[API Change] Export new module Text.Pandoc.Scripting

The module contains the central data structure for scripting engines.

pandoc.cabal

@@ -651,6 +651,7 @@ library
                    Text.Pandoc.Lua,
                    Text.Pandoc.PDF,
                    Text.Pandoc.UTF8,
+                   Text.Pandoc.Scripting,
                    Text.Pandoc.Templates,
                    Text.Pandoc.XML,
                    Text.Pandoc.SelfContained,

src/Text/Pandoc/Scripting.hs

@@ -0,0 +1,53 @@
+{-# LANGUAGE OverloadedStrings    #-}
+{-# LANGUAGE ImpredicativeTypes   #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{- |
+Module      : Text.Pandoc.Scripting
+Copyright   : © 2022 Albert Krewinkel
+License     : GPL-2.0-or-later
+Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+
+Central data structure for scripting engines.
+-}
+module Text.Pandoc.Scripting
+  ( ScriptingEngine (..)
+  , noEngine
+  )
+where
+
+import Control.Monad.IO.Class (MonadIO)
+import Data.Text (Text)
+import Text.Pandoc.Definition (Pandoc)
+import Text.Pandoc.Class.PandocMonad (PandocMonad)
+import Text.Pandoc.Filter.Environment (Environment)
+import Text.Pandoc.Options (ReaderOptions, WriterOptions)
+import Text.Pandoc.Sources (Sources)
+
+-- | Structure to define a scripting engine.
+data ScriptingEngine = ScriptingEngine
+  { engineName :: Text   -- ^ Name of the engine.
+
+  , engineApplyFilter :: forall m. (PandocMonad m, MonadIO m)
+                      => Environment -> [String] -> FilePath
+                      -> Pandoc -> m Pandoc
+    -- ^ Use the scripting engine to run a filter.
+
+  , engineReadCustom :: forall m. (PandocMonad m, MonadIO m)
+                     => FilePath -> ReaderOptions -> Sources -> m Pandoc
+    -- ^ Function to parse input into a 'Pandoc' document.
+
+  , engineWriteCustom :: forall m. (PandocMonad m, MonadIO m)
+                      => FilePath -> WriterOptions -> Pandoc -> m Text
+    -- ^ Invoke the given script file to convert to any custom format.
+  }
+
+noEngine :: ScriptingEngine
+noEngine = ScriptingEngine
+  { engineName = "none"
+  , engineApplyFilter = \_env _args _fp _doc ->
+      error "Custom filters are not supported."
+  , engineReadCustom = \_fp _ropts _sources ->
+      error "Custom readers are not supported."
+  , engineWriteCustom = \_fp _wopts _doc ->
+      error "Custom writers are not supported."
+  }