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Chess.hs
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Chess.hs
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module Chess where
import qualified Data.Map as M
import Data.List
import Logging
data Type = Pawn | Knight | Bishop | Rook | Queen | King deriving (Show, Eq)
data Color = Black | White deriving (Show, Eq)
data Piece = P Color Type deriving Eq
instance Show Piece where
show (P White Pawn ) = "♙"
show (P Black Pawn ) = "♟"
show (P White Knight) = "♘"
show (P Black Knight) = "♞"
show (P White Bishop) = "♗"
show (P Black Bishop) = "♝"
show (P White Rook ) = "♖"
show (P Black Rook ) = "♜"
show (P White Queen ) = "♕"
show (P Black Queen ) = "♛"
show (P White King ) = "♔"
show (P Black King ) = "♚"
data Col = A | B | C | D | E | F | G | H deriving Eq
type Position = (Col, Int)
type Pos_q = (Int, Int)
type Board = M.Map Pos_q Piece
data Game = Game { gBoard :: Board, gTurn :: Color , gLog :: [String]}
instance Show Game where
show (Game {gBoard = b, gTurn = t, gLog = l}) =
foldr
(\i s ->
let rank = 8-(div (i-1) 8)
index = ((mod (i-1) 8) + 1, rank)
hasPiece = M.member index b
in
if even (i + (div (i-1) 8)) then
let square = if hasPiece then (show $ b M.! index) ++ " " else "▓▓"
in
if mod i 8 == 0 then
square ++ (show rank ++ "\n") ++ s
else
square ++ s
else
let square = if hasPiece then (show $ b M.! index) ++ " " else " "
in
if mod i 8 == 0 then
square ++ (show rank ++ "\n") ++ s
else
square ++ s
) "" [1..64] ++
foldr (\i s -> (i:" ") ++ s)
"" ['a'..'h'] ++ "\n" ++ "\n" ++
foldr (\(i, e) s -> (show i) ++ "." ++ e ++ " " ++ s)
"" (zip [1..] $ reverse l)
initializeBoard :: Board
initializeBoard = M.fromList [
((1,8), P Black Rook),
((2,8), P Black Knight),
((3,8), P Black Bishop),
((4,8), P Black Queen),
((5,8), P Black King),
((6,8), P Black Bishop),
((7,8), P Black Knight),
((8,8), P Black Rook),
((1,7), P Black Pawn),
((2,7), P Black Pawn),
((3,7), P Black Pawn),
((4,7), P Black Pawn),
((5,7), P Black Pawn),
((6,7), P Black Pawn),
((7,7), P Black Pawn),
((8,7), P Black Pawn),
((1,1), P White Rook),
((2,1), P White Knight),
((3,1), P White Bishop),
((4,1), P White Queen),
((5,1), P White King),
((6,1), P White Bishop),
((7,1), P White Knight),
((8,1), P White Rook),
((1,2), P White Pawn),
((2,2), P White Pawn),
((3,2), P White Pawn),
((4,2), P White Pawn),
((5,2), P White Pawn),
((6,2), P White Pawn),
((7,2), P White Pawn),
((8,2), P White Pawn)
]
takeWhile' :: (a -> Bool) -> [a] -> [a]
takeWhile' p = foldr (\x ys -> if p x then x:ys else [x]) []
takePiece :: Board -> Pos_q -> Maybe Piece
takePiece b p = M.lookup p b
findPiece :: Board -> Piece -> Maybe Pos_q
findPiece b piece = fmap fst $ find ((==piece) . snd) $ M.toList b
move :: Position -> Position -> Game -> Game
move (c0, r0) (c1, r1) g = move' (cnum c0, r0) (cnum c1, r1) g
where cnum c = case c of A -> 1
B -> 2
C -> 3
D -> 4
E -> 5
F -> 6
G -> 7
H -> 8
move' :: Pos_q -> Pos_q -> Game -> Game
move' from to g = case (takePiece b from) of
Nothing -> Game { gBoard = b, gTurn = t, gLog = (("invalid location "++show from):l)}
Just piece ->
let (P color _) = piece in
case mconcat [ doesTurnMatch t color, validateMove b piece from to, isKingSafe b color from to] of
Ok -> Game { gBoard = makeMove b piece from to,
gTurn = if color == Black then White else Black,
gLog = genLog piece}
Fail msg -> Game { gBoard = b, gTurn = t, gLog = (msg:l)}
where
genLog p = ((show p ++ " " ++ ((['a'..'h']!!(c0-1)) : show r0) ++ ""++ show p ++ " " ++ ((['a'..'h']!!(c1-1)) : show r1) ++ ""):l)
b = gBoard g
t = gTurn g
l = gLog g
(c1, r1) = to
(c0, r0) = from
makeMove :: Board -> Piece -> Pos_q -> Pos_q -> Board
makeMove b piece from to = if isRook' b from to
then makeRookMove b piece from to
else if isEnPasse' b from to
then makeEnPasseMove b piece from to
else M.insert to piece $ M.delete from b
makeRookMove :: Board -> Piece -> Pos_q -> Pos_q -> Board
makeRookMove b (P c King) from to = undefined
makeRookMove b _ _ _ = b
makeEnPasseMove :: Board -> Piece -> Pos_q -> Pos_q -> Board
makeEnPasseMove b pawn from to = M.insert to pawn $ M.delete from $ M.delete (c1,r0) b
where (c0, r0) = from
(c1, r1) = to
doesTurnMatch :: Color -> Color -> Log
doesTurnMatch t c = mkLog (t==c) $ "not " ++ (show c) ++ "'s turn"
validateMove :: Board -> Piece -> Pos_q -> Pos_q -> Log
validateMove b (P _ Pawn) from to = mconcat [diffCheck from to, isInsideBoard to, isPawnMove b from to]
validateMove b (P _ Knight) from to = mconcat [diffCheck from to, isInsideBoard to, isLShaped from to, isFree b from to]
validateMove b (P _ Bishop) from to = mconcat [diffCheck from to, isInsideBoard to, isDiagonal from to 8, isFree b from to]
validateMove b (P _ Rook) from to = mconcat [diffCheck from to, isInsideBoard to, isStraight from to 8, isFree b from to]
validateMove b (P _ Queen) from to = mconcat [diffCheck from to, isInsideBoard to, (isStraight from to 8 <|> isDiagonal from to 8), isFree b from to]
validateMove b (P _ King) from to = mconcat [diffCheck from to, isInsideBoard to, (isStraight from to 1 <|> isDiagonal from to 1 <|> isRook b from to), isFree b from to]
diffCheck :: Pos_q -> Pos_q -> Log
diffCheck from to = mkLog (from/=to) "non-move"
isInsideBoard :: Pos_q -> Log
isInsideBoard (c,r)= mkLog (r>=1 && r<= 8 && c>=1 && c<=8) "out of the board"
isPawnMove :: Board -> Pos_q -> Pos_q -> Log
isPawnMove b (c0, r0) (c1, r1) = case takePiece b (c0,r0) of
Nothing -> Fail "empty cell"
Just (P c Pawn) -> mkLog (
(c0==c1 && r1==r0-1 && c==Black) || --regular (black)
(c0==c1 && r1==r0+1 && c==White) || --regular (white)
(c0==c1 && r0==7 && r1==5 && c==Black) || --2 rank (black)
(c0==c1 && r0==2 && r1==4 && c==White) || --2 rank (white)
(abs (c0-c1)==1 && r1==r0-1 && cpt c && c==Black) || --capture (black)
(abs (c0-c1)==1 && r1==r0+1 && cpt c && c==White) || --capture (white)
(isEnPasse' b (c0,r0) (c1, r1))
) "not a pawn move"
where
cpt color = case takePiece b (c1, r1) of
Just (P c _) -> color /= c
otherwise -> False
isStraight :: Pos_q -> Pos_q -> Int -> Log
isStraight (c0, r0) (c1,r1) span = mkLog (
(c0==c1 && foldr (\x y -> x==c1 || y) False [c0-span..c0+span]) || -- horizontal
(r0==r1 && foldr (\x y -> x==r1 || y) False [r0-span..r0+span]) -- vertical
) "this piece can only move on a straight line"
isDiagonal :: Pos_q -> Pos_q -> Int -> Log
isDiagonal (c0, r0) (c1,r1) span = mkLog (
abs (c1-c0) == abs (r1-r0) && abs (c1-c0)<=span
) "this piece can only move on a diagonal line"
isLShaped :: Pos_q -> Pos_q -> Log
isLShaped (c0, r0) (c1,r1) = mkLog (
abs (c1-c0) + abs (r1-r0) == 3
) "this piece can only move in L shape"
--special moves
isEnPasse :: Board -> Pos_q -> Pos_q -> Log
isEnPasse b from to = mkLog (isEnPasse' b from to) "invalid en passe"
isEnPasse' :: Board -> Pos_q -> Pos_q -> Bool
isEnPasse' b (c0, r0) (c1,r1) = case takePiece b (c0,r0) of
Nothing -> False
Just (P White Pawn) -> (r0==5 || r0==6) && (r1==r0+1) && (takePiece b (c1,r0))==(Just (P Black Pawn))
Just (P Black Pawn) -> (r0==3 || r0==4) && (r1==r0-1) && (takePiece b (c1,r0))==(Just (P White Pawn))
otherwise -> False
isRook :: Board -> Pos_q -> Pos_q -> Log
isRook b from to = mkLog (
isRook' b from to
) "invalid rook"
isRook' :: Board -> Pos_q -> Pos_q -> Bool
isRook' b from to = case takePiece b from of
Just (P c King) -> (nextToRook b from to) ||
(c==Black && from==(4,7)) ||
(c==White && from==(4,0)) ||
otherwise -> False
where nextToRook b f t = let next = in
isFree :: Board -> Pos_q -> Pos_q -> Log
isFree b from to = mkLog (
isFree' b from to
) "move is obstructed"
isFree' :: Board -> Pos_q -> Pos_q -> Bool
isFree' b from to = case takePiece b from of
Just (P c Pawn ) -> canMove b to c
Just (P c Knight) -> canMove b to c
Just (P c Bishop) -> diagonalCheck c && canMove b to c
Just (P c Rook ) -> straightCheck c && canMove b to c
Just (P c Queen ) -> (diagonalCheck c || straightCheck c) && canMove b to c
Just (P c King ) -> (diagonalCheck c || straightCheck c) && canMove b to c
where
(r0, c0) = from
(r1, c1) = to
difc = (c0 - c1)
dirc = if difc<0 then -1 else 1
difr = (r0 - r1)
dirr = if difr<0 then -1 else 1
canMove b pos color = case takePiece b pos of
Nothing -> True
Just (P c t) -> c /= color
straightCheck color = if r0==r1
then foldr (\i r -> r && canMove b (c0+i,r0) color) True [0,dirc..difc]
else foldr (\i r -> r && canMove b (c0,r0+i) color) True [0,dirr..difc]
diagonalCheck color = foldr (\(ic, ir) r -> r && canMove b (c0+ic, r0+ir) color) True (zip [0,dirc..difc] [0,dirr..difr])
isKingSafe :: Board -> Color -> Pos_q -> Pos_q -> Log
isKingSafe b turn from to = mkLog (
isKingSafe' b turn from to
) $ (show turn) ++ " king is not safe"
isKingSafe' :: Board -> Color -> Pos_q -> Pos_q -> Bool
isKingSafe' b turn from to = case (takePiece b from) of
Nothing -> False -- non-existent case: validateMove ensures this.
Just movingPiece -> iterDiagonal Queen myKing &&
iterStraight Queen myKing &&
iterLShaped myKing
where nb = makeMove b movingPiece from to --possible next state
myKing = findPiece nb (P turn King)
opponent = if turn == White then Black else White
iterDiagonal t (Just (c, r)) = True
iterStraight t (Just (c, r)) = and $ map ((/=(Just (P opponent t))).(takePiece nb)) $
map (\cx -> (cx,r)) (
(takeWhile' (\cx -> canMove nb (cx,r)) [(c+1)..8]) ++
(takeWhile' (\cx -> canMove nb (cx,r)) [(c-1),(c-2)..0]) ) ++
map (\rx -> (c,rx)) (
(takeWhile' (\rx -> canMove nb (c,rx)) [(r+1)..8]) ++
(takeWhile' (\rx -> canMove nb (c,rx)) [(r-1),(r-2)..0]) )
iterLShaped (Just (c, r)) = and $ map ((/=(Just (P opponent Knight))).(takePiece nb)) [(c-2,r-1), (c-2,r+1), (c+2,r-1), (c-2, r+1), (c-1,r-2), (c-1,r+2), (c+1,r-2), (c+1,r+2)]
canMove b pos = case takePiece b pos of
Nothing -> True
otherwise -> False