git-annex-3.20110902: Utility/Path.hs

{- path manipulation
 -
 - Copyright 2010-2011 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Utility.Path where

import Data.String.Utils
import System.Path
import System.FilePath
import System.Directory
import Data.List
import Data.Maybe
import Control.Applicative

{- Returns the parent directory of a path. Parent of / is "" -}
parentDir :: FilePath -> FilePath
parentDir dir =
	if not $ null dirs
	then slash ++ join s (take (length dirs - 1) dirs)
	else ""
		where
			dirs = filter (not . null) $ split s dir
			slash = if isAbsolute dir then s else ""
			s = [pathSeparator]

prop_parentDir_basics :: FilePath -> Bool
prop_parentDir_basics dir
	| null dir = True
	| dir == "/" = parentDir dir == ""
	| otherwise = p /= dir
	where
		p = parentDir dir

{- Checks if the first FilePath is, or could be said to contain the second.
 - For example, "foo/" contains "foo/bar". Also, "foo", "./foo", "foo/" etc
 - are all equivilant.
 -}
dirContains :: FilePath -> FilePath -> Bool
dirContains a b = a == b || a' == b' || (a'++"/") `isPrefixOf` b'
	where
		norm p = fromMaybe "" $ absNormPath p "."
		a' = norm a
		b' = norm b

{- Converts a filename into a normalized, absolute path. -}
absPath :: FilePath -> IO FilePath
absPath file = do
	cwd <- getCurrentDirectory
	return $ absPathFrom cwd file

{- Converts a filename into a normalized, absolute path
 - from the specified cwd. -}
absPathFrom :: FilePath -> FilePath -> FilePath
absPathFrom cwd file = fromMaybe bad $ absNormPath cwd file
	where
		bad = error $ "unable to normalize " ++ file

{- Constructs a relative path from the CWD to a file.
 -
 - For example, assuming CWD is /tmp/foo/bar:
 -    relPathCwdToFile "/tmp/foo" == ".."
 -    relPathCwdToFile "/tmp/foo/bar" == "" 
 -}
relPathCwdToFile :: FilePath -> IO FilePath
relPathCwdToFile f = relPathDirToFile <$> getCurrentDirectory <*> absPath f

{- Constructs a relative path from a directory to a file.
 -
 - Both must be absolute, and normalized (eg with absNormpath).
 -}
relPathDirToFile :: FilePath -> FilePath -> FilePath
relPathDirToFile from to = path
	where
		s = [pathSeparator]
		pfrom = split s from
		pto = split s to
		common = map fst $ filter same $ zip pfrom pto
		same (c,d) = c == d
		uncommon = drop numcommon pto
		dotdots = replicate (length pfrom - numcommon) ".."
		numcommon = length common
		path = join s $ dotdots ++ uncommon

prop_relPathDirToFile_basics :: FilePath -> FilePath -> Bool
prop_relPathDirToFile_basics from to
	| from == to = null r
	| otherwise = not (null r)
	where
		r = relPathDirToFile from to