{-
Copyright Alex Midgley 2011

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimer in the documentation and/or other materials provided
      with the distribution.

    * Neither the name of Alex Midgley nor the names of other
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-}

module Extract where

import qualified Codec.Archive.Tar as Tar
import qualified Codec.Compression.BZip as BZip
import qualified Codec.Compression.GZip as GZip
import qualified Data.ByteString.Lazy as BS
import Data.Char
import System.Directory
import System.FilePath

extractPackage :: FilePath -> FilePath -> IO FilePath
extractPackage package extractPath = do
  -- If the package is just a directory, leave it alone
  isDir <- doesDirectoryExist package
  if isDir
    then return package
    else runExtractionPipeline >> return extractPath

    where
      runExtractionPipeline = extractionPipeline package extractPath

extractionPipeline :: FilePath -> FilePath -> IO ()
extractionPipeline package destination =
    BS.readFile package >>= buildPipeline (segments package)

    where 
      segments [] = []
      segments str =
          let (rest, ext) = splitExtension str
          in ext : segments rest

      buildPipeline fileSegments =
          let (compression, fileSegments') = parseCompression fileSegments
              (archive, _) = parseArchive fileSegments'
          in archive . compression

      parseCompression :: [String] -> (BS.ByteString -> BS.ByteString, [String])
      parseCompression [] = (id, [])
      parseCompression (seg:rest) = case map toLower seg of
                                      ".gz"  -> (GZip.decompress, rest)
                                      ".bz2" -> (BZip.decompress, rest)
                                      _     -> (id, seg:rest)

      parseArchive :: [String] -> (BS.ByteString -> IO (), [String])
      parseArchive [] = (const $ return (), [])
      parseArchive (seg:rest) = case map toLower seg of
                                  ".tar" -> (Tar.unpack destination . Tar.read, rest)
                                  _     -> (const $ return (), seg:rest)
