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

third_party/WebKit/Source/devtools/front_end/services/ServiceManager.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.
+
+/**
+ * @constructor
+ */
+WebInspector.ServiceManager = function()
+{
+    this._lastId = 1;
+    /** @type {!Map<number, function(?Object)>}*/
+    this._callbacks = new Map();
+    /** @type {!Map<string, !WebInspector.ServiceManager.Service>}*/
+    this._services = new Map();
+}
+
+WebInspector.ServiceManager.prototype = {
+    /**
+     * @param {string} serviceName
+     * @return {!Promise<?WebInspector.ServiceManager.Service>}
+     */
+    lookupService: function(serviceName)

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

I'd say lookupService would return existing instance if any. This is more of
createService.

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

Done.

+    {
+        return this._sendCommand(serviceName + ".create").then(result => {
+            if (!result)
+                return null;

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

This is not compiled, because jscompiler requires null to be cast to ?T when it
does compile it.

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

It did compile though :)

+            var service = new WebInspector.ServiceManager.Service(this, serviceName, result.id);
+            this._services.set(serviceName + ":" + result.id, service);
+            return service;
+        });
+    },
+
+    /**
+     * @param {string} method
+     * @param {!Object=} params
+     * @return {!Promise<?Object>}
+     */
+    _sendCommand: function(method, params)
+    {
+        var id = this._lastId++;
+        var message = JSON.stringify({id: id, method: method, params: params || {}});
+        this._connect().then(() => this._socket ? this._socket.send(message) : this._callbacks.get(id)(null));
+        return new Promise(fulfill => this._callbacks.set(id, fulfill));
+    },
+
+    /**
+     * @return {!Promise}
+     */
+    _connect: function()
+    {
+        var url = Runtime.queryParam("service-backend");
+        if (!url) {
+            console.error("No endpoint address specified");
+            return Promise.resolve(null);
+        }
+
+        if (!this._connectionPromise)
+            this._connectionPromise = new Promise(promiseBody.bind(this));
+        return this._connectionPromise;
+
+        /**
+         * @param {function()} fulfill
+         * @param {function()} reject
+         * @this {WebInspector.ServiceManager}
+         */
+        function promiseBody(fulfill, reject)
+        {
+            var socket = new WebSocket(/** @type {string} */(url));
+            socket.onmessage = this._onMessage.bind(this);
+            socket.onopen = this._connectionOpened.bind(this, socket, fulfill);
+            socket.onclose = this._connectionClosed.bind(this);
+            socket.onerror = console.error.bind(console);
+        }
+    },
+
+    /**
+     * @param {!MessageEvent} message
+     */
+    _onMessage: function(message)
+    {
+        var data = /** @type {string} */ (message.data);
+        var object = JSON.parse(data);

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

try catch this

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

Done.

+        if (object.id) {
+            if (object.error)
+                console.error("Service error: " + object.error);
+            this._callbacks.get(object.id)(object.error ? null : object.result);
+            this._callbacks.delete(object.id);
+            return;
+        }
+
+        var tokens = object.method.split(".");
+        var serviceName = tokens[0];
+        var methodName = tokens[1];
+        var service = this._services.get(serviceName + ":" + object.params.id);
+        if (!service) {
+            console.error("Unable to lookup stub for " + serviceName + ":" + object.params.id);
+            return;
+        }
+        service._dispatchNotification(methodName, object.params);
+    },
+
+    /**
+     * @param {!WebSocket} socket
+     * @param {function()} callback
+     */
+    _connectionOpened: function(socket, callback)
+    {
+        this._socket = socket;
+        callback();
+    },
+
+    _connectionClosed: function()
+    {
+        for (var callback of this._callbacks.values())
+            callback(null);
+        this._callbacks.clear();
+        for (var service of this._services.values())
+            service._dispatchNotification("disposed");
+        this._services.clear();
+        delete this._connectionPromise;
+    }
+}
+
+/**
+ * @constructor
+ * @param {!WebInspector.ServiceManager} manager
+ * @param {string} serviceName
+ * @param {string} objectId
+ */
+WebInspector.ServiceManager.Service = function(manager, serviceName, objectId)
+{
+    this._manager = manager;
+    this._serviceName = serviceName;
+    this._objectId = objectId;
+    /** @type {!Map<string, function(!Object=)>}*/
+    this._notificationHandlers = new Map();
+}
+
+WebInspector.ServiceManager.Service.prototype = {
+    /**
+     * @return {!Promise}
+     */
+    dispose: function()
+    {
+        var params = { id: this._objectId };
+        this._manager._services.delete(this._serviceName + ":" + this._objectId);
+        return this._manager._sendCommand(this._serviceName + ".dispose", params);
+    },
+
+    /**
+     * @param {string} methodName
+     * @param {function(!Object=)} handler
+     */
+    on: function(methodName, handler)
+    {
+        this._notificationHandlers.set(methodName, handler);
+    },
+
+    /**
+     * @param {string} methodName
+     * @param {!Object=} params
+     * @return {!Promise}
+     */
+    send: function(methodName, params)
+    {
+        params = params || {};
+        params.id = this._objectId;
+        return this._manager._sendCommand(this._serviceName + "." + methodName, params);
+    },
+
+    /**
+     * @param {string} methodName
+     * @param {!Object=} params
+     */
+    _dispatchNotification: function(methodName, params)
+    {
+        var handler = this._notificationHandlers.get(methodName);
+        if (!handler) {
+            console.error("Could not report notification '" + methodName + "' on '" + this._objectId + "'");
+            return;
+        }
+        handler(params);
+    }
+}
+
+WebInspector.serviceManager = new WebInspector.ServiceManager();

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

Let's make it lazy instance().

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

It is lazy along with its module.