WebSocket client for VM service

runtime/bin/vmservice/message.dart

+// Copyright (c) 2013, 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.
+
+part of vmservice;
+
+class Message {
+  final Completer _completer = new Completer.sync();
+  bool get completed => _completer.isCompleted;
+  Future get future => _completer.future;

[turnidge, 2013/12/11 17:56:07]

I found myself looking for a less generic name here than 'future'.  I guess what
this is, is a a future for the response.  Perhaps responseFuture is too
long-winded.  Would it be misleading or wrong to call it 'response'?

Thinking out loud a bit.

[Cutch, 2013/12/12 22:37:42]

I think we can do this:

Future<String> response;

+  /// Path.
+  final List<String> path = new List<String>();
+  /// Options.
+  final Map<String, String> options = new Map<String, String>();
+
+  Message.fromUri(Uri uri) {
+    var split = uri.path.split('/');
+    if (split.length == 0) {
+      setErrorResponse('Invalid uri: $uri.');
+      return;
+    }
+    for (int i = 0; i < split.length; i++) {
+      var pathSegment = split[i];
+      if (pathSegment == '') {

[turnidge, 2013/12/11 17:56:07]

Does uri parsing often yield these empty path segments?  Do we need to edit out
empty segments in the fromMap constructor?

[Cutch, 2013/12/12 22:37:42]

Splitting the path on '/' yields many empty strings. If the path is "/foo/" the
result of the split is ['', 'foo', '']. I want the messages delivered to C++
code to be as easy to deal with as possible. 

Good point about the fromMap constructor, I will be sure to remove any empties
there.

+        continue;
+      }
+      path.add(pathSegment);
+    }
+    options.addAll(uri.queryParameters);
+  }
+
+  Message.fromMap(Map map) {
+    if (map['path'] != null) {
+      path.addAll(map['path']);
+    }
+    if (map['options'] != null) {
+      options.addAll(map['options']);
+    }
+  }
+
+  Map toJson() {
+    return {
+      'path': path,
+      'options': options
+    };
+  }
+
+  Future send(SendPort sendPort) {

[turnidge, 2013/12/11 17:56:07]

What do you think of making this return Future<String>?  If you agree, this
might apply to the caller of send, declaration of "future", etc.

[Cutch, 2013/12/12 22:37:42]

Done.

+    final receivePort = new RawReceivePort();
+    receivePort.handler = (value) {
+      receivePort.close();
+      if (value is Exception) {
+        _completer.completeError(value);
+      } else {
+        _completer.complete(value);
+      }
+    };
+    var keys = options.keys.toList();
+    var values = options.values.toList();
+    var request = [path, keys, values];
+    sendServiceMessage(sendPort, receivePort, request);
+    return _completer.future;
+  }
+
+  void setResponse(String response) {
+    _completer.complete(response);
+  }
+
+  void setErrorResponse(String error) {
+    _completer.complete(JSON.encode({
+        'type': 'Error',
+        'msg': error,
+        'path': path,
+        'options': options
+    }));
+  }
+}