{- |

Module : $Header$

Description : utility functions that can't be found in the libraries

Copyright : (c) Klaus L�ttich, Uni Bremen 2002-2006

License : similar to LGPL, see HetCATS/LICENSE.txt or LIZENZ.txt

Maintainer : luettich@tzi.de

Stability : provisional

Portability : portable

Utility functions that can't be found in the libraries

but should be shared across Hets.

-}

module Common.Utils

( joinWith

, keepMins

, splitOn

, basename

, dirname

, fileparse

, stripDir

, stripSuffix

, getEnvSave

, filterMapWithList

) where

import Data.List

import qualified Data.Map as Map

import qualified Data.Set as Set

import System.Environment

import System.IO.Error

import qualified Control.Exception as Exception

-- | keep only minimal elements

keepMins :: (a -> a -> Bool) -> [a] -> [a]

keepMins lt l = case l of

[] -> []

x : r -> let s = filter ( \ y -> not (lt x y)) r

m = keepMins lt s

in if any ( \ y -> lt y x) s then m

else x : m

{- |

A function inspired by perls join function. It joins a list of

lists of elements by seperating them with a seperator element.

-}

joinWith :: a -- ^ seperator element

-> [[a]] -- ^ list of lists of elements

-> [a]

joinWith sep = concat . intersperse [sep]

{- |

A function inspired by the perl function split. A list is splitted

on a seperator element in smaller non-empty lists.

The seperator element is dropped from the resulting list.

-}

splitOn :: Eq a => a -- ^ seperator

-> [a] -- ^ list to split

-> [[a]]

splitOn x xs = let (l, r) = break (==x) xs in

(if null l then [] else [l]) ++ (if null r then [] else splitOn x $ tail r)

{- |

A function inspired by a perl function from the standard perl-module

File::Basename. It removes the directory part of a filepath.

-}

basename :: FilePath -> FilePath

basename fp = (\(_path,basen) -> basen) (stripDir fp)

{- |

A function inspired by a perl function from the standard perl-module

File::Basename. It gives the directory part of a filepath.

-}

dirname :: FilePath -> FilePath

dirname fp = (\(path,_basen) -> path) (stripDir fp)

{- |

A function inspired by a perl function from the standard perl-module

File::Basename. It splits a filepath into the basename, the

directory and gives the suffix that matched from the list of

suffixes. If a suffix matched it is removed from the basename.

-}

fileparse :: [String] -- ^ list of suffixes

-> FilePath

-> (FilePath,FilePath,Maybe String)

-- ^ (basename,directory,matched suffix)

fileparse sufs fp = let (path,base) = stripDir fp

(base',suf) = stripSuffix sufs base

in (base',path,suf)

stripDir :: FilePath -> (FilePath,FilePath)

stripDir fp =

(\(x,y) -> (if not (null y) then reverse y else "./", reverse x))

(break (== '/') (reverse fp))

stripSuffix :: [String] -> FilePath -> (FilePath,Maybe String)

stripSuffix suf fp = case filter justs $ map (stripSuf fp) suf of

((Just (x,s)):_) -> (x,Just s)

_ -> (fp, Nothing)

where stripSuf f s | s `isSuffixOf` f =

Just (take (length f - length s) f, s)

| otherwise = Nothing

justs (Nothing) = False

justs (Just _) = True

{- | filter a map according to a given list of keys (it dosen't hurt

if a key is not present in the map) -}

filterMapWithList :: Ord k => [k] -> Map.Map k e -> Map.Map k e

filterMapWithList l = filterMapWithSet sl

where sl = Set.fromList l

{- | filter a map according to a given set of keys (it dosen't hurt if

a key is not present in the map) -}

filterMapWithSet :: Ord k => Set.Set k -> Map.Map k e -> Map.Map k e

filterMapWithSet s = Map.filterWithKey selected

where selected k _ = Set.member k s

{- | get, parse and check an environment variable; provide the default

value, only if the envionment variable is not set or the

parse-check-function returns a Left value -}

getEnvSave :: a -- ^ default value

-> String -- ^ name of environment variable

-> (String -> Either b a) -- ^ parse and check value of variable;

-- for every b the default value is returned

-> IO a

getEnvSave defValue envVar readFun = do

is <- Exception.catch (getEnv envVar >>= (return . Right))

(\e -> case e of

Exception.IOException ie ->

if isDoesNotExistError ie -- == NoSuchThing

then return $ Left defValue

else Exception.throwIO e

_ -> Exception.throwIO e)

return (either id (\s -> (either (const defValue) id (readFun s))) is)