    {-# LANGUAGE ScopedTypeVariables #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module       : XMonad.Hooks.XPropManage
    -- Copyright    : (c) Karsten Schoelzel <kuser@gmx.de>
    -- License      : BSD
    --
    -- Maintainer   : Karsten Schoelzel <kuser@gmx.de>
    -- Stability    : unstable
    -- Portability  : unportable
    --
    -- A ManageHook matching on XProperties.
    -----------------------------------------------------------------------------

    module XMonad.Hooks.XPropManage (
                     -- * Usage
                     -- $usage
                     xPropManageHook, XPropMatch, pmX, pmP
                     ) where

    import Control.Exception as E
    import Data.Char (chr)
    import Data.Monoid (mconcat, Endo(..))

    import Control.Monad.Trans (lift)

    import XMonad

    -- $usage
    -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
    --
    -- > import XMonad.Hooks.XPropManage
    -- > import qualified XMonad.StackSet as W
    -- > import XMonad.Actions.TagWindows
    -- > import Data.List
    --
    -- > manageHook = xPropManageHook xPropMatches
    -- >
    -- > xPropMatches :: [XPropMatch]
    -- > xPropMatches = [ ([ (wM_CLASS, any ("gimp"==))], (\w -> float w >> return (W.shift "2")))
    -- >                , ([ (wM_COMMAND, any ("screen" ==)), (wM_CLASS, any ("xterm" ==))], pmX (addTag "screen"))
    -- >                , ([ (wM_NAME, any ("Iceweasel" `isInfixOf`))], pmP (W.shift "3"))
    -- >                ]
    --
    -- Properties known to work: wM_CLASS, wM_NAME, wM_COMMAND
    --
    -- A XPropMatch consists of a list of conditions and function telling what to do.
    --
    -- The list entries are pairs of an XProperty to match on (like wM_CLASS, wM_NAME)^1,
    -- and an function which matches onto the value of the property (represented as a List
    -- of Strings).
    --
    -- If a match succeeds the function is called immediately, can perform any action and then return
    -- a function to apply in 'windows' (see Operations.hs). So if the action does only work on the
    -- WindowSet use just 'pmP function'.
    --
    -- \*1 You can get the available properties of an application with the xprop utility. STRING properties
    -- should work fine. Others might not work.
    --

    type XPropMatch = ([(Atom, [String] -> Bool)], (Window -> X (WindowSet -> WindowSet)))

    pmX :: (Window -> X ()) -> Window -> X (WindowSet -> WindowSet)
    pmX f w = f w >> return id

    pmP :: (WindowSet -> WindowSet) -> Window -> X (WindowSet -> WindowSet)
    pmP f _ = return f

    xPropManageHook :: [XPropMatch] -> ManageHook
    xPropManageHook tms = mconcat $ map propToHook tms
        where
          propToHook (ms, f) = fmap and (mapM mkQuery ms) --> mkHook f
          mkQuery (a, tf)    = fmap tf (getQuery a)
          mkHook func        = ask >>= Query . lift . fmap Endo . func

    getProp :: Display -> Window -> Atom -> X ([String])
    getProp d w p = do
        prop <- io $ E.catch (getTextProperty d w p >>= wcTextPropertyToTextList d) (\(_ :: IOException) -> return [[]])
        let filt q | q == wM_COMMAND = concat . map splitAtNull
                   | otherwise       = id
        return (filt p prop)

    getQuery ::  Atom -> Query [String]
    getQuery p = ask >>= \w ->  Query . lift $ withDisplay $ \d -> getProp d w p

    splitAtNull :: String -> [String]
    splitAtNull s = case dropWhile (== (chr 0)) s of
        "" -> []
        s' -> w : splitAtNull s''
              where (w, s'') = break (== (chr 0)) s'