[API Change] Extract Lua code into new package pandoc-lua-engine

The flag 'lua53` must now be used with that package if pandoc is to be
compiled against Lua 5.3.

1 files changed, 52 insertions, 0 deletions

diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua.hs
new file mode 100644
index 000000000..d6134fc01
--- /dev/null
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua.hs
@@ -0,0 +1,52 @@
+{-# LANGUAGE LambdaCase        #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeApplications  #-}
+{- |
+   Module      : Text.Pandoc.Lua
+   Copyright   : Copyright © 2017-2022 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Running pandoc Lua filters.
+-}
+module Text.Pandoc.Lua
+  ( -- * High-level functions
+    applyFilter
+  , readCustom
+  , writeCustom
+  -- * Low-level functions
+  , Global(..)
+  , setGlobals
+  , runLua
+  , runLuaNoEnv
+  -- * Engine
+  , getEngine
+  ) where
+
+import Control.Monad.IO.Class (MonadIO (liftIO))
+import HsLua.Core (getglobal, openlibs, run, top, tostring)
+import Text.Pandoc.Error (PandocError)
+import Text.Pandoc.Lua.Filter (applyFilter)
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
+import Text.Pandoc.Lua.Init (runLua, runLuaNoEnv)
+import Text.Pandoc.Lua.Reader (readCustom)
+import Text.Pandoc.Lua.Writer (writeCustom)
+import Text.Pandoc.Lua.Orphans ()
+import Text.Pandoc.Scripting (ScriptingEngine (..))
+import qualified Text.Pandoc.UTF8 as UTF8
+
+-- | Constructs the Lua scripting engine.
+getEngine :: MonadIO m => m ScriptingEngine
+getEngine = do
+  versionName <- liftIO . run @PandocError $ do
+    openlibs
+    getglobal "_VERSION"
+    tostring top
+  pure $ ScriptingEngine
+    { engineName = maybe "Lua (unknown version)" UTF8.toText versionName
+    , engineApplyFilter = applyFilter
+    , engineReadCustom = readCustom
+    , engineWriteCustom = writeCustom
+    }