Lua module: add readers submodule

Plain text readers are exposed to lua scripts via the `pandoc.reader`
submodule, which is further subdivided by format.  Converting e.g. a
markdown string into a pandoc document is possible from within lua:

    doc = pandoc.reader.markdown.read_doc("Hello, World!")

A `read_block` convenience function is provided for all formats,
although it will still parse the whole string but return only the first
block as the result.

Custom reader options are not supported yet, default options are used
for all parsing operations.

1 files changed, 3 insertions, 28 deletions

diff --git a/src/Text/Pandoc/Lua.hs b/src/Text/Pandoc/Lua.hs
index 6fa6b2020..d754b43b8 100644
--- a/src/Text/Pandoc/Lua.hs
+++ b/src/Text/Pandoc/Lua.hs
@@ -15,11 +15,7 @@ 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
 -}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# OPTIONS_GHC -fno-warn-orphans #-}
 {- |
    Module      : Text.Pandoc.Lua
    Copyright   : Copyright © 2017 Albert Krewinkel
@@ -34,24 +30,23 @@ module Text.Pandoc.Lua ( runLuaFilter ) where
 
 import Control.Monad ( (>=>), when )
 import Control.Monad.Trans ( MonadIO(..) )
-import Data.Aeson ( FromJSON(..), ToJSON(..), Result(..), Value, fromJSON )
 import Data.HashMap.Lazy ( HashMap )
 import Data.Text ( Text, pack, unpack )
 import Data.Text.Encoding ( decodeUtf8 )
 import Scripting.Lua ( LuaState, StackValue(..) )
-import Scripting.Lua.Aeson ()
+import Scripting.Lua.Aeson ( newstate )
 import Text.Pandoc.Definition ( Block(..), Inline(..), Pandoc(..) )
 import Text.Pandoc.Lua.PandocModule
+import Text.Pandoc.Lua.StackInstances ()
 import Text.Pandoc.Walk
 
 import qualified Data.HashMap.Lazy as HashMap
 import qualified Scripting.Lua as Lua
-import qualified Scripting.Lua as LuaAeson
 
 runLuaFilter :: (MonadIO m)
              => FilePath -> [String] -> Pandoc -> m Pandoc
 runLuaFilter filterPath args pd = liftIO $ do
-  lua <- LuaAeson.newstate
+  lua <- newstate
   Lua.openlibs lua
   Lua.newtable lua
   Lua.setglobal lua "PANDOC_FILTER_FUNCTIONS"  -- hack, store functions here
@@ -204,23 +199,3 @@ isLuaFunction lua fnName = do
   res <- Lua.isfunction lua (-1)
   Lua.pop lua (-1)
   return res
-
-maybeFromJson :: (FromJSON a) => Maybe Value -> Maybe a
-maybeFromJson mv = fromJSON <$> mv >>= \case
-  Success x -> Just x
-  _         -> Nothing
-
-instance StackValue Pandoc where
-  push lua = Lua.push lua . toJSON
-  peek lua i = maybeFromJson <$> peek lua i
-  valuetype _ = Lua.TTABLE
-
-instance StackValue Block where
-  push lua = Lua.push lua . toJSON
-  peek lua i = maybeFromJson <$> peek lua i
-  valuetype _ = Lua.TTABLE
-
-instance StackValue Inline where
-  push lua = Lua.push lua . toJSON
-  peek lua i = maybeFromJson <$> peek lua i
-  valuetype _ = Lua.TTABLE