Refactor the original NodeManager class

This patch splits the NodeManager into ResourceProvider and
SubscriptionManager.

- ResourceProvider will provide the functions of creating/destroying the
  publisher/subscription/client/service, and manage the handles used within
  the same bridge(websockets connection).
- SubscriptionManager will hold all subscription handles used by different
  bridges(websockets connection), because we may share a subscription
  across bridges.

Each instance of Bridge(connection) owns a
ResourceProvider and all instances of ResourceProvider share a
SubscriptionManager.

Also the patch extracts the handle class to a separate RefCountingHandle class.

Author: Minggang Wang

index.js

@@ -16,7 +16,6 @@
 
 const rclnodejs = require('rclnodejs');
 const {Server} = require('ws');
-const NodeManager = require('./lib/node_manager.js');
 const Bridge = require('./lib/bridge.js');
 const debug = require('debug')('ros2-web-bridge:index');
 
@@ -27,7 +26,6 @@ function createServer(options) {
 
   return rclnodejs.init().then(() => {
     let node = rclnodejs.createNode('ros2_web_bridge');
-    let nodeManager = new NodeManager(node);
     let bridgeMap = new Map();
 
     function closeAllBridges() {
@@ -37,7 +35,7 @@ function createServer(options) {
     }
 
     server.on('connection', (ws) => {
-      let bridge = new Bridge(nodeManager, ws);
+      let bridge = new Bridge(node, ws);
       bridgeMap.set(bridge.bridgeId, bridge);
 
       bridge.on('error', (error) => {

lib/bridge.js

@@ -15,6 +15,7 @@
 'use strict';
 
 const rclnodejs = require('rclnodejs');
+const ResourceProvider = require('./resource_provider.js');
 const debug = require('debug')('ros2-web-bridge:Bridge');
 const EventEmitter = require('events');
 const uuidv4 = require('uuid/v4');
@@ -64,17 +65,15 @@ class MessageParser {
 }
 
 class Bridge extends EventEmitter {
-  constructor(nodeManager, ws) {
+  constructor(node, ws) {
     super();
-    this._nodeManager = nodeManager;
     this._ws = ws;
     this._parser = new MessageParser();
     this._bridgeId = this._generateRandomId();
     this._servicesResponse = new Map();
     this._closed = false;
-
+    this._resourceProvider = new ResourceProvider(node, this._bridgeId);
     this._registerConnectionEvent(ws);
-
     this._rebuildOpMap();
   }
 
@@ -98,7 +97,7 @@ class Bridge extends EventEmitter {
 
   close() {
     if (!this._closed) {
-      this._nodeManager.cleanResourceByBridgeId(this._bridgeId);
+      this._resourceProvider.clean();
       this._servicesResponse.clear();
       this._closed = true;
     }
@@ -146,18 +145,18 @@ class Bridge extends EventEmitter {
   _rebuildOpMap() {
     this._registerOpMap('advertise', (command) => {
       debug(`advertise a topic: ${command.topic}`);
-      this._nodeManager.createPublisher(this._exractMessageType(command.type), command.topic, this._bridgeId);
+      this._resourceProvider.createPublisher(this._exractMessageType(command.type), command.topic);
     });
 
     this._registerOpMap('unadvertise', (command) => {
       debug(`unadvertise a topic: ${command.topic}`);
-      this._nodeManager.destroyPublisher(command.topic, this._bridgeId);
+      this._resourceProvider.destroyPublisher(command.topic);
     });
 
     this._registerOpMap('publish', (command) => {
       debug(`Publish a topic named ${command.topic} with ${JSON.stringify(command.msg)}`);
 
-      let publisher = this._nodeManager.getPublisherByTopic(command.topic, this._bridgeId);
+      let publisher = this._resourceProvider.getPublisherByTopicName(command.topic);
       if (publisher) {
         publisher.publish(command.msg);
       }
@@ -166,21 +165,20 @@ class Bridge extends EventEmitter {
     this._registerOpMap('subscribe', (command) => {
       debug(`subscribe a topic named ${command.topic}`);
 
-      this._nodeManager.createSubscription(this._exractMessageType(command.type),
-                                           command.topic,
-                                           this._bridgeId,
-                                           this._sendSubscriptionResponse.bind(this));
+      this._resourceProvider.createSubscription(this._exractMessageType(command.type),
+                                                command.topic,
+                                                this._sendSubscriptionResponse.bind(this));
     });
 
     this._registerOpMap('unsubscribe', (command) => {
       debug(`unsubscribe a topic named ${command.topic}`);
-      this._nodeManager.destroySubscription(command.topic, this._bridgeId);
+      this._resourceProvider.destroySubscription(command.topic);
     });
 
     this._registerOpMap('call_service', (command) => {
       let serviceName = command.service;
       let client =
-        this._nodeManager.createClient(this._exractServiceType(command.args.type), serviceName, this._bridgeId);
+        this._resourceProvider.createClient(this._exractServiceType(command.args.type), serviceName);
 
       if (client) {
         client.sendRequest(command.args.request, (response) => {
@@ -194,9 +192,9 @@ class Bridge extends EventEmitter {
 
     this._registerOpMap('advertise_service', (command) => {
       let serviceName = command.service;
-      let service = this._nodeManager.createService(
+      let service = this._resourceProvider.createService(
         this._exractServiceType(command.type),
-        serviceName, this._bridgeId,
+        serviceName,
         (request, response) => {
           let id = this._generateRandomId();
           let serviceRequest = {op: 'call_service', service: command.service, args: request, id: id};