{-# LANGUAGE CPP #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
-- | This module is __internal__ and its contents may change without a warning
-- or announcement. It is not subject to the PVP.
module System.Process.Typed.Internal where

import qualified Data.ByteString as S
import Data.ByteString.Lazy.Internal (defaultChunkSize)
import qualified Control.Exception as E
import Control.Exception hiding (bracket, finally, handle)
import Control.Monad (void)
import qualified System.Process as P
import Data.Typeable (Typeable)
import System.IO (Handle, hClose, IOMode(ReadWriteMode), withBinaryFile)
import Control.Concurrent.Async (async)
import Control.Concurrent.STM (newEmptyTMVarIO, atomically, putTMVar, readTMVar, STM, tryPutTMVar, throwSTM)
import System.Exit (ExitCode)
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Lazy.Char8 as L8
import Data.String (IsString (fromString))
import Control.Monad.IO.Unlift

#if MIN_VERSION_process(1, 4, 0) && !WINDOWS
import System.Posix.Types (GroupID, UserID)
#endif

#if !MIN_VERSION_base(4, 8, 0)
import Control.Applicative (Applicative (..), (<$>), (<$))
#endif

#if !MIN_VERSION_process(1, 3, 0)
import qualified System.Process.Internals as P (createProcess_)
#endif

-- | An abstract configuration for a process, which can then be
-- launched into an actual running 'Process'. Takes three type
-- parameters, providing the types of standard input, standard output,
-- and standard error, respectively.
--
-- There are three ways to construct a value of this type:
--
-- * With the 'proc' smart constructor, which takes a command name and
-- a list of arguments.
--
-- * With the 'shell' smart constructor, which takes a shell string
--
-- * With the 'IsString' instance via OverloadedStrings. If you
-- provide it a string with no spaces (e.g., @"date"@), it will
-- treat it as a raw command with no arguments (e.g., @proc "date"
-- []@). If it has spaces, it will use @shell@.
--
-- In all cases, the default for all three streams is to inherit the
-- streams from the parent process. For other settings, see the
-- [setters below](#processconfigsetters) for default values.
--
-- Once you have a @ProcessConfig@ you can launch a process from it
-- using the functions in the section [Launch a
-- process](#launchaprocess).
--
-- @since 0.1.0.0
data ProcessConfig stdin stdout stderr = ProcessConfig
    { pcCmdSpec :: !P.CmdSpec
    , pcStdin :: !(StreamSpec 'STInput stdin)
    , pcStdout :: !(StreamSpec 'STOutput stdout)
    , pcStderr :: !(StreamSpec 'STOutput stderr)
    , pcWorkingDir :: !(Maybe FilePath)
    , pcEnv :: !(Maybe [(String, String)])
    , pcCloseFds :: !Bool
    , pcCreateGroup :: !Bool
    , pcDelegateCtlc :: !Bool

#if MIN_VERSION_process(1, 3, 0)
    , pcDetachConsole :: !Bool
    , pcCreateNewConsole :: !Bool
    , pcNewSession :: !Bool
#endif

#if MIN_VERSION_process(1, 4, 0) && !WINDOWS
    , pcChildGroup :: !(Maybe GroupID)
    , pcChildUser :: !(Maybe UserID)
#endif
    }
instance Show (ProcessConfig stdin stdout stderr) where
    show pc = concat
        [ case pcCmdSpec pc of
            P.ShellCommand s -> "Shell command: " ++ s
            P.RawCommand x xs -> "Raw command: " ++ unwords (map escape (x:xs))
        , "\n"
        , case pcWorkingDir pc of
            Nothing -> ""
            Just wd -> concat
                [ "Run from: "
                , wd
                , "\n"
                ]
        , case pcEnv pc of
            Nothing -> ""
            Just e -> unlines
                $ "Modified environment:"
                : map (\(k, v) -> concat [k, "=", v]) e
        ]
      where
        escape x
            | any (`elem` " \\\"'") x = show x
            | x == "" = "\"\""
            | otherwise = x
instance (stdin ~ (), stdout ~ (), stderr ~ ())
  => IsString (ProcessConfig stdin stdout stderr) where
    fromString s
        | any (== ' ') s = shell s
        | otherwise = proc s []

-- | Whether a stream is an input stream or output stream. Note that
-- this is from the perspective of the /child process/, so that a
-- child's standard input stream is an @STInput@, even though the
-- parent process will be writing to it.
--
-- @since 0.1.0.0
data StreamType = STInput | STOutput

-- | A specification for how to create one of the three standard child
-- streams, @stdin@, @stdout@ and @stderr@. A 'StreamSpec' can be
-- thought of as containing
--
-- 1. A type safe version of 'P.StdStream' from "System.Process".
-- This determines whether the stream should be inherited from the
-- parent process, piped to or from a 'Handle', etc.
--
-- 2. A means of accessing the stream as a value of type @a@
--
-- 3. A cleanup action which will be run on the stream once the
-- process terminates
--
-- To create a @StreamSpec@ see the section [Stream
-- specs](#streamspecs).
--
-- @since 0.1.0.0
data StreamSpec (streamType :: StreamType) a = StreamSpec
    { ssStream :: !(forall b. (P.StdStream -> IO b) -> IO b)
    , ssCreate :: !(ProcessConfig () () () -> Maybe Handle -> Cleanup a)
    }
    deriving Functor

-- | This instance uses 'byteStringInput' to convert a raw string into
-- a stream of input for a child process.
--
-- @since 0.1.0.0
instance (streamType ~ 'STInput, res ~ ())
  => IsString (StreamSpec streamType res) where
    fromString = byteStringInput . fromString

-- | Internal type, to make for easier composition of cleanup actions.
--
-- @since 0.1.0.0
newtype Cleanup a = Cleanup { runCleanup :: IO (a, IO ()) }
    deriving Functor
instance Applicative Cleanup where
    pure x = Cleanup (return (x, return ()))
    Cleanup f <*> Cleanup x = Cleanup $ do
        (f', c1) <- f
        (`onException` c1) $ do
            (x', c2) <- x
            return (f' x', c1 `finally` c2)

-- | Internal helper
defaultProcessConfig :: ProcessConfig () () ()
defaultProcessConfig = ProcessConfig
    { pcCmdSpec = P.ShellCommand ""
    , pcStdin = inherit
    , pcStdout = inherit
    , pcStderr = inherit
    , pcWorkingDir = Nothing
    , pcEnv = Nothing
    , pcCloseFds = False
    , pcCreateGroup = False
    , pcDelegateCtlc = False

#if MIN_VERSION_process(1, 3, 0)
    , pcDetachConsole = False
    , pcCreateNewConsole = False
    , pcNewSession = False
#endif

#if MIN_VERSION_process(1, 4, 0) && !WINDOWS
    , pcChildGroup = Nothing
    , pcChildUser = Nothing
#endif
    }

-- | Create a 'ProcessConfig' from the given command and arguments.
--
-- @since 0.1.0.0
proc :: FilePath -> [String] -> ProcessConfig () () ()
proc cmd args = setProc cmd args defaultProcessConfig

-- | Internal helper
setProc :: FilePath -> [String]
        -> ProcessConfig stdin stdout stderr
        -> ProcessConfig stdin stdout stderr
setProc cmd args p = p { pcCmdSpec = P.RawCommand cmd args }

-- | Create a 'ProcessConfig' from the given shell command.
--
-- @since 0.1.0.0
shell :: String -> ProcessConfig () () ()
shell cmd = setShell cmd defaultProcessConfig

-- | Internal helper
setShell :: String
         -> ProcessConfig stdin stdout stderr
         -> ProcessConfig stdin stdout stderr
setShell cmd p = p { pcCmdSpec = P.ShellCommand cmd }

-- | Set the child's standard input stream to the given 'StreamSpec'.
--
-- Default: 'inherit'
--
-- @since 0.1.0.0
setStdin :: StreamSpec 'STInput stdin
         -- ^
         -> ProcessConfig stdin0 stdout stderr
         -- ^
         -> ProcessConfig stdin stdout stderr
setStdin spec pc = pc { pcStdin = spec }

-- | Set the child's standard output stream to the given 'StreamSpec'.
--
-- Default: 'inherit'
--
-- @since 0.1.0.0
setStdout :: StreamSpec 'STOutput stdout
          -- ^
          -> ProcessConfig stdin stdout0 stderr
          -- ^
          -> ProcessConfig stdin stdout stderr
setStdout spec pc = pc { pcStdout = spec }

-- | Set the child's standard error stream to the given 'StreamSpec'.
--
-- Default: 'inherit'
--
-- @since 0.1.0.0
setStderr :: StreamSpec 'STOutput stderr
          -- ^
          -> ProcessConfig stdin stdout stderr0
          -- ^
          -> ProcessConfig stdin stdout stderr
setStderr spec pc = pc { pcStderr = spec }

-- | Set the working directory of the child process.
--
-- Default: current process's working directory.
--
-- @since 0.1.0.0
setWorkingDir :: FilePath
              -- ^
              -> ProcessConfig stdin stdout stderr
              -- ^
              -> ProcessConfig stdin stdout stderr
setWorkingDir dir pc = pc { pcWorkingDir = Just dir }

-- | Inherit the working directory from the parent process.
--
-- @since 0.2.2.0
setWorkingDirInherit
  :: ProcessConfig stdin stdout stderr
  -- ^
  -> ProcessConfig stdin stdout stderr
setWorkingDirInherit pc = pc { pcWorkingDir = Nothing }

-- | Set the environment variables of the child process.
--
-- Default: current process's environment.
--
-- @since 0.1.0.0
setEnv :: [(String, String)]
       -- ^
       -> ProcessConfig stdin stdout stderr
       -- ^
       -> ProcessConfig stdin stdout stderr
setEnv env pc = pc { pcEnv = Just env }

-- | Inherit the environment variables from the parent process.
--
-- @since 0.2.2.0
setEnvInherit
  :: ProcessConfig stdin stdout stderr
  -- ^
  -> ProcessConfig stdin stdout stderr
setEnvInherit pc = pc { pcEnv = Nothing }

-- | Should we close all file descriptors besides stdin, stdout, and
-- stderr? See 'P.close_fds' for more information.
--
-- Default: False
--
-- @since 0.1.0.0
setCloseFds
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setCloseFds x pc = pc { pcCloseFds = x }

-- | Should we create a new process group?
--
-- Default: False
--
-- @since 0.1.0.0
setCreateGroup
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setCreateGroup x pc = pc { pcCreateGroup = x }

-- | Delegate handling of Ctrl-C to the child. For more information,
-- see 'P.delegate_ctlc'.
--
-- Default: False
--
-- @since 0.1.0.0
setDelegateCtlc
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setDelegateCtlc x pc = pc { pcDelegateCtlc = x }

#if MIN_VERSION_process(1, 3, 0)

-- | Detach console on Windows, see 'P.detach_console'.
--
-- Default: False
--
-- @since 0.1.0.0
setDetachConsole
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setDetachConsole x pc = pc { pcDetachConsole = x }

-- | Create new console on Windows, see 'P.create_new_console'.
--
-- Default: False
--
-- @since 0.1.0.0
setCreateNewConsole
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setCreateNewConsole x pc = pc { pcCreateNewConsole = x }

-- | Set a new session with the POSIX @setsid@ syscall, does nothing
-- on non-POSIX. See 'P.new_session'.
--
-- Default: False
--
-- @since 0.1.0.0
setNewSession
    :: Bool
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setNewSession x pc = pc { pcNewSession = x }
#endif

#if MIN_VERSION_process(1, 4, 0) && !WINDOWS
-- | Set the child process's group ID with the POSIX @setgid@ syscall,
-- does nothing on non-POSIX. See 'P.child_group'.
--
-- Default: False
--
-- @since 0.1.0.0
setChildGroup
    :: GroupID
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setChildGroup x pc = pc { pcChildGroup = Just x }

-- | Inherit the group from the parent process.
--
-- @since 0.2.2.0
setChildGroupInherit
  :: ProcessConfig stdin stdout stderr
  -- ^
  -> ProcessConfig stdin stdout stderr
setChildGroupInherit pc = pc { pcChildGroup = Nothing }

-- | Set the child process's user ID with the POSIX @setuid@ syscall,
-- does nothing on non-POSIX. See 'P.child_user'.
--
-- Default: False
--
-- @since 0.1.0.0
setChildUser
    :: UserID
    -- ^
    -> ProcessConfig stdin stdout stderr
    -- ^
    -> ProcessConfig stdin stdout stderr
setChildUser x pc = pc { pcChildUser = Just x }

-- | Inherit the user from the parent process.
--
-- @since 0.2.2.0
setChildUserInherit
  :: ProcessConfig stdin stdout stderr
  -- ^
  -> ProcessConfig stdin stdout stderr
setChildUserInherit pc = pc { pcChildUser = Nothing }
#endif

-- | Create a new 'StreamSpec' from the given 'P.StdStream' and a
-- helper function. This function:
--
-- * Takes as input the raw @Maybe Handle@ returned by the
-- 'P.createProcess' function. The handle will be @Just@ 'Handle' if the
-- 'P.StdStream' argument is 'P.CreatePipe' and @Nothing@ otherwise.
-- See 'P.createProcess' for more details.
--
-- * Returns the actual stream value @a@, as well as a cleanup
-- function to be run when calling 'stopProcess'.
--
-- If making a 'StreamSpec' with 'P.CreatePipe', prefer 'mkPipeStreamSpec',
-- which encodes the invariant that a 'Handle' is created.
--
-- @since 0.1.0.0
mkStreamSpec :: P.StdStream
             -- ^
             -> (ProcessConfig () () () -> Maybe Handle -> IO (a, IO ()))
             -- ^
             -> StreamSpec streamType a
mkStreamSpec ss f = mkManagedStreamSpec ($ ss) f

-- | Create a new 'P.CreatePipe' 'StreamSpec' from the given function.
-- This function:
--
-- * Takes as input the @Handle@ returned by the 'P.createProcess' function.
-- See 'P.createProcess' for more details.
--
-- * Returns the actual stream value @a@, as well as a cleanup
-- function to be run when calling 'stopProcess'.
--
-- @since 0.2.10.0
mkPipeStreamSpec :: (ProcessConfig () () () -> Handle -> IO (a, IO ()))
                 -- ^
                 -> StreamSpec streamType a
                 -- ^
mkPipeStreamSpec f = mkStreamSpec P.CreatePipe $ \pc mh ->
    case mh of
        Just h -> f pc h
        Nothing -> error "Invariant violation: making StreamSpec with CreatePipe unexpectedly did not return a Handle"

-- | Create a new 'StreamSpec' from a function that accepts a
-- 'P.StdStream' and a helper function.  This function is the same as
-- the helper in 'mkStreamSpec'
mkManagedStreamSpec :: (forall b. (P.StdStream -> IO b) -> IO b)
                    -- ^
                    -> (ProcessConfig () () () -> Maybe Handle -> IO (a, IO ()))
                    -- ^
                    -> StreamSpec streamType a
mkManagedStreamSpec ss f = StreamSpec ss (\pc mh -> Cleanup (f pc mh))

-- | A stream spec which simply inherits the stream of the parent
-- process.
--
-- @since 0.1.0.0
inherit :: StreamSpec anyStreamType ()
inherit = mkStreamSpec P.Inherit (\_ _ -> pure ((), return ()))

-- | A stream spec which is empty when used for for input and discards
-- output.  Note this requires your platform's null device to be
-- available when the process is started.
--
-- @since 0.2.5.0
nullStream :: StreamSpec anyStreamType ()
nullStream = mkManagedStreamSpec opener cleanup
  where
    opener f =
      withBinaryFile nullDevice ReadWriteMode $ \handle ->
        f (P.UseHandle handle)
    cleanup _ _ =
      pure ((), return ())

-- | A stream spec which will close the stream for the child process.
-- You usually do not want to use this, as it will leave the
-- corresponding file descriptor unassigned and hence available for
-- re-use in the child process.  Prefer 'nullStream' unless you're
-- certain you want this behavior.
--
-- @since 0.1.0.0
closed :: StreamSpec anyStreamType ()
#if MIN_VERSION_process(1, 4, 0)
closed = mkStreamSpec P.NoStream (\_ _ -> pure ((), return ()))
#else
closed = mkPipeStreamSpec (\_ h -> ((), return ()) <$ hClose h)
#endif

-- | An input stream spec which sets the input to the given
-- 'L.ByteString'. A separate thread will be forked to write the
-- contents to the child process.
--
-- @since 0.1.0.0
byteStringInput :: L.ByteString -> StreamSpec 'STInput ()
byteStringInput lbs = mkPipeStreamSpec $ \_ h -> do
    void $ async $ do
        L.hPut h lbs
        hClose h
    return ((), hClose h)

-- | Capture the output of a process in a 'L.ByteString'.
--
-- This function will fork a separate thread to consume all input from
-- the process, and will only make the results available when the
-- underlying 'Handle' is closed. As this is provided as an 'STM'
-- action, you can either check if the result is available, or block
-- until it's ready.
--
-- In the event of any exception occurring when reading from the
-- 'Handle', the 'STM' action will throw a
-- 'ByteStringOutputException'.
--
-- @since 0.1.0.0
byteStringOutput :: StreamSpec 'STOutput (STM L.ByteString)
byteStringOutput = mkPipeStreamSpec $ \pc h -> byteStringFromHandle pc h

-- | Helper function (not exposed) for both 'byteStringOutput' and
-- 'withProcessInterleave'. This will consume all of the output from
-- the given 'Handle' in a separate thread and provide access to the
-- resulting 'L.ByteString' via STM. Second action will close the
-- reader handle.
byteStringFromHandle
  :: ProcessConfig () () ()
  -> Handle -- ^ reader handle
  -> IO (STM L.ByteString, IO ())
byteStringFromHandle pc h = do
    mvar <- newEmptyTMVarIO

    void $ async $ do
        let loop front = do
                bs <- S.hGetSome h defaultChunkSize
                if S.null bs
                    then atomically $ putTMVar mvar $ Right $ L.fromChunks $ front []
                    else loop $ front . (bs:)
        loop id `catch` \e -> do
            atomically $ void $ tryPutTMVar mvar $ Left $ ByteStringOutputException e pc
            throwIO e

    return (readTMVar mvar >>= either throwSTM return, hClose h)

-- | Create a new pipe between this process and the child, and return
-- a 'Handle' to communicate with the child.
--
-- @since 0.1.0.0
createPipe :: StreamSpec anyStreamType Handle
createPipe = mkPipeStreamSpec $ \_ h -> return (h, hClose h)

-- | Use the provided 'Handle' for the child process, and when the
-- process exits, do /not/ close it. This is useful if, for example,
-- you want to have multiple processes write to the same log file
-- sequentially.
--
-- @since 0.1.0.0
useHandleOpen :: Handle -> StreamSpec anyStreamType ()
useHandleOpen h = mkStreamSpec (P.UseHandle h) $ \_ _ -> return ((), return ())

-- | Use the provided 'Handle' for the child process, and when the
-- process exits, close it. If you have no reason to keep the 'Handle'
-- open, you should use this over 'useHandleOpen'.
--
-- @since 0.1.0.0
useHandleClose :: Handle -> StreamSpec anyStreamType ()
useHandleClose h = mkStreamSpec (P.UseHandle h) $ \_ _ -> return ((), hClose h)

-- | Exception thrown by 'checkExitCode' in the event of a non-success
-- exit code. Note that 'checkExitCode' is called by other functions
-- as well, like 'runProcess_' or 'readProcess_'.
--
-- Note that several functions that throw an 'ExitCodeException' intentionally do not populate 'eceStdout' or 'eceStderr'.
-- This prevents unbounded memory usage for large stdout and stderrs.
--
-- @since 0.1.0.0
data ExitCodeException = ExitCodeException
    { eceExitCode :: ExitCode
    , eceProcessConfig :: ProcessConfig () () ()
    , eceStdout :: L.ByteString
    , eceStderr :: L.ByteString
    }
    deriving Typeable
instance Exception ExitCodeException
instance Show ExitCodeException where
    show ece = concat
        [ "Received "
        , show (eceExitCode ece)
        , " when running\n"
        -- Too much output for an exception if we show the modified
        -- environment, so hide it
        , show (eceProcessConfig ece) { pcEnv = Nothing }
        , if L.null (eceStdout ece)
            then ""
            else "Standard output:\n\n" ++ L8.unpack (eceStdout ece)
        , if L.null (eceStderr ece)
            then ""
            else "Standard error:\n\n" ++ L8.unpack (eceStderr ece)
        ]

-- | Wrapper for when an exception is thrown when reading from a child
-- process, used by 'byteStringOutput'.
--
-- @since 0.1.0.0
data ByteStringOutputException = ByteStringOutputException SomeException (ProcessConfig () () ())
    deriving (Show, Typeable)
instance Exception ByteStringOutputException

bracket :: MonadUnliftIO m => IO a -> (a -> IO b) -> (a -> m c) -> m c
bracket before after thing = withRunInIO $ \run -> E.bracket before after (run . thing)

finally :: MonadUnliftIO m => m a -> IO () -> m a
finally thing after = withRunInIO $ \run -> E.finally (run thing) after

-- | The name of the system null device
nullDevice :: FilePath
#if WINDOWS
nullDevice = "\\\\.\\NUL"
#else
nullDevice = "/dev/null"
#endif