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

import 'dart:convert';
import 'package:crypto/crypto.dart';

/// Represents a Nostr keypair (private and public keys).
class NostrKeyPair {
  /// Private key in hex format (32 bytes, 64 hex characters).
  final String privateKey;

  /// Public key in hex format (32 bytes, 64 hex characters).
  final String publicKey;

  /// Creates a [NostrKeyPair] with the provided keys.
  /// 
  /// [privateKey] - Private key in hex format.
  /// [publicKey] - Public key in hex format.
  NostrKeyPair({
    required this.privateKey,
    required this.publicKey,
  });

  /// Generates a new Nostr keypair.
  /// 
  /// Returns a new [NostrKeyPair] with random private and public keys.
  factory NostrKeyPair.generate() {
    // Generate random 32-byte private key
    final random = List<int>.generate(32, (i) => DateTime.now().microsecondsSinceEpoch % 256);
    final privateKeyBytes = sha256.convert(utf8.encode(DateTime.now().toString() + random.toString())).bytes.sublist(0, 32);
    final privateKey = privateKeyBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();

    // Derive public key from private key (simplified - in real Nostr, use secp256k1)
    final publicKeyBytes = sha256.convert(privateKeyBytes).bytes.sublist(0, 32);
    final publicKey = publicKeyBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();

    return NostrKeyPair(
      privateKey: privateKey,
      publicKey: publicKey,
    );
  }

  /// Creates a [NostrKeyPair] from a JSON map.
  factory NostrKeyPair.fromJson(Map<String, dynamic> json) {
    return NostrKeyPair(
      privateKey: json['privateKey'] as String,
      publicKey: json['publicKey'] as String,
    );
  }

  /// Converts the [NostrKeyPair] to a JSON map.
  Map<String, dynamic> toJson() {
    return {
      'privateKey': privateKey,
      'publicKey': publicKey,
    };
  }

  @override
  String toString() {
    return 'NostrKeyPair(publicKey: ${publicKey.substring(0, 8)}...)';
  }
}