Reorganize shared modules

shared/Utils.hs

@@ -0,0 +1,26 @@
+{-# LANGUAGE CPP #-}
+module Utils where
+
+import Control.Applicative
+import Data.Traversable
+import System.Directory
+import System.Directory.ModTime
+
+import Prelude
+
+data TimedFile = TimedFile { tfPath :: FilePath, tfTime :: ModTime }
+                 deriving (Eq)
+
+instance Ord TimedFile where
+    compare (TimedFile _ a) (TimedFile _ b) = compare a b
+
+timeFile :: FilePath -> IO TimedFile
+timeFile f = TimedFile <$> pure f <*> getModTime f
+
+mightExist :: FilePath -> IO (Maybe FilePath)
+mightExist f = do
+  exists <- doesFileExist f
+  return $ if exists then (Just f) else (Nothing)
+
+timeMaybe :: FilePath -> IO (Maybe TimedFile)
+timeMaybe f = traverse timeFile =<< mightExist f