Expose a new semi-public ddp.eventInterface API

This new API allows apps that need to monitor DDP events to do so without having to worry about the underlying DDP instance or websocket changing

lib/ddp.js

@@ -1,14 +1,12 @@
-/**
- * DDP.JS 2.1.0
- */
-
 import EventEmitter from 'wolfy87-eventemitter';
 import Queue from './queue';
 import Socket from './socket';
 import { uniqueId } from './utils';
 
 const DDP_VERSION = '1';
 const PUBLIC_EVENTS = [
+  'connected',
+  'disconnected',
   // Subscription messages
   'ready',
   'nosub',
@@ -23,13 +21,54 @@ const PUBLIC_EVENTS = [
 ];
 const DEFAULT_RECONNECT_INTERVAL = 10000;
 
+class EventInterface {
+   constructor() {
+     this.listeners = {};
+     PUBLIC_EVENTS.forEach(eventName => {
+       this.listeners[eventName] = {};
+     });
+   }
+
+   activate(ddp) {
+     this.ddp = ddp;
+     PUBLIC_EVENTS.forEach(eventName => {
+       this.ddp.addListener(eventName, event => {
+         this._handleEvent(eventName, event);
+       });
+     });
+   }
+
+   _handleEvent(eventName, event) {
+     for(let func of Object.values(this.listeners[eventName])) {
+       try {
+         func(event);
+       }
+       catch(e) {
+         console.error("@meteorrn/core failed to call DDP event handler for " + eventName, e);
+       }
+     }
+   }
+
+   on(eventName, func) {
+     const id = Math.random()+"";
+     if(!this.listeners[eventName]) throw new Error(`Unsupported event name "${eventName}"`);
+     this.listeners[eventName][id] = func;
+     return {remove:() => delete this.listeners[eventName][id]};
+   }
+}
+
+const eventInterface = new EventInterface();
+
 export default class DDP extends EventEmitter {
   emit() {
     setTimeout(super.emit.bind(this, ...arguments), 0);
   }
 
   constructor(options) {
     super();
+
+    this.eventInterface = eventInterface;
+    eventInterface.activate(this);
 
     this.status = 'disconnected';