split groups of related functions out of Utility

Utility/Path.hs

@@ -0,0 +1,92 @@
+{- 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.Monad (liftM2)
+
+{- 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 = liftM2 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