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{-
Copyright (C) 2008 John MacFarlane <jgm@berkeley.edu>
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.Pluigns
Copyright : Copyright (C) 2008 John MacFarlane
License : GNU GPL, version 2 or above
Maintainer : John MacFarlane <jgm@berkeley.edu>
Stability : alpha
Portability : portable
Support for plugins.
-}
module Text.Pandoc.Plugins (getPlugin)
where
import Language.Haskell.Interpreter
import Text.Pandoc
import Control.Monad (unless, liftM)
import Control.Monad.Error (throwError)
import Data.List (isInfixOf)
-- | Returns the function named @transform@ in the specified
-- module. The module may be identified either by module name
-- or by path name. The @transform@ function should have type
-- @a -> a@ or @a -> IO a@, where @a@ is an instance of 'Data':
-- for example, @Pandoc -> Pandoc@, @Inline -> IO Inline@,
-- @Block -> Block@, or @[Inline] -> IO [Inline]@.
getPlugin :: String -> IO (Pandoc -> IO Pandoc)
getPlugin modsrc = do
res <- runInterpreter (evaluatePlugin modsrc)
case res of
Right func -> return func
Left (WontCompile xs) -> error $ "WontCompile error for plugin '" ++ modsrc ++ "'\n" ++ unlines (map errMsg xs)
Left (NotAllowed x) -> error $ "NotAllowed error for plugin '" ++ modsrc ++ "'\n" ++ x
Left (UnknownError x) -> error $ "UnknownError for plugin '" ++ modsrc ++ "'\n" ++ x
Left (GhcException x) -> error $ "GhcException for plugin '" ++ modsrc ++ "'\n" ++ x
evaluatePlugin :: String -> Interpreter (Pandoc -> IO Pandoc)
evaluatePlugin modsrc = do
set [installedModulesInScope := False]
loadModules [modsrc]
modnames <- getLoadedModules
setTopLevelModules modnames
setImports ["Prelude", "Text.Pandoc", "Text.Pandoc.Definition"]
exports <- liftM concat $ mapM getModuleExports modnames
unless ((Fun "transform") `elem` exports) $
throwError $ UnknownError $ "The plugin module must define a function 'transform'."
transformType <- typeOf "transform"
if "-> IO" `isInfixOf` transformType
then interpret "processInM transform" (as :: Pandoc -> IO Pandoc)
else interpret "return . (processIn transform)" (as :: Pandoc -> IO Pandoc)
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