import System.IO

main = play [1,2,3,4,5] ["Player 1","Player 2"]

play :: [Int] -> [String] -> IO ()
play board players = do
    (newBoard,winner) <- takeTurns board players
    if null winner
      then play newBoard players
      else do putStrLn (winner ++ " won!")
              return ()

takeTurns :: [Int] -> [String] -> IO ([Int],String)
takeTurns board [] = return (board,[])
takeTurns board (player:players) = do
    newBoard <- takeTurn board player
    if sum newBoard == 0
      then return (newBoard,player)
      else takeTurns newBoard players

takeTurn :: [Int] -> String -> IO [Int]
takeTurn board player = do
    putStrLn ("\n" ++ player ++ "'s Turn")
    displayBoard board
    row <- getRow board
    count <- getInt "How many stars? " 1 (board!!row)
    return $ take row board ++ [board!!row - count] ++ drop (row+1) board

displayBoard :: [Int] -> IO ()
displayBoard [] = return ()
displayBoard board = do
    putStrLn $ show (length board) ++ " : " ++ replicate (last board) '*'
    displayBoard (init board)

getRow :: [Int] -> IO Int
getRow board = do
    row <- getInt "Which row? " 1 (length board)
    if board!!(row-1) == 0
      then do putStrLn "That row is empty!"
              getRow board
      else return (row-1)

getInt msg min max = do
    putStr msg
    input <- getLine
    let parsed = reads input :: [(Int,String)]
    if null parsed
      then badNumber "That's not a number!"
      else testNumber (fst (head parsed))
    where
        badNumber error = do putStrLn error
                             getInt msg min max
        testNumber number
            | number < min = badNumber "That number is too small."
            | number > max = badNumber "That number is too big."
            | otherwise = do return number