module Utils where

import Prelude hiding (catch)
import Control.Exception (catch, IOException)
import Control.Monad (forM)
import System.Directory (getDirectoryContents, doesFileExist, doesDirectoryExist)
import System.FilePath ((</>))

safeRead :: Read a => String -> Maybe a
safeRead s = case filter (null . snd) (reads s) of
  [(a, "")] -> Just a
  _ -> Nothing

catchIO :: IO a -> (IOException -> IO a) -> IO a
catchIO = catch

getFilesRecursive :: FilePath -> IO [([FilePath], FilePath)]
getFilesRecursive d = (do
  fs0 <- getDirectoryContents d
  let fs = filter (`notElem` [".", ".."]) fs0
  ffs <- forM fs $ \f -> do
    let df = d </> f
    fe <- doesFileExist df
    fd <- doesDirectoryExist df
    case (fe, fd) of
      (True, False) -> return [([], f)]
      (False, True) -> map (\(ds, f') -> (f:ds, f')) `fmap` getFilesRecursive df
      _ -> return []
  return (concat ffs)) `catchIO` (\_ -> return [])

safeLast :: [a] -> Maybe a
safeLast [] = Nothing
safeLast [x] = Just x
safeLast (_:xs) = safeLast xs