? ?? false,
      createdAt: DateTime.parse(json['createdAt'] as String),
    );
  }

  /// Encodes list.
  static String encodeList(List<ReminderItem> reminders) {
    return json.encode(reminders.map((r) => r.toJson()).toList());
  }

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