pandoc/src/Text/Pandoc/Lua.hs

{-# LANGUAGE CPP                   #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables   #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
{-
Copyright © 2017 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
   Copyright   : Copyright © 2017 Albert Krewinkel
   License     : GNU GPL, version 2 or above

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

Pandoc lua utils.
-}
module Text.Pandoc.Lua (LuaException (..), pushPandocModule, runLuaFilter) where

import Control.Monad (when, (>=>))
import Control.Monad.Identity (Identity)
import Control.Monad.Trans (MonadIO (..))
import Data.IORef (IORef, newIORef, readIORef)
import Foreign.Lua (FromLuaStack (peek), Lua, LuaException (..),
                    Status (OK), ToLuaStack (push))
import Text.Pandoc.Class (CommonState, PandocIO, getCommonState, getMediaBag,
                          setMediaBag)
import Text.Pandoc.Definition
import Text.Pandoc.Lua.PandocModule (pushMediaBagModule, pushPandocModule)
import Text.Pandoc.Lua.Filter (LuaFilter, walkMWithLuaFilter)
import Text.Pandoc.MediaBag (MediaBag)
import qualified Foreign.Lua as Lua

runLuaFilter :: Maybe FilePath -> FilePath -> String
             -> Pandoc -> PandocIO (Either LuaException Pandoc)
runLuaFilter datadir filterPath format pd = do
  commonState <- getCommonState
  mediaBag <- getMediaBag
  mediaBagRef <- liftIO (newIORef mediaBag)
  res <- liftIO . Lua.runLuaEither $
         runLuaFilter' commonState datadir filterPath format mediaBagRef pd
  newMediaBag <- liftIO (readIORef mediaBagRef)
  setMediaBag newMediaBag
  return res

runLuaFilter' :: CommonState
              -> Maybe FilePath -> FilePath -> String -> IORef MediaBag
              -> Pandoc -> Lua Pandoc
runLuaFilter' commonState datadir filterPath format mbRef pd = do
  Lua.openlibs
  -- store module in global "pandoc"
  pushPandocModule datadir
  Lua.setglobal "pandoc"
  addMediaBagModule
  registerFormat
  top <- Lua.gettop
  stat <- Lua.dofile filterPath
  if stat /= OK
    then do
      luaErrMsg <- peek (-1) <* Lua.pop 1
      Lua.throwLuaError luaErrMsg
    else do
      newtop <- Lua.gettop
      -- Use the implicitly defined global filter if nothing was returned
      when (newtop - top < 1) pushGlobalFilter
      luaFilters <- peek (-1)
      runAll luaFilters pd
 where
  addMediaBagModule = do
    Lua.getglobal "pandoc"
    push "mediabag"
    pushMediaBagModule commonState mbRef
    Lua.rawset (-3)
  registerFormat = do
    push format
    Lua.setglobal "FORMAT"


pushGlobalFilter :: Lua ()
pushGlobalFilter = do
  Lua.newtable
  Lua.getglobal' "pandoc.global_filter"
  Lua.call 0 1
  Lua.rawseti (-2) 1

runAll :: [LuaFilter] -> Pandoc -> Lua Pandoc
runAll = foldr ((>=>) . walkMWithLuaFilter) return

instance (FromLuaStack a) => FromLuaStack (Identity a) where
  peek = fmap return . peek