DevTools: enable front-end to use external services for additional capabilities.

third_party/WebKit/Source/devtools/backend/dispatcher.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var http = require("http");
+var ws = require("ws");
+
+function Dispatcher()
+{
+    this._constructors = new Map();
+    this._objects = new Map();
+    this._lastObjectId = 1;
+}
+
+Dispatcher.prototype = {
+    start: function(port)

[dgozman, 2016/09/27 21:01:34]

Should we adopt JSDoc here for future?

[pfeldman, 2016/09/27 21:48:59]

We could, but it would not compiler requires above anyways...

+    {
+        var http_server = http.createServer();
+        http_server.listen(port);
+
+        var WebSocketServer = ws.Server;
+        var options = { server: http_server, path: "/endpoint" };
+        var wss = new WebSocketServer(options);
+        wss.on("connection", (socket) => {
+            this._socket = socket;
+            this._socket.on("message", this._dispatchMessage.bind(this));
+            this._socket.on("close", this._connectionClosed.bind(this));
+        });
+    },
+
+    registerObject: function(name, constructor)
+    {
+        this._constructors.set(name, constructor);
+    },
+
+    _dispatchMessageWrapped: function(data)

[dgozman, 2016/09/27 21:01:34]

Unused.

[pfeldman, 2016/09/27 21:48:59]

Done.

+    {
+        try {
+            this._dispatchMessage(data);
+        } catch(e) {
+            console.error(e);
+        }
+    },
+
+    _dispatchMessage: function(data)
+    {
+        var message = JSON.parse(data);
+        var [objectName, method] = message.method.split(".");
+        var result = JSON.stringify({id: message.id});
+        var constructor = this._constructors.get(objectName);
+        if (!constructor) {
+            this._sendErrorResponse(message.id, "Could not resolve service '" + objectName + "'");
+            return;
+        }
+        if (method === "create") {
+            var id = String(this._lastObjectId++);
+            var object = new constructor();
+            this._objects.set(id, object);
+            object.setNotify(this._notify.bind(this, id, objectName));

[dgozman, 2016/09/27 21:01:34]

Maybe just pass notify in constructor?

[pfeldman, 2016/09/27 21:48:59]

Done.

+            this._sendResponse(message.id, { id: id });
+        } else if (method === "dispose") {
+            var object = this._objects.get(message.params.id);
+            if (!object) {
+                console.error("Could not look up object with id for " + data);
+                return;
+            }
+            this._objects.delete(message.params.id);
+            object.dispose().then(() => this._sendResponse(message.id));
+        } else {
+            if (!message.params) {
+                console.error("No params in the message: " + data);
+                return;
+            }
+            var object = this._objects.get(message.params.id);
+            if (!object) {
+                console.error("Could not look up object with id for " + data);
+                return;
+            }
+            var handler = object[method];
+            if (!(handler instanceof Function)) {
+                console.error("Handler for '" + method + "' is missing.");
+                return;
+            }
+            object[method](message.params).then(result => this._sendResponse(message.id, result));

[dgozman, 2016/09/27 21:01:34]

Let's catch calls into object and send error response.

[pfeldman, 2016/09/27 21:48:59]

Done.

+        }
+    },
+
+    _connectionClosed: function()
+    {
+        for (var object of this._objects.values())
+            object.dispose();
+        this._objects.clear();
+    },
+
+    _notify: function(objectId, objectName, method, params)
+    {
+        params["id"] = objectId;
+        var message = { method: objectName + "." + method, params: params };
+        this._socket.send(JSON.stringify(message));
+    },
+
+    _sendResponse: function(messageId, result)
+    {
+        var message = { id: messageId, result: result };
+        this._socket.send(JSON.stringify(message));
+    },
+
+    _sendErrorResponse: function(messageId, error)
+    {
+        var message = { id: messageId, error: error };
+        this._socket.send(JSON.stringify(message));
+    },
+}
+
+exports.Dispatcher = Dispatcher;