♟️ ChessKit

A Swift package for efficiently implementing chess logic.

For a related Swift package that contains chess engines such as Stockfish, see chesskit-engine.

Usage

1. Add chesskit-swift as a dependency
   • In an app built in Xcode,
   • or as a dependency to another Swift Package.

.package(url: "https://github.com/chesskit-app/chesskit-swift", from: "0.7.0")

2. Next, import ChessKit to use it in Swift code:

import ChessKit

// ...

Features

• Representation of chess elements
  • Piece
  • Square
  • Move
  • Position
  • Board
  • Clock
  • Game
  • Special moves (castling, en passant)
• Move validation
  • Implemented using highly performant UInt64 bitboards.
• Pawn promotion handling
• Game states (check, stalemate, checkmate, etc.)
• Chess notation string parsing
  • PGN
  • FEN
  • SAN

Examples

• Create a board with the standard starting position:

let board = Board()

• Create a board with a custom starting position using FEN:

if let position = Position(fen: "rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2") {
    let board = Board(position: position)
    print(board)
}

// 8 ♜ ♞ ♝ ♛ ♚ ♝ ♞ ♜
// 7 ♟ ♟ · ♟ ♟ ♟ ♟ ♟
// 6 · · · · · · · ·
// 5 · · ♟ · · · · ·
// 4 · · · · ♙ · · ·
// 3 · · · · · ♘ · ·
// 2 ♙ ♙ ♙ ♙ · ♙ ♙ ♙
// 1 ♖ ♘ ♗ ♕ ♔ ♗ · ♖
//   a b c d e f g h
//
// (see `ChessKitConfiguration` for printing options)

• Move pieces on the board

let board = Board()
board.move(pieceAt: .e2, to: .e4)           // move pawn at e2 to e4

• Check move legality

let board = Board()
print(board.canMove(pieceAt: .a1, to: .a8)) // false

• Check legal moves

let board = Board()
print(board.legalMoves(forPieceAt: .e2))    // [.e3, .e4]

• Parse FEN into a Position object

// parse FEN using Position initializer
let fen = "rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2"
let position = Position(fen: fen)

// convert Position to FEN string
let fenString = position.fen

• Similarly, parse PGN (into Game) or SAN (into Move).

// parse PGN using Game initializer
let game = Game(pgn: "1. e4 e5 2. Nf3")

// convert Game to PGN string
let pgnString = game.pgn

// parse the move text "e4" from the starting position
let move = Move(san: "e4", in: .standard)

// convert Move to SAN string
let sanString = move.san

License

ChessKit is distributed under the MIT License.