module Exercise_12 where

isPrime :: Int -> Bool
isPrime n
  | n <= 1 = False
  | otherwise = primeAux (n-1)
  where
    primeAux 1 = True
    primeAux i = n `mod` i /= 0 && primeAux (i-1)

-- returns all primes up to the passed number
primes :: Int -> [Int]
primes n = [i | i<-[2..n], isPrime i]

{-WETT-}
{-MCCOMMENT
This is my actual submission for the Competition. It timed out

encrypt :: String -> String
encrypt = gEncrypt 

gEncrypt list = getP True ++ getP False 
  where getP b = [list!!(c-1) | c <- [1..length list], isPrime c == b]

decrypt :: String -> String
decrypt message = [message!! head[j | j <-indices, v == gEncrypt indices!!j] |  v<-indices]
  where
    indices = [0..length message - 1]
-}  

--Below is not the submission for the competition

encrypt :: String -> String
encrypt = gEncrypt 

gEncrypt list = getP True ++ getP False 
  where getP b = [list!!(c-1) | c <- [1..length list], isPrime c == b]

decrypt :: String -> String
decrypt message = [message!!i |  v<-[0..lastIndex], let i = find v]
  where
    lastIndex = length message - 1
    find v = head[j | j <-[0..lastIndex], v == genc!!j]
    genc = gEncrypt [0.. lastIndex]

{-TTEW-}