{-# LINE 1 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
module System.Console.Haskeline.Backend.Win32(
{-# LINE 2 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                win32Term,
                win32TermStdin,
                fileRunTerm
                )where


import System.IO
import Foreign
import Foreign.C
import System.Win32 hiding (multiByteToWideChar)
import Graphics.Win32.Misc(getStdHandle, sTD_OUTPUT_HANDLE)
import Data.List(intercalate)
import Control.Concurrent hiding (throwTo)
import Data.Char(isPrint)
import Data.Maybe(mapMaybe)
import Control.Applicative
import Control.Monad

import System.Console.Haskeline.Key
import System.Console.Haskeline.Monads hiding (Handler)
import System.Console.Haskeline.LineState
import System.Console.Haskeline.Term
import System.Console.Haskeline.Backend.WCWidth

import Data.ByteString.Internal (createAndTrim)
import qualified Data.ByteString as B

#if defined(i386_HOST_ARCH)
# define WINDOWS_CCONV stdcall
#elif defined(x86_64_HOST_ARCH)
# define WINDOWS_CCONV ccall
#else
# error Unknown mingw32 arch
#endif


{-# LINE 38 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}

foreign import WINDOWS_CCONV "windows.h ReadConsoleInputW" c_ReadConsoleInput
    :: HANDLE -> Ptr () -> DWORD -> Ptr DWORD -> IO Bool
    
foreign import WINDOWS_CCONV "windows.h WaitForSingleObject" c_WaitForSingleObject
    :: HANDLE -> DWORD -> IO DWORD

foreign import WINDOWS_CCONV "windows.h GetNumberOfConsoleInputEvents"
    c_GetNumberOfConsoleInputEvents :: HANDLE -> Ptr DWORD -> IO Bool

getNumberOfEvents :: HANDLE -> IO Int
getNumberOfEvents h = alloca $ \numEventsPtr -> do
    failIfFalse_ "GetNumberOfConsoleInputEvents"
        $ c_GetNumberOfConsoleInputEvents h numEventsPtr
    fmap fromEnum $ peek numEventsPtr

getEvent :: HANDLE -> Chan Event -> IO Event
getEvent h = keyEventLoop (eventReader h)

eventReader :: HANDLE -> IO [Event]
eventReader h = do
    let waitTime = 500 -- milliseconds
    ret <- c_WaitForSingleObject h waitTime
    yield -- otherwise, the above foreign call causes the loop to never 
          -- respond to the killThread
    if ret /= (0)
{-# LINE 64 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        then eventReader h
        else do
            es <- readEvents h
            return $ mapMaybe processEvent es

consoleHandles :: MaybeT IO Handles
consoleHandles = do
    h_in <- open "CONIN$"
    h_out <- open "CONOUT$"
    return Handles { hIn = h_in, hOut = h_out }
  where
   open file = handle (\(_::IOException) -> mzero) $ liftIO
                $ createFile file (gENERIC_READ .|. gENERIC_WRITE)
                        (fILE_SHARE_READ .|. fILE_SHARE_WRITE) Nothing
                        oPEN_EXISTING 0 Nothing

                       
processEvent :: InputEvent -> Maybe Event
processEvent KeyEvent {keyDown = True, unicodeChar = c, virtualKeyCode = vc,
                    controlKeyState = cstate}
    = fmap (\e -> KeyInput [Key modifier' e]) $ keyFromCode vc `mplus` simpleKeyChar
  where
    simpleKeyChar = guard (c /= '\NUL') >> return (KeyChar c)
    testMod ck = (cstate .&. ck) /= 0
    modifier' = if hasMeta modifier && hasControl modifier
                    then noModifier {hasShift = hasShift modifier}
                    else modifier
    modifier = Modifier {hasMeta = testMod ((1) 
{-# LINE 92 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                                        .|. (2))
{-# LINE 93 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                        ,hasControl = testMod ((4) 
{-# LINE 94 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                                        .|. (8))
{-# LINE 95 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                                    && not (c > '\NUL' && c <= '\031')
                        ,hasShift = testMod (16)
{-# LINE 97 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                                    && not (isPrint c)
                        }

processEvent WindowEvent = Just WindowResize
processEvent _ = Nothing

keyFromCode :: WORD -> Maybe BaseKey
keyFromCode (8) = Just Backspace
{-# LINE 105 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (37) = Just LeftKey
{-# LINE 106 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (39) = Just RightKey
{-# LINE 107 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (38) = Just UpKey
{-# LINE 108 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (40) = Just DownKey
{-# LINE 109 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (46) = Just Delete
{-# LINE 110 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (36) = Just Home
{-# LINE 111 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (35) = Just End
{-# LINE 112 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (33) = Just PageUp
{-# LINE 113 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
keyFromCode (34) = Just PageDown
{-# LINE 114 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
-- The Windows console will return '\r' when return is pressed.
keyFromCode (13) = Just (KeyChar '\n')
{-# LINE 116 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
-- TODO: KillLine?
-- TODO: function keys.
keyFromCode _ = Nothing
    
data InputEvent = KeyEvent {keyDown :: BOOL,
                          repeatCount :: WORD,
                          virtualKeyCode :: WORD,
                          virtualScanCode :: WORD,
                          unicodeChar :: Char,
                          controlKeyState :: DWORD}
            -- TODO: WINDOW_BUFFER_SIZE_RECORD
            -- I cant figure out how the user generates them.
           | WindowEvent
           | OtherEvent
                        deriving Show

peekEvent :: Ptr () -> IO InputEvent
peekEvent pRecord = do
    eventType :: WORD <- ((\hsc_ptr -> peekByteOff hsc_ptr 0)) pRecord
{-# LINE 135 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    let eventPtr = ((\hsc_ptr -> hsc_ptr `plusPtr` 4)) pRecord
{-# LINE 136 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    case eventType of
        (1) -> getKeyEvent eventPtr
{-# LINE 138 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        (4) -> return WindowEvent
{-# LINE 139 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        _ -> return OtherEvent

readEvents :: HANDLE -> IO [InputEvent]
readEvents h = do
    n <- getNumberOfEvents h
    alloca $ \numEventsPtr -> 
        allocaBytes (n * (20)) $ \pRecord -> do
{-# LINE 146 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
            failIfFalse_ "ReadConsoleInput" 
                $ c_ReadConsoleInput h pRecord (toEnum n) numEventsPtr
            numRead <- fmap fromEnum $ peek numEventsPtr
            forM [0..toEnum numRead-1] $ \i -> peekEvent
                $ pRecord `plusPtr` (i * (20))
{-# LINE 151 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}

getKeyEvent :: Ptr () -> IO InputEvent
getKeyEvent p = do
    kDown' <- ((\hsc_ptr -> peekByteOff hsc_ptr 0)) p
{-# LINE 155 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    repeat' <- ((\hsc_ptr -> peekByteOff hsc_ptr 4)) p
{-# LINE 156 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    keyCode <- ((\hsc_ptr -> peekByteOff hsc_ptr 6)) p
{-# LINE 157 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    scanCode <- ((\hsc_ptr -> peekByteOff hsc_ptr 8)) p
{-# LINE 158 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    char :: CWchar <- ((\hsc_ptr -> peekByteOff hsc_ptr 10)) p
{-# LINE 159 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    state <- ((\hsc_ptr -> peekByteOff hsc_ptr 12)) p
{-# LINE 160 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    return KeyEvent {keyDown = kDown',
                            repeatCount = repeat',
                            virtualKeyCode = keyCode,
                            virtualScanCode = scanCode,
                            unicodeChar = toEnum (fromEnum char),
                            controlKeyState = state}

data Coord = Coord {coordX, coordY :: Int}
                deriving Show
                

{-# LINE 171 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
instance Storable Coord where
    sizeOf _ = ((4))
{-# LINE 173 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    alignment _ = (2)
{-# LINE 174 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    peek p = do
        x :: CShort <- ((\hsc_ptr -> peekByteOff hsc_ptr 0)) p
{-# LINE 176 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        y :: CShort <- ((\hsc_ptr -> peekByteOff hsc_ptr 2)) p
{-# LINE 177 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        return Coord {coordX = fromEnum x, coordY = fromEnum y}
    poke p c = do
        ((\hsc_ptr -> pokeByteOff hsc_ptr 0)) p (toEnum (coordX c) :: CShort)
{-# LINE 180 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        ((\hsc_ptr -> pokeByteOff hsc_ptr 2)) p (toEnum (coordY c) :: CShort)
{-# LINE 181 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                
                            
foreign import ccall "haskeline_SetPosition"
    c_SetPosition :: HANDLE -> Ptr Coord -> IO Bool
    
setPosition :: HANDLE -> Coord -> IO ()
setPosition h c = with c $ failIfFalse_ "SetConsoleCursorPosition" 
                    . c_SetPosition h
                    
foreign import WINDOWS_CCONV "windows.h GetConsoleScreenBufferInfo"
    c_GetScreenBufferInfo :: HANDLE -> Ptr () -> IO Bool
    
getPosition :: HANDLE -> IO Coord
getPosition = withScreenBufferInfo $ 
    ((\hsc_ptr -> peekByteOff hsc_ptr 4))
{-# LINE 196 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}

withScreenBufferInfo :: (Ptr () -> IO a) -> HANDLE -> IO a
withScreenBufferInfo f h = allocaBytes ((22))
{-# LINE 199 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
                                $ \infoPtr -> do
        failIfFalse_ "GetConsoleScreenBufferInfo"
            $ c_GetScreenBufferInfo h infoPtr
        f infoPtr

getBufferSize :: HANDLE -> IO Layout
getBufferSize = withScreenBufferInfo $ \p -> do
    c <- ((\hsc_ptr -> peekByteOff hsc_ptr 0)) p
{-# LINE 207 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
    return Layout {width = coordX c, height = coordY c}

foreign import WINDOWS_CCONV "windows.h WriteConsoleW" c_WriteConsoleW
    :: HANDLE -> Ptr TCHAR -> DWORD -> Ptr DWORD -> Ptr () -> IO Bool

writeConsole :: HANDLE -> String -> IO ()
-- For some reason, Wine returns False when WriteConsoleW is called on an empty
-- string.  Easiest fix: just don't call that function.
writeConsole _ "" = return ()
writeConsole h str = writeConsole' >> writeConsole h ys
  where
    (xs,ys) = splitAt limit str
    -- WriteConsoleW has a buffer limit which is documented as 32768 word8's,
    -- but bug reports from online suggest that the limit may be lower (~25000).
    -- To be safe, we pick a round number we know to be less than the limit.
    limit = 20000 -- known to be less than WriteConsoleW's buffer limit
    writeConsole'
        = withArray (map (toEnum . fromEnum) xs)
            $ \t_arr -> alloca $ \numWritten -> do
                    failIfFalse_ "WriteConsoleW"
                        $ c_WriteConsoleW h t_arr (toEnum $ length xs)
                                numWritten nullPtr
                        
foreign import WINDOWS_CCONV "windows.h MessageBeep" c_messageBeep :: UINT -> IO Bool

messageBeep :: IO ()
messageBeep = c_messageBeep (-1) >> return ()-- intentionally ignore failures.


----------
-- Console mode
foreign import WINDOWS_CCONV "windows.h GetConsoleMode" c_GetConsoleMode
    :: HANDLE -> Ptr DWORD -> IO Bool

foreign import WINDOWS_CCONV "windows.h SetConsoleMode" c_SetConsoleMode
    :: HANDLE -> DWORD -> IO Bool

withWindowMode :: MonadException m => Handles -> m a -> m a
withWindowMode hs f = do
    let h = hIn hs
    bracket (getConsoleMode h) (setConsoleMode h)
            $ \m -> setConsoleMode h (m .|. (8)) >> f
{-# LINE 249 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
  where
    getConsoleMode h = liftIO $ alloca $ \p -> do
            failIfFalse_ "GetConsoleMode" $ c_GetConsoleMode h p
            peek p
    setConsoleMode h m = liftIO $ failIfFalse_ "SetConsoleMode" $ c_SetConsoleMode h m

----------------------------
-- Drawing

data Handles = Handles { hIn, hOut :: HANDLE }

closeHandles :: Handles -> IO ()
closeHandles hs = closeHandle (hIn hs) >> closeHandle (hOut hs)

newtype Draw m a = Draw {runDraw :: ReaderT Handles m a}
    deriving (Functor, Applicative, Monad, MonadIO, MonadException, MonadReader Handles)

type DrawM a = forall m . (MonadIO m, MonadReader Layout m) => Draw m a

instance MonadTrans Draw where
    lift = Draw . lift

getPos :: MonadIO m => Draw m Coord
getPos = asks hOut >>= liftIO . getPosition
    
setPos :: Coord -> DrawM ()
setPos c = do
    h <- asks hOut
    -- SetPosition will fail if you give it something out of bounds of
    -- the window buffer (i.e., the input line doesn't fit in the window).
    -- So we do a simple guard against that uncommon case.
    -- However, we don't throw away the x coord since it produces sensible
    -- results for some cases.
    maxY <- liftM (subtract 1) $ asks height
    liftIO $ setPosition h c { coordY = max 0 $ min maxY $ coordY c }

printText :: MonadIO m => String -> Draw m ()
printText txt = do
    h <- asks hOut
    liftIO (writeConsole h txt)
    
printAfter :: [Grapheme] -> DrawM ()
printAfter gs = do
    -- NOTE: you may be tempted to write
    -- do {p <- getPos; printText (...); setPos p}
    -- Unfortunately, that would be WRONG, because if printText wraps
    -- a line at the bottom of the window, causing the window to scroll,
    -- then the old value of p will be incorrect.
    printText (graphemesToString gs)
    movePosLeft gs
    
drawLineDiffWin :: LineChars -> LineChars -> DrawM ()
drawLineDiffWin (xs1,ys1) (xs2,ys2) = case matchInit xs1 xs2 of
    ([],[])     | ys1 == ys2            -> return ()
    (xs1',[])   | xs1' ++ ys1 == ys2    -> movePosLeft xs1'
    ([],xs2')   | ys1 == xs2' ++ ys2    -> movePosRight xs2'
    (xs1',xs2')                         -> do
        movePosLeft xs1'
        let m = gsWidth xs1' + gsWidth ys1 - (gsWidth xs2' + gsWidth ys2)
        let deadText = stringToGraphemes $ replicate m ' '
        printText (graphemesToString xs2')
        printAfter (ys2 ++ deadText)

movePosRight, movePosLeft :: [Grapheme] -> DrawM ()
movePosRight str = do
    p <- getPos
    w <- asks width
    setPos $ moveCoord w p str
  where
    moveCoord _ p [] = p
    moveCoord w p cs = case splitAtWidth (w - coordX p) cs of
                        (_,[],len) | len < w - coordX p -- stayed on same line
                            -> Coord { coordY = coordY p,
                                       coordX = coordX p + len
                                     }
                        (_,cs',_) -- moved to next line
                            -> moveCoord w Coord {
                                            coordY = coordY p + 1,
                                            coordX = 0
                                           } cs'

movePosLeft str = do
    p <- getPos
    w <- asks width
    setPos $ moveCoord w p str
  where
    moveCoord _ p [] = p
    moveCoord w p cs = case splitAtWidth (coordX p) cs of
                        (_,[],len) -- stayed on same line
                            -> Coord { coordY = coordY p,
                                       coordX = coordX p - len
                                     }
                        (_,_:cs',_) -- moved to previous line
                            -> moveCoord w Coord {
                                            coordY = coordY p - 1,
                                            coordX = w-1
                                           } cs'

crlf :: String
crlf = "\r\n"

instance (MonadException m, MonadReader Layout m) => Term (Draw m) where
    drawLineDiff (xs1,ys1) (xs2,ys2) = let
        fixEsc = filter ((/= '\ESC') . baseChar)
        in drawLineDiffWin (fixEsc xs1, fixEsc ys1) (fixEsc xs2, fixEsc ys2)
    -- TODO now that we capture resize events.
    -- first, looks like the cursor stays on the same line but jumps
    -- to the beginning if cut off.
    reposition _ _ = return ()

    printLines [] = return ()
    printLines ls = printText $ intercalate crlf ls ++ crlf
    
    clearLayout = clearScreen
    
    moveToNextLine s = do
        movePosRight (snd s)
        printText "\r\n" -- make the console take care of creating a new line
    
    ringBell True = liftIO messageBeep
    ringBell False = return () -- TODO

win32TermStdin :: MaybeT IO RunTerm
win32TermStdin = do
    liftIO (hIsTerminalDevice stdin) >>= guard
    win32Term

win32Term :: MaybeT IO RunTerm
win32Term = do
    hs <- consoleHandles
    ch <- liftIO newChan
    fileRT <- liftIO $ fileRunTerm stdin
    return fileRT {
                            termOps = Left TermOps {
                                getLayout = getBufferSize (hOut hs)
                                , withGetEvent = withWindowMode hs
                                                    . win32WithEvent hs ch
                                , saveUnusedKeys = saveKeys ch
                                , evalTerm = EvalTerm (runReaderT' hs . runDraw)
                                                    (Draw . lift)
                                },
                            closeTerm = closeHandles hs
                        }

win32WithEvent :: MonadException m => Handles -> Chan Event
                                        -> (m Event -> m a) -> m a
win32WithEvent h eventChan f = f $ liftIO $ getEvent (hIn h) eventChan

-- stdin is not a terminal, but we still need to check the right way to output unicode to stdout.
fileRunTerm :: Handle -> IO RunTerm
fileRunTerm h_in = do
    putter <- putOut
    cp <- getCodePage
    return RunTerm {
                    closeTerm = return (),
                    putStrOut = putter,
                    wrapInterrupt = withCtrlCHandler,
                    termOps = Right FileOps
                                { inputHandle = h_in
                                , wrapFileInput = hWithBinaryMode h_in
                                , getLocaleChar = getMultiByteChar cp h_in
                                , maybeReadNewline = hMaybeReadNewline h_in
                                , getLocaleLine = hGetLocaleLine h_in
                                            >>= liftIO . codePageToUnicode cp
                                }

                    }

-- On Windows, Unicode written to the console must be written with the WriteConsole API call.
-- And to make the API cross-platform consistent, Unicode to a file should be UTF-8.
putOut :: IO (String -> IO ())
putOut = do
    outIsTerm <- hIsTerminalDevice stdout
    if outIsTerm
        then do
            h <- getStdHandle sTD_OUTPUT_HANDLE
            return (writeConsole h)
        else do
            cp <- getCodePage
            return $ \str -> unicodeToCodePage cp str >>= B.putStr >> hFlush stdout


type Handler = DWORD -> IO BOOL

foreign import ccall "wrapper" wrapHandler :: Handler -> IO (FunPtr Handler)

foreign import WINDOWS_CCONV "windows.h SetConsoleCtrlHandler" c_SetConsoleCtrlHandler
    :: FunPtr Handler -> BOOL -> IO BOOL

-- sets the tv to True when ctrl-c is pressed.
withCtrlCHandler :: MonadException m => m a -> m a
withCtrlCHandler f = bracket (liftIO $ do
                                    tid <- myThreadId
                                    fp <- wrapHandler (handler tid)
                                -- don't fail if we can't set the ctrl-c handler
                                -- for example, we might not be attached to a console?
                                    _ <- c_SetConsoleCtrlHandler fp True
                                    return fp)
                                (\fp -> liftIO $ c_SetConsoleCtrlHandler fp False)
                                (const f)
  where
    handler tid (0) = do
{-# LINE 451 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}
        throwTo tid Interrupt
        return True
    handler _ _ = return False



------------------------
-- Multi-byte conversion

foreign import WINDOWS_CCONV "WideCharToMultiByte" wideCharToMultiByte
        :: CodePage -> DWORD -> LPCWSTR -> CInt -> LPCSTR -> CInt
                -> LPCSTR -> LPBOOL -> IO CInt

unicodeToCodePage :: CodePage -> String -> IO B.ByteString
unicodeToCodePage cp wideStr = withCWStringLen wideStr $ \(wideBuff, wideLen) -> do
    -- first, ask for the length without filling the buffer.
    outSize <- wideCharToMultiByte cp 0 wideBuff (toEnum wideLen)
                    nullPtr 0 nullPtr nullPtr
    -- then, actually perform the encoding.
    createAndTrim (fromEnum outSize) $ \outBuff -> 
        fmap fromEnum $ wideCharToMultiByte cp 0 wideBuff (toEnum wideLen)
                    (castPtr outBuff) outSize nullPtr nullPtr

foreign import WINDOWS_CCONV "MultiByteToWideChar" multiByteToWideChar
        :: CodePage -> DWORD -> LPCSTR -> CInt -> LPWSTR -> CInt -> IO CInt

codePageToUnicode :: CodePage -> B.ByteString -> IO String
codePageToUnicode cp bs = B.useAsCStringLen bs $ \(inBuff, inLen) -> do
    -- first ask for the size without filling the buffer.
    outSize <- multiByteToWideChar cp 0 inBuff (toEnum inLen) nullPtr 0
    -- then, actually perform the decoding.
    allocaArray0 (fromEnum outSize) $ \outBuff -> do
    outSize' <- multiByteToWideChar cp 0 inBuff (toEnum inLen) outBuff outSize
    peekCWStringLen (outBuff, fromEnum outSize')
                

getCodePage :: IO CodePage
getCodePage = do
    conCP <- getConsoleCP
    if conCP > 0
        then return conCP
        else getACP

foreign import WINDOWS_CCONV "IsDBCSLeadByteEx" c_IsDBCSLeadByteEx
        :: CodePage -> BYTE -> BOOL

getMultiByteChar :: CodePage -> Handle -> MaybeT IO Char
getMultiByteChar cp h = do
        b1 <- hGetByte h
        bs <- if c_IsDBCSLeadByteEx cp b1
                then hGetByte h >>= \b2 -> return [b1,b2]
                else return [b1]
        cs <- liftIO $ codePageToUnicode cp (B.pack bs)
        case cs of
            [] -> getMultiByteChar cp h
            (c:_) -> return c

----------------------------------
-- Clearing screen
-- WriteConsole has a limit of ~20,000-30000 characters, which is
-- less than a 200x200 window, for example.
-- So we'll use other Win32 functions to clear the screen.

getAttribute :: HANDLE -> IO WORD
getAttribute = withScreenBufferInfo $
    ((\hsc_ptr -> peekByteOff hsc_ptr 8))
{-# LINE 517 "libraries\haskeline\System\Console\Haskeline\Backend\Win32.hsc" #-}

fillConsoleChar :: HANDLE -> Char -> Int -> Coord -> IO ()
fillConsoleChar h c n start = with start $ \startPtr -> alloca $ \numWritten -> do
    failIfFalse_ "FillConsoleOutputCharacter"
        $ c_FillConsoleCharacter h (toEnum $ fromEnum c)
            (toEnum n) startPtr numWritten

foreign import ccall "haskeline_FillConsoleCharacter" c_FillConsoleCharacter 
    :: HANDLE -> TCHAR -> DWORD -> Ptr Coord -> Ptr DWORD -> IO BOOL

fillConsoleAttribute :: HANDLE -> WORD -> Int -> Coord -> IO ()
fillConsoleAttribute h a n start = with start $ \startPtr -> alloca $ \numWritten -> do
    failIfFalse_ "FillConsoleOutputAttribute"
        $ c_FillConsoleAttribute h a
            (toEnum n) startPtr numWritten
            
foreign import ccall "haskeline_FillConsoleAttribute" c_FillConsoleAttribute
    :: HANDLE -> WORD -> DWORD -> Ptr Coord -> Ptr DWORD -> IO BOOL

clearScreen :: DrawM ()
clearScreen = do
    lay <- ask
    h <- asks hOut
    let windowSize = width lay * height lay
    let origin = Coord 0 0
    attr <- liftIO $ getAttribute h
    liftIO $ fillConsoleChar h ' ' windowSize origin
    liftIO $ fillConsoleAttribute h attr windowSize origin
    setPos origin