module Hcompta.Lib.Path where

import           Control.Applicative ((<$>))
import           Control.Monad (Monad(..), liftM)
import           Control.Monad.IO.Class (liftIO)
import           Prelude (($), FilePath, IO, id)
import           System.Directory (getHomeDirectory)
import           System.FilePath ((</>))
import qualified System.FilePath.Posix as Path


-- | Return an absolute 'FilePath', given the current working directory and a path.
--
--   * "~" as prefix is expanded to the process's user's home directory
--   * "-" as path is unchanged
--   * ~USER is not supported
abs :: FilePath -> FilePath -> IO FilePath
abs _ "-" = return "-"
abs cwd path =
	liftM
	 (if Path.isRelative path
		then (cwd </>)
		else id)
	 (expand path)
	where
		expand :: FilePath -> IO FilePath
		expand ('~':sep:p) =
			if Path.isPathSeparator sep
			then liftIO $ (</> p) <$> getHomeDirectory
			else fail "~USERNAME in path is not supported"
		expand p = return p