    -----------------------------------------------------------------------------
    -- |
    -- Module      :  XMonad.Layout.FloatSnap
    -- Copyright   :  (c) 2009 Anders Engstrom <ankaan@gmail.com>
    -- License     :  BSD3-style (see LICENSE)
    --
    -- Maintainer  :  Anders Engstrom <ankaan@gmail.com>
    -- Stability   :  unstable
    -- Portability :  unportable
    --
    -- Move and resize floating windows using other windows and the edge of the
    -- screen as guidelines.
    -----------------------------------------------------------------------------

    module XMonad.Actions.FloatSnap (
                    -- * Usage
                    -- $usage
                    Direction2D(..),
                    snapMove,
                    snapGrow,
                    snapShrink,
                    snapMagicMove,
                    snapMagicResize,
                    snapMagicMouseResize) where

    import XMonad
    import Control.Applicative((<$>))
    import Data.List (sort)
    import Data.Maybe (listToMaybe,fromJust,isNothing)
    import qualified XMonad.StackSet as W

    import XMonad.Hooks.ManageDocks (calcGap)
    import XMonad.Util.Types (Direction2D(..))

    import qualified Data.Set as S

    -- $usage
    -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
    --
    -- >    import XMonad.Actions.FloatSnap
    --
    -- Then add appropriate key bindings, for example:
    --
    -- >        , ((modm,               xK_Left),  withFocused $ snapMove L Nothing)
    -- >        , ((modm,               xK_Right), withFocused $ snapMove R Nothing)
    -- >        , ((modm,               xK_Up),    withFocused $ snapMove U Nothing)
    -- >        , ((modm,               xK_Down),  withFocused $ snapMove D Nothing)
    -- >        , ((modm .|. shiftMask, xK_Left),  withFocused $ snapShrink R Nothing)
    -- >        , ((modm .|. shiftMask, xK_Right), withFocused $ snapGrow R Nothing)
    -- >        , ((modm .|. shiftMask, xK_Up),    withFocused $ snapShrink D Nothing)
    -- >        , ((modm .|. shiftMask, xK_Down),  withFocused $ snapGrow D Nothing)
    --
    -- For detailed instructions on editing your key bindings, see
    -- "XMonad.Doc.Extending#Editing_key_bindings".
    --
    -- And possibly add an appropriate mouse binding, for example:
    --
    -- >        , ((modm,               button1), (\w -> focus w >> mouseMoveWindow w >> snapMagicMove (Just 50) (Just 50) w))
    -- >        , ((modm .|. shiftMask, button1), (\w -> focus w >> mouseMoveWindow w >> snapMagicResize [L,R,U,D] (Just 50) (Just 50) w))
    -- >        , ((modm,               button3), (\w -> focus w >> mouseResizeWindow w >> snapMagicResize [R,D] (Just 50) (Just 50) w))
    --
    -- For detailed instructions on editing your mouse bindings, see
    -- "XMonad.Doc.Extending#Editing_mouse_bindings".
    --
    -- Using these mouse bindings, it will not snap while moving, but allow you to click the window once after it has been moved or resized to snap it into place.
    -- Note that the order in which the commands are applied in the mouse bindings are important.
    --
    -- Interesting values for the distance to look for window in the orthogonal axis are Nothing (to snap against every window), Just 0 (to only snap
    -- against windows that we should collide with geometrically while moving) and Just 1 (to also snap against windows we brush against).
    --
    -- For 'snapMagicMove', 'snapMagicResize' and 'snapMagicMouseResize', try instead setting it to the same as the maximum snapping distance.
    --
    -- When a value is specified it can be geometrically conceived as adding a border with the specified width around the window and then checking which
    -- windows it should collide with.

    -- | Resize the window by each edge independently to snap against the closest part of other windows or the edge of the screen. Use the location of the
    --   mouse over the window to decide which edges to snap. In corners, the two adjoining edges will be snapped, along the middle of an edge only that edge
    --   will be snapped. In the center of the window all edges will snap. Intended to be used together with "XMonad.Actions.FlexibleResize" or
    --   "XMonad.Actions.FlexibleManipulate".
    snapMagicMouseResize
        :: Rational  -- ^ How big the middle snap area of each axis should be.
        -> Maybe Int -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Maybe Int -- ^ The maximum distance to snap. Use Nothing to not impose any boundary.
        -> Window    -- ^ The window to move and resize.
        -> X ()
    snapMagicMouseResize middle collidedist snapdist w = whenX (isClient w) $ withDisplay $ \d -> do
        wa <- io $ getWindowAttributes d w
        (_, _, _, px, py, _, _, _) <- io $ queryPointer d w
        let x = (fromIntegral px - wx wa)/(ww wa)
            y = (fromIntegral py - wy wa)/(wh wa)
            ml = if x <= (0.5 - middle/2) then [L] else []
            mr = if x >  (0.5 + middle/2) then [R] else []
            mu = if y <= (0.5 - middle/2) then [U] else []
            md = if y >  (0.5 + middle/2) then [D] else []
            mdir = ml++mr++mu++md
            dir = if mdir == []
                  then [L,R,U,D]
                  else mdir
        snapMagicResize dir collidedist snapdist w
        where
            wx = fromIntegral.wa_x
            wy = fromIntegral.wa_y
            ww = fromIntegral.wa_width
            wh = fromIntegral.wa_height

    -- | Resize the window by each edge independently to snap against the closest part of other windows or the edge of the screen.
    snapMagicResize
        :: [Direction2D] -- ^ The edges to snap.
        -> Maybe Int   -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Maybe Int   -- ^ The maximum distance to snap. Use Nothing to not impose any boundary.
        -> Window      -- ^ The window to move and resize.
        -> X ()
    snapMagicResize dir collidedist snapdist w = whenX (isClient w) $ withDisplay $ \d -> do
        io $ raiseWindow d w
        wa <- io $ getWindowAttributes d w

        (xbegin,xend) <- handleAxis True d wa
        (ybegin,yend) <- handleAxis False d wa

        let xbegin' = if L `elem` dir then xbegin else (wx wa)
            xend'   = if R `elem` dir then xend   else (wx wa + ww wa)
            ybegin' = if U `elem` dir then ybegin else (wy wa)
            yend'   = if D `elem` dir then yend   else (wy wa + wh wa)

        io $ moveWindow d w (fromIntegral $ xbegin') (fromIntegral $ ybegin')
        io $ resizeWindow d w (fromIntegral $ xend' - xbegin') (fromIntegral $ yend' - ybegin')
        float w
        where
            wx = fromIntegral.wa_x
            wy = fromIntegral.wa_y
            ww = fromIntegral.wa_width
            wh = fromIntegral.wa_height

            handleAxis horiz d wa = do
                ((mbl,mbr,bs),(mfl,mfr,fs)) <- getSnap horiz collidedist d w
                let begin = if bs
                            then wpos wa
                            else case (mbl,mbr) of
                                (Just bl,Just br) -> if wpos wa - bl < br - wpos wa then bl else br
                                (Just bl,Nothing) -> bl
                                (Nothing,Just br) -> br
                                (Nothing,Nothing) -> wpos wa
                    end = if fs
                          then wpos wa + wdim wa
                          else case (if mfl==(Just begin) then Nothing else mfl,mfr) of
                              (Just fl,Just fr) -> if wpos wa + wdim wa - fl < fr - wpos wa - wdim wa then fl else fr
                              (Just fl,Nothing) -> fl
                              (Nothing,Just fr) -> fr
                              (Nothing,Nothing) -> wpos wa + wdim wa
                    begin' = if isNothing snapdist || abs (begin - wpos wa) <= fromJust snapdist then begin else (wpos wa)
                    end' = if isNothing snapdist || abs (end - wpos wa - wdim wa) <= fromJust snapdist then end else (wpos wa + wdim wa)
                return (begin',end')
                where
                    (wpos, wdim, _, _) = constructors horiz

    -- | Move a window by both axises in any direction to snap against the closest part of other windows or the edge of the screen.
    snapMagicMove
        :: Maybe Int -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Maybe Int -- ^ The maximum distance to snap. Use Nothing to not impose any boundary.
        -> Window    -- ^ The window to move.
        -> X ()
    snapMagicMove collidedist snapdist w = whenX (isClient w) $ withDisplay $ \d -> do
        io $ raiseWindow d w
        wa <- io $ getWindowAttributes d w

        nx <- handleAxis True d wa
        ny <- handleAxis False d wa

        io $ moveWindow d w (fromIntegral nx) (fromIntegral ny)
        float w
        where
            handleAxis horiz d wa = do
                ((mbl,mbr,bs),(mfl,mfr,fs)) <- getSnap horiz collidedist d w
                return $ if bs || fs
                         then wpos wa
                         else let b = case (mbl,mbr) of
                                        (Just bl,Just br) -> if wpos wa - bl < br - wpos wa then bl else br
                                        (Just bl,Nothing) -> bl
                                        (Nothing,Just br) -> br
                                        (Nothing,Nothing) -> wpos wa
                                  f = case (mfl,mfr) of
                                        (Just fl,Just fr) -> if wpos wa + wdim wa - fl < fr - wpos wa - wdim wa then fl else fr
                                        (Just fl,Nothing) -> fl
                                        (Nothing,Just fr) -> fr
                                        (Nothing,Nothing) -> wpos wa
                                  newpos = if abs (b - wpos wa) <= abs (f - wpos wa - wdim wa) then b else (f - wdim wa)
                              in if isNothing snapdist || abs (newpos - wpos wa) <= fromJust snapdist then newpos else (wpos wa)
                where
                    (wpos, wdim, _, _) = constructors horiz

    -- | Move a window in the specified direction until it snaps against another window or the edge of the screen.
    snapMove
        :: Direction2D -- ^ What direction to move the window in.
        -> Maybe Int -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Window    -- ^ The window to move.
        -> X ()
    snapMove L = doSnapMove True True
    snapMove R = doSnapMove True False
    snapMove U = doSnapMove False True
    snapMove D = doSnapMove False False

    doSnapMove :: Bool -> Bool -> Maybe Int -> Window -> X ()
    doSnapMove horiz rev collidedist w = whenX (isClient w) $ withDisplay $ \d -> do
        io $ raiseWindow d w
        wa <- io $ getWindowAttributes d w
        ((bl,br,_),(fl,fr,_)) <- getSnap horiz collidedist d w

        let (mb,mf) = if rev then (bl,fl)
                             else (br,fr)

            newpos = fromIntegral $ case (mb,mf) of
                                        (Just b,Nothing) -> b
                                        (Nothing,Just f) -> f - wdim wa
                                        (Just b,Just f) -> if rev /= (b < f - wdim wa)
                                                           then b
                                                           else f - wdim wa
                                        _ -> wpos wa

        if horiz then io $ moveWindow d w newpos (fromIntegral $ wa_y wa)
                 else io $ moveWindow d w (fromIntegral $ wa_x wa) newpos
        float w

        where
            (wpos, wdim, _, _) = constructors horiz

    -- | Grow the specified edge of a window until it snaps against another window or the edge of the screen.
    snapGrow
        :: Direction2D -- ^ What edge of the window to grow.
        -> Maybe Int -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Window    -- ^ The window to grow.
        -> X ()
    snapGrow = snapResize True

    -- | Shrink the specified edge of a window until it snaps against another window or the edge of the screen.
    snapShrink
        :: Direction2D -- ^ What edge of the window to shrink.
        -> Maybe Int -- ^ The distance in the orthogonal axis to look for windows to snap against. Use Nothing to snap against every window.
        -> Window    -- ^ The window to shrink.
        -> X ()
    snapShrink = snapResize False

    snapResize :: Bool -> Direction2D -> Maybe Int -> Window -> X ()
    snapResize grow dir collidedist w = whenX (isClient w) $ withDisplay $ \d -> do
        io $ raiseWindow d w
        wa <- io $ getWindowAttributes d w
        mr <- case dir of
                  L -> do ((mg,ms,_),(_,_,_)) <- getSnap True collidedist d w
                          return $ case (if grow then mg else ms) of
                                       Just v -> Just (v, wy wa, ww wa + wx wa - v, wh wa)
                                       _ -> Nothing
                  R -> do ((_,_,_),(ms,mg,_)) <- getSnap True collidedist d w
                          return $ case (if grow then mg else ms) of
                                       Just v -> Just (wx wa, wy wa, v - wx wa, wh wa)
                                       _ -> Nothing
                  U -> do ((mg,ms,_),(_,_,_)) <- getSnap False collidedist d w
                          return $ case (if grow then mg else ms) of
                                       Just v -> Just (wx wa, v, ww wa, wh wa + wy wa - v)
                                       _ -> Nothing
                  D -> do ((_,_,_),(ms,mg,_)) <- getSnap False collidedist d w
                          return $ case (if grow then mg else ms) of
                                       Just v -> Just (wx wa, wy wa, ww wa, v - wy wa)
                                       _ -> Nothing

        case mr of
            Nothing -> return ()
            Just (nx,ny,nw,nh) -> if nw>0 && nh>0 then do io $ moveWindow d w (fromIntegral nx) (fromIntegral ny)
                                                          io $ resizeWindow d w (fromIntegral nw) (fromIntegral nh)
                                                  else return ()
        float w
        where
            wx = fromIntegral.wa_x
            wy = fromIntegral.wa_y
            ww = fromIntegral.wa_width
            wh = fromIntegral.wa_height

    getSnap :: Bool -> Maybe Int -> Display -> Window -> X ((Maybe Int,Maybe Int,Bool),(Maybe Int,Maybe Int,Bool))
    getSnap horiz collidedist d w = do
        wa <- io $ getWindowAttributes d w
        screen <- W.current <$> gets windowset
        let sr = screenRect $ W.screenDetail screen
            wl = W.integrate' . W.stack $ W.workspace screen
        gr <- fmap ($sr) $ calcGap $ S.fromList [minBound .. maxBound]
        wla <- filter (collides wa) `fmap` (io $ mapM (getWindowAttributes d) $ filter (/=w) wl)

        return ( neighbours (back wa sr gr wla) (wpos wa)
               , neighbours (front wa sr gr wla) (wpos wa + wdim wa)
               )

        where
            wborder = fromIntegral.wa_border_width

            (wpos, wdim, rpos, rdim) = constructors horiz
            (refwpos, refwdim, _, _) = constructors $ not horiz

            back wa sr gr wla = dropWhile (< rpos sr) $
                                takeWhile (< rpos sr + rdim sr) $
                                sort $ (rpos sr):(rpos gr):(rpos gr + rdim gr):
                                       foldr (\a as -> (wpos a):(wpos a + wdim a + wborder a + wborder wa):as) [] wla

            front wa sr gr wla = dropWhile (<= rpos sr) $
                                 takeWhile (<= rpos sr + rdim sr) $
                                 sort $ (rpos gr - 2*wborder wa):(rpos gr + rdim gr - 2*wborder wa):(rpos sr + rdim sr - 2*wborder wa):
                                        foldr (\a as -> (wpos a - wborder a - wborder wa):(wpos a + wdim a):as) [] wla

            neighbours l v = ( listToMaybe $ reverse $ takeWhile (< v) l
                             , listToMaybe $ dropWhile (<= v) l
                             , v `elem` l
                             )

            collides wa oa = case collidedist of
                                 Nothing -> True
                                 Just dist -> (  refwpos oa - wborder oa < refwpos wa + refwdim wa + wborder wa + dist
                                              && refwpos wa - wborder wa - dist < refwpos oa + refwdim oa + wborder oa )

    constructors :: Bool -> (WindowAttributes -> Int, WindowAttributes -> Int, Rectangle -> Int, Rectangle -> Int)
    constructors True = ( fromIntegral.wa_x
                        , fromIntegral.wa_width
                        , fromIntegral.rect_x
                        , fromIntegral.rect_width
                        )
    constructors False = ( fromIntegral.wa_y
                         , fromIntegral.wa_height
                         , fromIntegral.rect_y
                         , fromIntegral.rect_height
                         )