5 files changed, 109 insertions, 22 deletions
diff --git a/src/Text/Pandoc/Lua/Filter.hs b/src/Text/Pandoc/Lua/Filter.hs
index 9e109bb52..cc2b9d47e 100644
--- a/src/Text/Pandoc/Lua/Filter.hs
+++ b/src/Text/Pandoc/Lua/Filter.hs
@@ -11,6 +11,7 @@ module Text.Pandoc.Lua.Filter ( LuaFilterFunction
                               , inlineElementNames
                               ) where
 import Control.Monad (mplus, unless, when, (>=>))
+import Control.Monad.Catch (finally)
 import Text.Pandoc.Definition
 import Data.Foldable (foldrM)
 import Data.Map (Map)
@@ -22,6 +23,7 @@ import Text.Pandoc.Walk (walkM, Walkable)
 import Data.Data (Data, DataType, dataTypeConstrs, dataTypeName, dataTypeOf,
                   showConstr, toConstr, tyconUQname)
 import Text.Pandoc.Lua.StackInstances()
+import Text.Pandoc.Lua.Util (typeCheck)
 
 type FunctionMap = Map String LuaFilterFunction
 
@@ -65,7 +67,7 @@ registerFilterFunction idx = do
 
 elementOrList :: FromLuaStack a => a -> Lua [a]
 elementOrList x = do
-  let topOfStack = Lua.StackIndex (-1)
+  let topOfStack = Lua.stackTop
   elementUnchanged <- Lua.isnil topOfStack
   if elementUnchanged
     then [x] <$ Lua.pop 1
@@ -73,7 +75,9 @@ elementOrList x = do
        mbres <- Lua.peekEither topOfStack
        case mbres of
          Right res -> [res] <$ Lua.pop 1
-         Left _    -> Lua.toList topOfStack <* Lua.pop 1
+         Left _    -> do
+           typeCheck Lua.stackTop Lua.TypeTable
+           Lua.toList topOfStack `finally` Lua.pop 1
 
 -- | Try running a filter for the given element
 tryFilter :: (Data a, FromLuaStack a, ToLuaStack a)
diff --git a/src/Text/Pandoc/Lua/Module/Utils.hs b/src/Text/Pandoc/Lua/Module/Utils.hs
index b453b38d7..f8eb96dc7 100644
--- a/src/Text/Pandoc/Lua/Module/Utils.hs
+++ b/src/Text/Pandoc/Lua/Module/Utils.hs
@@ -30,22 +30,26 @@ module Text.Pandoc.Lua.Module.Utils
   ) where
 
 import Control.Applicative ((<|>))
+import Data.Default (def)
 import Foreign.Lua (FromLuaStack, Lua, LuaInteger, NumResults)
+import Text.Pandoc.Class (runIO, setUserDataDir)
 import Text.Pandoc.Definition (Pandoc, Meta, MetaValue, Block, Inline)
 import Text.Pandoc.Lua.StackInstances ()
-import Text.Pandoc.Lua.Util (addFunction)
+import Text.Pandoc.Lua.Util (addFunction, popValue)
 
 import qualified Data.Digest.Pure.SHA as SHA
 import qualified Data.ByteString.Lazy as BSL
 import qualified Foreign.Lua as Lua
+import qualified Text.Pandoc.Filter.JSON as JSONFilter
 import qualified Text.Pandoc.Shared as Shared
 
 -- | Push the "pandoc.utils" module to the lua stack.
-pushModule :: Lua NumResults
-pushModule = do
+pushModule :: Maybe FilePath -> Lua NumResults
+pushModule mbDatadir = do
   Lua.newtable
   addFunction "hierarchicalize" hierarchicalize
   addFunction "normalize_date" normalizeDate
+  addFunction "run_json_filter" (runJSONFilter mbDatadir)
   addFunction "sha1" sha1
   addFunction "stringify" stringify
   addFunction "to_roman_numeral" toRomanNumeral
@@ -62,6 +66,25 @@ hierarchicalize = return . Shared.hierarchicalize
 normalizeDate :: String -> Lua (Lua.Optional String)
 normalizeDate = return . Lua.Optional . Shared.normalizeDate
 
+-- | Run a JSON filter on the given document.
+runJSONFilter :: Maybe FilePath
+              -> Pandoc
+              -> FilePath
+              -> Lua.Optional [String]
+              -> Lua NumResults
+runJSONFilter mbDatadir doc filterFile optArgs = do
+  args <- case Lua.fromOptional optArgs of
+            Just x -> return x
+            Nothing -> do
+              Lua.getglobal "FORMAT"
+              (:[]) <$> popValue
+  filterRes <- Lua.liftIO . runIO $ do
+    setUserDataDir mbDatadir
+    JSONFilter.apply def args filterFile doc
+  case filterRes of
+    Left err -> Lua.raiseError (show err)
+    Right d -> (1 :: NumResults) <$ Lua.push d
+
 -- | Calculate the hash of the given contents.
 sha1 :: BSL.ByteString
      -> Lua String
diff --git a/src/Text/Pandoc/Lua/Packages.hs b/src/Text/Pandoc/Lua/Packages.hs
index dda2dd2fe..1e6ff22fe 100644
--- a/src/Text/Pandoc/Lua/Packages.hs
+++ b/src/Text/Pandoc/Lua/Packages.hs
@@ -78,7 +78,8 @@ pandocPackageSearcher luaPkgParams pkgName =
     "pandoc.mediabag" -> let st    = luaPkgCommonState luaPkgParams
                              mbRef = luaPkgMediaBag luaPkgParams
                          in pushWrappedHsFun (MediaBag.pushModule st mbRef)
-    "pandoc.utils"    -> pushWrappedHsFun Utils.pushModule
+    "pandoc.utils"    -> let datadirMb = luaPkgDataDir luaPkgParams
+                         in pushWrappedHsFun (Utils.pushModule datadirMb)
     _ -> searchPureLuaLoader
  where
   pushWrappedHsFun f = do
@@ -112,4 +113,3 @@ dataDirScript datadir moduleFile = do
   return $ case res of
     Left _ -> Nothing
     Right s -> Just (unpack s)
-
diff --git a/src/Text/Pandoc/Lua/StackInstances.hs b/src/Text/Pandoc/Lua/StackInstances.hs
index 531261099..a504e5626 100644
--- a/src/Text/Pandoc/Lua/StackInstances.hs
+++ b/src/Text/Pandoc/Lua/StackInstances.hs
@@ -16,8 +16,9 @@ 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 FlexibleInstances #-}
-{-# LANGUAGE LambdaCase        #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE LambdaCase           #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 {- |
    Module      : Text.Pandoc.Lua.StackInstances
@@ -34,30 +35,43 @@ module Text.Pandoc.Lua.StackInstances () where
 
 import Control.Applicative ((<|>))
 import Control.Monad (when)
+import Control.Monad.Catch (finally)
+import Data.Data (showConstr, toConstr)
+import Data.Foldable (forM_)
 import Foreign.Lua (FromLuaStack (peek), Lua, LuaInteger, LuaNumber, StackIndex,
                     ToLuaStack (push), Type (..), throwLuaError, tryLua)
 import Text.Pandoc.Definition
-import Text.Pandoc.Lua.Util (adjustIndexBy, getTable, pushViaConstructor)
+import Text.Pandoc.Extensions (Extensions)
+import Text.Pandoc.Lua.Util (adjustIndexBy, getTable, pushViaConstructor,
+                             typeCheck)
+import Text.Pandoc.Options (ReaderOptions (..), TrackChanges)
 import Text.Pandoc.Shared (Element (Blk, Sec), safeRead)
 
 import qualified Foreign.Lua as Lua
+import qualified Data.Set as Set
 import qualified Text.Pandoc.Lua.Util as LuaUtil
 
+defineHowTo :: String -> Lua a -> Lua a
+defineHowTo ctx op = op `Lua.modifyLuaError` (("Could not " ++ ctx ++ ": ") ++)
+
 instance ToLuaStack Pandoc where
   push (Pandoc meta blocks) =
     pushViaConstructor "Pandoc" blocks meta
 
 instance FromLuaStack Pandoc where
-  peek idx = do
+  peek idx = defineHowTo "get Pandoc value" $ do
+    typeCheck idx Lua.TypeTable
     blocks <- getTable idx "blocks"
-    meta   <- getTable idx "meta"
+    meta   <- Lua.getfield idx "meta" *> (Lua.peek Lua.stackTop `finally` Lua.pop 1)
     return $ Pandoc meta blocks
 
 instance ToLuaStack Meta where
   push (Meta mmap) =
     pushViaConstructor "Meta" mmap
 instance FromLuaStack Meta where
-  peek idx = Meta <$> peek idx
+  peek idx = defineHowTo "get Meta value" $ do
+    typeCheck idx Lua.TypeTable
+    Meta <$> peek idx
 
 instance ToLuaStack MetaValue where
   push = pushMetaValue
@@ -154,7 +168,7 @@ pushMetaValue = \case
 
 -- | Interpret the value at the given stack index as meta value.
 peekMetaValue :: StackIndex -> Lua MetaValue
-peekMetaValue idx = do
+peekMetaValue idx = defineHowTo "get MetaValue" $ do
   -- Get the contents of an AST element.
   let elementContent :: FromLuaStack a => Lua a
       elementContent = peek idx
@@ -203,7 +217,8 @@ pushBlock = \case
 
 -- | Return the value at the given index as block if possible.
 peekBlock :: StackIndex -> Lua Block
-peekBlock idx = do
+peekBlock idx = defineHowTo "get Block value" $ do
+  typeCheck idx Lua.TypeTable
   tag <- getTag idx
   case tag of
       "BlockQuote"     -> BlockQuote <$> elementContent
@@ -254,7 +269,8 @@ pushInline = \case
 
 -- | Return the value at the given index as inline if possible.
 peekInline :: StackIndex -> Lua Inline
-peekInline idx = do
+peekInline idx = defineHowTo "get Inline value" $ do
+  typeCheck idx Lua.TypeTable
   tag <- getTag idx
   case tag of
     "Cite"       -> uncurry Cite <$> elementContent
@@ -290,11 +306,7 @@ getTag idx = do
   hasMT <- Lua.getmetatable idx
   push "tag"
   if hasMT then Lua.rawget (-2) else Lua.rawget (idx `adjustIndexBy` 1)
-  r <- tryLua (peek (-1))
-  Lua.settop top
-  case r of
-    Left (Lua.LuaException err) -> throwLuaError err
-    Right res                   -> return res
+  peek Lua.stackTop `finally` Lua.settop top
 
 withAttr :: (Attr -> a -> b) -> (LuaAttr, a) -> b
 withAttr f (attributes, x) = f (fromLuaAttr attributes) x
@@ -307,7 +319,7 @@ instance ToLuaStack LuaAttr where
     pushViaConstructor "Attr" id' classes kv
 
 instance FromLuaStack LuaAttr where
-  peek idx = LuaAttr <$> peek idx
+  peek idx = defineHowTo "get Attr value" (LuaAttr <$> peek idx)
 
 --
 -- Hierarchical elements
@@ -332,3 +344,42 @@ instance ToLuaStack Element where
             Lua.push "__index"
             Lua.pushvalue (-2)
             Lua.rawset (-3)
+
+
+--
+-- Reader Options
+--
+instance ToLuaStack Extensions where
+  push exts = push (show exts)
+
+instance ToLuaStack TrackChanges where
+  push = push . showConstr . toConstr
+
+instance ToLuaStack a => ToLuaStack (Set.Set a) where
+  push set = do
+    Lua.newtable
+    forM_ set (`LuaUtil.addValue` True)
+
+instance ToLuaStack ReaderOptions where
+  push ro = do
+    let ReaderOptions
+          (extensions            :: Extensions)
+          (standalone            :: Bool)
+          (columns               :: Int)
+          (tabStop               :: Int)
+          (indentedCodeClasses   :: [String])
+          (abbreviations         :: Set.Set String)
+          (defaultImageExtension :: String)
+          (trackChanges          :: TrackChanges)
+          (stripComments         :: Bool)
+          = ro
+    Lua.newtable
+    LuaUtil.addValue "extensions" extensions
+    LuaUtil.addValue "standalone" standalone
+    LuaUtil.addValue "columns" columns
+    LuaUtil.addValue "tabStop" tabStop
+    LuaUtil.addValue "indentedCodeClasses" indentedCodeClasses
+    LuaUtil.addValue "abbreviations" abbreviations
+    LuaUtil.addValue "defaultImageExtension" defaultImageExtension
+    LuaUtil.addValue "trackChanges" trackChanges
+    LuaUtil.addValue "stripComments" stripComments
diff --git a/src/Text/Pandoc/Lua/Util.hs b/src/Text/Pandoc/Lua/Util.hs
index 799b45b72..a3af155c9 100644
--- a/src/Text/Pandoc/Lua/Util.hs
+++ b/src/Text/Pandoc/Lua/Util.hs
@@ -36,6 +36,7 @@ module Text.Pandoc.Lua.Util
   , getRawInt
   , setRawInt
   , addRawInt
+  , typeCheck
   , raiseError
   , popValue
   , PushViaCall
@@ -100,6 +101,14 @@ setRawInt idx key value = do
 addRawInt :: ToLuaStack a => Int -> a -> Lua ()
 addRawInt = setRawInt (-1)
 
+typeCheck :: StackIndex -> Lua.Type -> Lua ()
+typeCheck idx expected = do
+  actual <- Lua.ltype idx
+  when (actual /= expected) $ do
+    expName <- Lua.typename expected
+    actName <- Lua.typename actual
+    Lua.throwLuaError $ "expected " ++ expName ++ " but got " ++ actName ++ "."
+
 raiseError :: ToLuaStack a => a -> Lua NumResults
 raiseError e = do
   Lua.push e