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

Maintainer  :  Andrea Rossato <andrea.rossato@unibz.it>,
               Matthew Sackman <matthew@wellquite.org>
Stability   :  unstable
Portability :  unportable

A module for accessing and manipulating X Window's mouse selection (the buffer used in copy and pasting).
'getSelection' and 'putSelection' are adaptations 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
                                 putSelection) where

import Control.Concurrent (forkIO)
import Control.Exception as E (catch)
import Control.Monad(Monad (return, (>>)), Functor(..), liftM, join)
import Data.Bits (shiftL, (.&.), (.|.))
import Data.Char (chr, ord)
import Data.Maybe (fromMaybe)
import Data.Word (Word8)
import XMonad
import XMonad.Util.Run (safeSpawn, unsafeSpawn)

{- $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:

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

   There are a number of known problems with XSelection:

    * Unicode handling is busted. But it's still better than calling
      'chr' to translate to ASCII, at least.
      As near as I can tell, the mangling happens when the String is
      outputted somewhere, such as via promptSelection's passing through
      the shell, or GHCi printing to the terminal. utf-string has IO functions
      which can fix this, though I do not know have to use them here. It's
      a complex issue; see
      and <http://www.haskell.org/pipermail/xmonad/2007-September/001966.html>.

    * Needs 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. Note that this is
-- really only reliable for ASCII text and currently escapes or otherwise mangles more complex UTF-8 characters.
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
                     (internAtom dpy "UTF8_STRING" False)
                     (\_ -> internAtom dpy "COMPOUND_TEXT" False))
             (\_ -> 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
    if ev_event_type ev == selectionNotify
       then do res <- getWindowProperty8 dpy clp win
               return $ decode . map fromIntegral . fromMaybe [] $ res
       else destroyWindow dpy win >> return ""

-- | Set the current X Selection to a specified string.
putSelection :: MonadIO m => String -> m ()
putSelection text = 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 <- internAtom dpy "UTF8_STRING" False
  xSetSelectionOwner dpy p win currentTime
  winOwn <- xGetSelectionOwner dpy p
  if winOwn == win
    then do forkIO ((allocaXEvent $ processEvent dpy ty text) >> destroyWindow dpy win) >> return ()
    else do putStrLn "Unable to obtain ownership of the selection" >> destroyWindow dpy win
  return ()
                       processEvent :: Display -> Atom -> [Char] -> XEventPtr -> IO ()
                       processEvent dpy ty txt e = do
                                                      nextEvent dpy e
                                                      ev <- getEvent e
                                                      if ev_event_type ev == selectionRequest
                                                       then do print ev
                                                               allocaXEvent $ \replyPtr -> do
                                                                 changeProperty8 (ev_event_display ev)
                                                                                 (ev_requestor ev)
                                                                                 (ev_property ev)
                                                                                 (map (fromIntegral . ord) txt)
                                                                 setSelectionNotify replyPtr (ev_requestor ev) (ev_selection ev)
                                                                                        (ev_target ev) (ev_property ev) (ev_time ev)
                                                                 sendEvent dpy (ev_requestor ev) False noEventMask replyPtr
                                                                 sync dpy False
                                                       else do putStrLn "Unexpected Message Received"
                                                               print ev
                                                      processEvent dpy ty text e

{- | 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) (getSelection)
unsafePromptSelection app = join $ io $ liftM unsafeSpawn $ fmap (\x -> app ++ " " ++ x) getSelection

{- | Decode a UTF8 string packed into a list of Word8 values, directly to
   String; does not deal with CChar, hence you will want the counter-intuitive @map fromIntegral@
   UTF-8 decoding for internal use in getSelection.

   This code is copied from Eric Mertens's "utf-string" library <http://code.haskell.org/utf8-string/>
   (as of version 0.1),\which is BSD-3 licensed like this module.
   It'd be better to just @import Codec.Binary.UTF8.String (decode)@, but then users of this would need to install it; XMonad has enough
   dependencies already. -}
decode :: [Word8] -> String
decode [    ] = ""
decode (c:cs)
  | c < 0x80  = chr (fromEnum c) : decode cs
  | c < 0xc0  = replacement_character : decode cs
  | c < 0xe0  = multi_byte 1 0x1f 0x80
  | c < 0xf0  = multi_byte 2 0xf  0x800
  | c < 0xf8  = multi_byte 3 0x7  0x10000
  | c < 0xfc  = multi_byte 4 0x3  0x200000
  | c < 0xfe  = multi_byte 5 0x1  0x4000000
  | otherwise = replacement_character : decode cs

    replacement_character :: Char
    replacement_character = '\xfffd'

    multi_byte :: Int -> Word8 -> Int -> [Char]
    multi_byte i mask overlong = aux i cs (fromEnum (c .&. mask))
        aux 0 rs acc
          | overlong <= acc && acc <= 0x10ffff &&
            (acc < 0xd800 || 0xdfff < acc)     &&
            (acc < 0xfffe || 0xffff < acc)      = chr acc : decode rs
          | otherwise = replacement_character : decode rs
        aux n (r:rs) acc
          | r .&. 0xc0 == 0x80 = aux (n-1) rs
                               $ shiftL acc 6 .|. fromEnum (r .&. 0x3f)
        aux _ rs     _ = replacement_character : decode rs