-- | This module defines the HFiaR monad and all the actions you can perform in it module HFiaR ( -- * MonadTrans controls HFiaRT, play, eval, -- * Monad controls HFiaR, justPlay, justEval, -- * Types Game, Player(..), Tile(..), HFiaRError(..), HFiaRResult(..), -- * Actions dropIn, player, board, result ) where import Control.Monad.State -- | Posible errors in the HFiaR Monad data HFiaRError = GameEnded | GameNotEnded | InvalidColumn | FullColumn deriving (Eq) instance Show HFiaRError where show GameEnded = "Game ended" show GameNotEnded = "Game is on course yet" show InvalidColumn = "That column doesn't exist" show FullColumn = "That column is full" -- | Posible tiles (just green or red ones) data Tile = Red | Green deriving (Eq, Show) -- | Posible players (each one with his tile colour) data Player = Pl {tiles :: Tile} deriving (Eq) instance Show Player where show (Pl t) = show t -- | Posible results for the game data HFiaRResult = Tie | WonBy Player deriving (Eq, Show) -- | Game description data Game = OnCourse {gamePlayer :: Player, gameBoard :: [[Tile]]} | Ended {gameResult :: HFiaRResult, gameBoard :: [[Tile]]} deriving (Eq, Show) -- | Generic HFiaRT type newtype HFiaRT m a = HFT {state :: StateT Game m a} deriving (Monad, MonadIO, MonadTrans) instance Monad m => MonadState Game (HFiaRT m) where get = HFT $ get put = HFT . put -- | Basic HFiaR type - ready to /just/ play HFiaR actions type HFiaR = HFiaRT Maybe -- | Starts a game, run the /HFiaRT/ actions and returns the game justPlay :: HFiaR a -> Game justPlay actions = let Just r = play actions in r -- | Starts a game, run the /HFiaRT/ actions and returns the result of the last one justEval :: HFiaR a -> a justEval actions = let Just r = eval actions in r -- | Starts a game, run the /HFiaRT/ actions and returns the game wrapped up in the /m/ monad play :: Monad m => HFiaRT m a -> m Game play actions = (state actions) `execStateT` (OnCourse (Pl Green) (replicate 7 [])) -- | Starts a game, run the /HFiaRT/ actions and returns the result of the last one wrapped up in the /m/ monad eval :: Monad m => HFiaRT m a -> m a eval actions = (state actions) `evalStateT` (OnCourse (Pl Green) (replicate 7 [])) -------------------------------------------------------------------------------- -- | Drop a tile in a column dropIn :: Monad m => Int -- ^ Column number -> HFiaRT m (Either HFiaRError ()) dropIn c | c < 0 = return $ Left InvalidColumn | 6 < c = return $ Left InvalidColumn | otherwise = do game <- get case game of Ended{} -> return $ Left GameEnded OnCourse{gameBoard = board, gamePlayer= player} -> if length (board !! c) == 7 then return $ Left FullColumn else let newBoard = insertAt c (tiles player) board newResult= if (isWinner c player newBoard) then WonBy player else Tie newGame = if (full newBoard || (newResult == WonBy player)) then Ended{gameResult = newResult, gameBoard = newBoard} else OnCourse{gameBoard = newBoard, gamePlayer= otherPlayer player} in put newGame >>= return . Right where insertAt :: Int -> a -> [[a]] -> [[a]] insertAt i x xss = (take i xss) ++ ( (x : (xss !! i)) : drop (i+1) xss) otherPlayer :: Player -> Player otherPlayer Pl{tiles=Green} = Pl Red otherPlayer Pl{tiles=Red} = Pl Green full :: [[a]] -> Bool full = all (\x -> 7 == length x) isWinner :: Int -> Player -> [[Tile]] -> Bool isWinner c Pl{tiles=p} b = let col = b !! c in ([p,p,p,p] == take 4 col) || fourIn (getRow (length col - 1) b) || fourIn (getDiagUpRight c (length col - 1) b) || fourIn (getDiagUpLeft c (length col - 1) b) getRow :: Int -> [[Tile]] -> [Maybe Tile] getRow r = map (cell r) getDiagUpRight :: Int -> Int -> [[Tile]] -> [Maybe Tile] getDiagUpRight c r xss = map (\i -> cell (i+r-c) (xss !! i)) [0..6] getDiagUpLeft :: Int -> Int -> [[Tile]] -> [Maybe Tile] getDiagUpLeft c r xss = map (\i -> cell (r+c-i) (xss !! i)) [0..6] cell :: Int -> [Tile] -> Maybe Tile cell c xs = if (c >= 0 && c < length xs) then Just $ (reverse xs) !! c else Nothing fourIn :: [Maybe Tile] -> Bool fourIn [] = False fourIn (Nothing:xs) = fourIn xs fourIn (Just p :xs) = ([Just p, Just p, Just p] == take 3 xs) || fourIn xs -- | Player who's supposed to play the next tile player :: Monad m => HFiaRT m (Either HFiaRError Player) player = get >>= \game -> return $ case game of Ended{} -> Left GameEnded OnCourse{gamePlayer = p} -> Right p -- | Current board distribution board :: Monad m => HFiaRT m [[Tile]] board = get >>= return . gameBoard -- | If the game ended, returns the result of it result :: Monad m => HFiaRT m (Either HFiaRError HFiaRResult) result = get >>= \game -> return $ case game of OnCourse{} -> Left GameNotEnded Ended{gameResult = r} -> Right r