Terminal.hs

{-# LANGUAGE NoImplicitPrelude        #-}
{-# LANGUAGE OverloadedStrings        #-}

-- | The module of this name differs as between Windows and non-Windows builds.
-- This is the Windows version.
module System.Terminal
  ( fixCodePage
  , getTerminalWidth
  , hIsTerminalDeviceOrMinTTY
  ) where

import           Distribution.Types.Version ( mkVersion )
import           Foreign.Marshal.Alloc ( allocaBytes )
import           Foreign.Ptr ( Ptr )
import           Foreign.Storable ( peekByteOff )
import           Stack.Prelude
import           System.IO ( hGetContents )
import           System.Process
                   ( StdStream (..), createProcess, shell, std_err, std_in
                   , std_out, waitForProcess
                   )
import           System.Win32 ( isMinTTYHandle, withHandleToHANDLE )
import           System.Win32.Console
                   ( setConsoleCP, setConsoleOutputCP, getConsoleCP
                   , getConsoleOutputCP
                   )

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 :: Int
c_STD_OUTPUT_HANDLE = -11

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

foreign import ccall unsafe "windows.h GetStdHandle"
  c_GetStdHandle :: Int -> IO HANDLE


getTerminalWidth :: IO (Maybe Int)
getTerminalWidth = 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
            , std_err = CreatePipe
            }
        (_, mbStdout, _, rStty) <- createProcess stty
        exStty <- waitForProcess rStty
        case exStty of
          ExitFailure _ -> pure Nothing
          ExitSuccess ->
            maybe (pure Nothing)
                  (\hSize -> do
                      sizeStr <- hGetContents hSize
                      case map readMaybe $ words sizeStr :: [Maybe Int] of
                        [Just _r, Just c] -> pure $ Just c
                        _ -> pure Nothing
                  )
                  mbStdout
      else do
        [left,_top,right,_bottom] <- forM [0..3] $ \i -> do
          v <- peekByteOff p (i * 2 + posCONSOLE_SCREEN_BUFFER_INFO_srWindow)
          pure $ fromIntegral (v :: Word16)
        pure $ Just (1 + right - left)

-- | Set the code page for this process as necessary. Only applies to Windows.
-- See: https://github.com/commercialhaskell/stack/issues/738
fixCodePage ::
     HasTerm env
  => Bool -- ^ modify code page?
  -> Version -- ^ GHC version
  -> RIO env a
  -> RIO env a
fixCodePage mcp ghcVersion inner =
  if mcp && ghcVersion < mkVersion [7, 10, 3]
    then fixCodePage'
    -- GHC >=7.10.3 doesn't need this code page hack.
    else inner
 where
  fixCodePage' = do
    origCPI <- liftIO getConsoleCP
    origCPO <- liftIO getConsoleOutputCP

    let setInput = origCPI /= expected
        setOutput = origCPO /= expected
        fixInput
          | setInput = bracket_
              (liftIO $ setConsoleCP expected)
              (liftIO $ setConsoleCP origCPI)
          | otherwise = id
        fixOutput
          | setOutput = bracket_
              (liftIO $ setConsoleOutputCP expected)
              (liftIO $ setConsoleOutputCP origCPO)
          | otherwise = id

    case (setInput, setOutput) of
      (False, False) -> pure ()
      (True, True) -> warn []
      (True, False) -> warn ["input"]
      (False, True) -> warn ["output"]

    fixInput $ fixOutput inner
  expected = 65001 -- UTF-8
  warn typ = prettyInfoL $
       "Setting"
    :  typ
    <> [ flow "codepage to UTF-8 (65001) to ensure correct output from GHC." ]

-- | hIsTerminaDevice does not recognise handles to mintty terminals as terminal
-- devices, but isMinTTYHandle does.
hIsTerminalDeviceOrMinTTY :: MonadIO m => Handle -> m Bool
hIsTerminalDeviceOrMinTTY h = do
  isTD <- hIsTerminalDevice h
  if isTD
    then pure True
    else liftIO $ withHandleToHANDLE h isMinTTYHandle