module Exercise_12 where

import Data.List
import Data.Ord
import System.IO
import Data.Maybe
import Test.QuickCheck

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
Hey MC, if you dont mind O(n!), this is my token-optimized encrypt function.
Suggested activities while this is running are, depending on the input length:
-get a cup of coffee (11)
-watch the heat death of the unviverse (anything over 24)

encrypt' cs = fromJust $ find (\x -> decrypt x == cs) $ permutations cs
-}

encrypt :: String -> String
encrypt cs = map fst (filter (isPrime.snd) xs ++ filter (not.isPrime.snd) xs) where xs = zip cs [1..]

decrypt :: String -> String
decrypt cs = map fst $ sortOn snd $ zip cs $ primes (length cs) ++ filter (not.isPrime) [1..]
{-TTEW-}

decrypt' :: String -> String
decrypt' cs = map fst $ sortOn snd $ zip cs $ primes l ++ ([1..l] \\ primes l) where l = length cs

decrypt'' :: String -> String
decrypt'' cs = undefined

encrypt' :: String -> String  
encrypt' cs = fromJust $ find (\x-> decrypt x == cs) $ permutations cs