Server: begin a server documentation

support/doc/server/code.md

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+# Server code documentation
+
+The server is a web server developed with [NodeJS](https://nodejs.org)/[Express](http://expressjs.com).
+
+
+## Technologies
+
+  * [NodeJS](https://nodejs.org) -> Language
+  * [MongoDB](https://www.mongodb.com/) -> Database
+  * [Express](http://expressjs.com) -> Web server framework
+  * [Mongoose](http://mongoosejs.com/) -> MongoDB object modeling
+  * [WebTorrent](https://webtorrent.io/) -> BitTorrent over WebRTC
+  * [Electron](http://electron.atom.io/) -> To make WebRTC inside NodeJS
+  * [Mocha](https://mochajs.org/) -> Test framework
+
+
+## Files
+
+The server main file is [server.js](https://github.com/Chocobozzz/PeerTube/blob/master/server.js).
+The server modules description are in the [package.json](https://github.com/Chocobozzz/PeerTube/blob/master/package.json) at the project root.
+All other server files are in the [server](https://github.com/Chocobozzz/PeerTube/tree/master/server) directory:
+
+    server.js -> app initilization, main routes configuration (static routes...)
+    config    -> server YAML configurations (for tests, production...)
+    scripts   -> Scripts files for npm run
+    server
+    |__ controllers  -> API routes/controllers files
+    |__ helpers      -> functions used by different part of the project (logger, utils...)
+    |__ initializers -> functions used at the server startup (installer, database, constants...)
+    |__ lib          -> library function (WebTorrent, OAuth2, friends logic...)
+    |__ middlewares  -> middlewares for controllers (requests validators, requests pagination...)
+    |__ models       -> Mongoose models for each MongoDB collection (videos, users, pods...)
+    |__ tests        -> API tests and real world simulations (to test the decentralized feature...)
+
+
+## Conventions
+
+Uses [JavaScript Standard Style](http://standardjs.com/).
+
+
+## Developing
+
+  * Install [the dependencies](https://github.com/Chocobozzz/PeerTube#dependencies)
+  * Run `npm install` at the root directory to install all the dependencies
+  * Run MongoDB
+  * Run `npm run dev` to compile the client and automatically run the server. If the client files are already compiled you can simply run `NODE_ENV=test node server`
+
+The `NODE_ENV=test` is set to speed up communications between pods (see [constants.js](https://github.com/Chocobozzz/PeerTube/blob/master/server/initializers/constants.js#L71)).
+
+`npm run help` give you all available commands.
+
+If you want to test the decentralization feature, you can easily run 3 pods by runnin `npm run play`. The pods password are `test1`, `test2` and `test3`.
+
+
+## Architecture
+
+The server is composed by:
+
+  * a REST API
+  * a WebTorrent Tracker
+  * A separate Electron process
+
+The seperate Electron process has the goal to seed videos through WebRTC because WebRTC directly in NodeJS is not usable for now.
+
+![Architecture scheme](https://github.com/Chocobozzz/PeerTube/blob/master/support/doc/server/upload-video.png)
+
+When an user upload a video, the rest API asks the Electron process to seed it (communicate with IPC) and then adds it to its Mongo database.
+
+If an user wants to watch the video, the tracker will indicate all other users that are watching the video + the Electron process.
+
+## Newcomers
+
+The server entrypoint is [server.js](https://github.com/Chocobozzz/PeerTube/blob/master/server.js). You can begin to look at this file.
+Then you can try to understand the [controllers](https://github.com/Chocobozzz/PeerTube/tree/master/server/controllers): they are the entrypoint of each API request.