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SUM Developement Guide

This is a short introduction in the architecture of SUM. This guide is for all who plan to enhance or change SUM.

SUM uses nw.js as environment, jquery for the frontend, node for the backend. Ensure that you understand the basics of this frameworks.


For running SUM in development mode, building SUM executable or building setup, you have to install following tools:

  1. install node.js
  2. npm install nw -g installs node webkit which is a webkit browser with build in node
  3. npm install grunt-cli -g installs the build tool grunt
  4. npm install in SUM folder install all development dependencies
  5. if you plan to build a setup then install InnoSetup and add it to your path environment variable


After doing basic setup you can run, build and test SUM. Open your command line and change into the SUM directory.

  • nw starts SUM
  • grunt build compiles SUM executable
  • grunt check runs tests and jshint
  • grunt version --newversion=1.2.3 updates the version information in package.json, setup.iss and
  • grunt tests SUM, compiles the SUM executable and builds the setup
  • grunt --newversion=1.2.3 updates version information, tests SUM, compiles the SUM executable and builds the setup


For defining classes I use John Resigs little classes script. Currently there is no inheritance in SUM but its nice to have this option and I like how classes are defined. You can find this in libs/class.js

This shows, how Johns class definition will be used:

var Person = Class.extend({
  init: function(isDancing){
    this.dancing = isDancing;
var Ninja = Person.extend({
  init: function(){
    this._super( false );
var p = new Person(true);
p.dancing; // => true
var n = new Ninja();
n.dancing; // => false

Dependency Injection

I use a simple self made dependency injection script for creating instances of classes. The value injected('classname') of a object property will be replaced with an instance of the given class. The dependency injection script is defined in libs/injector.js

Following example shows how you can use di:

define('oneclass', function() { = 'bar';

define('anotherclass', function() {
    this.oneclass = injected('oneclass');

var anotherclass = inject('anotherclass');; // 'bar'


SUM consists of two parts:

frontend knows backend, but backend doesn't know frontend

  • frontend: this handels all UI events, and showing any new messages and data coming from backend
  • backend: this handels chat communication, updating the userlist and encryption

The frontend knows the backend and uses the backend (only the sum-backend class). Backend doesn't know and call the frontend. The frontend registers a few callbacks at backend, which will be called for backend events as receiving new messages or informing the frontend about a new user which is now online.


The frontend consits of following parts:

sums frontend

  • sum-frontend the basic entry point which initialize the frontend. This class refreshes the userlist, roomlist and conversation view. Frontend will always repaint the whole user and roomlist.
  • sum-frontend-events defines all event handler on ui events (like button click handler, menue clicks, ...). It calls directly the backend (e.g. sends a message).
  • sum-frontend-command handles any command input like /exit or /reload in the message input field
  • sum-frontend-messages renders the single messages, depending on the message type (text message, code message, file invite, ...)
  • sum-frontend-helpers holds a few helpers for formatting or popup creation or any other simple repeating thing

Basic page layout is defined in index.html and main.css.


The Backend has a few helper classes:

sums frontend

  • sum-backend-client execute HTTP requests
  • sum-backend-crypto encryption and decryption
  • sum-backend-filesystem any filesystem operation
  • sum-backend-helpers static helpers for sorting lists, search in lists, ...
  • sum-backend-storage saves and loads from local storage

List of all users

For finding other users SUM supports two userfile types: on filesystem (sum-backend-userlist-file) or using a little backend.php script (sum-backend-userlist-web):

sums frontend

SUM updates the current user periodicaly with an updated timestamp and removes timedout users from list. A second file per user holds rarely updated informations as avatar, ip and the public key.


For receiving messages from other users and sending files SUM starts an server (sum-backend-server). This server receives the messages of other users, validates them, and updates the backend and informs the frontend (using the callbacks which was registered at the backend on application startup).

sums frontend

login, config, language

In sum-init.js the application shows the login screen (if key management is activated), parses the config.ini and reads the current language file.