import 'dart:convert';

/// Represents a shared photo entry in the trip album.
///
/// Stores a remote [url], optional [caption], and the uploader identifier for
/// basic attribution. Persistence is local/offline via JSON helpers.
class AlbumPhoto {
  /// Unique identifier for the photo entry.
  final String id;

  /// Public or signed URL of the photo.
  final String url;

  /// Optional caption provided by the user.
  final String? caption;

  /// Name or ID of the uploader for display.
  final String? uploadedBy;

  /// Creation timestamp.
  final DateTime createdAt;

  /// Creates an album photo.
  const AlbumPhoto({
    required this.id,
    required this.url,
    required this.createdAt,
    this.caption,
    this.uploadedBy,
  });

  /// Convenience builder for a new entry.
  factory AlbumPhoto.newPhoto({
    required String id,
    required String url,
    String? caption,
    String? uploadedBy,
  }) {
    return AlbumPhoto(
      id: id,
      url: url,
      caption: caption,
      uploadedBy: uploadedBy,
      createdAt: DateTime.now().toUtc(),
    );
  }

  /// Copy with updates.
  AlbumPhoto copyWith({
    String? id,
    String? url,
    String? caption,
    String? uploadedBy,
    DateTime? createdAt,
  }) {
    return AlbumPhoto(
      id: id ?? this.id,
      url: url ?? this.url,
      caption: caption ?? this.caption,
      uploadedBy: uploadedBy ?? this.uploadedBy,
      createdAt: createdAt ?? this.createdAt,
    );
  }

  /// Serialize to JSON.
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'url': url,
      'caption': caption,
      'uploadedBy': uploadedBy,
      'createdAt': createdAt.toIso8601String(),
    };
  }

  /// Deserialize from JSON.
  factory AlbumPhoto.fromJson(Map<String, dynamic> json) {
    return AlbumPhoto(
      id: json['id'] as String,
      url: json['url'] as String,
      caption: json['caption'] as String?,
      uploadedBy: json['uploadedBy'] as String?,
      createdAt: DateTime.parse(json['createdAt'] as String),
    );
  }

  /// Encode list to string.
  static String encodeList(List<AlbumPhoto> photos) {
    return json.encode(photos.map((p) => p.toJson()).toList());
  }

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