{-# LANGUAGE GeneralizedNewtypeDeriving, DeriveDataTypeable #-}
{-
Copyright (C) 2014 John MacFarlane <jgm@berkeley.edu>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

{- |
   Module      : Text.Pandoc.MediaBag
   Copyright   : Copyright (C) 2014 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

Definition of a MediaBag object to hold binary resources, and an
interface for interacting with it.
-}
module Text.Pandoc.MediaBag (
                     MediaBag,
                     lookupMedia,
                     insertMedia,
                     mediaDirectory,
                     extractMediaBag
                     ) where
import System.FilePath
import qualified System.FilePath.Posix as Posix
import System.Directory (createDirectoryIfMissing)
import qualified Data.Map as M
import qualified Data.ByteString.Lazy as BL
import Data.Monoid (Monoid)
import Control.Monad (when)
import Text.Pandoc.MIME (MimeType, getMimeTypeDef)
import qualified Text.Pandoc.UTF8 as UTF8
import Data.Maybe (fromMaybe)
import System.IO (stderr)
import Data.Data (Data)
import Data.Typeable (Typeable)

-- | A container for a collection of binary resources, with names and
-- mime types.  Note that a 'MediaBag' is a Monoid, so 'mempty'
-- can be used for an empty 'MediaBag', and '<>' can be used to append
-- two 'MediaBag's.
newtype MediaBag = MediaBag (M.Map [String] (MimeType, BL.ByteString))
        deriving (Monoid, Data, Typeable)

instance Show MediaBag where
  show bag = "MediaBag " ++ show (mediaDirectory bag)

-- | Insert a media item into a 'MediaBag', replacing any existing
-- value with the same name.
insertMedia :: FilePath       -- ^ relative path and canonical name of resource
            -> Maybe MimeType -- ^ mime type (Nothing = determine from extension)
            -> BL.ByteString  -- ^ contents of resource
            -> MediaBag
            -> MediaBag
insertMedia fp mbMime contents (MediaBag mediamap) =
  MediaBag (M.insert (splitDirectories fp) (mime, contents) mediamap)
  where mime = fromMaybe fallback mbMime
        fallback = case takeExtension fp of
                        ".gz"   -> getMimeTypeDef $ dropExtension fp
                        _       -> getMimeTypeDef fp

-- | Lookup a media item in a 'MediaBag', returning mime type and contents.
lookupMedia :: FilePath
            -> MediaBag
            -> Maybe (MimeType, BL.ByteString)
lookupMedia fp (MediaBag mediamap) = M.lookup (splitDirectories fp) mediamap

-- | Get a list of the file paths stored in a 'MediaBag', with
-- their corresponding mime types and the lengths in bytes of the contents.
mediaDirectory :: MediaBag -> [(String, MimeType, Int)]
mediaDirectory (MediaBag mediamap) =
  M.foldWithKey (\fp (mime,contents) ->
      (((Posix.joinPath fp), mime, fromIntegral $ BL.length contents):)) [] mediamap

-- | Extract contents of MediaBag to a given directory.  Print informational
-- messages if 'verbose' is true.
extractMediaBag :: Bool
                -> FilePath
                -> MediaBag
                -> IO ()
extractMediaBag verbose dir (MediaBag mediamap) = do
  sequence_ $ M.foldWithKey
     (\fp (_ ,contents) ->
        ((writeMedia verbose dir (Posix.joinPath fp, contents)):)) [] mediamap

writeMedia :: Bool -> FilePath -> (FilePath, BL.ByteString) -> IO ()
writeMedia verbose dir (subpath, bs) = do
  -- we join and split to convert a/b/c to a\b\c on Windows;
  -- in zip containers all paths use /
  let fullpath = dir </> normalise subpath
  createDirectoryIfMissing True $ takeDirectory fullpath
  when verbose $ UTF8.hPutStrLn stderr $ "pandoc: extracting " ++ fullpath
  BL.writeFile fullpath bs


