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-- | Auxiliary functions for working with directories.
module System.Directory.Extra
    ( copyDirectoryRecursive
    , copyFile'
    )
  where

-- External imports
import qualified Control.Exception         as E
import           Distribution.Simple.Utils ( getDirectoryContentsRecursive )
import           System.Directory          ( copyFile,
                                             createDirectoryIfMissing )
import           System.Exit               ( ExitCode (ExitFailure), exitWith )
import           System.FilePath           ( takeDirectory, (</>) )
import           System.IO                 ( hPutStrLn, stderr )

-- | Copy all files from one directory to another.
copyDirectoryRecursive :: FilePath  -- ^ Source directory
                       -> FilePath  -- ^ Target directory
                       -> IO ()
copyDirectoryRecursive sourceDir targetDir =
  E.handle (copyDirectoryRecursiveErrorHandler sourceDir targetDir) $ do
    -- Obtain files in source directory
    files <- getDirectoryContentsRecursive sourceDir

    -- Determine the actual source and destination path for a file.
    let sourceAndDest file = (src, dest)
          where
            src  = sourceDir </> file
            dest = targetDir </> file

    -- Copy all the files, replacing the top directory.
    mapM_ (copyFile' . sourceAndDest) files

-- | Copy file origin to dest, creating the target directory if it does not
-- exist.
copyFile' :: (FilePath, FilePath) -> IO ()
copyFile' (origin, dest) = do
  createDirectoryIfMissing True (takeDirectory dest)
  copyFile origin dest

-- | Handle the case in which the source directory cannot be copied or the
-- target directory cannot be created/written.
copyDirectoryRecursiveErrorHandler :: FilePath
                                   -> FilePath
                                   -> E.SomeException
                                   -> IO ()
copyDirectoryRecursiveErrorHandler sourceDir targetDir _exception = do
  hPutStrLn stderr $
    "ogma: error: cannot copy " ++ sourceDir ++ " to " ++ targetDir
  exitWith (ExitFailure 1)