{-# LANGUAGE CPP #-}
{-# OPTIONS_HADDOCK hide #-}

{- HLINT ignore "Use fewer imports" -}

module Distribution.Compat.CopyFile
  ( copyFile
  , copyFileChanged
  , filesEqual
  , copyOrdinaryFile
  , copyExecutableFile
  , setFileOrdinary
  , setFileExecutable
  , setDirOrdinary
  ) where

import Distribution.Compat.Prelude
import Prelude ()

import qualified Data.ByteString.Lazy as BSL
import System.Directory
  ( doesFileExist
  )
import System.IO
  ( IOMode (ReadMode)
  , hFileSize
  , withBinaryFile
  )

#ifndef mingw32_HOST_OS
import Control.Exception
         ( bracketOnError )
import Data.Bits
         ( (.|.) )
import System.IO.Error
         ( ioeSetLocation )
import System.Directory
         ( renameFile, removeFile )
import System.FilePath
         ( takeDirectory )
import System.IO
         ( hClose, hGetBuf, hPutBuf, openBinaryTempFile )
import Foreign
         ( allocaBytes )

import System.Posix.Types
         ( FileMode )
import System.Posix.Files
         ( getFileStatus, fileMode, setFileMode )

#else /* else mingw32_HOST_OS */

import System.Directory
  ( copyFileWithMetadata )

#endif /* mingw32_HOST_OS */

copyOrdinaryFile, copyExecutableFile :: FilePath -> FilePath -> IO ()
copyOrdinaryFile src dest = copyFile src dest >> setFileOrdinary dest
copyExecutableFile src dest = copyFile src dest >> setFileExecutable dest

setFileOrdinary, setFileExecutable, setDirOrdinary :: FilePath -> IO ()
#ifndef mingw32_HOST_OS
-- When running with a restrictive UMASK such as 0077 we still want to
-- install files and directories that are accessible to other users.
setFileOrdinary   path = addFileMode path 0o644 -- file perms -rw-r--r--
setFileExecutable path = addFileMode path 0o755 -- file perms -rwxr-xr-x

addFileMode :: FilePath -> FileMode -> IO ()
addFileMode name m = do
  o <- fileMode <$> getFileStatus name
  setFileMode name (m .|. o)
#else
setFileOrdinary   _ = return ()
setFileExecutable _ = return ()
#endif
-- This happens to be true on Unix and currently on Windows too:
setDirOrdinary = setFileExecutable

-- | Copies a file to a new destination.
-- Often you should use `copyFileChanged` instead.
copyFile :: FilePath -> FilePath -> IO ()
#ifndef mingw32_HOST_OS
copyFile fromFPath toFPath =
  copy
    `catchIO` (\ioe -> throwIO (ioeSetLocation ioe "copyFile"))
  where
      copy = withBinaryFile fromFPath ReadMode $ \hFrom ->
             bracketOnError openTmp cleanTmp $ \(tmpFPath, hTmp) ->
             do allocaBytes bufferSize $ copyContents hFrom hTmp
                hClose hTmp
                renameFile tmpFPath toFPath
      openTmp = openBinaryTempFile (takeDirectory toFPath) ".copyFile.tmp"
      cleanTmp (tmpFPath, hTmp) = do
        hClose hTmp          `catchIO` \_ -> return ()
        removeFile tmpFPath  `catchIO` \_ -> return ()
      bufferSize = 4096

      copyContents hFrom hTo buffer = do
              count <- hGetBuf hFrom buffer bufferSize
              when (count > 0) $ do
                      hPutBuf hTo buffer count
                      copyContents hFrom hTo buffer
#else
copyFile = copyFileWithMetadata
#endif /* mingw32_HOST_OS */

-- | Like `copyFile`, but does not touch the target if source and destination
-- are already byte-identical. This is recommended as it is useful for
-- time-stamp based recompilation avoidance.
copyFileChanged :: FilePath -> FilePath -> IO ()
copyFileChanged src dest = do
  equal <- filesEqual src dest
  unless equal $ copyFile src dest

-- | Checks if two files are byte-identical.
-- Returns False if either of the files do not exist or if files
-- are of different size.
filesEqual :: FilePath -> FilePath -> IO Bool
filesEqual f1 f2 = do
  ex1 <- doesFileExist f1
  ex2 <- doesFileExist f2
  if not (ex1 && ex2)
    then return False
    else withBinaryFile f1 ReadMode $ \h1 ->
      withBinaryFile f2 ReadMode $ \h2 -> do
        s1 <- hFileSize h1
        s2 <- hFileSize h2
        if s1 /= s2
          then return False
          else do
            c1 <- BSL.hGetContents h1
            c2 <- BSL.hGetContents h2
            return $! c1 == c2