{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, DeriveDataTypeable #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  XMonad.Layout.Mosaic
-- Copyright   :  (c) 2009 Adam Vogt, 2007 James Webb
-- License     :  BSD-style (see xmonad/LICENSE)
--
-- Maintainer  :  vogt.adam<at>gmail.com
-- Stability   :  unstable
-- Portability :  unportable
--
-- Based on MosaicAlt, but aspect ratio messages always change the aspect
-- ratios, and rearranging the window stack changes the window sizes.
--
-----------------------------------------------------------------------------

module XMonad.Layout.Mosaic (
    -- * Usage
    -- $usage
    Mosaic(Mosaic)
    ,Aspect(..)
    ,shallower
    ,steeper
    ,growMaster
    ,shrinkMaster
    )
    where

import Prelude hiding (sum)

import XMonad(Typeable,
              LayoutClass(doLayout , pureMessage, description), Message,
              fromMessage, splitHorizontallyBy, splitVerticallyBy, Rectangle)
import XMonad.StackSet(integrate)
import Data.Foldable(Foldable(foldMap), sum)
import Data.Monoid(Monoid(mappend, mempty))

-- $usage
-- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
--
-- > import XMonad.Layout.Mosaic
--
-- Then edit your @layoutHook@ by adding the Mosaic layout:
--
-- > myLayouts = Mosaic (take 5 $ iterate (*0.7) 1 ||| Mosaic [3,1,1,1,1,1] ||| Full ||| etc..
-- > main = xmonad defaultConfig { layoutHook = myLayouts }
--
-- Unfortunately, infinite lists break serialization, so don't use them.
--
-- To change the choice in aspect ratio and the relative sizes of windows, add
-- to your keybindings:
--
--  > , ((modMask, xK_a), sendMessage Taller)
--  > , ((modMask, xK_z), sendMessage Wider)
--  > , ((modMask, xK_h), sendMessage Shrink >> sendMessage (SlopeMod shallower))
--  > , ((modMask, xK_l), sendMessage Expand >> sendMessage (SlopeMod steeper))
--
--  > , ((modMask, xK_r), sendMessage Reset)
--
-- For more detailed instructions on editing the layoutHook see:
--
-- "XMonad.Doc.Extending#Editing_the_layout_hook"

data Aspect
    = Taller
    | Wider
    | Reset
    | SlopeMod ([Rational] -> [Rational])
    deriving (Typeable)

instance Message Aspect

data Mosaic a
    {- | The relative magnitudes of the positive rational numbers provided
         determine the relative areas that the windows receive. The first
         number represents the size of the master window, the second is for the
         next window in the stack, and so on.
    -}
    = Mosaic [Rational]
    -- override the aspect? current index, maximum index
    | MosaicSt Bool Rational Int [Rational]
    deriving (Read, Show)

instance LayoutClass Mosaic a where
    description = const "Mosaic"

    pureMessage (Mosaic _ss) _ms = Nothing
    pureMessage (MosaicSt _ ix mix ss) ms = fromMessage ms >>= ixMod
        where ixMod Taller | rix >= mix = Nothing
                           | otherwise = Just $ MosaicSt False (succ ix) mix ss
              ixMod Wider  | rix <= 0   = Nothing
                           | otherwise = Just $ MosaicSt False (pred ix) mix ss
              ixMod Reset              = Just $ Mosaic ss
              ixMod (SlopeMod f)       = Just $ MosaicSt False ix mix (f ss)
              rix = round ix

    doLayout (Mosaic ss) r st = return (zip (integrate st) rect, newLayout)
        where rects = splits (length $ integrate st) r ss
              lrects = length rects
              rect = rects !! (lrects `div` 2)
              newLayout = Just $ MosaicSt True (fromIntegral lrects / 2) (pred lrects) ss

    doLayout (MosaicSt override ix mix ss) r st
                                = return (zip (integrate st) rect, newLayout)
        where rects = splits (length $ integrate st) r ss
              lrects = length rects
              nix = if mix == 0 || override then fromIntegral $ lrects `div` 2
                        else max 0 $ min (fromIntegral $ pred lrects)
                            $ fromIntegral (pred lrects) * ix / fromIntegral mix
              rect = rects !! round nix
              newLayout = Just $ MosaicSt override nix (pred lrects) ss

-- | These sample functions are meant to be applied to the list of window sizes
-- through the 'SlopeMod' message.
--
-- Steeper and shallower scale the ratios of successive windows.
--
-- growMaster and shrinkMaster just increase and decrease the size of the first
-- element, and thus they change the layout very similarily to the standard
-- 'Expand' or 'Shrink' for the 'Tall' layout.
--
-- It may be possible to resize the specific focused window; however the same
-- result could probably be achieved by promoting it, or moving it to a higher
-- place in the list of windows; when you have a decreasing list of window
-- sizes, the change in position will also result in a change in size.

steeper :: [Rational] -> [Rational]
steeper [] = []
steeper xs = map (subtract (minimum xs*0.8)) xs

shallower :: [Rational] -> [Rational]
shallower [] = []
shallower xs = map (+(minimum xs*2)) xs

growMaster :: [Rational] -> [Rational]
growMaster [] = []
growMaster (x:xs) = 2*x:xs

shrinkMaster :: [Rational] -> [Rational]
shrinkMaster [] = []
shrinkMaster (x:xs) = x/2:xs

splits :: Int -> Rectangle -> [Rational] -> [[Rectangle]]
splits num rect sz = splitsL rect $ makeTree $ normalize $ reverse $ take num sz

-- recursively enumerate splits
splitsL :: Rectangle -> Tree Rational -> [[Rectangle]]
splitsL _rect Empty = []
splitsL rect (Leaf _) = [[rect]]
splitsL rect (Branch l r) = do
    let mkSplit f = f (sum l / (sum l + sum r)) rect
    (rl,rr) <- map mkSplit [splitVerticallyBy,splitHorizontallyBy]
    splitsL rl l `interleave` splitsL rr r

-- like zipWith (++), but when one list is shorter, its elements are duplicated
-- so that they match
interleave :: [[a]] -> [[a]] -> [[a]]
interleave xs ys | lx > ly = zc xs (extend lx ys)
                 | otherwise = zc (extend ly xs) ys
    where lx = length xs
          ly = length ys
          zc = zipWith (++)

extend :: Int -> [a] -> [a]
extend n pat = do
    (p,e') <- zip pat $ take m (repeat True) ++ repeat False
    let e = if e' then [p] else []
    (e++) $ take d $ repeat p
    where (d,m) = n `divMod` length pat

normalize :: Fractional a => [a] -> [a]
normalize x = let s = sum x
    in map (/s) x

data Tree a = Branch (Tree a) (Tree a) | Leaf a | Empty
    deriving (Show)

instance Foldable Tree where
   foldMap _f Empty = mempty
   foldMap f (Leaf x) = f x
   foldMap f (Branch l r) = foldMap f l `mappend` foldMap f r

instance Monoid (Tree a) where
    mempty = Empty
    mappend Empty x = x
    mappend x Empty = x
    mappend x y = Branch x y

makeTree :: [Rational] -> Tree Rational
makeTree [] = Empty
makeTree [x] = Leaf x
makeTree xs = Branch (makeTree a) (makeTree b)
    where ((a,b),_) = foldr w (([],[]),(0,0)) xs
          w n ((ls,rs),(l,r)) = if l > r then ((ls,n:rs),(l,n+r))
                                        else ((n:ls,rs),(n+l,r))