app-boilerplate/lib/data/nostr/models/nostr_event.dart

import 'package:nostr_tools/nostr_tools.dart';

/// Represents a Nostr event.
class NostrEvent {
  /// Event ID (32-byte hex string).
  final String id;

  /// Public key of the event creator (pubkey).
  final String pubkey;

  /// Unix timestamp in seconds.
  final int createdAt;

  /// Event kind (integer).
  final int kind;

  /// Event tags (array of arrays).
  final List<List<String>> tags;

  /// Event content (string).
  final String content;

  /// Event signature (64-byte hex string).
  final String sig;

  /// Event API instance for event operations.
  static final _eventApi = EventApi();
  static final _keyApi = KeyApi();

  /// Creates a [NostrEvent] with the provided values.
  NostrEvent({
    required this.id,
    required this.pubkey,
    required this.createdAt,
    required this.kind,
    required this.tags,
    required this.content,
    required this.sig,
  });

  /// Creates a [NostrEvent] from a JSON array (Nostr event format).
  factory NostrEvent.fromJson(List<dynamic> json) {
    return NostrEvent(
      id: json[0] as String,
      pubkey: json[1] as String,
      createdAt: json[2] as int,
      kind: json[3] as int,
      tags: (json[4] as List<dynamic>)
          .map((tag) => (tag as List<dynamic>).map((e) => e.toString()).toList())
          .toList(),
      content: json[5] as String,
      sig: json[6] as String,
    );
  }

  /// Creates a [NostrEvent] from a nostr_tools Event object.
  factory NostrEvent.fromNostrToolsEvent(Event event) {
    return NostrEvent(
      id: event.id,
      pubkey: event.pubkey,
      createdAt: event.created_at,
      kind: event.kind,
      tags: event.tags,
      content: event.content,
      sig: event.sig,
    );
  }

  /// Converts this [NostrEvent] to a nostr_tools Event object.
  Event toNostrToolsEvent() {
    return Event(
      id: id,
      pubkey: pubkey,
      created_at: createdAt,
      kind: kind,
      tags: tags,
      content: content,
      sig: sig,
      verify: false, // Already verified if coming from our model
    );
  }

  /// Converts the [NostrEvent] to a JSON array (Nostr event format).
  List<dynamic> toJson() {
    return [
      id,
      pubkey,
      createdAt,
      kind,
      tags,
      content,
      sig,
    ];
  }

  /// Creates an event from content and signs it with a private key using nostr_tools.
  /// 
  /// [content] - Event content.
  /// [kind] - Event kind (default: 1 for text note).
  /// [privateKey] - Private key in hex format for signing.
  /// [tags] - Optional tags for the event.
  factory NostrEvent.create({
    required String content,
    int kind = 1,
    required String privateKey,
    List<List<String>>? tags,
  }) {
    // Get public key from private key using nostr_tools
    final pubkey = _keyApi.getPublicKey(privateKey);
    
    final createdAt = DateTime.now().millisecondsSinceEpoch ~/ 1000;
    final eventTags = tags ?? [];

    // Create event using nostr_tools Event model
    final event = Event(
      kind: kind,
      tags: eventTags,
      content: content,
      created_at: createdAt,
      pubkey: pubkey,
      verify: false, // We'll sign it next
    );

    // Get event hash (ID) using nostr_tools
    event.id = _eventApi.getEventHash(event);

    // Sign the event using nostr_tools
    event.sig = _eventApi.signEvent(event, privateKey);

    // Convert to our NostrEvent model
    return NostrEvent.fromNostrToolsEvent(event);
  }

  /// Verifies the event signature using nostr_tools.
  /// 
  /// Returns true if the signature is valid, false otherwise.
  bool verifySignature() {
    try {
      final event = toNostrToolsEvent();
      return _eventApi.verifySignature(event);
    } catch (e) {
      return false;
    }
  }

  @override
  String toString() {
    return 'NostrEvent(id: ${id.substring(0, 8)}..., kind: $kind, content: ${content.substring(0, content.length > 20 ? 20 : content.length)}...)';
  }
}