module Nim where

import Random (randomRIO)

wins :: Int-> Maybe Int
wins n = 
  if m == 0 then Nothing else Just m where 
     m = (n- 1) `mod` 4

play :: Int-> IO ()
play n = 
  do putStrLn ("Der Haufen enthält "++ show n ++
               " Hölzchen.")
     if n== 1 then putStrLn "Ich habe gewonnen!" 
       else
         do m<- getInput
            case wins (n-m) of 
              Nothing -> putStrLn "Ich gebe auf."
              Just l  -> do putStrLn ("Ich nehme " 
                                      ++ show l)
                            play (n-(m+l))

getInput' :: IO Int
getInput' = 
  do putStr "Wieviele nehmen Sie? "
     n <- do s<- getLine 
             return (read s)
     if n<= 0 || n>3 then 
       do putStrLn "Ungültige Eingabe!" 
          getInput'
       else return n    

getInput :: IO Int
getInput = 
  do putStr "Wieviele nehmen Sie? "
     n <- catch (do s<- getLine
                    readIO s)
                (\_ -> do putStrLn "Eingabefehler!" 
                          getInput)
     if n<= 0 || n>3 then 
       do putStrLn "Ungültige Eingabe!" 
          getInput
       else return n

main :: IO ()
main = do putStrLn "\nWillkommen bei Nim!\n"
          n <- randomRIO(5,49)
          play n