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{-# LANGUAGE FlexibleContexts #-}
module Text.Pandoc.Lua.Filter ( LuaFilterFunction
, LuaFilter
, tryFilter
, runFilterFunction
, walkMWithLuaFilter
, walkInlines
, walkBlocks
, blockElementNames
, 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)
import qualified Data.Map as Map
import qualified Foreign.Lua as Lua
import Foreign.Lua (FromLuaStack (peek), Lua, StackIndex,
Status (OK), ToLuaStack (push))
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
newtype LuaFilterFunction = LuaFilterFunction { functionIndex :: Int }
instance ToLuaStack LuaFilterFunction where
push = pushFilterFunction
instance FromLuaStack LuaFilterFunction where
peek = registerFilterFunction
newtype LuaFilter = LuaFilter FunctionMap
instance FromLuaStack LuaFilter where
peek idx =
let constrs = metaFilterName : pandocFilterNames
++ blockElementNames
++ inlineElementNames
fn c acc = do
Lua.getfield idx c
filterFn <- Lua.tryLua (peek (-1))
Lua.pop 1
return $ case filterFn of
Left _ -> acc
Right f -> (c, f) : acc
in LuaFilter . Map.fromList <$> foldrM fn [] constrs
-- | Push the filter function to the top of the stack.
pushFilterFunction :: LuaFilterFunction -> Lua ()
pushFilterFunction lf =
-- The function is stored in a lua registry table, retrieve it from there.
Lua.rawgeti Lua.registryindex (functionIndex lf)
registerFilterFunction :: StackIndex -> Lua LuaFilterFunction
registerFilterFunction idx = do
isFn <- Lua.isfunction idx
unless isFn . Lua.throwLuaError $ "Not a function at index " ++ show idx
Lua.pushvalue idx
refIdx <- Lua.ref Lua.registryindex
return $ LuaFilterFunction refIdx
elementOrList :: FromLuaStack a => a -> Lua [a]
elementOrList x = do
let topOfStack = Lua.stackTop
elementUnchanged <- Lua.isnil topOfStack
if elementUnchanged
then [x] <$ Lua.pop 1
else do
mbres <- Lua.peekEither topOfStack
case mbres of
Right res -> [res] <$ 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)
=> LuaFilter -> a -> Lua [a]
tryFilter (LuaFilter fnMap) x =
let filterFnName = showConstr (toConstr x)
catchAllName = tyconUQname $ dataTypeName (dataTypeOf x)
in
case Map.lookup filterFnName fnMap `mplus` Map.lookup catchAllName fnMap of
Just fn -> runFilterFunction fn x *> elementOrList x
Nothing -> return [x]
-- | Push a value to the stack via a lua filter function. The filter function is
-- called with given element as argument and is expected to return an element.
-- Alternatively, the function can return nothing or nil, in which case the
-- element is left unchanged.
runFilterFunction :: ToLuaStack a => LuaFilterFunction -> a -> Lua ()
runFilterFunction lf x = do
pushFilterFunction lf
push x
z <- Lua.pcall 1 1 Nothing
when (z /= OK) $ do
let addPrefix = ("Error while running filter function: " ++)
Lua.throwTopMessageAsError' addPrefix
walkMWithLuaFilter :: LuaFilter -> Pandoc -> Lua Pandoc
walkMWithLuaFilter f =
walkInlines f >=> walkBlocks f >=> walkMeta f >=> walkPandoc f
mconcatMapM :: (Monad m, Functor m) => (a -> m [a]) -> [a] -> m [a]
mconcatMapM f = fmap mconcat . mapM f
hasOneOf :: LuaFilter -> [String] -> Bool
hasOneOf (LuaFilter fnMap) = any (\k -> Map.member k fnMap)
walkInlines :: Walkable [Inline] a => LuaFilter -> a -> Lua a
walkInlines f =
if f `hasOneOf` inlineElementNames
then walkM (mconcatMapM (tryFilter f :: Inline -> Lua [Inline]))
else return
walkBlocks :: Walkable [Block] a => LuaFilter -> a -> Lua a
walkBlocks f =
if f `hasOneOf` blockElementNames
then walkM (mconcatMapM (tryFilter f :: Block -> Lua [Block]))
else return
walkMeta :: LuaFilter -> Pandoc -> Lua Pandoc
walkMeta (LuaFilter fnMap) =
case Map.lookup "Meta" fnMap of
Just fn -> walkM (\(Pandoc meta blocks) -> do
meta' <- runFilterFunction fn meta *> singleElement meta
return $ Pandoc meta' blocks)
Nothing -> return
walkPandoc :: LuaFilter -> Pandoc -> Lua Pandoc
walkPandoc (LuaFilter fnMap) =
case foldl mplus Nothing (map (`Map.lookup` fnMap) pandocFilterNames) of
Just fn -> \x -> runFilterFunction fn x *> singleElement x
Nothing -> return
constructorsFor :: DataType -> [String]
constructorsFor x = map show (dataTypeConstrs x)
inlineElementNames :: [String]
inlineElementNames = "Inline" : constructorsFor (dataTypeOf (Str []))
blockElementNames :: [String]
blockElementNames = "Block" : constructorsFor (dataTypeOf (Para []))
metaFilterName :: String
metaFilterName = "Meta"
pandocFilterNames :: [String]
pandocFilterNames = ["Pandoc", "Doc"]
singleElement :: FromLuaStack a => a -> Lua a
singleElement x = do
elementUnchanged <- Lua.isnil (-1)
if elementUnchanged
then x <$ Lua.pop 1
else do
mbres <- Lua.peekEither (-1)
case mbres of
Right res -> res <$ Lua.pop 1
Left err -> do
Lua.pop 1
Lua.throwLuaError $
"Error while trying to get a filter's return " ++
"value from lua stack.\n" ++ err
|
