{-# LANGUAGE ExistentialQuantification, FlexibleInstances, GeneralizedNewtypeDeriving, MultiParamTypeClasses #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  XMonad.hs
-- Copyright   :  (c) Spencer Janssen 2007
-- License     :  BSD3-style (see LICENSE)
--
-- Maintainer  :  sjanssen@cse.unl.edu
-- Stability   :  unstable
-- Portability :  not portable, uses cunning newtype deriving
--
-- The X monad, a state monad transformer over IO, for the window
-- manager state, and support routines.
--
-----------------------------------------------------------------------------

module XMonad (
    X, WindowSet, WindowSpace, WorkspaceId, ScreenId(..), ScreenDetail(..), XState(..), XConf(..), XConfig(..), LayoutClass(..), Layout(..), readsLayout, Typeable, Message, SomeMessage(..), fromMessage, runLayout, LayoutMessages(..),
    runX, catchX, userCode, io, catchIO, withDisplay, withWindowSet, isRoot, getAtom, spawn, restart, trace, whenJust, whenX,
    atom_WM_STATE, atom_WM_PROTOCOLS, atom_WM_DELETE_WINDOW
  ) where

import StackSet

import Prelude hiding ( catch )
import Control.Exception (catch, throw, Exception(ExitException))
import Control.Monad.State
import Control.Monad.Reader
import System.IO
import System.Posix.Process (executeFile, forkProcess, getProcessStatus, createSession)
import System.Exit
import System.Environment
import Graphics.X11.Xlib
import Graphics.X11.Xlib.Extras (Event)
import Data.Typeable

import qualified Data.Map as M
import qualified Data.Set as S

-- | XState, the window manager state.
-- Just the display, width, height and a window list
data XState = XState
    { windowset    :: !WindowSet           -- ^ workspace list
    , mapped       :: !(S.Set Window)      -- ^ the Set of mapped windows
    , waitingUnmap :: !(M.Map Window Int)  -- ^ the number of expected UnmapEvents
    , dragging     :: !(Maybe (Position -> Position -> X (), X ())) }

data XConf = XConf
    { display       :: Display        -- ^ the X11 display
    , config        :: !XConfig       -- ^ initial user configuration
    , theRoot       :: !Window        -- ^ the root window
    , normalBorder  :: !Pixel         -- ^ border color of unfocused windows
    , focusedBorder :: !Pixel     }   -- ^ border color of the focused window

-- todo, better name
data XConfig = XConfig { normalBorderColor :: !String
                       , focusedBorderColor :: !String
                       , terminal :: !String
                       , layoutHook :: !(Layout Window)
                       , manageHook :: !(Window -> String -> String -> String -> X (WindowSet -> WindowSet))
                       , workspaces :: ![String]
                       , defaultGaps :: ![(Int,Int,Int,Int)]
                       , numlockMask :: KeyMask
                       , keys :: !(M.Map (ButtonMask,KeySym) (X ()))
                       , mouseBindings :: !(M.Map (ButtonMask, Button) (Window -> X ()))
                       , borderWidth :: !Dimension
                       , logHook :: !(X ()) }

type WindowSet   = StackSet  WorkspaceId (Layout Window) Window ScreenId ScreenDetail
type WindowSpace = Workspace WorkspaceId (Layout Window) Window

-- | Virtual workspace indicies
type WorkspaceId = String

-- | Physical screen indicies
newtype ScreenId    = S Int deriving (Eq,Ord,Show,Read,Enum,Num,Integral,Real)

-- | TODO Comment me
data ScreenDetail   = SD { screenRect :: !Rectangle
                         , statusGap  :: !(Int,Int,Int,Int) -- ^ width of status bar on the screen
                         } deriving (Eq,Show, Read)

------------------------------------------------------------------------

-- | The X monad, a StateT transformer over IO encapsulating the window
-- manager state
--
-- Dynamic components may be retrieved with 'get', static components
-- with 'ask'. With newtype deriving we get readers and state monads
-- instantiated on XConf and XState automatically.
--
newtype X a = X (ReaderT XConf (StateT XState IO) a)
    deriving (Functor, Monad, MonadIO, MonadState XState, MonadReader XConf)

-- | Run the X monad, given a chunk of X monad code, and an initial state
-- Return the result, and final state
runX :: XConf -> XState -> X a -> IO (a, XState)
runX c st (X a) = runStateT (runReaderT a c) st

-- | Run in the X monad, and in case of exception, and catch it and log it
-- to stderr, and run the error case.
catchX :: X a -> X a -> X a
catchX job errcase = do
    st <- get
    c <- ask
    (a, s') <- io $ runX c st job `catch`
                    \e -> case e of
                            ExitException {} -> throw e
                            _ -> do hPrint stderr e; runX c st errcase
    put s'
    return a

-- | Execute the argument, catching all exceptions.  Either this function or
-- catchX should be used at all callsites of user customized code.
userCode :: X () -> X ()
userCode a = catchX (a >> return ()) (return ())

-- ---------------------------------------------------------------------
-- Convenient wrappers to state

-- | Run a monad action with the current display settings
withDisplay :: (Display -> X a) -> X a
withDisplay   f = asks display >>= f

-- | Run a monadic action with the current stack set
withWindowSet :: (WindowSet -> X a) -> X a
withWindowSet f = gets windowset >>= f

-- | True if the given window is the root window
isRoot :: Window -> X Bool
isRoot w = liftM (w==) (asks theRoot)

-- | Wrapper for the common case of atom internment
getAtom :: String -> X Atom
getAtom str = withDisplay $ \dpy -> io $ internAtom dpy str False

-- | Common non-predefined atoms
atom_WM_PROTOCOLS, atom_WM_DELETE_WINDOW, atom_WM_STATE :: X Atom
atom_WM_PROTOCOLS       = getAtom "WM_PROTOCOLS"
atom_WM_DELETE_WINDOW   = getAtom "WM_DELETE_WINDOW"
atom_WM_STATE           = getAtom "WM_STATE"

------------------------------------------------------------------------
-- | LayoutClass handling. See particular instances in Operations.hs

-- | An existential type that can hold any object that is in Read and LayoutClass.
data Layout a = forall l. (LayoutClass l a, Read (l a)) => Layout (l a)

-- | Using the 'Layout' as a witness, parse existentially wrapped windows
-- from a 'String'
readsLayout :: Layout a -> String -> [(Layout a, String)]
readsLayout (Layout l) s = [(Layout (asTypeOf x l), rs) | (x, rs) <- reads s]

-- | The different layout modes
--
-- 'doLayout': given a Rectangle and a Stack, layout the stack elements
-- inside the given Rectangle.  If an element is not given a Rectangle
-- by 'doLayout', then it is not shown on screen.  Windows are restacked
-- according to the order they are returned by 'doLayout'.
--
class Show (layout a) => LayoutClass layout a where

    -- | Given a Rectangle in which to place the windows, and a Stack of
    -- windows, return a list of windows and their corresponding Rectangles.
    -- The order of windows in this list should be the desired stacking order.
    -- Also return a modified layout, if this layout needs to be modified
    -- (e.g. if we keep track of the windows we have displayed).
    doLayout    :: layout a -> Rectangle -> Stack a -> X ([(a, Rectangle)], Maybe (layout a))
    doLayout l r s   = return (pureLayout l r s, Nothing)

    -- | This is a pure version of doLayout, for cases where we don't need
    -- access to the X monad to determine how to layou out the windows, and
    -- we don't need to modify our layout itself.
    pureLayout  :: layout a -> Rectangle -> Stack a -> [(a, Rectangle)]
    pureLayout _ r s = [(focus s, r)]

    -- | 'handleMessage' performs message handling for that layout.  If
    -- 'handleMessage' returns Nothing, then the layout did not respond to
    -- that message and the screen is not refreshed.  Otherwise, 'handleMessage'
    -- returns an updated 'LayoutClass' and the screen is refreshed.
    --
    handleMessage :: layout a -> SomeMessage -> X (Maybe (layout a))
    handleMessage l  = return . pureMessage l

    -- | Respond to a message by (possibly) changing our layout, but taking
    -- no other action.  If the layout changes, the screen will be refreshed.
    pureMessage :: layout a -> SomeMessage -> Maybe (layout a)
    pureMessage _ _  = Nothing

    -- | This should be a human-readable string that is used when selecting
    -- layouts by name.
    description :: layout a -> String
    description      = show

instance LayoutClass Layout Window where
    doLayout (Layout l) r s  = fmap (fmap Layout) `liftM` doLayout l r s
    handleMessage (Layout l) = fmap (fmap Layout) . handleMessage l
    description (Layout l)   = description l

instance Show (Layout a) where show (Layout l) = show l

-- | This calls doLayout if there are any windows to be laid out.
runLayout :: LayoutClass l a => l a -> Rectangle -> Maybe (Stack a) -> X ([(a, Rectangle)], Maybe (l a))
runLayout l r = maybe (return ([], Nothing)) (doLayout l r)

-- | Based on ideas in /An Extensible Dynamically-Typed Hierarchy of Exceptions/,
-- Simon Marlow, 2006. Use extensible messages to the handleMessage handler.
--
-- User-extensible messages must be a member of this class.
--
class Typeable a => Message a

-- |
-- A wrapped value of some type in the Message class.
--
data SomeMessage = forall a. Message a => SomeMessage a

-- |
-- And now, unwrap a given, unknown Message type, performing a (dynamic)
-- type check on the result.
--
fromMessage :: Message m => SomeMessage -> Maybe m
fromMessage (SomeMessage m) = cast m

-- | X Events are valid Messages
instance Message Event

-- | LayoutMessages are core messages that all layouts (especially stateful
-- layouts) should consider handling.
data LayoutMessages = Hide              -- ^ sent when a layout becomes non-visible
                    | ReleaseResources  -- ^ sent when xmonad is exiting or restarting
    deriving (Typeable, Eq)

instance Message LayoutMessages

-- ---------------------------------------------------------------------
-- | General utilities
--
-- Lift an IO action into the X monad
io :: IO a -> X a
io = liftIO

-- | Lift an IO action into the X monad.  If the action results in an IO
-- exception, log the exception to stderr and continue normal execution.
catchIO :: IO () -> X ()
catchIO f = liftIO (f `catch` \e -> hPrint stderr e >> hFlush stderr)

-- | spawn. Launch an external application
spawn :: String -> X ()
spawn x = io $ do
    pid <- forkProcess $ do
        forkProcess (createSession >> executeFile "/bin/sh" False ["-c", x] Nothing)
        exitWith ExitSuccess
    getProcessStatus True False pid
    return ()

-- | Restart xmonad via exec().
--
-- If the first parameter is 'Just name', restart will attempt to execute the
-- program corresponding to 'name'.  Otherwise, xmonad will attempt to execute
-- the name of the current program.
--
-- When the second parameter is 'True', xmonad will attempt to resume with the
-- current window state.
restart :: Maybe String -> Bool -> X ()
restart mprog resume = do
    prog <- maybe (io getProgName) return mprog
    args <- if resume then gets (("--resume":) . return . showWs . windowset) else return []
    catchIO (executeFile prog True args Nothing)
 where showWs = show . mapLayout show

-- | Run a side effecting action with the current workspace. Like 'when' but
whenJust :: Maybe a -> (a -> X ()) -> X ()
whenJust mg f = maybe (return ()) f mg

-- | Conditionally run an action, using a X event to decide
whenX :: X Bool -> X () -> X ()
whenX a f = a >>= \b -> when b f

-- | A 'trace' for the X monad. Logs a string to stderr. The result may
-- be found in your .xsession-errors file
trace :: String -> X ()
trace msg = io $! do hPutStrLn stderr msg; hFlush stderr