    {-# LANGUAGE CPP #-}
    {- |
    Module      :  XMonad.Util.XSelection
    Copyright   :  (C) 2007 Andrea Rossato, Matthew Sackman
    License     :  BSD3

    Maintainer  : Gwern Branwen <gwern0@gmail.com>
    Stability   :  unstable
    Portability :  unportable

    A module for accessing and manipulating X Window's mouse selection (the buffer used in copy and pasting).
    'getSelection' is an adaptation of Hxsel.hs and Hxput.hs from the XMonad-utils, available:

    > $ darcs get <http://gorgias.mine.nu/repos/xmonad-utils>
    -}

    module XMonad.Util.XSelection (  -- * Usage
                                     -- $usage
                                     getSelection,
                                     promptSelection,
                                     safePromptSelection,
                                     transformPromptSelection,
                                     transformSafePromptSelection) where

    import Control.Exception.Extensible as E (catch,SomeException(..))
    import Control.Monad (liftM, join)
    import Data.Maybe (fromMaybe)
    import XMonad
    import XMonad.Util.Run (safeSpawn, unsafeSpawn)

    import Codec.Binary.UTF8.String (decode)

    {- $usage
       Add @import XMonad.Util.XSelection@ to the top of Config.hs
       Then make use of getSelection or promptSelection as needed; if
       one wanted to run Firefox with the selection as an argument (perhaps
       the selection string is an URL you just highlighted), then one could add
       to the xmonad.hs a line like thus:

       > , ((modm .|. shiftMask, xK_b), promptSelection "firefox")

       Future improvements for XSelection:

       * More elaborate functionality: Emacs' registers are nice; if you
          don't know what they are, see <http://www.gnu.org/software/emacs/manual/html_node/emacs/Registers.html#Registers> -}

    -- | Returns a String corresponding to the current mouse selection in X;
    --   if there is none, an empty string is returned.
    --
    -- WARNING: this function is fundamentally implemented incorrectly and may, among other possible failure modes,
    -- deadlock or crash. For details, see <http://code.google.com/p/xmonad/issues/detail?id=573>.
    -- (These errors are generally very rare in practice, but still exist.)
    getSelection :: MonadIO m => m String
    getSelection = io $ do
      dpy <- openDisplay ""
      let dflt = defaultScreen dpy
      rootw  <- rootWindow dpy dflt
      win <- createSimpleWindow dpy rootw 0 0 1 1 0 0 0
      p <- internAtom dpy "PRIMARY" True
      ty <- E.catch
                   (E.catch
                         (internAtom dpy "UTF8_STRING" False)
                         (\(E.SomeException _) -> internAtom dpy "COMPOUND_TEXT" False))
                 (\(E.SomeException _) -> internAtom dpy "sTring" False)
      clp <- internAtom dpy "BLITZ_SEL_STRING" False
      xConvertSelection dpy p ty clp win currentTime
      allocaXEvent $ \e -> do
        nextEvent dpy e
        ev <- getEvent e
        result <- if ev_event_type ev == selectionNotify
                     then do res <- getWindowProperty8 dpy clp win
                             return $ decode . map fromIntegral . fromMaybe [] $ res
                     else destroyWindow dpy win >> return ""
        closeDisplay dpy
        return result

    {- | A wrapper around 'getSelection'. Makes it convenient to run a program with the current selection as an argument.
      This is convenient for handling URLs, in particular. For example, in your Config.hs you could bind a key to
             @promptSelection \"firefox\"@;
      this would allow you to highlight a URL string and then immediately open it up in Firefox.

      'promptSelection' passes strings through the system shell, \/bin\/sh; if you do not wish your selected text
      to be interpreted or mangled by the shell, use 'safePromptSelection'. safePromptSelection will bypass the
      shell using 'safeSpawn' from "XMonad.Util.Run"; see its documentation for more
      details on the advantages and disadvantages of using safeSpawn. -}
    promptSelection, safePromptSelection, unsafePromptSelection :: String -> X ()
    promptSelection = unsafePromptSelection
    safePromptSelection app = join $ io $ liftM (safeSpawn app . return) getSelection
    unsafePromptSelection app = join $ io $ liftM unsafeSpawn $ fmap (\x -> app ++ " " ++ x) getSelection

    {- | A wrapper around 'promptSelection' and its safe variant. They take two parameters, the
         first is a function that transforms strings, and the second is the application to run.
         The transformer essentially transforms the selection in X.
         One example is to wrap code, such as a command line action copied out of the browser
         to be run as @"sudo" ++ cmd@ or @"su - -c \""++ cmd ++"\""@. -}
    transformPromptSelection, transformSafePromptSelection :: (String -> String) -> String -> X ()
    transformPromptSelection f app = join $ io $ liftM (safeSpawn app . return) (fmap f getSelection)
    transformSafePromptSelection f app = join $ io $ liftM unsafeSpawn $ fmap (\x -> app ++ " " ++ x) (fmap f getSelection)