{-# LANGUAGE ExistentialQuantification, StandaloneDeriving, FlexibleContexts, MultiParamTypeClasses, FunctionalDependencies #-}

module Phi.Widget ( Display(..)
                  , withDisplay
                  , getAtoms
                  , getScreenWindows
                  , getScreens
                  , unionArea
                  , Widget(..)
                  , CompoundWidget
                  , (<~>)
                  , Separator
                  , separator
                  ) where

import Control.Arrow
import Control.Arrow.Transformer
import Control.CacheArrow
import Control.Concurrent.MVar
import Control.Monad
import Control.Monad.IO.Class

import Data.Traversable hiding (forM)

import qualified Graphics.X11.Xlib as Xlib
import Graphics.Rendering.Cairo

import Phi.Phi
import Phi.X11.Atoms


data Display = Display !(MVar Xlib.Display) !Atoms ![(Xlib.Rectangle, Xlib.Window)]

withDisplay :: MonadIO m => Display -> (Xlib.Display -> m a) -> m a
withDisplay (Display dispvar _ _) f = do
  disp <- liftIO $ takeMVar dispvar
  a <- f disp
  liftIO $ putMVar dispvar disp
  return a

getAtoms :: Display -> Atoms
getAtoms (Display _ atoms _) = atoms

getScreenWindows :: Display -> [(Xlib.Rectangle, Xlib.Window)]
getScreenWindows (Display _ _ screenWindows) = screenWindows

getScreens :: Display -> [Xlib.Rectangle]
getScreens = map fst . getScreenWindows


unionArea :: Xlib.Rectangle -> Xlib.Rectangle -> Int
unionArea a b = fromIntegral $ uw*uh
  where
    uw = max 0 $ (min ax2 bx2) - (max ax1 bx1)
    uh = max 0 $ (min ay2 by2) - (max ay1 by1)
    
    Xlib.Rectangle ax1 ay1 aw ah = a
    Xlib.Rectangle bx1 by1 bw bh = b
    
    ax2 = ax1 + fromIntegral aw
    ay2 = ay1 + fromIntegral ah
    
    bx2 = bx1 + fromIntegral bw
    by2 = by1 + fromIntegral bh


class (Show a, Eq a, Eq d) => Widget a d | a -> d where
  initWidget :: a -> Phi -> Display -> IO d
  
  minSize :: a -> d -> Int -> Xlib.Rectangle -> Int
  
  weight :: a -> Float
  weight _ = 0

  layout :: a -> d -> Int -> Int -> Xlib.Rectangle -> d
  layout _ priv _ _ _ = priv
  
  render :: a -> d -> Int -> Int -> Int -> Int -> Xlib.Rectangle -> Render ()
  
  handleMessage :: a -> d -> Message -> d
  handleMessage _ priv _ = priv

{-createStateRender :: Widget a d => CacheArrow (Kleisli IO) (a, d, Int, Int, Int, Int, Xlib.Rectangle) Surface
createStateRender = lift . Kleisli $ \(widget, state, x, y, w, h, screen) -> do
  surface <- createImageSurface FormatARGB32 w h
  renderWith surface $ do
    setOperator OperatorClear
    paint
    setOperator OperatorOver
    render widget state x y w h screen
  return surface-}

data CompoundWidget a da b db = (Widget a da, Widget b db) => CompoundWidget !a !b
deriving instance Eq (CompoundWidget a da b db)
deriving instance Show (CompoundWidget a da b db)

data CompoundState a da b db = (Widget a da, Widget b db) => CompoundState !da !db !Int
deriving instance Eq (CompoundState a da b db)

instance Widget (CompoundWidget a da b db) (CompoundState a da b db) where
  initWidget (CompoundWidget a b) phi disp = liftM3 CompoundState (initWidget a phi disp) (initWidget b phi disp) (return 0)
  
  minSize (CompoundWidget a b) (CompoundState da db _) height screen = minSize a da height screen + minSize b db height screen
  
  weight (CompoundWidget a b) = weight' a + weight' b

  layout c@(CompoundWidget a b) d@(CompoundState da db _) width height screen = CompoundState da' db' xb
    where
      sizesum = minSize c d height screen
      wsum = let wsum = weight c
             in if wsum > 0 then wsum else 1
    
      surplus = width - sizesum
      
      (xb, da') = layoutWidget a da
      (_, db') = layoutWidget b db
      
      layoutWidget w priv = let wWidth = floor $ (fromIntegral $ minSize w priv height screen) + (fromIntegral surplus)*(weight' w)/wsum
                            in (wWidth, layout w priv wWidth height screen)
  
  render (CompoundWidget a b) (CompoundState da db xb) x y w h screen = do
    save
    render a da x y xb h screen
    restore
    translate (fromIntegral xb) 0
    render b db (x+xb) y (w-xb) h screen
    
  handleMessage (CompoundWidget a b) (CompoundState da db xb) message = CompoundState (handleMessage a da message) (handleMessage b db message) xb

weight' :: (Widget a da) => a -> Float
weight' = max 0 . weight

(<~>) :: (Widget a da, Widget b db) => a -> b -> CompoundWidget a da b db
a <~> b = CompoundWidget a b

data Separator = Separator !Int !Float deriving (Show, Eq)

instance Widget Separator () where
  initWidget _ _ _ = return ()
  
  minSize (Separator s _) _ _ _ = s
  weight (Separator _ w) = w
  render _ _ _ _ _ _ _ = return ()

separator :: Int -> Float -> Separator
separator = Separator