{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
module Flameshot.Internal.Process (Callbacks(..),run,runAway,writeDaemon) where

import Control.Concurrent (forkIO,threadDelay)
import Control.Concurrent.Async (race)
import Control.Exception
import Control.Monad.Extended (untilM_,unless,void)
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import Data.Text (Text)
import qualified Data.Text.IO as T
import System.Exit
import System.IO (BufferMode(LineBuffering),hSetBuffering)
import System.IO (Handle,hClose,hIsEOF)
import System.IO.Error (catchIOError,isDoesNotExistError)
import System.Process
import System.Posix.Directory (changeWorkingDirectory)
import System.Posix.Files (setFileCreationMask)
import System.Posix.IO (closeFd,dupTo,openFd,stdError,stdInput,stdOutput)
import System.Posix.IO (defaultFileFlags,OpenMode(WriteOnly))
import System.Posix.Process (createSession,forkProcess,getProcessStatus)
import System.Posix.Process (getProcessGroupIDOf)
import System.Posix.Signals (Signal,signalProcessGroup,killProcess)
import System.Posix.Types (ProcessGroupID)


data Callbacks = Callbacks
    { onOutLine :: Pid -> Text -> IO ()
    , onErrLine :: Pid -> Text -> IO ()
    , onError :: Pid -> SomeException -> IO ()
    , onExit :: Pid -> ExitCode -> IO ()
    , onStart :: Pid -> IO ()
    }

instance Semigroup Callbacks where
  a <> b =
      Callbacks
        { onOutLine = \pid s -> do
          onOutLine a pid s
          onOutLine b pid s

        , onErrLine = \pid s -> do
          onErrLine a pid s
          onErrLine b pid s

        , onError = \pid err -> do
          onError a pid err
          onError b pid err

        , onExit = \pid status -> do
          onExit a pid status
          onExit b pid status

        , onStart = \pid -> do
          onStart a pid
          onStart b pid
        }

instance Monoid Callbacks where
  mempty =
    Callbacks
      { onOutLine = \_pid _s -> return ()
      , onErrLine = \_pid _s -> return ()
      , onError = \_pid _err -> return ()
      , onExit = \_pid _status -> return ()
      , onStart = \_pid -> return ()
      }

run :: FilePath
     -> [String]
     -> Maybe FilePath
     -> Maybe [(String, String)]
     -> ByteString
     -> Maybe Int
     -> Callbacks
     -> IO ()
run path args cwd env input hTimeout Callbacks{..} =
    f `catch` onError (-1)
  where
    f = withCreateProcess p $ \(Just inh) (Just outh) (Just errh) ph -> do
      Just pid <- getPid ph
      pgid <- getProcessGroupIDOf pid

      onStart pid

      mapM_ forkIO [
          BS.hPutStr inh input `finally` hClose inh,
          hWithLines outh (onOutLine pid),
          hWithLines errh (onErrLine pid)
        ]

      case hTimeout of
        Just time ->
          race (threadDelay time) (waitForProcess ph) >>= \case
            Left () -> onError pid (SomeException (ErrorCall "timeout"))
            Right code -> onExit pid code
        Nothing ->
          waitForProcess ph >>= onExit pid

      killProcessGroup pgid

    p = (proc path args)
          { cwd = cwd
          , env = env
          , std_in = CreatePipe
          , std_out = CreatePipe
          , std_err = CreatePipe
          , close_fds = True
          , create_group = True
          , new_session = True
          }


writeDaemon :: FilePath -> [String] -> ByteString -> IO ()
writeDaemon path args input = do
    pid <- forkProcess $ do
      _ <- setFileCreationMask 0o0027
      _ <- createSession
      changeWorkingDirectory "/"
      closeFd stdInput
      bracket (openFd "/dev/null" WriteOnly Nothing defaultFileFlags) closeFd
        $ \hnull -> mapM_ (dupTo hnull) [stdOutput, stdError]
      (Just hin, _, _, _) <-
        createProcess (proc path args) { std_in = CreatePipe }
      BS.hPut hin input
      hClose hin
    void (getProcessStatus True False pid)

runAway :: FilePath
     -> [String]
     -> Maybe FilePath
     -> Maybe [(String, String)]
     -> ByteString
     -> Maybe Int
     -> Callbacks
     -> IO ()
runAway path args cwd env input hTimeout Callbacks{..} =
    f `catch` onError (-1)
  where
    f = do
      (Just inh, Just outh, Just errh, ph) <- createProcess p

      Just pid <- getPid ph

      onStart pid

      mapM_ forkIO [
          BS.hPutStr inh input `finally` hClose inh,
          hWithLines outh (onOutLine pid),
          hWithLines errh (onErrLine pid)
        ]

      case hTimeout of
        Just time ->
          race (threadDelay time) (waitForProcess ph) >>= \case
            Left () -> onError pid (SomeException (ErrorCall "timeout"))
            Right code -> onExit pid code
        Nothing ->
          waitForProcess ph >>= onExit pid

    p = (proc path args)
          { cwd = cwd
          , env = env
          , std_in = CreatePipe
          , std_out = CreatePipe
          , std_err = CreatePipe
          , close_fds = True
          , create_group = True
          , new_session = True
          }

killProcessGroup :: ProcessGroupID -> IO ()
killProcessGroup = signalProcessGroup' killProcess

signalProcessGroup' :: Signal -> ProcessGroupID -> IO ()
signalProcessGroup' sig pgid =
    catchIOError
      (signalProcessGroup sig pgid)
      (\e -> unless (isDoesNotExistError e) $ ioError e)

hWithLines :: Handle -> (Text -> IO ()) -> IO ()
hWithLines h f = do
    hSetBuffering h LineBuffering
    untilM_ (hIsEOF h) (T.hGetLine h >>= f) `finally` hClose h