    {-# LANGUAGE NoImplicitPrelude #-}
    {-
    Copyright © 2017-2018 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>

    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.Lua.Module.MediaBag
       Copyright   : Copyright © 2017-2018 Albert Krewinkel
       License     : GNU GPL, version 2 or above

       Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
       Stability   : alpha

    The lua module @pandoc.mediabag@.
    -}
    module Text.Pandoc.Lua.Module.MediaBag
      ( pushModule
      ) where

    import Prelude
    import Control.Monad (zipWithM_)
    import Data.IORef (IORef, modifyIORef', readIORef)
    import Data.Maybe (fromMaybe)
    import Foreign.Lua (Lua, NumResults, Optional, liftIO)
    import Text.Pandoc.Class (CommonState (..), fetchItem, putCommonState,
                              runIOorExplode, setMediaBag)
    import Text.Pandoc.Lua.StackInstances ()
    import Text.Pandoc.Lua.Util (addFunction)
    import Text.Pandoc.MIME (MimeType)

    import qualified Data.ByteString.Lazy as BL
    import qualified Foreign.Lua as Lua
    import qualified Text.Pandoc.MediaBag as MB

    --
    -- MediaBag submodule
    --
    pushModule :: CommonState -> IORef MB.MediaBag -> Lua NumResults
    pushModule commonState mediaBagRef = do
      Lua.newtable
      addFunction "insert" (insertMediaFn mediaBagRef)
      addFunction "lookup" (lookupMediaFn mediaBagRef)
      addFunction "list" (mediaDirectoryFn mediaBagRef)
      addFunction "fetch" (fetch commonState mediaBagRef)
      return 1

    insertMediaFn :: IORef MB.MediaBag
                  -> FilePath
                  -> Optional MimeType
                  -> BL.ByteString
                  -> Lua NumResults
    insertMediaFn mbRef fp optionalMime contents = do
      liftIO . modifyIORef' mbRef $
        MB.insertMedia fp (Lua.fromOptional optionalMime) contents
      return 0

    lookupMediaFn :: IORef MB.MediaBag
                  -> FilePath
                  -> Lua NumResults
    lookupMediaFn mbRef fp = do
      res <- MB.lookupMedia fp <$> liftIO (readIORef mbRef)
      case res of
        Nothing -> Lua.pushnil *> return 1
        Just (mimeType, contents) -> do
          Lua.push mimeType
          Lua.push contents
          return 2

    mediaDirectoryFn :: IORef MB.MediaBag
                     -> Lua NumResults
    mediaDirectoryFn mbRef = do
      dirContents <- MB.mediaDirectory <$> liftIO (readIORef mbRef)
      Lua.newtable
      zipWithM_ addEntry [1..] dirContents
      return 1
     where
      addEntry :: Lua.Integer -> (FilePath, MimeType, Int) -> Lua ()
      addEntry idx (fp, mimeType, contentLength) = do
        Lua.newtable
        Lua.push "path" *> Lua.push fp *> Lua.rawset (-3)
        Lua.push "type" *> Lua.push mimeType *> Lua.rawset (-3)
        Lua.push "length" *> Lua.push contentLength *> Lua.rawset (-3)
        Lua.rawseti (-2) idx

    fetch :: CommonState
          -> IORef MB.MediaBag
          -> String
          -> Lua NumResults
    fetch commonState mbRef src = do
      mediaBag <- liftIO $ readIORef mbRef
      (bs, mimeType) <- liftIO . runIOorExplode $ do
        putCommonState commonState
        setMediaBag mediaBag
        fetchItem src
      Lua.push $ fromMaybe "" mimeType
      Lua.push bs
      return 2 -- returns 2 values: contents, mimetype