{-# LANGUAGE QuasiQuotes       #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell   #-}

module GHCup.Utils.File where

import           GHCup.Utils.Dirs
import           GHCup.Utils.Prelude

import           Control.Concurrent
import           Control.Exception.Safe
import           Control.Monad
import           Data.ByteString                ( ByteString )
import           Data.ByteString.Unsafe         ( unsafeUseAsCStringLen )
import           Data.Char
import           Data.Foldable
import           Data.Functor
import           Data.IORef
import           Data.Maybe
import           GHC.Foreign                    ( peekCStringLen )
import           GHC.IO.Encoding                ( getLocaleEncoding )
import           GHC.IO.Exception
import           HPath
import           HPath.IO
import           Optics
import           Streamly
import           Streamly.External.ByteString
import           Streamly.External.ByteString.Lazy
import           System.Console.Pretty
import           System.Console.Regions
import           System.IO
import           System.IO.Error
import           System.Posix.Directory.ByteString
import           System.Posix.FD               as FD
import           System.Posix.FilePath   hiding ( (</>) )
import           System.Posix.Foreign           ( oExcl )
import "unix"    System.Posix.IO.ByteString
                                         hiding ( openFd )
import           System.Posix.Process           ( ProcessStatus(..) )
import           System.Posix.Types


import qualified Control.Exception             as EX
import qualified Data.Text                     as T
import qualified Data.Text.Encoding            as E
import qualified System.Posix.Process.ByteString
                                               as SPPB
import           Streamly.External.Posix.DirStream
import qualified Streamly.Internal.Memory.ArrayStream
                                               as AS
import qualified Streamly.FileSystem.Handle    as FH
import qualified Streamly.Internal.Data.Unfold as SU
import qualified Streamly.Prelude              as S
import qualified Data.ByteString               as BS
import qualified Data.ByteString.Lazy          as L
import qualified "unix-bytestring" System.Posix.IO.ByteString
                                               as SPIB


data StopThread = StopThread Bool
  deriving Show

instance Exception StopThread


data ProcessError = NonZeroExit Int ByteString [ByteString]
                  | PTerminated ByteString [ByteString]
                  | PStopped ByteString [ByteString]
                  | NoSuchPid ByteString [ByteString]
                  deriving Show


data CapturedProcess = CapturedProcess
  { _exitCode :: ExitCode
  , _stdOut   :: ByteString
  , _stdErr   :: ByteString
  }
  deriving (Eq, Show)

makeLenses ''CapturedProcess


readFd :: Fd -> IO L.ByteString
readFd fd = do
  handle' <- fdToHandle fd
  fromChunksIO $ (S.unfold (SU.finallyIO hClose FH.readChunks) handle')


-- | Read the lines of a file into a stream. The stream holds
-- a file handle as a resource and will close it once the stream
-- terminates (either through exception or because it's drained).
readFileLines :: Path b -> IO (SerialT IO ByteString)
readFileLines p = do
  stream <- readFileStream p
  pure
    . (fmap fromArray)
    . AS.splitOn (fromIntegral $ ord '\n')
    . (fmap toArray)
    $ stream


-- | Find the given executable by searching all *absolute* PATH components.
-- Relative paths in PATH are ignored.
--
-- This shouldn't throw IO exceptions, unless getting the environment variable
-- PATH does.
findExecutable :: Path Rel -> IO (Maybe (Path Abs))
findExecutable ex = do
  sPaths <- fmap catMaybes . (fmap . fmap) parseAbs $ getSearchPath
  -- We don't want exceptions to mess up our result. If we can't
  -- figure out if a file exists, then treat it as a negative result.
  asum $ fmap (handleIO (\_ -> pure Nothing)) $ fmap
    -- asum for short-circuiting behavior
    (\s' -> (isExecutable (s' </> ex) >>= guard) $> (Just (s' </> ex)))
    sPaths


-- | Execute the given command and collect the stdout, stderr and the exit code.
-- The command is run in a subprocess.
executeOut :: Path b            -- ^ command as filename, e.g. 'ls'
           -> [ByteString]      -- ^ arguments to the command
           -> Maybe (Path Abs)  -- ^ chdir to this path
           -> IO CapturedProcess
executeOut path args chdir = captureOutStreams $ do
  maybe (pure ()) (changeWorkingDirectory . toFilePath) chdir
  SPPB.executeFile (toFilePath path) True args Nothing


execLogged :: ByteString       -- ^ thing to execute
           -> Bool             -- ^ whether to search PATH for the thing
           -> [ByteString]     -- ^ args for the thing
           -> Path Rel         -- ^ log filename
           -> Maybe (Path Abs) -- ^ optionally chdir into this
           -> Maybe [(ByteString, ByteString)] -- ^ optional environment
           -> IO (Either ProcessError ())
execLogged exe spath args lfile chdir env = do
  ldir    <- ghcupLogsDir
  logfile <- (ldir </>) <$> parseRel (toFilePath lfile <> ".log")
  bracket (createFile (toFilePath logfile) newFilePerms) closeFd action
 where
  action fd = do
    actionWithPipes $ \(stdoutRead, stdoutWrite) -> do
      -- start the thread that logs to stdout in a region
      done <- newEmptyMVar
      tid  <-
        forkIO
        $ EX.handle (\(_ :: StopThread) -> pure ())
        $ EX.handle (\(_ :: IOException) -> pure ())
        $ flip finally (putMVar done ())
        $ printToRegion fd stdoutRead 6

      -- fork our subprocess
      pid <- SPPB.forkProcess $ do
        void $ dupTo stdoutWrite stdOutput
        void $ dupTo stdoutWrite stdError
        closeFd stdoutWrite
        closeFd stdoutRead

        -- execute the action
        maybe (pure ()) (changeWorkingDirectory . toFilePath) chdir
        SPPB.executeFile exe spath args env

      closeFd stdoutWrite

      -- wait for the subprocess to finish
      e <- SPPB.getProcessStatus True True pid >>= \case
        i@(Just (SPPB.Exited _)) -> pure $ toProcessError exe args i
        i                        -> pure $ toProcessError exe args i

      -- make sure the logging thread stops
      case e of
        Left  _ -> EX.throwTo tid (StopThread False)
        Right _ -> EX.throwTo tid (StopThread True)
      takeMVar done

      closeFd stdoutRead
      pure e

  -- Reads fdIn and logs the output in a continous scrolling area
  -- of 'size' terminal lines. Also writes to a log file.
  printToRegion fileFd fdIn size = do
    ref <- newIORef ([] :: [ByteString])
    displayConsoleRegions $ do
      rs <- sequence . replicate size . openConsoleRegion $ Linear
      flip finally (readTilEOF (lineAction ref rs) fdIn) -- make sure the last few lines don't get cut off
        $ handle
            (\(StopThread b) -> do
              when b (forM_ rs closeConsoleRegion)
              EX.throw (StopThread b)
            )
        $ readForever (lineAction ref rs) fdIn

   where
    -- action to perform line by line
    lineAction ref rs bs' = do
      modifyIORef' ref (swapRegs bs')
      regs <- readIORef ref
      forM (zip regs rs) $ \(bs, r) -> do
        setConsoleRegion r $ do
          w <- consoleWidth
          return
            . T.pack
            . color Blue
            . T.unpack
            . E.decodeUtf8
            . trim w
            . (\b -> "[ " <> toFilePath lfile <> " ] " <> b)
            $ bs
        SPIB.fdWrite fileFd (bs <> "\n")


    swapRegs bs regs | length regs < size = regs ++ [bs]
                     | otherwise          = tail regs ++ [bs]

    -- trim output line to terminal width
    trim w bs | BS.length bs > w && w > 5 = BS.take (w - 4) bs <> "..."
              | otherwise                 = bs

    -- read an entire line from the file descriptor (removes the newline char)
    readLine fd' = do
      bs <-
        handle
            (\(e :: IOError) -> do
              if isEOFError e then threadDelay 1000 >> pure "" else throw e
            )
          $ SPIB.fdRead fd' 1
      if
        | bs == "\n" -> pure ""
        | bs == ""   -> pure ""
        | otherwise  -> fmap (bs <>) $ readLine fd'

    readForever action' fd' = do
      bs <- readLine fd'
      if not $ BS.null bs
        then action' bs >> readForever action' fd'
        else readForever action' fd'

    readTilEOF action' fd' = do
      bs <- readLine fd'
      when (not $ BS.null bs) (action' bs >> readTilEOF action' fd')


-- | Capture the stdout and stderr of the given action, which
-- is run in a subprocess. Stdin is closed. You might want to
-- 'race' this to make sure it terminates.
captureOutStreams :: IO a
                     -- ^ the action to execute in a subprocess
                  -> IO CapturedProcess
captureOutStreams action =
  actionWithPipes $ \(parentStdoutRead, childStdoutWrite) ->
    actionWithPipes $ \(parentStderrRead, childStderrWrite) -> do
      pid <- SPPB.forkProcess $ do
        -- dup stdout
        void $ dupTo childStdoutWrite stdOutput
        closeFd childStdoutWrite
        closeFd parentStdoutRead

        -- dup stderr
        void $ dupTo childStderrWrite stdError
        closeFd childStderrWrite
        closeFd parentStderrRead

        -- execute the action
        void $ action

      -- close everything we don't need
      closeFd childStdoutWrite
      closeFd childStderrWrite

      SPPB.getProcessStatus True True pid >>= \case
        -- readFd will take care of closing the fd
        Just (SPPB.Exited es) -> do
          stdout' <- L.toStrict <$> readFd parentStdoutRead
          stderr' <- L.toStrict <$> readFd parentStderrRead
          pure $ CapturedProcess { _exitCode = es
                                 , _stdOut   = stdout'
                                 , _stdErr   = stderr'
                                 }
        _ -> throwIO $ userError $ ("No such PID " ++ show pid)


actionWithPipes :: ((Fd, Fd) -> IO b) -> IO b
actionWithPipes a =
  createPipe >>= \(p1, p2) -> (flip finally) (cleanup [p1, p2]) $ a (p1, p2)

cleanup :: [Fd] -> IO ()
cleanup fds = for_ fds $ \fd -> handleIO (\_ -> pure ()) $ closeFd fd



-- | Create a new regular file in write-only mode. The file must not exist.
createRegularFileFd :: FileMode -> Path b -> IO Fd
createRegularFileFd fm dest =
  FD.openFd (toFilePath dest) WriteOnly [oExcl] (Just fm)


-- | Thin wrapper around `executeFile`.
exec :: ByteString       -- ^ thing to execute
     -> Bool             -- ^ whether to search PATH for the thing
     -> [ByteString]     -- ^ args for the thing
     -> Maybe (Path Abs) -- ^ optionally chdir into this
     -> Maybe [(ByteString, ByteString)] -- ^ optional environment
     -> IO (Either ProcessError ())
exec exe spath args chdir env = do
  pid <- SPPB.forkProcess $ do
    maybe (pure ()) (changeWorkingDirectory . toFilePath) chdir
    SPPB.executeFile exe spath args env

  fmap (toProcessError exe args) $ SPPB.getProcessStatus True True pid


toProcessError :: ByteString
               -> [ByteString]
               -> Maybe ProcessStatus
               -> Either ProcessError ()
toProcessError exe args mps = case mps of
  Just (SPPB.Exited (ExitFailure i)) -> Left $ NonZeroExit i exe args
  Just (SPPB.Exited ExitSuccess    ) -> Right ()
  Just (Terminated _ _             ) -> Left $ PTerminated exe args
  Just (Stopped _                  ) -> Left $ PStopped exe args
  Nothing                            -> Left $ NoSuchPid exe args


-- | Convert the String to a ByteString with the current
-- system encoding.
unsafePathToString :: Path b -> IO FilePath
unsafePathToString p = do
  enc <- getLocaleEncoding
  unsafeUseAsCStringLen (toFilePath p) (peekCStringLen enc)


-- | Search for a file in the search paths.
--
-- Catches `PermissionDenied` and `NoSuchThing` and returns `Nothing`.
searchPath :: [Path Abs] -> Path Rel -> IO (Maybe (Path Abs))
searchPath paths needle = go paths
 where
  go [] = pure Nothing
  go (x : xs) =
    hideErrorDefM PermissionDenied (go xs)
      $ hideErrorDefM NoSuchThing (go xs)
      $ do
          dirStream <- openDirStream (toFilePath x)
          S.findM (\(_, p) -> isMatch x p) (dirContentsStream dirStream)
            >>= \case
                  Just _  -> pure $ Just (x </> needle)
                  Nothing -> go xs
  isMatch basedir p = do
    if p == toFilePath needle
      then isExecutable (basedir </> needle)
      else pure False