Text.Pandoc.Lua: move globals handling to separate module

2 files changed, 126 insertions, 21 deletions

diff --git a/src/Text/Pandoc/Lua/Global.hs b/src/Text/Pandoc/Lua/Global.hs
new file mode 100644
index 000000000..237c8b500
--- /dev/null
+++ b/src/Text/Pandoc/Lua/Global.hs
@@ -0,0 +1,108 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-
+Copyright © 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
+-}
+{- |
+   Module      : Text.Pandoc.Lua
+   Copyright   : Copyright © 2017-2018 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Pandoc's Lua globals.
+-}
+module Text.Pandoc.Lua.Global
+  ( Global (..)
+  , setGlobals
+  ) where
+
+import Prelude
+import Data.Data (Data)
+import Data.Version (Version (versionBranch))
+import Foreign.Lua (Lua, Peekable, Pushable)
+import Foreign.Lua.Userdata ( ensureUserdataMetatable, pushAnyWithMetatable
+                            , metatableName)
+import Paths_pandoc (version)
+import Text.Pandoc.Class (CommonState)
+import Text.Pandoc.Definition (Pandoc (Pandoc), pandocTypesVersion)
+import Text.Pandoc.Lua.StackInstances ()
+import Text.Pandoc.Lua.Util (addFunction)
+import Text.Pandoc.Options (ReaderOptions)
+
+import qualified Foreign.Lua as Lua
+
+-- | Permissible global Lua variables.
+data Global =
+    FORMAT String
+  | PANDOC_API_VERSION
+  | PANDOC_DOCUMENT Pandoc
+  | PANDOC_READER_OPTIONS ReaderOptions
+  | PANDOC_SCRIPT_FILE FilePath
+  | PANDOC_STATE CommonState
+  | PANDOC_VERSION
+  -- Cannot derive instance of Data because of CommonState
+
+-- | Set all given globals.
+setGlobals :: [Global] -> Lua ()
+setGlobals = mapM_ setGlobal
+
+setGlobal :: Global -> Lua ()
+setGlobal global = case global of
+  -- This could be simplified if Global was an instance of Data.
+  FORMAT format -> do
+    Lua.push format
+    Lua.setglobal "FORMAT"
+  PANDOC_API_VERSION -> do
+    Lua.push (versionBranch pandocTypesVersion)
+    Lua.setglobal "PANDOC_API_VERSION"
+  PANDOC_DOCUMENT doc -> do
+    Lua.push (LazyPandoc doc)
+    Lua.setglobal "PANDOC_DOCUMENT"
+  PANDOC_READER_OPTIONS ropts -> do
+    Lua.push ropts
+    Lua.setglobal "PANDOC_READER_OPTIONS"
+  PANDOC_SCRIPT_FILE filePath -> do
+    Lua.push filePath
+    Lua.setglobal "PANDOC_SCRIPT_FILE"
+  PANDOC_STATE commonState -> do
+    Lua.push commonState
+    Lua.setglobal "PANDOC_STATE"
+  PANDOC_VERSION              -> do
+    Lua.push (versionBranch version)
+    Lua.setglobal "PANDOC_VERSION"
+
+-- | Readonly and lazy pandoc objects.
+newtype LazyPandoc = LazyPandoc Pandoc
+  deriving (Data)
+
+instance Pushable LazyPandoc where
+  push lazyDoc = pushAnyWithMetatable pushPandocMetatable lazyDoc
+   where
+    pushPandocMetatable = ensureUserdataMetatable (metatableName lazyDoc) $
+                          addFunction "__index" indexLazyPandoc
+
+instance Peekable LazyPandoc where
+  peek = Lua.peekAny
+
+indexLazyPandoc :: LazyPandoc -> String -> Lua Lua.NumResults
+indexLazyPandoc (LazyPandoc (Pandoc meta blks)) field = 1 <$
+  case field of
+    "blocks" -> Lua.push blks
+    "meta"   -> Lua.push meta
+    _        -> Lua.pushnil
diff --git a/src/Text/Pandoc/Lua/Init.hs b/src/Text/Pandoc/Lua/Init.hs
index 78fb6204e..c9ee7267a 100644
--- a/src/Text/Pandoc/Lua/Init.hs
+++ b/src/Text/Pandoc/Lua/Init.hs
@@ -32,20 +32,17 @@ module Text.Pandoc.Lua.Init
   , runPandocLua
   , initLuaState
   , luaPackageParams
-  , registerScriptPath
   ) where
 
 import Prelude
 import Control.Monad.Trans (MonadIO (..))
 import Data.Data (Data, dataTypeConstrs, dataTypeOf, showConstr)
 import Data.IORef (newIORef, readIORef)
-import Data.Version (Version (versionBranch))
 import Foreign.Lua (Lua)
 import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
-import Paths_pandoc (version)
-import Text.Pandoc.Class (CommonState, PandocIO, getCommonState,
-                          getUserDataDir, getMediaBag, setMediaBag)
-import Text.Pandoc.Definition (pandocTypesVersion)
+import Text.Pandoc.Class (PandocIO, getCommonState, getUserDataDir,
+                          getMediaBag, setMediaBag)
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
 import Text.Pandoc.Lua.Packages (LuaPackageParams (..),
                                  installPandocPackageSearcher)
 import Text.Pandoc.Lua.Util (loadScriptFromDataDir)
@@ -61,11 +58,12 @@ newtype LuaException = LuaException String deriving (Show)
 -- initialization.
 runPandocLua :: Lua a -> PandocIO (Either LuaException a)
 runPandocLua luaOp = do
-  commonState <- getCommonState
   luaPkgParams <- luaPackageParams
+  globals <- defaultGlobals
   enc <- liftIO $ getForeignEncoding <* setForeignEncoding utf8
   res <- liftIO . Lua.runEither $ do
-    initLuaState commonState luaPkgParams
+    setGlobals globals
+    initLuaState luaPkgParams
     luaOp
   liftIO $ setForeignEncoding enc
   newMediaBag <- liftIO (readIORef (luaPkgMediaBag luaPkgParams))
@@ -74,6 +72,16 @@ runPandocLua luaOp = do
     Left (Lua.Exception msg) -> Left (LuaException msg)
     Right x -> Right x
 
+-- | Global variables which should always be set.
+defaultGlobals :: PandocIO [Global]
+defaultGlobals = do
+  commonState <- getCommonState
+  return
+    [ PANDOC_API_VERSION
+    , PANDOC_STATE commonState
+    , PANDOC_VERSION
+    ]
+
 -- | Generate parameters required to setup pandoc's lua environment.
 luaPackageParams :: PandocIO LuaPackageParams
 luaPackageParams = do
@@ -87,25 +95,14 @@ luaPackageParams = do
     }
 
 -- Initialize the lua state with all required values
-initLuaState :: CommonState -> LuaPackageParams -> Lua ()
-initLuaState commonState luaPkgParams = do
+initLuaState :: LuaPackageParams -> Lua ()
+initLuaState luaPkgParams = do
   Lua.openlibs
   Lua.preloadTextModule "text"
-  Lua.push (versionBranch version)
-  Lua.setglobal "PANDOC_VERSION"
-  Lua.push (versionBranch pandocTypesVersion)
-  Lua.setglobal "PANDOC_API_VERSION"
-  Lua.push commonState
-  Lua.setglobal "PANDOC_STATE"
   installPandocPackageSearcher luaPkgParams
   loadScriptFromDataDir (luaPkgDataDir luaPkgParams) "init.lua"
   putConstructorsInRegistry
 
-registerScriptPath :: FilePath -> Lua ()
-registerScriptPath fp = do
-  Lua.push fp
-  Lua.setglobal "PANDOC_SCRIPT_FILE"
-
 putConstructorsInRegistry :: Lua ()
 putConstructorsInRegistry = do
   Lua.getglobal "pandoc"