Lua module: add readers submodule

Plain text readers are exposed to lua scripts via the `pandoc.reader`
submodule, which is further subdivided by format.  Converting e.g. a
markdown string into a pandoc document is possible from within lua:

    doc = pandoc.reader.markdown.read_doc("Hello, World!")

A `read_block` convenience function is provided for all formats,
although it will still parse the whole string but return only the first
block as the result.

Custom reader options are not supported yet, default options are used
for all parsing operations.

1 files changed, 72 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Lua/PandocModule.hs b/src/Text/Pandoc/Lua/PandocModule.hs
index 87d1fa6b9..d0c78f562 100644
--- a/src/Text/Pandoc/Lua/PandocModule.hs
+++ b/src/Text/Pandoc/Lua/PandocModule.hs
@@ -28,11 +28,25 @@ Pandoc module for lua.
 module Text.Pandoc.Lua.PandocModule ( pushPandocModule ) where
 
 import Data.ByteString.Char8 ( unpack )
-import Scripting.Lua ( LuaState, call)
+import Data.Default ( Default(..) )
+import Scripting.Lua ( LuaState, call, newtable, push, pushhsfunction, rawset)
+import Text.Pandoc.Class hiding ( readDataFile )
+import Text.Pandoc.Definition ( Pandoc(..), Block(..) )
 import Text.Pandoc.Lua.Compat ( loadstring )
+import Text.Pandoc.Lua.StackInstances ()
+import Text.Pandoc.Readers.DocBook ( readDocBook )
+import Text.Pandoc.Readers.HTML ( readHtml )
+import Text.Pandoc.Readers.LaTeX ( readLaTeX )
+import Text.Pandoc.Readers.Native ( readNative )
+import Text.Pandoc.Readers.Markdown ( readMarkdown )
+import Text.Pandoc.Readers.MediaWiki ( readMediaWiki )
+import Text.Pandoc.Readers.Org ( readOrg )
+import Text.Pandoc.Readers.RST ( readRST )
+import Text.Pandoc.Readers.Textile ( readTextile )
+import Text.Pandoc.Readers.TWiki ( readTWiki )
+import Text.Pandoc.Readers.Txt2Tags ( readTxt2Tags )
 import Text.Pandoc.Shared ( readDataFile )
 
-
 -- | Push the "pandoc" on the lua stack.
 pushPandocModule :: LuaState -> IO ()
 pushPandocModule lua = do
@@ -42,7 +56,63 @@ pushPandocModule lua = do
     then return ()
     else do
       call lua 0 1
+  push lua "reader"
+  pushReadersModule lua readers
+  rawset lua (-3)
+
+readers :: [(String, String -> PandocIO Pandoc)]
+readers =
+  [ ("docbook", readDocBook def)
+  , ("html", readHtml def)
+  , ("latex", readLaTeX def)
+  , ("native", readNative def)
+  , ("markdown", readMarkdown def)
+  , ("mediawiki", readMediaWiki def)
+  , ("org", readOrg def)
+  , ("rst", readRST def)
+  , ("textile", readTextile def)
+  , ("twiki", readTWiki def)
+  , ("txt2tags", readTxt2Tags def)
+  ]
 
 -- | Get the string representation of the pandoc module
 pandocModuleScript :: IO String
 pandocModuleScript = unpack <$> readDataFile Nothing "pandoc.lua"
+
+-- | Push a lua table containing readers of the given formats.
+pushReadersModule :: LuaState
+                 -> [(String, String -> PandocIO Pandoc)]
+                 -> IO ()
+pushReadersModule lua readerFns = do
+  newtable lua
+  mapM_ (uncurry $ addReaderTable) readerFns
+ where
+   addReaderTable :: String
+                  -> (String -> PandocIO Pandoc)
+                  -> IO ()
+   addReaderTable formatName readerFn = do
+     let readDoc :: String -> IO Pandoc
+         readDoc s = do
+           res <- runIO $ readerFn s
+           case res of
+             (Left x) -> error (show x)
+             (Right x) -> return x
+     let readBlock :: String -> IO Block
+         readBlock s = do
+           Pandoc _ blks <- readDoc s
+           return $ case blks of
+             x:_ -> x
+             _   -> Null
+     -- Push table containing all functions for this format
+     push lua formatName
+     newtable lua
+     -- set document-reading function
+     push lua "read_doc"
+     pushhsfunction lua readDoc
+     rawset lua (-3)
+     -- set block-reading function
+     push lua "read_block"
+     pushhsfunction lua readBlock
+     rawset lua (-3)
+     -- store table in readers module
+     rawset lua (-3)