basic nostr actors

lib/src/nostr_fetch_actor.dart

@@ -0,0 +1,102 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:math';
+import 'package:actors/actors.dart';
+import 'relay_connection.dart';
+
+sealed class FetchMessage {
+  const FetchMessage();
+}
+
+final class FetchEvents extends FetchMessage {
+  final String filter;
+  const FetchEvents(this.filter);
+}
+
+sealed class FetchResult {
+  const FetchResult();
+}
+
+final class EventsFetched extends FetchResult {
+  final List<String> events;
+  const EventsFetched(this.events);
+}
+
+class NostrFetchActor with Handler<FetchMessage, FetchResult> {
+  final List<String> _relayUrls;
+  final Duration _eoseDeadline;
+  final RelayConnection Function(String url) _connectionFactory;
+
+  NostrFetchActor({
+    required List<String> relayUrls,
+    Duration eoseDeadline = const Duration(seconds: 5),
+    RelayConnection Function(String url) connectionFactory =
+        WebSocketRelayConnection.new,
+  })  : _relayUrls = relayUrls,
+        _eoseDeadline = eoseDeadline,
+        _connectionFactory = connectionFactory;
+
+  @override
+  Future<FetchResult> handle(FetchMessage message) => switch (message) {
+        FetchEvents(:final filter) => _fetchEvents(filter),
+      };
+
+  Future<FetchResult> _fetchEvents(String filter) async {
+    final results = await Future.wait(
+      _relayUrls.map(
+        (url) => _fetchFromRelay(url, filter).catchError((_) => <String>[]),
+      ),
+    );
+    final seen = <String>{};
+    final merged = <String>[];
+    for (final batch in results) {
+      for (final eventJson in batch) {
+        final id =
+            (jsonDecode(eventJson) as Map<String, dynamic>)['id'] as String;
+        if (seen.add(id)) {
+          merged.add(eventJson);
+        }
+      }
+    }
+    return EventsFetched(merged);
+  }
+
+  Future<List<String>> _fetchFromRelay(String url, String filter) async {
+    final rng = Random();
+    final subId = List.generate(
+      32,
+      (_) => rng.nextInt(16).toRadixString(16),
+    ).join();
+
+    final conn = _connectionFactory(url);
+    final collected = <String>[];
+
+    try {
+      await conn.connect();
+      await conn.send(jsonEncode(['REQ', subId, jsonDecode(filter)]));
+      try {
+        await for (final raw in conn.messages.timeout(_eoseDeadline)) {
+          try {
+            final list = jsonDecode(raw) as List;
+            if (list[0] == 'EVENT') {
+              collected.add(jsonEncode(list[2]));
+            } else if (list[0] == 'EOSE') {
+              break;
+            }
+          } catch (_) {
+            // malformed message, skip
+          }
+        }
+      } on TimeoutException {
+        // return whatever was collected so far
+      }
+    } finally {
+      try {
+        await conn.send(jsonEncode(['CLOSE', subId]));
+      } catch (_) {}
+      await conn.close();
+    }
+
+    return collected;
+  }
+}

lib/src/nostr_publish_actor.dart

@@ -0,0 +1,144 @@
+import 'dart:async';
+import 'dart:convert';
+import 'package:actors/actors.dart';
+import 'package:retry/retry.dart';
+import 'relay_connection.dart';
+
+final class RetryConfig {
+  final int maxAttempts;
+  final Duration baseDelay;
+  final Duration maxDelay;
+  final bool jitter;
+  const RetryConfig({
+    this.maxAttempts = 3,
+    this.baseDelay = const Duration(seconds: 1),
+    this.maxDelay = const Duration(seconds: 32),
+    this.jitter = true,
+  });
+}
+
+sealed class RelayOutcome {
+  const RelayOutcome();
+}
+
+final class RelayConfirmed extends RelayOutcome {
+  const RelayConfirmed();
+}
+
+final class RelayRejected extends RelayOutcome {
+  final String reason;
+  const RelayRejected(this.reason);
+}
+
+final class RelayFailed extends RelayOutcome {
+  const RelayFailed();
+}
+
+sealed class PublishMessage {
+  const PublishMessage();
+}
+
+final class PublishBatch extends PublishMessage {
+  final List<String> events;
+  const PublishBatch(this.events);
+}
+
+sealed class PublishResult {
+  const PublishResult();
+}
+
+final class BatchPublished extends PublishResult {
+  final Map<String, RelayOutcome> outcomes;
+  const BatchPublished(this.outcomes);
+}
+
+final class _RelayRejectedException implements Exception {
+  final String reason;
+  const _RelayRejectedException(this.reason);
+}
+
+class NostrPublishActor with Handler<PublishMessage, PublishResult> {
+  final List<String> _relayUrls;
+  final RetryConfig _retryConfig;
+  final Duration _batchTimeout;
+  final RelayConnection Function(String url) _connectionFactory;
+
+  NostrPublishActor({
+    required List<String> relayUrls,
+    RetryConfig retryConfig = const RetryConfig(),
+    Duration batchTimeout = const Duration(seconds: 10),
+    RelayConnection Function(String url) connectionFactory =
+        WebSocketRelayConnection.new,
+  })  : _relayUrls = relayUrls,
+        _retryConfig = retryConfig,
+        _batchTimeout = batchTimeout,
+        _connectionFactory = connectionFactory;
+
+  @override
+  Future<PublishResult> handle(PublishMessage message) => switch (message) {
+        PublishBatch(:final events) => _publishBatch(events),
+      };
+
+  Future<PublishResult> _publishBatch(List<String> events) async {
+    final ids = events
+        .map((e) => (jsonDecode(e) as Map<String, dynamic>)['id'] as String)
+        .toList();
+    final outcomes = await Future.wait(
+      _relayUrls.map((url) => _publishToRelay(url, events, ids)),
+    );
+    return BatchPublished(Map.fromIterables(_relayUrls, outcomes));
+  }
+
+  Future<RelayOutcome> _publishToRelay(
+    String url,
+    List<String> events,
+    List<String> ids,
+  ) async {
+    try {
+      await retry(
+        () => _attemptPublish(url, events, ids),
+        retryIf: (e) => e is! _RelayRejectedException,
+        maxAttempts: _retryConfig.maxAttempts,
+        delayFactor: _retryConfig.baseDelay,
+        maxDelay: _retryConfig.maxDelay,
+        randomizationFactor: _retryConfig.jitter ? 0.25 : 0.0,
+      );
+      return const RelayConfirmed();
+    } on _RelayRejectedException catch (e) {
+      return RelayRejected(e.reason);
+    } catch (_) {
+      return const RelayFailed();
+    }
+  }
+
+  Future<void> _attemptPublish(
+    String url,
+    List<String> events,
+    List<String> ids,
+  ) async {
+    final conn = _connectionFactory(url);
+    final pending = {...ids};
+    try {
+      await conn.connect();
+      for (final e in events) {
+        await conn.send(jsonEncode(['EVENT', jsonDecode(e)]));
+      }
+      await for (final raw in conn.messages.timeout(_batchTimeout)) {
+        try {
+          final list = jsonDecode(raw) as List;
+          if (list[0] != 'OK') continue;
+          if (list[2] == false) {
+            throw _RelayRejectedException(list[3] as String);
+          }
+          pending.remove(list[1] as String);
+          if (pending.isEmpty) break;
+        } catch (e) {
+          if (e is _RelayRejectedException) rethrow;
+          // malformed message, skip
+        }
+      }
+    } finally {
+      await conn.close();
+    }
+  }
+}

lib/src/nostr_signer_actor.dart

@@ -0,0 +1,85 @@
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:actors/actors.dart';
+import 'package:bip340/bip340.dart' as bip340;
+import 'package:crypto/crypto.dart';
+
+sealed class SignerMessage {
+  const SignerMessage();
+}
+
+final class SignEvent extends SignerMessage {
+  final int kind;
+  final List<List<String>> tags;
+  final String content;
+  final int? createdAt;
+  const SignEvent({
+    required this.kind,
+    this.tags = const [],
+    required this.content,
+    this.createdAt,
+  });
+}
+
+final class GetPublicKey extends SignerMessage {
+  const GetPublicKey();
+}
+
+sealed class SignerResult {
+  const SignerResult();
+}
+
+final class EventSigned extends SignerResult {
+  final String event;
+  const EventSigned(this.event);
+}
+
+final class PublicKeyResult extends SignerResult {
+  final String publicKey;
+  const PublicKeyResult(this.publicKey);
+}
+
+class NostrSignerActor with Handler<SignerMessage, SignerResult> {
+  final String _privateKey;
+  final String _publicKey;
+
+  NostrSignerActor(String privateKey)
+      : _privateKey = privateKey,
+        _publicKey = bip340.getPublicKey(privateKey);
+
+  @override
+  Future<SignerResult> handle(SignerMessage message) => switch (message) {
+        SignEvent(:final kind, :final tags, :final content, :final createdAt) =>
+          Future.value(_signEvent(kind, tags, content, createdAt)),
+        GetPublicKey() => Future.value(PublicKeyResult(_publicKey)),
+      };
+
+  EventSigned _signEvent(
+    int kind,
+    List<List<String>> tags,
+    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 auxBytes = List.generate(32, (_) => rng.nextInt(256));
+    final aux = auxBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+
+    final sig = bip340.sign(_privateKey, id, aux);
+
+    return EventSigned(jsonEncode({
+      'id': id,
+      'pubkey': _publicKey,
+      'created_at': ts,
+      'kind': kind,
+      'tags': tags,
+      'content': content,
+      'sig': sig,
+    }));
+  }
+}

lib/src/relay_connection.dart

@@ -0,0 +1,42 @@
+import 'dart:async';
+import 'package:web_socket_channel/web_socket_channel.dart';
+
+abstract interface class RelayConnection {
+  Future<void> connect();
+  Future<void> send(String message);
+  Stream<String> get messages;
+  Future<void> close();
+}
+
+final class WebSocketRelayConnection implements RelayConnection {
+  final String _url;
+  WebSocketChannel? _channel;
+  StreamController<String>? _controller;
+
+  WebSocketRelayConnection(String url) : _url = url;
+
+  @override
+  Future<void> connect() async {
+    _channel = WebSocketChannel.connect(Uri.parse(_url));
+    await _channel!.ready;
+    _controller = StreamController<String>();
+    _channel!.stream.cast<String>().listen(
+          _controller!.add,
+          onError: _controller!.addError,
+          onDone: _controller!.close,
+        );
+  }
+
+  @override
+  Future<void> send(String message) async => _channel!.sink.add(message);
+
+  @override
+  Stream<String> get messages => _controller!.stream;
+
+  @override
+  Future<void> close() async {
+    await _channel?.sink.close();
+    _channel = null;
+    _controller = null;
+  }
+}

lib/swarm.dart

@@ -1 +1,5 @@
 export 'src/file_actor.dart';
+export 'src/relay_connection.dart';
+export 'src/nostr_publish_actor.dart';
+export 'src/nostr_fetch_actor.dart';
+export 'src/nostr_signer_actor.dart';