2 files changed, 67 insertions, 1 deletions
diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/Init.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/Init.hs
index a05d68355..f5f73c5b4 100644
--- a/pandoc-lua-engine/src/Text/Pandoc/Lua/Init.hs
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/Init.hs
@@ -37,6 +37,7 @@ import qualified HsLua.Module.DocLayout as Module.Layout
 import qualified HsLua.Module.Path as Module.Path
 import qualified HsLua.Module.Text as Module.Text
 import qualified HsLua.Module.Zip as Module.Zip
+import qualified Text.Pandoc.Lua.Module.CLI as Pandoc.CLI
 import qualified Text.Pandoc.Lua.Module.Format as Pandoc.Format
 import qualified Text.Pandoc.Lua.Module.MediaBag as Pandoc.MediaBag
 import qualified Text.Pandoc.Lua.Module.Pandoc as Module.Pandoc
@@ -82,7 +83,8 @@ runLuaNoEnv action = do
 -- it must be handled separately.
 loadedModules :: [Module PandocError]
 loadedModules =
-  [ Pandoc.Format.documentedModule
+  [ Pandoc.CLI.documentedModule
+  , Pandoc.Format.documentedModule
   , Pandoc.MediaBag.documentedModule
   , Pandoc.Scaffolding.documentedModule
   , Pandoc.System.documentedModule
diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/CLI.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/CLI.hs
new file mode 100644
index 000000000..01c94cdbb
--- /dev/null
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/CLI.hs
@@ -0,0 +1,64 @@
+{-# LANGUAGE LambdaCase        #-}
+{-# LANGUAGE OverloadedStrings #-}
+{- |
+   Module      : Text.Pandoc.Lua.Module.CLI
+   Copyright   : © 2022 Albert Krewinkel
+   License     : GPL-2.0-or-later
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+
+Command line helpers
+-}
+module Text.Pandoc.Lua.Module.CLI
+  ( documentedModule
+  ) where
+
+import Control.Applicative ((<|>))
+import HsLua ( Field (..), Module (..), (###), (<#>), (=#>), (#?)
+             , defun, failLua, functionResult, liftIO, parameter, pop
+             , pushViaJSON, rawgeti, top)
+import HsLua.Marshalling (lastly, liftLua, peekList, peekString)
+import Text.Pandoc.App (defaultOpts, options, parseOptionsFromArgs)
+import Text.Pandoc.Error (PandocError)
+import Text.Pandoc.Lua.PandocLua ()
+import qualified Data.Text as T
+
+-- | Push the pandoc.types module on the Lua stack.
+documentedModule :: Module PandocError
+documentedModule = Module
+  { moduleName = "pandoc.cli"
+  , moduleDescription =
+      "Command line options and argument parsing."
+  , moduleFields =
+      [ Field
+        { fieldName = "default_options"
+        , fieldDescription = "Default CLI options, using a JSON-like " <>
+          "representation."
+        , fieldPushValue = pushViaJSON defaultOpts
+        }
+      ]
+  , moduleFunctions =
+      [ defun "parse_options"
+        ### parseOptions
+        <#> parameter peekArgs "{string,...}" "args"
+              "list of command line arguments"
+        =#> functionResult pushViaJSON "table"
+              "parsed options, using their JSON-like representation."
+        #? T.unlines
+           [ "Parses command line arguments into pandoc options."
+           , "Typically this function will be used in stand-alone pandoc Lua"
+           , "scripts, taking the list of arguments from the global `arg`."
+           ]
+      ]
+  , moduleOperations = []
+  }
+ where
+  peekArgs idx =
+    (,)
+    <$> (liftLua (rawgeti idx 0) *> (peekString top <|> pure "") `lastly` pop 1)
+    <*> peekList peekString idx
+
+  parseOptions (prg, args) =
+    liftIO (parseOptionsFromArgs options defaultOpts prg args) >>=
+    \case
+      Left e     -> failLua $ "Cannot process info option: " ++ show e
+      Right opts -> pure opts