{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleContexts  #-}

{-|
Module      : GHCup.Utils.File.Posix
Description : File and unix APIs
Copyright   : (c) Julian Ospald, 2020
License     : LGPL-3.0
Maintainer  : hasufell@hasufell.de
Stability   : experimental
Portability : POSIX

This module handles file and executable handling.
Some of these functions use sophisticated logging.
-}
module GHCup.Utils.File.Posix where

import           GHCup.Utils.File.Common
import           GHCup.Utils.Prelude
import           GHCup.Utils.Logger
import           GHCup.Types
import           GHCup.Types.Optics

import           Control.Concurrent
import           Control.Concurrent.Async
import           Control.Exception              ( evaluate )
import           Control.Exception.Safe
import           Control.Monad
import           Control.Monad.Reader
import           Control.Monad.Trans.State.Strict
import           Data.ByteString                ( ByteString )
import           Data.Foldable
import           Data.IORef
import           Data.Sequence                  ( Seq, (|>) )
import           Data.List
import           Data.Word8
import           Foreign.C.String
import           Foreign.C.Types
import           GHC.IO.Exception
import           System.IO                      ( stderr, hClose, hSetBinaryMode )
import           System.IO.Error
import           System.FilePath
import           System.Directory      hiding   ( copyFile )
import           System.Posix.Directory
import           System.Posix.Error             ( throwErrnoPathIfMinus1Retry )
import           System.Posix.Internals         ( withFilePath )
import           System.Posix.Files
import           System.Posix.IO
import           System.Posix.Process           ( ProcessStatus(..) )
import           System.Posix.Types


import qualified Control.Exception             as EX
import qualified Data.Sequence                 as Sq
import qualified Data.Text                     as T
import qualified Data.Text.Encoding            as E
import qualified System.Posix.Files            as PF
import qualified System.Posix.Process          as SPP
import qualified System.Posix.IO               as SPI
import qualified System.Console.Terminal.Size  as TP
import qualified System.Posix as Posix
import qualified Data.ByteString               as BS
import qualified Data.ByteString.Lazy          as BL
import qualified "unix-bytestring" System.Posix.IO.ByteString
                                               as SPIB
import qualified Streamly.FileSystem.Handle    as FH
import qualified Streamly.Internal.FileSystem.Handle
                                               as IFH
import qualified Streamly.Prelude              as S
import qualified GHCup.Utils.File.Posix.Foreign as FD



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


execLogged :: ( MonadReader env m
              , HasSettings env
              , HasLog env
              , HasDirs env
              , MonadIO m
              , MonadThrow m)
           => FilePath         -- ^ thing to execute
           -> [String]         -- ^ args for the thing
           -> Maybe FilePath   -- ^ optionally chdir into this
           -> FilePath         -- ^ log filename (opened in append mode)
           -> Maybe [(String, String)] -- ^ optional environment
           -> m (Either ProcessError ())
execLogged exe args chdir lfile env = do
  Settings {..} <- getSettings
  Dirs {..} <- getDirs
  logDebug $ T.pack $ "Running " <> exe <> " with arguments " <> show args
  let logfile = logsDir </> lfile <> ".log"
  liftIO $ bracket (openFd logfile WriteOnly (Just newFilePerms) defaultFileFlags{ append = True })
                   closeFd
                   (action verbose noColor)
 where
  action verbose no_color fd = do
    actionWithPipes $ \(stdoutRead, stdoutWrite) -> do
      -- start the thread that logs to stdout
      pState <- newEmptyMVar
      done   <- newEmptyMVar
      void
        $ forkIO
        $ EX.handle (\(_ :: IOException) -> pure ())
        $ EX.finally
            (if verbose
              then tee fd stdoutRead
              else printToRegion fd stdoutRead 6 pState no_color
            )
            (putMVar done ())

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

        -- execute the action
        maybe (pure ()) changeWorkingDirectory chdir
        void $ SPP.executeFile exe (not ("./" `isPrefixOf` exe)) args env

      closeFd stdoutWrite

      -- wait for the subprocess to finish
      e <- toProcessError exe args <$!> SPP.getProcessStatus True True pid
      putMVar pState (either (const False) (const True) e)

      void $ race (takeMVar done) (threadDelay (1000000 * 3))
      closeFd stdoutRead

      pure e

  tee :: Fd -> Fd -> IO ()
  tee fileFd = readTilEOF lineAction

   where
    lineAction :: ByteString -> IO ()
    lineAction bs' = do
      void $ SPIB.fdWrite fileFd (bs' <> "\n")
      void $ SPIB.fdWrite stdOutput (bs' <> "\n")

  -- Reads fdIn and logs the output in a continous scrolling area
  -- of 'size' terminal lines. Also writes to a log file.
  printToRegion :: Fd -> Fd -> Int -> MVar Bool -> Bool -> IO ()
  printToRegion fileFd fdIn size pState no_color = do
    -- init region
    forM_ [1..size] $ \_ -> BS.hPut stderr "\n"

    void $ flip runStateT mempty
      $ do
        handle
          (\(ex :: SomeException) -> do
            ps <- liftIO $ takeMVar pState
            when ps (liftIO $ BS.hPut stderr (pos1 <> moveLineUp size <> clearScreen))
            throw ex
          ) $ readTilEOF lineAction fdIn

   where
    clearScreen :: ByteString
    clearScreen = "\x1b[0J"
    clearLine :: ByteString
    clearLine = "\x1b[2K"
    moveLineUp :: Int -> ByteString
    moveLineUp n = "\x1b[" <> E.encodeUtf8 (T.pack (show n)) <> "A"
    moveLineDown :: Int -> ByteString
    moveLineDown n = "\x1b[" <> E.encodeUtf8 (T.pack (show n)) <> "B"
    pos1 :: ByteString
    pos1 = "\r"
    overwriteNthLine :: Int -> ByteString -> ByteString
    overwriteNthLine n str = pos1 <> moveLineUp n <> clearLine <> str <> moveLineDown n <> pos1

    blue :: ByteString -> ByteString
    blue bs 
      | no_color = bs
      | otherwise = "\x1b[0;34m" <> bs <> "\x1b[0m"

    -- action to perform line by line
    lineAction :: (MonadMask m, MonadIO m)
               => ByteString
               -> StateT (Seq ByteString) m ()
    lineAction = \bs' -> do
      void $ liftIO $ SPIB.fdWrite fileFd (bs' <> "\n")
      modify (swapRegs bs')
      liftIO TP.size >>= \case
        Nothing -> pure ()
        Just (TP.Window _ w) -> do
          regs <- get
          liftIO $ forM_ (Sq.zip regs (Sq.fromList [0..(Sq.length regs - 1)])) $ \(bs, i) -> do
              BS.hPut stderr
              . overwriteNthLine (size - i)
              . trim w
              . blue
              . (\b -> "[ " <> E.encodeUtf8 (T.pack lfile) <> " ] " <> b)
              $ bs

    swapRegs :: a -> Seq a -> Seq a
    swapRegs bs = \regs -> if
      | Sq.length regs < size -> regs |> bs
      | otherwise             -> Sq.drop 1 regs |> bs

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

  -- Consecutively read from Fd in 512 chunks until we hit
  -- newline or EOF.
  readLine :: MonadIO m
           => Fd          -- ^ input file descriptor
           -> ByteString  -- ^ rest buffer (read across newline)
           -> m (ByteString, ByteString, Bool) -- ^ (full line, rest, eof)
  readLine fd = go
   where
    go inBs = do
      -- if buffer is not empty, process it first
      mbs <- if BS.length inBs == 0
               -- otherwise attempt read
               then liftIO
                    $ handleIO (\e -> if isEOFError e then pure Nothing else ioError e)
                    $ fmap Just
                    $ SPIB.fdRead fd 512
               else pure $ Just inBs
      case mbs of
        Nothing -> pure ("", "", True)
        Just bs -> do
          -- split on newline
          let (line, rest) = BS.span (/= _lf) bs
          if
            | BS.length rest /= 0 -> pure (line, BS.tail rest, False)
            -- if rest is empty, then there was no newline, process further
            | otherwise           -> (\(l, r, b) -> (line <> l, r, b)) <$!> go mempty

  readTilEOF :: MonadIO m => (ByteString -> m a) -> Fd -> m ()
  readTilEOF ~action' fd' = go mempty
   where
    go bs' = do
      (bs, rest, eof) <- readLine fd' bs'
      if eof
         then liftIO $ ioError (mkIOError eofErrorType "" Nothing Nothing)
         else void (action' bs) >> go rest


-- | 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 = do
  actionWithPipes $ \(parentStdoutRead, childStdoutWrite) ->
    actionWithPipes $ \(parentStderrRead, childStderrWrite) -> do
      pid <- SPP.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
        a <- action
        void $ evaluate a

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

      -- start thread that writes the output
      refOut <- newIORef BL.empty
      refErr <- newIORef BL.empty
      done   <- newEmptyMVar
      _      <-
        forkIO
        $ EX.handle (\(_ :: IOException) -> pure ())
        $ flip EX.finally (putMVar done ())
        $ writeStds parentStdoutRead parentStderrRead refOut refErr

      status <- SPP.getProcessStatus True True pid
      void $ race (takeMVar done) (threadDelay (1000000 * 3))

      case status of
        -- readFd will take care of closing the fd
        Just (SPP.Exited es) -> do
          stdout' <- readIORef refOut
          stderr' <- readIORef refErr
          pure $ CapturedProcess { _exitCode = es
                                 , _stdOut   = stdout'
                                 , _stdErr   = stderr'
                                 }

        _ -> throwIO $ userError ("No such PID " ++ show pid)

 where
  writeStds :: Fd -> Fd -> IORef BL.ByteString -> IORef BL.ByteString -> IO ()
  writeStds pout perr rout rerr = do
    doneOut <- newEmptyMVar
    void
      $ forkIO
      $ hideError eofErrorType
      $ flip EX.finally (putMVar doneOut ())
      $ readTilEOF (\x -> modifyIORef' rout (<> BL.fromStrict x)) pout
    doneErr <- newEmptyMVar
    void
      $ forkIO
      $ hideError eofErrorType
      $ flip EX.finally (putMVar doneErr ())
      $ readTilEOF (\x -> modifyIORef' rerr (<> BL.fromStrict x)) perr
    takeMVar doneOut
    takeMVar doneErr

  readTilEOF ~action' fd' = do
    bs <- SPIB.fdRead fd' 512
    void $ action' bs
    readTilEOF action' fd'


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 -> FilePath -> IO Fd
createRegularFileFd fm dest =
  openFd dest WriteOnly (Just fm) defaultFileFlags{ exclusive = True }


-- | Thin wrapper around `executeFile`.
exec :: MonadIO m
     => String           -- ^ thing to execute
     -> [String]         -- ^ args for the thing
     -> Maybe FilePath   -- ^ optionally chdir into this
     -> Maybe [(String, String)] -- ^ optional environment
     -> m (Either ProcessError ())
exec exe args chdir env = liftIO $ do
  pid <- SPP.forkProcess $ do
    maybe (pure ()) changeWorkingDirectory chdir
    SPP.executeFile exe (not ("./" `isPrefixOf` exe)) args env

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


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



chmod_755 :: (MonadReader env m, HasLog env, MonadIO m) => FilePath -> m ()
chmod_755 fp = do
  let exe_mode =
          nullFileMode
            `unionFileModes` ownerExecuteMode
            `unionFileModes` ownerReadMode
            `unionFileModes` ownerWriteMode
            `unionFileModes` groupExecuteMode
            `unionFileModes` groupReadMode
            `unionFileModes` otherExecuteMode
            `unionFileModes` otherReadMode
  logDebug ("chmod 755 " <> T.pack fp)
  liftIO $ setFileMode fp exe_mode


-- |Default permissions for a new file.
newFilePerms :: FileMode
newFilePerms =
  ownerWriteMode
    `unionFileModes` ownerReadMode
    `unionFileModes` groupWriteMode
    `unionFileModes` groupReadMode
    `unionFileModes` otherWriteMode
    `unionFileModes` otherReadMode


-- | Checks whether the binary is a broken link.
isBrokenSymlink :: FilePath -> IO Bool
isBrokenSymlink fp = do
  try (pathIsSymbolicLink fp) >>= \case
    Right True -> do
      let symDir = takeDirectory fp
      tfp <- getSymbolicLinkTarget fp
      not <$> doesPathExist
        -- this drops 'symDir' if 'tfp' is absolute
        (symDir </> tfp)
    Right b -> pure b
    Left e | isDoesNotExistError e -> pure False
           | otherwise -> throwIO e

copyFile :: FilePath   -- ^ source file
         -> FilePath   -- ^ destination file
         -> Bool       -- ^ fail if file exists
         -> IO ()
copyFile from to fail' = do
  bracket
      (do
        fd     <- openFd' from SPI.ReadOnly [FD.oNofollow] Nothing
        handle' <- SPI.fdToHandle fd
        pure (fd, handle')
      )
      (\(_, handle') -> hClose handle')
    $ \(fromFd, fH) -> do
        sourceFileMode <- fileMode
          <$> getFdStatus fromFd
        let dflags =
              [ FD.oNofollow
              , case fail' of
                True    -> FD.oExcl
                False   -> FD.oTrunc
              ]
        bracketeer
            (do
              fd     <- openFd' to SPI.WriteOnly dflags $ Just sourceFileMode
              handle' <- SPI.fdToHandle fd
              pure (fd, handle')
            )
            (\(_, handle') -> hClose handle')
            (\(_, handle') -> do
              hClose handle'
              case fail' of
                   -- if we created the file and copying failed, it's
                   -- safe to clean up
                True  -> PF.removeLink to
                False -> pure ()
            )
          $ \(_, tH) -> do
              hSetBinaryMode fH True
              hSetBinaryMode tH True
              streamlyCopy (fH, tH)
 where
  streamlyCopy (fH, tH) =
    S.fold (FH.writeChunks tH) $ IFH.toChunksWithBufferOf (256 * 1024) fH

foreign import ccall unsafe "open"
   c_open :: CString -> CInt -> Posix.CMode -> IO CInt


open_  :: CString
       -> Posix.OpenMode
       -> [FD.Flags]
       -> Maybe Posix.FileMode
       -> IO Posix.Fd
open_ str how optional_flags maybe_mode = do
    fd <- c_open str all_flags mode_w
    return (Posix.Fd fd)
  where
    all_flags  = FD.unionFlags $ optional_flags ++ [open_mode] ++ creat


    (creat, mode_w) = case maybe_mode of
                        Nothing -> ([],0)
                        Just x  -> ([FD.oCreat], x)

    open_mode = case how of
                   Posix.ReadOnly  -> FD.oRdonly
                   Posix.WriteOnly -> FD.oWronly
                   Posix.ReadWrite -> FD.oRdwr


-- |Open and optionally create this file. See 'System.Posix.Files'
-- for information on how to use the 'FileMode' type.
--
-- Note that passing @Just x@ as the 4th argument triggers the
-- `oCreat` status flag, which must be set when you pass in `oExcl`
-- to the status flags. Also see the manpage for @open(2)@.
openFd' :: FilePath
        -> Posix.OpenMode
        -> [FD.Flags]               -- ^ status flags of @open(2)@
        -> Maybe Posix.FileMode  -- ^ @Just x@ => creates the file with the given modes, Nothing => the file must exist.
        -> IO Posix.Fd
openFd' name how optional_flags maybe_mode =
   withFilePath name $ \str ->
     throwErrnoPathIfMinus1Retry "openFd" name $
       open_ str how optional_flags maybe_mode


-- |Deletes the given file. Raises `eISDIR`
-- if run on a directory. Does not follow symbolic links.
--
-- Throws:
--
--    - `InappropriateType` for wrong file type (directory)
--    - `NoSuchThing` if the file does not exist
--    - `PermissionDenied` if the directory cannot be read
--
-- Notes: calls `unlink`
deleteFile :: FilePath -> IO ()
deleteFile = removeLink


-- |Recreate a symlink.
--
-- In `Overwrite` copy mode only files and empty directories are deleted.
--
-- Safety/reliability concerns:
--
--    * `Overwrite` mode is inherently non-atomic
--
-- Throws:
--
--    - `InvalidArgument` if source file is wrong type (not a symlink)
--    - `PermissionDenied` if output directory cannot be written to
--    - `PermissionDenied` if source directory cannot be opened
--    - `SameFile` if source and destination are the same file
--      (`HPathIOException`)
--
--
-- Throws in `Strict` mode only:
--
--    - `AlreadyExists` if destination already exists
--
-- Throws in `Overwrite` mode only:
--
--    - `UnsatisfiedConstraints` if destination file is non-empty directory
--
-- Notes:
--
--    - calls `symlink`
recreateSymlink :: FilePath   -- ^ the old symlink file
                -> FilePath   -- ^ destination file
                -> Bool       -- ^ fail if destination file exists
                -> IO ()
recreateSymlink symsource newsym fail' = do
  sympoint <- readSymbolicLink symsource
  case fail' of
    True  -> pure ()
    False ->
      hideError doesNotExistErrorType $ deleteFile newsym
  createSymbolicLink sympoint newsym


-- copys files, recreates symlinks, fails on all other types
install :: FilePath -> FilePath -> Bool -> IO ()
install from to fail' = do
  fs <- PF.getSymbolicLinkStatus from
  decide fs
 where
  decide fs | PF.isRegularFile fs     = copyFile from to fail'
            | PF.isSymbolicLink fs    = recreateSymlink from to fail'
            | otherwise               = ioError $ mkIOError illegalOperationErrorType "install: not a regular file or symlink" Nothing (Just from)