{-# OPTIONS_HADDOCK not-home #-}
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE InterruptibleFFI #-}

-- |
-- Module      :  System.Process.Internals
-- Copyright   :  (c) The University of Glasgow 2004
-- License     :  BSD-style (see the file libraries/base/LICENSE)
-- Maintainer  :  libraries@haskell.org
-- Stability   :  experimental
-- Portability :  portable
-- __Note:__ This module exports internal implementation details that may
-- change anytime.  If you want a more stable API, use "System.Process"
-- instead.

module System.Process.Internals (
    ProcessHandle(..), ProcessHandle__(..),
    PHANDLE, closePHANDLE, mkProcessHandle,
    modifyProcessHandle, withProcessHandle,
    CmdSpec(..), StdStream(..), ProcRetHandles (..),
    runGenProcess_, --deprecated
#ifdef WINDOWS
    pPrPr_disableITimers, c_execvpe,
    ignoreSignal, defaultSignal,
    withFilePathException, withCEnvironment,
    ) where

import Foreign.C
import System.IO

import GHC.IO.Handle.FD (fdToHandle)
import System.Posix.Internals (FD)

import System.Process.Common

#ifdef WINDOWS
import System.Process.Windows
import System.Process.Posix

-- ----------------------------------------------------------------------------
-- | This function is almost identical to
-- 'System.Process.createProcess'. The only differences are:
-- * 'Handle's provided via 'UseHandle' are not closed automatically.
-- * This function takes an extra @String@ argument to be used in creating
--   error messages.
-- * 'use_process_jobs' can be set in CreateProcess since in order to create
--   an I/O completion port to monitor a process tree's progress on Windows.
-- The function also returns two new handles:
--   * an I/O Completion Port handle on which events
--     will be signaled.
--   * a Job handle which can be used to kill all running
--     processes.
--  On POSIX platforms these two new handles will always be Nothing
-- This function has been available from the "System.Process.Internals" module
-- for some time, and is part of the "System.Process" module since version
-- @since
  :: String                     -- ^ function name (for error messages)
  -> CreateProcess
  -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
createProcess_ msg proc_ = unwrapHandles `fmap` createProcess_Internal msg proc_
{-# INLINE createProcess_ #-}

-- ------------------------------------------------------------------------
-- Escaping commands for shells

On Windows we also use this for running commands.  We use CreateProcess,
passing a single command-line string (lpCommandLine) as its argument.
(CreateProcess is well documented on http://msdn.microsoft.com.)

      - It parses the beginning of the string to find the command. If the
        file name has embedded spaces, it must be quoted, using double
        quotes thus
                "foo\this that\cmd" arg1 arg2

      - The invoked command can in turn access the entire lpCommandLine string,
        and the C runtime does indeed do so, parsing it to generate the
        traditional argument vector argv[0], argv[1], etc.  It does this
        using a complex and arcane set of rules which are described here:


        (if this URL stops working, you might be able to find it by
        searching for "Parsing C Command-Line Arguments" on MSDN.  Also,
        the code in the Microsoft C runtime that does this translation
        is shipped with VC++).

Our goal in runProcess is to take a command filename and list of
arguments, and construct a string which inverts the translatsions
described above, such that the program at the other end sees exactly
the same arguments in its argv[] that we passed to rawSystem.

This inverse translation is implemented by 'translate' below.

Here are some pages that give informations on Windows-related
limitations and deviations from Unix conventions:

    Command lines and environment variables effectively limited to 8191
    characters on Win XP, 2047 on NT/2000 (probably even less on Win 9x):

    Command-line substitution under Windows XP. IIRC these facilities (or at
    least a large subset of them) are available on Win NT and 2000. Some
    might be available on Win 9x.

    How CMD.EXE processes command lines.

Note: CreateProcess does have a separate argument (lpApplicationName)
with which you can specify the command, but we have to slap the
command into lpCommandLine anyway, so that argv[0] is what a C program
expects (namely the application name).  So it seems simpler to just
use lpCommandLine alone, which CreateProcess supports.

translate :: String -> String
translate = translateInternal
{-# INLINE translate #-}

-- ---------------------------------------------------------------------------
-- unwrapHandles
unwrapHandles :: ProcRetHandles -> (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
unwrapHandles r = (hStdInput r, hStdOutput r, hStdError r, procHandle r)

-- ----------------------------------------------------------------------------
-- Deprecated / compat

{-# DEPRECATED runGenProcess_
      "Please do not use this anymore, use the ordinary 'System.Process.createProcess'. If you need the SIGINT handling, use delegate_ctlc = True (runGenProcess_ is now just an imperfectly emulated stub that probably duplicates or overrides your own signal handling)." #-}
 :: String                     -- ^ function name (for error messages)
 -> CreateProcess
 -> Maybe CLong                -- ^ handler for SIGINT
 -> Maybe CLong                -- ^ handler for SIGQUIT
 -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
-- On Windows, setting delegate_ctlc has no impact
runGenProcess_ fun c (Just sig) (Just sig') | isDefaultSignal sig && sig == sig'
                         = createProcess_ fun c { delegate_ctlc = True }
runGenProcess_ fun c _ _ = createProcess_ fun c

-- ---------------------------------------------------------------------------
-- createPipe

-- | Create a pipe for interprocess communication and return a
-- @(readEnd, writeEnd)@ `Handle` pair.
-- @since
createPipe :: IO (Handle, Handle)
createPipe = createPipeInternal
{-# INLINE createPipe #-}

-- ---------------------------------------------------------------------------
-- createPipeFd

-- | Create a pipe for interprocess communication and return a
-- @(readEnd, writeEnd)@ `FD` pair.
-- @since
createPipeFd :: IO (FD, FD)
createPipeFd = createPipeInternalFd
{-# INLINE createPipeFd #-}

-- ----------------------------------------------------------------------------
-- interruptProcessGroupOf

-- | Sends an interrupt signal to the process group of the given process.
-- On Unix systems, it sends the group the SIGINT signal.
-- On Windows systems, it generates a CTRL_BREAK_EVENT and will only work for
-- processes created using 'createProcess' and setting the 'create_group' flag

    :: ProcessHandle    -- ^ A process in the process group
    -> IO ()
interruptProcessGroupOf = interruptProcessGroupOfInternal