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{-# LANGUAGE NoImplicitPrelude #-}
{-
Copyright © 2012-2018 John MacFarlane <jgm@berkeley.edu>
2017-2018 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 : © 2012–2018 John MacFarlane,
© 2017-2018 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
( getTag
, rawField
, addField
, addFunction
, addValue
, typeCheck
, popValue
, PushViaCall
, pushViaCall
, pushViaConstructor
, loadScriptFromDataDir
, dostring'
) where
import Prelude
import Control.Monad (when)
import Control.Monad.Catch (finally)
import Data.ByteString.Char8 (unpack)
import Foreign.Lua (FromLuaStack, Lua, NumArgs, StackIndex, Status,
ToLuaStack, ToHaskellFunction)
import Text.Pandoc.Class (readDataFile, runIOorExplode, setUserDataDir)
import qualified Foreign.Lua as Lua
-- | Get value behind key from table at given index.
rawField :: FromLuaStack a => StackIndex -> String -> Lua a
rawField idx key = do
absidx <- Lua.absindex idx
Lua.push key
Lua.rawget absidx
popValue
-- | Add a value to the table at the top of the stack at a string-index.
addField :: ToLuaStack a => String -> a -> Lua ()
addField = addValue
-- | Add a key-value pair to the table at the top of the stack.
addValue :: (ToLuaStack a, ToLuaStack b) => a -> b -> Lua ()
addValue key value = do
Lua.push key
Lua.push value
Lua.rawset (Lua.nthFromTop 3)
-- | Add a function to the table at the top of the stack, using the given name.
addFunction :: ToHaskellFunction a => String -> a -> Lua ()
addFunction name fn = do
Lua.push name
Lua.pushHaskellFunction fn
Lua.wrapHaskellFunction
Lua.rawset (-3)
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 ++ "."
-- | Get, then pop the value at the top of the stack.
popValue :: FromLuaStack a => Lua a
popValue = do
resOrError <- Lua.peekEither (-1)
Lua.pop 1
case resOrError of
Left err -> Lua.throwLuaError err
Right x -> return x
-- | Helper class for pushing a single value to the stack via a lua function.
-- See @pushViaCall@.
class PushViaCall a where
pushViaCall' :: String -> Lua () -> NumArgs -> a
instance PushViaCall (Lua ()) where
pushViaCall' fn pushArgs num = do
Lua.push fn
Lua.rawget Lua.registryindex
pushArgs
Lua.call num 1
instance (ToLuaStack a, PushViaCall b) => PushViaCall (a -> b) where
pushViaCall' fn pushArgs num x =
pushViaCall' fn (pushArgs *> Lua.push 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 => String -> a
pushViaCall fn = pushViaCall' fn (return ()) 0
-- | Call a pandoc element constructor within lua, passing all given arguments.
pushViaConstructor :: PushViaCall a => String -> a
pushViaConstructor pandocFn = pushViaCall ("pandoc." ++ pandocFn)
-- | Load a file from pandoc's data directory.
loadScriptFromDataDir :: Maybe FilePath -> FilePath -> Lua ()
loadScriptFromDataDir datadir scriptFile = do
script <- fmap unpack . Lua.liftIO . runIOorExplode $
setUserDataDir datadir >> readDataFile scriptFile
status <- dostring' script
when (status /= Lua.OK) .
Lua.throwTopMessageAsError' $ \msg ->
"Couldn't load '" ++ scriptFile ++ "'.\n" ++ msg
-- | Load a string and immediately perform a full garbage collection. This is
-- important to keep the program from hanging: If the program containes a call
-- to @require@, then a new loader function is created which then becomes
-- garbage. If that function is collected at an inopportune time, i.e. when the
-- Lua API is called via a function that doesn't allow calling back into Haskell
-- (getraw, setraw, …), then the function's finalizer, and the full program,
-- will hang.
dostring' :: String -> Lua Status
dostring' script = do
loadRes <- Lua.loadstring script
if loadRes == Lua.OK
then Lua.pcall 0 1 Nothing <* Lua.gc Lua.GCCOLLECT 0
else return loadRes
-- | Get the tag of a value. This is an optimized and specialized version of
-- @Lua.getfield idx "tag"@. It only checks for the field on the table at index
-- @idx@ and on its metatable, also ignoring any @__index@ value on the
-- metatable.
getTag :: StackIndex -> Lua String
getTag idx = do
-- push metatable or just the table
Lua.getmetatable idx >>= \hasMT -> when (not hasMT) (Lua.pushvalue idx)
Lua.push "tag"
Lua.rawget (Lua.nthFromTop 2)
Lua.peek Lua.stackTop `finally` Lua.pop 2
|
