FEN.hs

-- |
-- Module      :  Chess.FEN
-- Copyright   :  Miika-Petteri Matikainen 2014
-- License     :  GPL-2
--
-- Maintainer  :  miikapetteri@gmail.com
-- Stability   :  experimental
-- Portability :  unknown
--
-- Parsing chess games from FEN notation
-- (https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notation).
module Chess.FEN (writeFEN, readFEN) where

import Chess.Internal.Move
import Chess.Internal.FEN

-- | Write the current game state as FEN notation
writeFEN :: GameState -> String
writeFEN state = unwords [writeBoard (stateBoard state),
                          writePlayer (currentPlayer state),
                          writeCastlings (whiteCastlingsPossible state) (blackCastlingsPossible state),
                          writeEnPassant (enPassantSquare state),
                          show (halfmoveClock state),
                          show (moveNumber state)]

-- | Parse game state from FEN notation
readFEN :: String -> Maybe GameState
readFEN str | length parts /= 6 = Nothing
            | otherwise = do board' <- readBoard $ head parts
                             player <- readPlayer $ parts !! 1
                             castlings <- readCastlings $ parts !! 2
                             enPassant <- readEnPassant $ parts !! 3
                             halfmoves <- readNumberWithLimit 0 $ parts !! 4
                             moves <- readNumberWithLimit 1 $ parts !! 5
                             return $ uncurry (State board' player) castlings enPassant halfmoves moves
        where parts = words str