make require('engine.io')() return a new Server instance

fixes #212

README.md

@@ -120,6 +120,30 @@ These are exposed by `require('engine.io')`:
 
 ##### Methods
 
+- `()`
+    - Returns a new `Server` instance. If the first argument is an `http.Server` then the
+      new `Server` instance will be attached to it. Otherwise, the arguments are passed
+      directly to the `Server` constructor.
+    - **Parameters**
+      - `http.Server`: optional, server to attach to.
+      - `Object`: optional, options object (see `Server#constructor` api docs below)
+
+  The following are identical ways to instantiate a server and then attach it.
+  ```js
+  var httpServer; // previously created with `http.createServer();` from node.js api.
+
+  // create a server first, and then attach
+  var eioServer = require('engine.io').Server();
+  eioServer.attach(httpServer);
+
+  // or call the module as a function to get `Server`
+  var eioServer = require('engine.io')();
+  eioServer.attach(httpServer);
+
+  // immediately attach
+  var eioServer = require('engine.io')(http_server);
+  ```
+
 - `listen`
     - Creates an `http.Server` which listens on the given port and attaches WS
       to it. It returns `501 Not Implemented` for regular http requests.

lib/engine.io.js

@@ -5,16 +5,27 @@
 var http = require('http');
 
 /**
- * Invoking the library as a function delegates to attach
+ * Invoking the library as a function delegates to attach if the first argument
+ * is an `http.Server`.
  *
- * @param {http.Server} server
+ * If there are no arguments or the first argument is an options object, then
+ * a new Server instance is returned.
+ *
+ * @param {http.Server} server (if specified, will be attached to by the new Server instance)
  * @param {Object} options
  * @return {Server} engine server
  * @api public
  */
 
 exports = module.exports = function() {
-  return attach.apply(this, arguments);
+  // backwards compatible use as `.attach`
+  // if first argument is an http server
+  if (arguments.length && arguments[0] instanceof http.Server) {
+    return attach.apply(this, arguments);
+  }
+
+  // if first argument is not an http server, then just make a regular eio server
+  return exports.Server.apply(null, arguments);
 };
 
 /**

lib/server.js

@@ -28,6 +28,10 @@ module.exports = Server;
  */
 
 function Server(opts){
+  if (!(this instanceof Server)) {
+    return new Server(opts);
+  }
+
   this.clients = {};
   this.clientsCount = 0;
 

test/engine.io.js

@@ -26,6 +26,13 @@ describe('engine', function () {
     expect(version).to.be(require('engine.io-client/package').version);
   });
 
+  describe('engine()', function () {
+    it('should create a Server when require called with no arguments', function () {
+      var engine = eio();
+      expect(engine).to.be.an(eio.Server);
+    });
+  });
+
   describe('listen', function () {
     it('should open a http server that returns 501', function (done) {
       var server = listen(function (port) {