Basic communication protocol for server

pkg/analysis_server/lib/src/channel.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library channel;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'protocol.dart';
+
+/**
+ * The abstract class [CommunicationChannel] defines the behavior of objects
+ * that allow an [AnalysisServer] to receive [Request]s and to return both
+ * [Response]s and [Notification]s.
+ */
+abstract class CommunicationChannel {
+  /**
+   * Listen to the channel for requests. If a request is received, invoke the
+   * [onRequest] function. If an error is encountered while trying to read from
+   * the socket, invoke the [onError] function. If the socket is closed by the
+   * client, invoke the [onDone] function.
+   */
+  void listen(void onRequest(Request request), {void onError(), void onDone()});

[devoncarew, 2014/01/20 22:35:01]

My guess is that you want this to be a Stream. So something like:

  Stream<Request> get onRequest;

Implementations of this class would then have a StreamController field:

StreamController<Request> _controller = new StreamController.asBroadcast();
Stream<Request> get onRequest => _controller.stream;
void _add(Request request) => _controller.add(request);

[Brian Wilkerson, 2014/01/21 03:21:20]

I don't understand why that would be better. Let's talk FTF so you can explain
it to me.

+
+  /**
+   * Send the given [Response] or [Notification] to the client.
+   */
+  void send(Object value);

[devoncarew, 2014/01/20 22:35:01]

Perhaps have separate methods for the two types? You then get support from the
tools, which is good.

sendResponse(Response r)
sendNotification(Notification n)

[Brian Wilkerson, 2014/01/21 03:21:20]

I like that! Done.

+}
+
+/**
+ * Instances of the class [WebSocketChannel] implement a [CommunicationChannel]
+ * that uses a [WebSocket] to communicate with clients.
+ */
+class WebSocketChannel implements CommunicationChannel {
+  /**
+   * The socket being wrapped.
+   */
+  final WebSocket socket;
+
+  /**
+   * Initialize a newly create [WebSocket] wrapper to wrap the given [socket].
+   */
+  WebSocketChannel(this.socket);
+
+  @override
+  void listen(void onRequest(Request request), {void onError(), void onDone()}) {
+    socket.listen((data) => _readRequest(data, onRequest), onError: onError, onDone: onDone);
+  }
+
+  @override
+  void send(Object value) {
+    if (value is Response) {
+      JsonEncoder encoder = const JsonEncoder(null);
+      socket.add(encoder.convert(value.toJson()));
+    } else if (value is Notification) {
+      JsonEncoder encoder = const JsonEncoder(null);
+      socket.add(encoder.convert(value.toJson()));
+    }
+  }
+
+  /**
+   * Read a request from the given [data] and use the given function to handle
+   * the request.
+   */
+  void _readRequest(Object data, void onRequest(Request request)) {
+    if (data is List<int>) {
+      send(new Response.invalidRequestFormat());
+      return;
+    }
+    if (data is String) {
+      // Parse the string as a JSON descriptor and process the resulting
+      // structure as a request.
+      Request request = new Request.fromString(data);
+      if (request == null) {
+        send(new Response.invalidRequestFormat());
+        return;
+      }
+      onRequest(request);
+    }
+  }
+}