{-# LANGUAGE CPP #-}
{-# LANGUAGE RecordWildCards #-}
module System.Process.Common
    ( CreateProcess (..)
    , CmdSpec (..)
    , StdStream (..)
    , ProcessHandle(..)
    , ProcessHandle__(..)
    , withFilePathException
    , PHANDLE
    , modifyProcessHandle
    , withProcessHandle
    , fd_stdin
    , fd_stdout
    , fd_stderr
    , mbFd
    , mbPipe
    , pfdToHandle

-- Avoid a warning on Windows
#ifdef WINDOWS
    , CGid (..)
#else
    , CGid
#endif
    ) where

import Control.Concurrent
import Control.Exception
import Data.String
import Foreign.Ptr
import Foreign.Storable

import System.Posix.Internals
import GHC.IO.Exception
import GHC.IO.Encoding
import qualified GHC.IO.FD as FD
import GHC.IO.Device
import GHC.IO.Handle.FD
import GHC.IO.Handle.Internals
import GHC.IO.Handle.Types hiding (ClosedHandle)
import System.IO.Error
import Data.Typeable
import GHC.IO.IOMode

-- We do a minimal amount of CPP here to provide uniform data types across
-- Windows and POSIX.
#ifdef WINDOWS
import Data.Word (Word32)
import System.Win32.DebugApi (PHANDLE)
#else
import System.Posix.Types
#endif

#ifdef WINDOWS
-- Define some missing types for Windows compatibility. Note that these values
-- will never actually be used, as the setuid/setgid system calls are not
-- applicable on Windows. No value of this type will ever exist.
newtype CGid = CGid Word32
type GroupID = CGid
type UserID = CGid
#else
type PHANDLE = CPid
#endif

data CreateProcess = CreateProcess{
  cmdspec      :: CmdSpec,                 -- ^ Executable & arguments, or shell command
  cwd          :: Maybe FilePath,          -- ^ Optional path to the working directory for the new process
  env          :: Maybe [(String,String)], -- ^ Optional environment (otherwise inherit from the current process)
  std_in       :: StdStream,               -- ^ How to determine stdin
  std_out      :: StdStream,               -- ^ How to determine stdout
  std_err      :: StdStream,               -- ^ How to determine stderr
  close_fds    :: Bool,                    -- ^ Close all file descriptors except stdin, stdout and stderr in the new process (on Windows, only works if std_in, std_out, and std_err are all Inherit)
  create_group :: Bool,                    -- ^ Create a new process group
  delegate_ctlc:: Bool,                    -- ^ Delegate control-C handling. Use this for interactive console processes to let them handle control-C themselves (see below for details).
                                           --
                                           --   On Windows this has no effect.
                                           --
                                           --   @since 1.2.0.0
  detach_console :: Bool,                  -- ^ Use the windows DETACHED_PROCESS flag when creating the process; does nothing on other platforms.
                                           --
                                           --   @since 1.3.0.0
  create_new_console :: Bool,              -- ^ Use the windows CREATE_NEW_CONSOLE flag when creating the process; does nothing on other platforms.
                                           --
                                           --   Default: @False@
                                           --
                                           --   @since 1.3.0.0
  new_session :: Bool,                     -- ^ Use posix setsid to start the new process in a new session; does nothing on other platforms.
                                           --
                                           --   @since 1.3.0.0
  child_group :: Maybe GroupID,            -- ^ Use posix setgid to set child process's group id; does nothing on other platforms.
                                           --
                                           --   Default: @Nothing@
                                           --
                                           --   @since 1.4.0.0
  child_user :: Maybe UserID               -- ^ Use posix setuid to set child process's user id; does nothing on other platforms.
                                           --
                                           --   Default: @Nothing@
                                           --
                                           --   @since 1.4.0.0
 }

data CmdSpec
  = ShellCommand String
      -- ^ A command line to execute using the shell
  | RawCommand FilePath [String]
      -- ^ The name of an executable with a list of arguments
      --
      -- The 'FilePath' argument names the executable, and is interpreted
      -- according to the platform's standard policy for searching for
      -- executables. Specifically:
      --
      -- * on Unix systems the
      --   <http://pubs.opengroup.org/onlinepubs/9699919799/functions/execvp.html execvp(3)>
      --   semantics is used, where if the executable filename does not
      --   contain a slash (@/@) then the @PATH@ environment variable is
      --   searched for the executable.
      --
      -- * on Windows systems the Win32 @CreateProcess@ semantics is used.
      --   Briefly: if the filename does not contain a path, then the
      --   directory containing the parent executable is searched, followed
      --   by the current directory, then some standard locations, and
      --   finally the current @PATH@.  An @.exe@ extension is added if the
      --   filename does not already have an extension.  For full details
      --   see the
      --   <http://msdn.microsoft.com/en-us/library/windows/desktop/aa365527%28v=vs.85%29.aspx documentation>
      --   for the Windows @SearchPath@ API.


-- | construct a `ShellCommand` from a string literal
--
-- @since 1.2.1.0
instance IsString CmdSpec where
  fromString = ShellCommand

data StdStream
  = Inherit                  -- ^ Inherit Handle from parent
  | UseHandle Handle         -- ^ Use the supplied Handle
  | CreatePipe               -- ^ Create a new pipe.  The returned
                             -- @Handle@ will use the default encoding
                             -- and newline translation mode (just
                             -- like @Handle@s created by @openFile@).
  | NoStream                 -- ^ No stream handle will be passed

-- ----------------------------------------------------------------------------
-- ProcessHandle type

{- | A handle to a process, which can be used to wait for termination
     of the process using 'System.Process.waitForProcess'.

     None of the process-creation functions in this library wait for
     termination: they all return a 'ProcessHandle' which may be used
     to wait for the process later.
-}
data ProcessHandle__ = OpenHandle PHANDLE | ClosedHandle ExitCode
data ProcessHandle = ProcessHandle !(MVar ProcessHandle__) !Bool

withFilePathException :: FilePath -> IO a -> IO a
withFilePathException fpath act = handle mapEx act
  where
    mapEx ex = ioError (ioeSetFileName ex fpath)

modifyProcessHandle
        :: ProcessHandle
        -> (ProcessHandle__ -> IO (ProcessHandle__, a))
        -> IO a
modifyProcessHandle (ProcessHandle m _) io = modifyMVar m io

withProcessHandle
        :: ProcessHandle
        -> (ProcessHandle__ -> IO a)
        -> IO a
withProcessHandle (ProcessHandle m _) io = withMVar m io

fd_stdin, fd_stdout, fd_stderr :: FD
fd_stdin  = 0
fd_stdout = 1
fd_stderr = 2

mbFd :: String -> FD -> StdStream -> IO FD
mbFd _   _std CreatePipe      = return (-1)
mbFd _fun std Inherit         = return std
mbFd _fn _std NoStream        = return (-2)
mbFd fun _std (UseHandle hdl) =
  withHandle fun hdl $ \Handle__{haDevice=dev,..} ->
    case cast dev of
      Just fd -> do
         -- clear the O_NONBLOCK flag on this FD, if it is set, since
         -- we're exposing it externally (see #3316)
         fd' <- FD.setNonBlockingMode fd False
         return (Handle__{haDevice=fd',..}, FD.fdFD fd')
      Nothing ->
          ioError (mkIOError illegalOperationErrorType
                      "createProcess" (Just hdl) Nothing
                   `ioeSetErrorString` "handle is not a file descriptor")

mbPipe :: StdStream -> Ptr FD -> IOMode -> IO (Maybe Handle)
mbPipe CreatePipe pfd  mode = fmap Just (pfdToHandle pfd mode)
mbPipe _std      _pfd _mode = return Nothing

pfdToHandle :: Ptr FD -> IOMode -> IO Handle
pfdToHandle pfd mode = do
  fd <- peek pfd
  let filepath = "fd:" ++ show fd
  (fD,fd_type) <- FD.mkFD (fromIntegral fd) mode
                       (Just (Stream,0,0)) -- avoid calling fstat()
                       False {-is_socket-}
                       False {-non-blocking-}
  fD' <- FD.setNonBlockingMode fD True -- see #3316
#if __GLASGOW_HASKELL__ >= 704
  enc <- getLocaleEncoding
#else
  let enc = localeEncoding
#endif
  mkHandleFromFD fD' fd_type filepath mode False {-is_socket-} (Just enc)
