module Exercise_12 where

import Data.List
import Data.Set (Set)
import System.IO
import Control.Monad

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 = fst . unzip . sortOn (not . isPrime . snd) . ap zip (enumFromTo 1 . length)

decrypt :: String -> String
decrypt = fst . unzip . sortOn snd . ap zip (sortOn (not . isPrime) . enumFromTo 1 . length)
{-TTEW-}

-- encrypt s = fst . unzip $ sortOn (not . isPrime . snd) $ zip s [1..length s]
-- encrypt s =  fst $ unzip $ sortOn snd $ zip s $ map (\n -> if isPrime n then n else n+10000) [1..length s]
-- sortOn (not . isPrime . snd) zip s [1..length s]

--decrypt s = fst $ unzip $ sortOn snd $ zip s $ sortOn (not . isPrime) [1..length s]
--decrypt s = fst $ unzip $ sortOn snd $ zip s $ sortOn (not . isPrime) [1..length s]
--decrypt s = fst $ unzip $ sortOn snd $ zip s $ primes (length s) ++ filter (not . isPrime) [1..length s]
--sortOn (`notElem` )

--[('a',1),('l',2),('o',3),('H',4),('l',5)]