module Encoding.Rotate
  ( rotate ) where

import Data.Maybe (fromMaybe)

upperCase = ['A' .. 'Z']
lowerCase = ['a' .. 'z']

-- rotate :: Int * -> String
rotate :: Int -> String -> String
rotate n s = map (rotchar n) s
  where
    rotchar n c = 
      case (lookup c $ transp n lowerCase) of
        Just x -> x
        Nothing -> fromMaybe c (lookup c $ transp n upperCase)

transp :: Int -> [Char] -> [(Char, Char)]
transp n x = zip x ((drop n x) ++ (take n x))