    {-# LANGUAGE DeriveDataTypeable, FlexibleInstances, GeneralizedNewtypeDeriving, MultiParamTypeClasses, TypeSynonymInstances, PatternGuards #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  XMonad.Layout.WindowNavigation
    -- Copyright   :  (c) 2007  David Roundy <droundy@darcs.net>
    -- License     :  BSD3-style (see LICENSE)
    --
    -- Maintainer  :  Devin Mullins <me@twifkak.com>
    -- Stability   :  unstable
    -- Portability :  unportable
    --
    -- WindowNavigation is an extension to allow easy navigation of a workspace.
    --
    -----------------------------------------------------------------------------

    module XMonad.Layout.WindowNavigation (
                                       -- * Usage
                                       -- $usage
                                       windowNavigation, configurableNavigation,
                                       Navigate(..), Direction2D(..),
                                       MoveWindowToWindow(..),
                                       navigateColor, navigateBrightness,
                                       noNavigateBorders, defaultWNConfig
                                      ) where

    import Data.List ( nub, sortBy, (\\) )
    import XMonad hiding (Point)
    import qualified XMonad.StackSet as W
    import XMonad.Layout.LayoutModifier
    import XMonad.Util.Invisible
    import XMonad.Util.Types (Direction2D(..))
    import XMonad.Util.XUtils

    -- $usage
    -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
    --
    -- > import XMonad.Layout.WindowNavigation
    --
    -- Then edit your @layoutHook@ by adding the WindowNavigation layout modifier
    -- to some layout:
    --
    -- > myLayout = windowNavigation (Tall 1 (3/100) (1/2))  ||| Full ||| etc..
    -- > main = xmonad defaultConfig { layoutHook = myLayout }
    --
    -- For more detailed instructions on editing the layoutHook see:
    --
    -- "XMonad.Doc.Extending#Editing_the_layout_hook"
    --
    -- In keybindings:
    --
    -- >    , ((modm,                 xK_Right), sendMessage $ Go R)
    -- >    , ((modm,                 xK_Left ), sendMessage $ Go L)
    -- >    , ((modm,                 xK_Up   ), sendMessage $ Go U)
    -- >    , ((modm,                 xK_Down ), sendMessage $ Go D)
    -- >    , ((modm .|. controlMask, xK_Right), sendMessage $ Swap R)
    -- >    , ((modm .|. controlMask, xK_Left ), sendMessage $ Swap L)
    -- >    , ((modm .|. controlMask, xK_Up   ), sendMessage $ Swap U)
    -- >    , ((modm .|. controlMask, xK_Down ), sendMessage $ Swap D)
    --
    -- For detailed instruction on editing the key binding see:
    --
    -- "XMonad.Doc.Extending#Editing_key_bindings".

    data MoveWindowToWindow a = MoveWindowToWindow a a deriving ( Read, Show, Typeable )
    instance Typeable a => Message (MoveWindowToWindow a)

    data Navigate = Go Direction2D | Swap Direction2D | Move Direction2D
                  | Apply (Window -> X()) Direction2D -- ^ Apply action with destination window
            deriving ( Typeable )
    instance Message Navigate

    data WNConfig =
        WNC { brightness    :: Maybe Double -- Indicates a fraction of the focus color.
            , upColor       :: String
            , downColor     :: String
            , leftColor     :: String
            , rightColor    :: String
            } deriving (Show, Read)

    noNavigateBorders :: WNConfig
    noNavigateBorders =
        defaultWNConfig {brightness = Just 0}

    navigateColor :: String -> WNConfig
    navigateColor c =
        WNC Nothing c c c c

    navigateBrightness :: Double -> WNConfig
    navigateBrightness f = defaultWNConfig { brightness = Just $ max 0 $ min 1 f }

    defaultWNConfig :: WNConfig
    defaultWNConfig = WNC (Just 0.4) "#0000FF" "#00FFFF" "#FF0000" "#FF00FF"

    data NavigationState a = NS Point [(a,Rectangle)]

    data WindowNavigation a = WindowNavigation WNConfig (Invisible Maybe (NavigationState a)) deriving ( Read, Show )

    windowNavigation :: LayoutClass l a => l a -> ModifiedLayout WindowNavigation l a
    windowNavigation = ModifiedLayout (WindowNavigation defaultWNConfig (I Nothing))

    configurableNavigation :: LayoutClass l a => WNConfig -> l a -> ModifiedLayout WindowNavigation l a
    configurableNavigation conf = ModifiedLayout (WindowNavigation conf (I Nothing))

    instance LayoutModifier WindowNavigation Window where
        redoLayout (WindowNavigation conf (I state)) rscr (Just s) origwrs =
            do XConf { normalBorder = nbc, focusedBorder = fbc, display = dpy } <- ask
               [uc,dc,lc,rc] <-
                   case brightness conf of
                   Just frac -> do myc <- averagePixels fbc nbc frac
                                   return [myc,myc,myc,myc]
                   Nothing -> mapM (stringToPixel dpy) [upColor conf, downColor conf,
                                                        leftColor conf, rightColor conf]
               let dirc U = uc
                   dirc D = dc
                   dirc L = lc
                   dirc R = rc
               let w    = W.focus s
                   r    = case filter ((==w).fst) origwrs of ((_,x):_) -> x
                                                             []        -> rscr
                   pt   = case state of Just (NS ptold _) | ptold `inrect` r -> ptold
                                        _ -> center r
                   existing_wins = W.integrate s
                   wrs = filter ((`elem` existing_wins) . fst) $ filter ((/=r) . snd) $
                         filter ((/=w) . fst) origwrs
                   wnavigable = nub $ concatMap
                                (\d -> take 1 $ navigable d pt wrs) [U,D,R,L]
                   wnavigablec = nub $ concatMap
                                (\d -> map (\(win,_) -> (win,dirc d)) $
                                       take 1 $ navigable d pt wrs) [U,D,R,L]
                   wothers = case state of Just (NS _ wo) -> map fst wo
                                           _              -> []
               mapM_ (sc nbc) (wothers \\ map fst wnavigable)
               mapM_ (\(win,c) -> sc c win) wnavigablec
               return (origwrs, Just $ WindowNavigation conf $ I $ Just $ NS pt wnavigable)
        redoLayout _ _ _ origwrs = return (origwrs, Nothing)

        handleMessOrMaybeModifyIt (WindowNavigation conf (I (Just (NS pt wrs)))) m
            | Just (Go d) <- fromMessage m =
                             case navigable d pt wrs of
                             []        -> return Nothing
                             ((w,r):_) -> do modify focusWindowHere
                                             return $ Just $ Left $ WindowNavigation conf $ I $ Just $
                                                    NS (centerd d pt r) wrs
                                 where focusWindowHere :: XState -> XState
                                       focusWindowHere s
                                           | Just w == W.peek (windowset s) = s
                                           | has w $ W.stack $ W.workspace $ W.current $ windowset s =
                                               s { windowset = until ((Just w ==) . W.peek)
                                                               W.focusUp $ windowset s }
                                           | otherwise = s
                                       has _ Nothing         = False
                                       has x (Just (W.Stack t l rr)) = x `elem` (t : l ++ rr)

            | Just (Swap d) <- fromMessage m =
                 case navigable d pt wrs of
                 []        -> return Nothing
                 ((w,_):_) -> do let swap st = unint (W.focus st) $ map (swapw (W.focus st)) $ W.integrate st
                                     swapw y x | x == w = y
                                               | x == y = w
                                               | otherwise = x
                                     unint f xs = case span (/= f) xs of
                                                  (u,_:dn) -> W.Stack { W.focus = f
                                                                      , W.up = reverse u
                                                                      , W.down = dn }
                                                  _ -> W.Stack { W.focus = f
                                                               , W.down = xs
                                                               , W.up = [] }
                                 windows $ W.modify' swap
                                 return Nothing
            | Just (Move d) <- fromMessage m =
                 case navigable d pt wrs of
                 []        -> return Nothing
                 ((w,_):_) -> do mst <- gets (W.stack . W.workspace . W.current . windowset)
                                 return $ do st <- mst
                                             Just $ Right $ SomeMessage $ MoveWindowToWindow (W.focus st) w
            | Just (Apply f d) <- fromMessage m =
                 case navigable d pt wrs of
                 []         -> return Nothing
                 ((w,_):_)  -> f w >> return Nothing
            | Just Hide <- fromMessage m =
                           do XConf { normalBorder = nbc } <- ask
                              mapM_ (sc nbc . fst) wrs
                              return $ Just $ Left $ WindowNavigation conf $ I $ Just $ NS pt []
            | Just ReleaseResources <- fromMessage m =
                   handleMessOrMaybeModifyIt (WindowNavigation conf (I $ Just (NS pt wrs))) (SomeMessage Hide)
        handleMessOrMaybeModifyIt _ _ = return Nothing

    navigable :: Direction2D -> Point -> [(Window, Rectangle)] -> [(Window, Rectangle)]
    navigable d pt = sortby d . filter (inr d pt . snd)

    sc :: Pixel -> Window -> X ()
    sc c win = withDisplay $ \dpy -> io $ setWindowBorder dpy win c

    center :: Rectangle -> Point
    center (Rectangle x y w h) = P (fromIntegral x + fromIntegral w/2)  (fromIntegral y + fromIntegral h/2)

    centerd :: Direction2D -> Point -> Rectangle -> Point
    centerd d (P xx yy) (Rectangle x y w h) | d == U || d == D = P xx (fromIntegral y + fromIntegral h/2)
                                            | otherwise = P (fromIntegral x + fromIntegral w/2) yy

    inr :: Direction2D -> Point -> Rectangle -> Bool
    inr D (P x y) (Rectangle l yr w h) = x >= fromIntegral l && x < fromIntegral l + fromIntegral w &&
                                         y <  fromIntegral yr + fromIntegral h
    inr U (P x y) (Rectangle l yr w _) = x >= fromIntegral l && x < fromIntegral l + fromIntegral w &&
                                         y >  fromIntegral yr
    inr R (P a x) (Rectangle b l _ w)  = x >= fromIntegral l && x < fromIntegral l + fromIntegral w &&
                                         a <  fromIntegral b
    inr L (P a x) (Rectangle b l c w)  = x >= fromIntegral l && x < fromIntegral l + fromIntegral w &&
                                         a >  fromIntegral b + fromIntegral c

    inrect :: Point -> Rectangle -> Bool
    inrect (P x y) (Rectangle a b w h) = x >  fromIntegral a && x < fromIntegral a + fromIntegral w &&
                                         y >  fromIntegral b && y < fromIntegral b + fromIntegral h

    sortby :: Direction2D -> [(a,Rectangle)] -> [(a,Rectangle)]
    sortby U = sortBy (\(_,Rectangle _ y _ _) (_,Rectangle _ y' _ _) -> compare y' y)
    sortby D = sortBy (\(_,Rectangle _ y _ _) (_,Rectangle _ y' _ _) -> compare y y')
    sortby R = sortBy (\(_,Rectangle x _ _ _) (_,Rectangle x' _ _ _) -> compare x x')
    sortby L = sortBy (\(_,Rectangle x _ _ _) (_,Rectangle x' _ _ _) -> compare x' x)

    data Point = P Double Double