import 'dart:convert';

/// Represents a document attached to a trip (billet, passeport, assurance, etc.).
///
/// The model stores a human-friendly [title], a [category] to filter in the UI,
/// an optional [downloadUrl] when the file is hosted remotely, and an optional
/// [expiresAt] date for reminders (ex: passeport ou ESTA).
class TripDocument {
  /// Unique identifier for the document entry.
  final String id;

  /// Display name chosen by the user (ex: « Billet retour AF763 »).
  final String title;

  /// Type/category (ex: `billet`, `passeport`, `assurance`, `hebergement`).
  final String category;

  /// Optional URL to open/download the document (cloud storage or external).
  final String? downloadUrl;

  /// Optional local file path when offline-only; kept for future sync.
  final String? localPath;

  /// Optional expiration date to trigger reminders.
  final DateTime? expiresAt;

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

  /// Creates a trip document entry.
  const TripDocument({
    required this.id,
    required this.title,
    required this.category,
    required this.createdAt,
    this.downloadUrl,
    this.localPath,
    this.expiresAt,
  });

  /// Builds a new entry with defaults.
  factory TripDocument.newEntry({
    required String id,
    required String title,
    required String category,
    String? downloadUrl,
    String? localPath,
    DateTime? expiresAt,
  }) {
    return TripDocument(
      id: id,
      title: title,
      category: category,
      downloadUrl: downloadUrl,
      localPath: localPath,
      expiresAt: expiresAt,
      createdAt: DateTime.now().toUtc(),
    );
  }

  /// Returns a copy with updated fields.
  TripDocument copyWith({
    String? id,
    String? title,
    String? category,
    String? downloadUrl,
    String? localPath,
    DateTime? expiresAt,
    DateTime? createdAt,
  }) {
    return TripDocument(
      id: id ?? this.id,
      title: title ?? this.title,
      category: category ?? this.category,
      downloadUrl: downloadUrl ?? this.downloadUrl,
      localPath: localPath ?? this.localPath,
      expiresAt: expiresAt ?? this.expiresAt,
      createdAt: createdAt ?? this.createdAt,
    );
  }

  /// Serializes the entry to JSON for persistence.
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'title': title,
      'category': category,
      'downloadUrl': downloadUrl,
      'localPath': localPath,
      'expiresAt': expiresAt?.toIso8601String(),
      'createdAt': createdAt.toIso8601String(),
    };
  }

  /// Deserializes a trip document from JSON.
  factory TripDocument.fromJson(Map<String, dynamic> json) {
    return TripDocument(
      id: json['id'] as String,
      title: json['title'] as String,
      category: json['category'] as String,
      downloadUrl: json['downloadUrl'] as String?,
      localPath: json['localPath'] as String?,
      expiresAt: json['expiresAt'] != null
          ? DateTime.tryParse(json['expiresAt'] as String)
          : null,
      createdAt: DateTime.parse(json['createdAt'] as String),
    );
  }

  /// Encodes a list of documents to a JSON string.
  static String encodeList(List<TripDocument> docs) {
    return json.encode(docs.map((d) => d.toJson()).toList());
  }

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