module Files (
      File(..)
    , absolute
    , absoluteLink
    , filePath
    , filePathMaybe
    , find
  ) where

import System.Exit (die)
import System.Directory (doesDirectoryExist, doesFileExist, listDirectory, makeAbsolute)
import System.FilePath ((</>))

data File = File FilePath | Dir FilePath

absolute :: File -> IO (FilePath)
absolute file = filePath file >>= makeAbsolute

absoluteLink :: FilePath -> FilePath
absoluteLink ('.':path) = path
absoluteLink path = "/" </> path

filePathMaybe :: File -> IO (Maybe FilePath)
filePathMaybe = filePathAux
  where
    filePathAux (File path) = ifToMaybe path <$> doesFileExist path
    filePathAux (Dir path) = ifToMaybe path <$> doesDirectoryExist path
    ifToMaybe path bool = if bool then return path else Nothing

filePath :: File -> IO FilePath
filePath file = filePathMaybe file >>= maybe (die $ notExist file) return
  where
    notExist (File path) = path ++ ": no such file"
    notExist (Dir path) = path ++ ": no such directory"

find :: FilePath -> IO [FilePath]
find path =
  filePathMaybe (Dir path) >>= maybe (return []) (fmap ((path </>) <$>) . listDirectory)