module System.Console.Terminal.Windows(size) where

import System.Console.Terminal.Common

import Control.Monad
import Data.Word
import Foreign.Ptr
import Foreign.Storable
import Foreign.Marshal.Alloc
import System.Exit
import System.IO
import System.Process

type HANDLE = Ptr ()

data CONSOLE_SCREEN_BUFFER_INFO

sizeCONSOLE_SCREEN_BUFFER_INFO :: Int
sizeCONSOLE_SCREEN_BUFFER_INFO = 22

posCONSOLE_SCREEN_BUFFER_INFO_srWindow :: Int
posCONSOLE_SCREEN_BUFFER_INFO_srWindow = 10 -- 4 x Word16 Left,Top,Right,Bottom

c_STD_OUTPUT_HANDLE :: Word32
c_STD_OUTPUT_HANDLE = -11

foreign import stdcall unsafe "windows.h GetConsoleScreenBufferInfo"
    c_GetConsoleScreenBufferInfo :: HANDLE -> Ptr CONSOLE_SCREEN_BUFFER_INFO -> IO Bool

foreign import stdcall unsafe "windows.h GetStdHandle"
    c_GetStdHandle :: Word32 -> IO HANDLE


size :: Integral n => IO (Maybe (Window n))
size = do
    hdl <- c_GetStdHandle c_STD_OUTPUT_HANDLE
    allocaBytes sizeCONSOLE_SCREEN_BUFFER_INFO $ \p -> do
        b <- c_GetConsoleScreenBufferInfo hdl p
        if not b
            then do -- This could happen on Cygwin or MSYS
                let stty = (shell "stty size") {
                      std_in  = UseHandle stdin
                    , std_out = CreatePipe
                    }
                (_, mbStdout, _, rStty) <- createProcess stty
                exStty <- waitForProcess rStty
                case exStty of
                    ExitFailure _ -> return Nothing
                    ExitSuccess ->
                        maybe (return Nothing)
                              (\hSize -> do
                                  sizeStr <- hGetContents hSize
                                  let [r, c] = map read $ words sizeStr :: [Int]
                                  return $ Just $ Window (fromIntegral r) (fromIntegral c)
                              )
                              mbStdout
            else do
                [left,top,right,bottom] <- forM [0..3] $ \i -> do
                    v <- peekByteOff p ((i*2) + posCONSOLE_SCREEN_BUFFER_INFO_srWindow)
                    return $ fromIntegral (v :: Word16)
                return $ Just $ Window (1+bottom-top) (1+right-left)