Word reorderer (writing)

-- It's an educational app that turns sentences into sets of words and
-- shuffles the words. Characters that don't make up words, e.g.
-- punctuation marks, are removed, capital letters are replaced with
-- their lowercase counterparts. The sentences are read from stdin.
-- Each sentence should be on a separate line. If a sentence consists
-- of only one word, the app changes the order of the letters in the
-- word. The result is written to stdout as sets of comma-separated
-- words, each set is on a separate line. The order of the shuffled
-- words isn't random, but its "randomness" is sufficient. A
-- "sentence" like this "One two three, four five six — seven eight
-- nine; ten eleven twelve: thirteen fourteen fifteen." will be
-- changed into the following set of words: "four, eleven, seven,
-- twelve, two, thirteen, eight, fourteen, one, fifteen, nine, five,
-- ten, six, three".

import Data.List (intercalate, sort)
import Data.Char (toLower)
import System.Exit (die)

main :: IO ()
main = do
  input <- getContents
  if null input
    then die "No input given!"
    else mapM_ putStrLn $
         listsOfWordsToLines $
         map
           ((shuffleList . processSingleWords) . words)
           (lines $ proccessChars input)

processChars :: String -> String
processChars [] = []
processChars string =
  filter (`elem` "abcdefghijklmnopqrstuvwxyz’'- \n") $ map toLower string

processSingleWords :: [String] -> [String]
processSingleWords [] = []
processSingleWords [x]
  | x == sort x =  [reverse x]
  | otherwise =  [sort x]
processSingleWords x = x

increasingChunks :: [String] -> [[String]]
increasingChunks [] = []
increasingChunks list = aux 1 list
  where
    aux _ [] = []
    aux n lst = take n lst : aux (n + 1) (drop n lst)

interlaceLists :: [String] -> [String] -> [String]
interlaceLists x [] = x
interlaceLists [] x = x
interlaceLists listOne@(x:xs) listTwo@(y:ys)
  | length listOne > length listTwo = x : y : interlaceLists xs ys
  | otherwise = y : x : interlaceLists ys xs

shuffleList :: [String] -> [String]
shuffleList [] = []
shuffleList list = foldl1 interlaceLists $ increasingChunks list

listsOfWordsToLines :: [[String]] -> [String]
listsOfWordsToLines [[]] = []
listsOfWordsToLines list = map (intercalate ", ") list