module Main where

import Random (randomRIO)

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

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

play :: Int-> IO ()
play n = 
  do putStrLn ("Es sind "++ show n ++" Hölzchen im Haufen.")
     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))

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