ovladisluvv/haskell-chess-2026

Purpose and Runtime

A desktop, local-hotseat chess game with optional built-in AI. It runs as a Haskell executable using Gloss for 2D/OpenGL graphics and loads bitmap piece sprites at runtime from assets/pieces/. The build/package definition is haskell-chess.cabal and package.yaml; Stack is the expected development runtime.

Application Entry and Game Loop

app/Main.hs is the executable entry point and delegates application startup to src/Lib.hs. The library establishes the Gloss-driven application loop: render the current game/UI state, accept input events, and transition state over time. This is an in-process desktop application; there is no server, persistence layer, or network service.

Core Domain State

src/Types.hs defines the shared chess and UI model: board/piece representation, colors, moves, game status, history, and likely menu/promotion/selection state. It is the contract between rules, AI, rendering, and event handling. src/Board.hs owns initial-position construction, board updates, coordinate conversion, and board-oriented utilities.

Move Generation and Rules Boundary

src/Moves.hs generates candidate movements by piece type. src/Rules.hs is the authoritative legality and game-resolution layer: it filters candidates against king safety and applies chess-specific state transitions, including castling, en passant, promotion, check/checkmate, stalemate, repetition, fifty-move, and insufficient-material outcomes. UI and bot decisions should cross this boundary through legal moves rather than directly mutating board state.

Bot Decision Stage

src/Bot.hs consumes legal game positions and selects a move for computer-controlled turns. Its architecture is minimax search with alpha-beta pruning at depth 4, using material and piece-square-table evaluation, including endgame-aware king evaluation. Bot execution is coordinated by the main state/event flow, rather than a separate process or external AI service.

Input, UI State, and Rendering

src/Events.hs translates Gloss mouse and keyboard events into state transitions: menu selection, board-square selection, move attempts, promotion choices, reset/menu navigation, and undo behavior. It invokes the rules and bot stages as appropriate. src/Render.hs converts current state into Gloss pictures: chessboard, sprites, legal-move/check highlights, captured pieces, history, controls, menus, promotion overlay, and terminal-game displays. Sprite resources are assets/pieces/wk.bmp, assets/pieces/bk.bmp, and peer piece files.

Primary Control Flow

Startup initializes resources and menu/game state (app/Main.hs → src/Lib.hs). Menu events choose PvP or bot mode; gameplay events select a source and destination, request legal validation/application from src/Rules.hs, then update history/status. In bot mode, a completed human turn triggers src/Bot.hs, whose selected legal move returns through the same rules/state-update path. Every resulting state is rendered by src/Render.hs; undo restores prior state and may account for an AI response.

Delivery

Release automation is defined in .github/workflows/release.yml. Released binaries must be distributed with or retain access to the runtime bitmap assets under assets/pieces/.