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RabiRiichi

RabiRiichi (兔兔立直) is a riichi mahjong engine written in C# for .NET, together with an ASP.NET server that hosts it over WebSockets.

The project is split into two independently useful pieces:

  • The Core engine (RabiRiichi.csproj) — a self-contained, headless rules engine. It knows tiles, hands, walls, yaku, scoring, and the full event flow of a hand. It has no networking and no UI; you drive it through an event queue and a small player-action interface. This is what you embed if you want to run, analyze, or bot mahjong.
  • The Server (RabiRiichi.Server) — an ASP.NET Core app that turns the engine into a multiplayer service: rooms, seats, reconnection, AI substitution, god-view replays, and a Protobuf-over-WebSocket protocol.

Who this is for​

  • Players & self-hosters — you want to play, run your own server, or host the web client. Start with the User Guide (or jump straight to Play online).
  • Engine integrators — you want to run games in-process (simulation, analysis, a custom front end). Start with the Core Engine.
  • Server / protocol developers — you want to host games, or write a client that speaks the wire protocol. Start with the Server.
  • Contributors — you're adding a yaku, fixing a rule, or writing tests. Read the Core Engine docs, then the Testing guides.

A taste of the API​

Creating and running a game is a matter of building a GameConfig, plugging in an IActionCenter (how players are asked to act), and calling Start:

var config = new GameConfig {
  playerCount = 4,
  actionCenter = myActionCenter, // decides how inquiries are answered
  seed = 1145141919810ul,        // optional: deterministic shuffles
};
var game = new Game(config);
await game.Start();               // runs the whole match to completion

Everything else — dealing, drawing, claims, scoring, dealer rotation — is driven internally by the event system.

Tile notation in these docs​

Throughout the docs, hands are drawn with real tile images generated from RabiRiichi's compact tile notation — the same notation used in the test suite. For example, 123m456p789s11z renders as:

123m456p789s11z

The full grammar (suits, red fives, called melds, concealed kan, winning tile) is described in Tile notation.

Project facts​

  • Language / runtime: C#, .NET 9.
  • License: AGPL v3.
  • Repositories: the engine + server and these docs.
  • Shared protos: wire messages live in a Protos git submodule shared with the web client, compiled at build time.