#!/usr/bin/runghc

module TranspositionDecrypt (decryptString, numOfColumns) where

import Data.List
import Data.List.Split
import TranspositionEncrypt

-- |
-- >>> numOfColumns 8 "Cenoonommstmme oo snnio. s  s c "
-- 4
numOfColumns = numOfRows

-- | Actual dercyption function.
-- >>> decryptString 4 "Cenoonommstmme oo snnio. s  s c "
-- "Common sense is not so common.  "
decryptString :: Int -> String -> String
decryptString numCols = intercalate "" . transpose . chunksOf numCols . messagePad numCols

main :: IO ()
main = do
  let message = "Common sense is not so common."
  let key = 8
  putStrLn "Your encrypted message is:"
  putStrLn (encryptString key message)
  let numCols = numOfColumns key message
  putStrLn "Your decrypted message is:"
  putStrLn (decryptString numCols . encryptString key $ message)