2 files changed, 47 insertions, 10 deletions
diff --git a/src/Text/Pandoc/Lua/Module/Utils.hs b/src/Text/Pandoc/Lua/Module/Utils.hs
index 496fdbc0a..3a3727355 100644
--- a/src/Text/Pandoc/Lua/Module/Utils.hs
+++ b/src/Text/Pandoc/Lua/Module/Utils.hs
@@ -29,22 +29,51 @@ module Text.Pandoc.Lua.Module.Utils
   ( pushModule
   ) where
 
-import Data.Digest.Pure.SHA (sha1, showDigest)
-import Foreign.Lua (Lua, NumResults)
+import Control.Applicative ((<|>))
+import Foreign.Lua (FromLuaStack, Lua, NumResults)
+import Text.Pandoc.Definition (Pandoc, Meta, Block, Inline)
 import Text.Pandoc.Lua.StackInstances ()
 import Text.Pandoc.Lua.Util (addFunction)
 
+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.Shared as Shared
 
 -- | Push the "pandoc.utils" module to the lua stack.
 pushModule :: Lua NumResults
 pushModule = do
   Lua.newtable
-  addFunction "sha1" sha1HashFn
+  addFunction "sha1" sha1
+  addFunction "stringify" stringify
   return 1
 
 -- | Calculate the hash of the given contents.
-sha1HashFn :: BSL.ByteString
-           -> Lua String
-sha1HashFn = return . showDigest . sha1
+sha1 :: BSL.ByteString
+     -> Lua String
+sha1 = return . SHA.showDigest . SHA.sha1
+
+stringify :: AstElement -> Lua String
+stringify el = return $ case el of
+  PandocElement pd -> Shared.stringify pd
+  InlineElement i  -> Shared.stringify i
+  BlockElement b   -> Shared.stringify b
+  MetaElement m    -> Shared.stringify m
+
+data AstElement
+  = PandocElement Pandoc
+  | MetaElement Meta
+  | BlockElement Block
+  | InlineElement Inline
+  deriving (Show)
+
+instance FromLuaStack AstElement where
+  peek idx  = do
+    res <- Lua.tryLua $  (PandocElement <$> Lua.peek idx)
+                     <|> (InlineElement <$> Lua.peek idx)
+                     <|> (BlockElement <$> Lua.peek idx)
+                     <|> (MetaElement <$> Lua.peek idx)
+    case res of
+      Right x -> return x
+      Left _ -> Lua.throwLuaError
+        "Expected an AST element, but could not parse value as such."
diff --git a/src/Text/Pandoc/Lua/Util.hs b/src/Text/Pandoc/Lua/Util.hs
index e688ad255..28d09d339 100644
--- a/src/Text/Pandoc/Lua/Util.hs
+++ b/src/Text/Pandoc/Lua/Util.hs
@@ -67,7 +67,7 @@ getTable :: (ToLuaStack a, FromLuaStack b) => StackIndex -> a -> Lua b
 getTable idx key = do
   push key
   rawget (idx `adjustIndexBy` 1)
-  peek (-1) <* pop 1
+  popValue
 
 -- | Add a key-value pair to the table at the top of the stack.
 addValue :: (ToLuaStack a, ToLuaStack b) => a -> b -> Lua ()
@@ -86,10 +86,9 @@ addFunction name fn = do
 
 -- | Get value behind key from table at given index.
 getRawInt :: FromLuaStack a => StackIndex -> Int -> Lua a
-getRawInt idx key =
+getRawInt idx key = do
   rawgeti idx key
-  *> peek (-1)
-  <* pop 1
+  popValue
 
 -- | Set numeric key/value in table at the given index
 setRawInt :: ToLuaStack a => StackIndex -> Int -> a -> Lua ()
@@ -106,6 +105,15 @@ raiseError e = do
   Lua.push e
   fromIntegral <$> Lua.lerror
 
+-- | Get, then pop the value at the top of the stack.
+popValue :: FromLuaStack a => Lua a
+popValue = do
+  resOrError <- Lua.peekEither (-1)
+  pop 1
+  case resOrError of
+    Left err -> Lua.throwLuaError err
+    Right x -> return x
+
 -- | Newtype wrapper intended to be used for optional Lua values. Nesting this
 -- type is strongly discouraged and will likely lead to a wrong result.
 newtype OrNil a = OrNil { toMaybe :: Maybe a }