basic nostr actors

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;
+  }
+}