Architecture

Components

Transport Layer (`internal/http`)

Fiber web server handling HTTP requests/responses. Implements routing, rate limiting, content-type validation, request parsing. Translates HTTP to internal Command objects.

Processing Layer (`internal/processor`)

Central command handler containing business logic. Single Execute(Command) entry point decouples transport from logic. Uses synchronous UCI engine for validation, asynchronous EngineQueue for computer moves.

Service Layer (`internal/service`)

In-memory state storage without chess logic. Thread-safe game map protected by RWMutex. Manages game lifecycle, snapshots, and player configuration.

Supporting Modules

Engine (internal/engine): UCI protocol wrapper for Stockfish process communication
Game (internal/game): Game state with snapshot history
Board (internal/board): FEN parsing and ASCII generation
Core (internal/core): Shared types, API models, error constants

Request Flow

Human Move

HTTP handler receives POST /games/{id}/moves with UCI move
Creates MakeMoveCommand, calls processor.Execute()
Processor validates move via locked validation engine
If legal, gets new FEN from engine
Calls service.ApplyMove() to update state
Returns GameResponse

Computer Move

HTTP handler receives POST /games/{id}/moves with {"move": "cccc"}
Processor sets game state to pending
Submits task to EngineQueue, returns immediately
Worker goroutine calculates move with dedicated Stockfish instance
Callback updates game state via service
Client polls for completion

Concurrency

HTTP Server: Fiber handles concurrent connections
Game State: Single RWMutex protects game map (concurrent reads, serial writes)
Engine Workers: Fixed pool (2 workers) with dedicated Stockfish processes
Validation Engine: Single mutex-protected instance for synchronous validation

Data Structures

Game Snapshot

type Snapshot struct {
    FEN           string
    PreviousMove  string
    NextTurnColor Color
    PlayerID      string
}

Command Pattern

Commands encapsulate operations with type and arguments, processed by single Execute method.

Player Configuration

Players identified by UUID, configured with type (human/computer), skill level, and search time.

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