module SPure where 

import Data.Char
import SecLib.LatticeLH
import SecLib.Untrustworthy

-- f1 reimplemented using Sec s monad 
f1 :: (Sec H Char, Int) -> (Sec H Char, Int)
f1 (sec_c,i) = (do c <- sec_c 
                   return $ chr(ord c + i)
               , i)

-- f2 cannot be reimplemented since it does not satisfy non-interference
-- Try to see if you can make it work!
-- f2 :: (Sec H Char, Int) -> (Sec H Char, Int)
-- f2 (sec_c, i) = ( do c <- sec_c 
--                      return $ chr(ord c + i)
--                 , do c <- sec_c 
--                      return $ ord c)


fup :: Sec L Int -> Sec H Char 
fup sec_i = do i <- up sec_i 
               return $ chr i

-- Making instances that break the security lattice structure
instance Less H L where 
   -- If you uncomment the following line, it is not possible to compile the code.
   -- However, as you see, we are able to indicate that H is lower than L.
   -- less _ _ = () 


secret_char :: Sec H Char
secret_char = return 'A'

fhack :: Sec H Char -> Sec L Int 
fhack sec_c = do c <- up sec_c 
                 return $ ord c

-- let's try to run our fhack function to see what happens!
test = fhack secret_char `seq` True