module Exercise_12 where

import Prelude hiding (lookup)
import Data.List (nub)
import Data.List (sortOn)

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-}


encrypt :: String -> String
encrypt s = fst $ unzip $ filter zippedIsPrime mapped ++ filter (not . zippedIsPrime) mapped 
            where mapped = zip s $ enumFromTo 1 $ length s
                  zippedIsPrime x = isPrime $ snd x

decrypt :: String -> String
-- 51 Token
-- decrypt s = snd $ unzip $ sortOn fst $ (zip p $ take pl s) ++ (zip withoutprimes $ drop pl s)
            -- where sl = length s
                  -- p = primes sl
                  -- pl = length p
                  -- withoutprimes = filter (`notElem` p) $ enumFromTo 1 sl 

-- 50 Token
decrypt s = snd $ unzip $ sortOn fst $ (zip p $ take pl s) ++ (zip (filter (`notElem` p) $ enumFromTo 1 sl) $ drop pl s)
            where sl = length s
                  p = primes sl
                  pl = length p  
                  
-- decrypt s = snd $ unzip $ sortOn fst $ (zip p $ take pl s) ++ (zip (filter (`notElem` p) $ enumFromTo 1 sl) $ drop pl s)
            -- where sl = length s
                  -- p = primes sl
                  -- pl = length p
                  
                 
{-TTEW-}