add a middleware manager based on socket.

Author: front-thinking

middlewareManager.js

@@ -0,0 +1,55 @@
+/*
+* A middleware Manager based on socket.
+* */
+"use strict";
+
+
+module.exports = class ZmqMiddlewareManager {
+    constructor(socket) {
+        this.socket = socket;
+        this.inboundMiddleware = [];           //[1]
+        this.outboundMiddleware = [];
+        socket.on('message', message => {       //[2]
+            this.executeMiddleware(this.inboundMiddleware, {
+                data: message
+            });
+        });
+    }
+
+    send(data) {
+        const message = {
+            data: data
+        };
+
+        this.executeMiddleware(this.outboundMiddleware, message,
+            () => {
+                this.socket.send(message.data);
+            }
+        );
+    }
+
+    use(middleware) {
+        if (middleware.inbound) {
+            this.inboundMiddleware.push(middleware.inbound);
+        }
+        if (middleware.outbound) {
+            this.outboundMiddleware.unshift(middleware.outbound);
+        }
+    }
+
+    executeMiddleware(middleware, arg, finish) {
+        function iterator(index) {
+            if (index === middleware.length) {
+                return finish && finish();
+            }
+            middleware[index].call(this, arg, err => {
+                if (err) {
+                    return console.log('There was an error: ' + err.message);
+                }
+                iterator.call(this, ++index);
+            });
+        }
+
+        iterator.call(this, 0);
+    }
+};