Pokemon Showdown architecture
=============================

At the highest level, PS is split into three parts:

- Client
- Login server
- Game server

The game server is in this repository, **[smogon/pokemon-showdown](https://github.com/smogon/pokemon-showdown)**, while the client and login server are in **[smogon/pokemon-showdown-client](https://github.com/smogon/pokemon-showdown-client)**. All three communicate directly with each other.


Game server
-----------

The game server is written in TypeScript and runs on Node.js.

Its entry point is [server/index.ts](./server/index.ts), which launches several major components:

- [server/sockets.ts](./server/sockets.ts) sets up a SockJS (abstracted WebSocket) server to accept connections from clients

- [server/users.ts](./server/users.ts) sets up `Users`, which wraps the SockJS connections in a system that handles users

- [server/rooms.ts](./server/rooms.ts) sets up `Rooms`, which handles the individual chat rooms and battle rooms

- [server/chat.ts](./server/chat.ts) sets up `Chat`, which handles chat commands and messages coming in from users (all client-to-server commands are routed through there)

`Rooms` also includes support for battle rooms, which is where the game simulation itself is done. Game simulation code is in [sim/](./sim/).


Client
------

The client is built in a mix of TypeScript and JavaScript, with a mostly hand-rolled framework built on Backbone. There’s a rewrite to migrate it to Preact but it’s very stalled.

Its entry point is [index.template.html](https://github.com/smogon/pokemon-showdown-client/blob/master/index.template.html).

It was written long ago, so instead of a single JS entry point, it includes a lot of JS files. Everything important is launched from [js/client.js](https://github.com/smogon/pokemon-showdown-client/blob/master/js/client.js).


Login server
------------

The client’s login server, which handles logins and most database interaction, is written in PHP, with a rewrite to TypeScript in progress. The backend is split between a MySQL InnoDB database and a Percona database, with a migration to Postgres planned.

Its entry point is [action.php](https://github.com/smogon/pokemon-showdown-client/blob/master/action.php).