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{-
Copyright © 2012-2017 John MacFarlane <jgm@berkeley.edu>
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
-}
{-# LANGUAGE FlexibleInstances #-}
{- |
Module : Text.Pandoc.Lua.Util
Copyright : © 2012–2016 John MacFarlane,
© 2017 Albert Krewinkel
License : GNU GPL, version 2 or above
Maintainer : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
Stability : alpha
Lua utility functions.
-}
module Text.Pandoc.Lua.Util
( adjustIndexBy
, getTable
, setTable
, addValue
, getRawInt
, setRawInt
, addRawInt
, keyValuePairs
, PushViaCall
, pushViaCall
, pushViaConstructor
) where
import Scripting.Lua (LuaState, StackValue (..), call, getglobal2, gettable,
next, pop, pushnil, rawgeti, rawseti, settable)
-- | Adjust the stack index, assuming that @n@ new elements have been pushed on
-- the stack.
adjustIndexBy :: Int -> Int -> Int
adjustIndexBy idx n =
if idx < 0
then idx - n
else idx
-- | Get value behind key from table at given index.
getTable :: (StackValue a, StackValue b) => LuaState -> Int -> a -> IO (Maybe b)
getTable lua idx key = do
push lua key
gettable lua (idx `adjustIndexBy` 1)
peek lua (-1) <* pop lua 1
-- | Set value for key for table at the given index
setTable :: (StackValue a, StackValue b) => LuaState -> Int -> a -> b -> IO ()
setTable lua idx key value = do
push lua key
push lua value
settable lua (idx `adjustIndexBy` 2)
-- | Add a key-value pair to the table at the top of the stack
addValue :: (StackValue a, StackValue b) => LuaState -> a -> b -> IO ()
addValue lua = setTable lua (-1)
-- | Get value behind key from table at given index.
getRawInt :: StackValue a => LuaState -> Int -> Int -> IO (Maybe a)
getRawInt lua idx key =
rawgeti lua idx key
*> peek lua (-1)
<* pop lua 1
-- | Set numeric key/value in table at the given index
setRawInt :: StackValue a => LuaState -> Int -> Int -> a -> IO ()
setRawInt lua idx key value = do
push lua value
rawseti lua (idx `adjustIndexBy` 1) key
-- | Set numeric key/value in table at the top of the stack.
addRawInt :: StackValue a => LuaState -> Int -> a -> IO ()
addRawInt lua = setRawInt lua (-1)
-- | Try reading the table under the given index as a list of key-value pairs.
keyValuePairs :: (StackValue a, StackValue b)
=> LuaState -> Int -> IO (Maybe [(a, b)])
keyValuePairs lua idx = do
pushnil lua
sequence <$> remainingPairs
where
remainingPairs = do
res <- nextPair
case res of
Nothing -> return []
Just a -> (a:) <$> remainingPairs
nextPair :: (StackValue a, StackValue b) => IO (Maybe (Maybe (a,b)))
nextPair = do
hasNext <- next lua (idx `adjustIndexBy` 1)
if hasNext
then do
val <- peek lua (-1)
key <- peek lua (-2)
pop lua 1 -- removes the value, keeps the key
return $ Just <$> ((,) <$> key <*> val)
else do
return Nothing
-- | Helper class for pushing a single value to the stack via a lua function.
-- See @pushViaCall@.
class PushViaCall a where
pushViaCall' :: LuaState -> String -> IO () -> Int -> a
instance PushViaCall (IO ()) where
pushViaCall' lua fn pushArgs num = do
getglobal2 lua fn
pushArgs
call lua num 1
instance (StackValue a, PushViaCall b) => PushViaCall (a -> b) where
pushViaCall' lua fn pushArgs num x =
pushViaCall' lua fn (pushArgs *> push lua x) (num + 1)
-- | Push an value to the stack via a lua function. The lua function is called
-- with all arguments that are passed to this function and is expected to return
-- a single value.
pushViaCall :: PushViaCall a => LuaState -> String -> a
pushViaCall lua fn = pushViaCall' lua fn (return ()) 0
-- | Call a pandoc element constructor within lua, passing all given arguments.
pushViaConstructor :: PushViaCall a => LuaState -> String -> a
pushViaConstructor lua pandocFn = pushViaCall lua ("pandoc." ++ pandocFn)
|
