    {-# LANGUAGE CPP #-}
    {-# OPTIONS_HADDOCK hide #-}
    module Distribution.Compat.Internal.TempFile (
      openTempFile,
      openBinaryTempFile,
      openNewBinaryFile,
      createTempDirectory,
      ) where

    import Distribution.Compat.Exception

    import System.FilePath        ((</>))
    import Foreign.C              (CInt, eEXIST, getErrno, errnoToIOError)

    import System.IO              (Handle, openTempFile, openBinaryTempFile)
    import Data.Bits              ((.|.))
    import System.Posix.Internals (c_open, c_close, o_CREAT, o_EXCL, o_RDWR,
                                   o_BINARY, o_NONBLOCK, o_NOCTTY,
                                   withFilePath, c_getpid)
    import System.IO.Error        (isAlreadyExistsError)
    import GHC.IO.Handle.FD       (fdToHandle)
    import Control.Exception      (onException)

    #if defined(mingw32_HOST_OS) || defined(ghcjs_HOST_OS)
    import System.Directory       ( createDirectory )
    #else
    import qualified System.Posix
    #endif

    -- ------------------------------------------------------------
    -- * temporary files
    -- ------------------------------------------------------------

    -- This is here for Haskell implementations that do not come with
    -- System.IO.openTempFile. This includes nhc-1.20, hugs-2006.9.
    -- TODO: Not sure about JHC
    -- TODO: This file should probably be removed.

    -- This is a copy/paste of the openBinaryTempFile definition, but
    -- if uses 666 rather than 600 for the permissions. The base library
    -- needs to be changed to make this better.
    openNewBinaryFile :: FilePath -> String -> IO (FilePath, Handle)
    openNewBinaryFile dir template = do
      pid <- c_getpid
      findTempName pid
      where
        -- We split off the last extension, so we can use .foo.ext files
        -- for temporary files (hidden on Unix OSes). Unfortunately we're
        -- below file path in the hierarchy here.
        (prefix,suffix) =
           case break (== '.') $ reverse template of
             -- First case: template contains no '.'s. Just re-reverse it.
             (rev_suffix, "")       -> (reverse rev_suffix, "")
             -- Second case: template contains at least one '.'. Strip the
             -- dot from the prefix and prepend it to the suffix (if we don't
             -- do this, the unique number will get added after the '.' and
             -- thus be part of the extension, which is wrong.)
             (rev_suffix, '.':rest) -> (reverse rest, '.':reverse rev_suffix)
             -- Otherwise, something is wrong, because (break (== '.')) should
             -- always return a pair with either the empty string or a string
             -- beginning with '.' as the second component.
             _                      -> error "bug in System.IO.openTempFile"

        oflags = rw_flags .|. o_EXCL .|. o_BINARY

        findTempName x = do
          fd <- withFilePath filepath $ \ f ->
                  c_open f oflags 0o666
          if fd < 0
           then do
             errno <- getErrno
             if errno == eEXIST
               then findTempName (x+1)
               else ioError (errnoToIOError "openNewBinaryFile" errno Nothing (Just dir))
           else do
             -- TODO: We want to tell fdToHandle what the file path is,
             -- as any exceptions etc will only be able to report the
             -- FD currently
             h <- fdToHandle fd `onException` c_close fd
             return (filepath, h)
          where
            filename        = prefix ++ show x ++ suffix
            filepath        = dir `combine` filename

            -- FIXME: bits copied from System.FilePath
            combine a b
                      | null b = a
                      | null a = b
                      | last a == pathSeparator = a ++ b
                      | otherwise = a ++ [pathSeparator] ++ b

    -- FIXME: Should use System.FilePath library
    pathSeparator :: Char
    #ifdef mingw32_HOST_OS
    pathSeparator = '\\'
    #else
    pathSeparator = '/'
    #endif

    -- FIXME: Copied from GHC.Handle
    std_flags, output_flags, rw_flags :: CInt
    std_flags    = o_NONBLOCK   .|. o_NOCTTY
    output_flags = std_flags    .|. o_CREAT
    rw_flags     = output_flags .|. o_RDWR

    createTempDirectory :: FilePath -> String -> IO FilePath
    createTempDirectory dir template = do
      pid <- c_getpid
      findTempName pid
      where
        findTempName x = do
          let dirpath = dir </> template ++ "-" ++ show x
          r <- tryIO $ mkPrivateDir dirpath
          case r of
            Right _ -> return dirpath
            Left  e | isAlreadyExistsError e -> findTempName (x+1)
                    | otherwise              -> ioError e

    mkPrivateDir :: String -> IO ()
    #if defined(mingw32_HOST_OS) || defined(ghcjs_HOST_OS)
    mkPrivateDir s = createDirectory s
    #else
    mkPrivateDir s = System.Posix.createDirectory s 0o700
    #endif