code review

lib/src/nostr_event.dart

@@ -0,0 +1,36 @@
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:bip340/bip340.dart' as bip340;
+import 'package:crypto/crypto.dart';
+
+String signNostrEvent({
+  required String privateKey,
+  required String publicKey,
+  required int kind,
+  required List<List<String>> tags,
+  required String content,
+  int? createdAt,
+}) {
+  final ts = createdAt ?? DateTime.now().millisecondsSinceEpoch ~/ 1000;
+  final ser = jsonEncode([0, publicKey, ts, kind, tags, content]);
+  final idBytes = sha256.convert(utf8.encode(ser)).bytes;
+  final id = idBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+
+  final rng = Random.secure();
+  final aux = List.generate(32, (_) => rng.nextInt(256))
+      .map((b) => b.toRadixString(16).padLeft(2, '0'))
+      .join();
+
+  final sig = bip340.sign(privateKey, id, aux);
+
+  return jsonEncode({
+    'id': id,
+    'pubkey': publicKey,
+    'created_at': ts,
+    'kind': kind,
+    'tags': tags,
+    'content': content,
+    'sig': sig,
+  });
+}