Would appreciate any correction, better way to do it or generic advices on this practice code.

Interop.hs

{-
  Functionality: 
    - Read all folders and sub-folders with structure like below
    - store all folder and file info in State monad, 
    - at the end of the loop, print it.

    ├── aaa
    │   ├── b
    │   │   ├── b1
    │   │   │   ├── b1-1
    │   │   │   └── b1-2
    │   │   └── b2
    │   │       └── 2-1
    │   │           └── b2-1-1
    │   └── c
    │       ├── c1
    │       └── c2
  
  Goal: to practice using State and IO monad together by leveraging liftIO and unsafePerformIO

  Would appreciate any correction, better way to do it or generic advices

-}
module Main where

import Control.Monad.State
import Control.Monad.State
import System.Directory
import System.Exit
import System.FilePath

main :: IO ([Dir], [File], Root)
main
 = do
  ~(_, s@(d, f, r)) <- runStateT k ([], [], "aaa")
  putStrLn $ "Root: " ++ r
  pretty d True "DIR:"
  pretty f True "FILE:"
  return s

pretty :: Show a => [a] -> Bool -> String -> IO ()
pretty src rev prefix = do
  putStrLn $ "\n" ++ prefix ++ "\n"
  if rev
    then mapM_ print $ reverse src
    else mapM_ print src

data File = File
  { name :: String
  , date :: String
  , size :: Integer
  , content :: String
  } deriving (Show)

data Dir = Dir
  { dirName :: String
  , dirDate :: String
  , dirContent :: [FilePath]
  } deriving (Show)

type Root = String

k :: StateT ([Dir], [File], Root) IO ()
k = do
  (_, _, root) <- get
  liftIO $ do
    isDir <- doesDirectoryExist root
    unless isDir $ die "not a dir"
  list root
  where
    list :: String -> StateT ([Dir], [File], Root) IO ()
    list path = do
      dir <-
        liftIO $
         do
          children <- withCurrentDirectory path $ listDirectory "."
          dt <- getModificationTime path
          return Dir {dirName = path, dirContent = children, dirDate = show dt}
      _ <- withStateT (\(ds, fs, root) -> (dir : ds, fs, root)) get
      n <-
        liftIO $
        foldM
          (\acc@(dirs, files) f -> do
             let fullPath = path </> f
             if (f == ".DS_Store")
               then return acc
               else do
                 bool <- doesDirectoryExist fullPath
                 if bool
                   then return (dirs ++ [fullPath], files)
                   else return (dirs, files ++ [fullPath]))
          ([], []) -- acc, ([dirs], [files])
         $
        dirContent dir
      forM_ (fst n) list
      files <-
        liftIO $
        mapM
          (\f -> do
             s <- getFileSize f
             dt <- getModificationTime f
             c <- readFile f
             return File {name = f, date = show dt, size = s, content = c})
          (snd n)
      _ <- withStateT (\(ds, fs, root) -> (ds, files ++ fs, root)) get
      return ()