#!/usr/bin/env runhaskell
-- filter.hs
{--
A filter to help convert a vimwiki file to an org file.
It does the following:
1. Remove metadata
2. Add filename or empty as a level three heading
3. Remove all other headings
--}
import Text.Pandoc.JSON
import Data.Text
import Data.Map.Strict

main :: IO ()
main = toJSONFilter filter''

filter'' :: Pandoc -> Pandoc
filter'' (Pandoc meta blocks) =
  Pandoc (Meta {unMeta = Data.Map.Strict.empty}) ((Header 3 (makeCustomId $ getFilename meta) ((docDate meta) ++ [Str $ pack ": "] ++ (getFilenameInlines meta))) : (filter' <$> blocks))

getFilename :: Meta -> Text
getFilename meta =
  case lookupMeta (pack "filename") meta of
    Just (MetaString s) -> s
    _ -> pack ""

makeInlines :: Text -> [Inline]
makeInlines s = [Str s]

getFilenameInlines :: Meta -> [Inline]
getFilenameInlines = makeInlines . getFilename

makeCustomId :: Text -> Attr
makeCustomId s = (pack "", [], [(pack "CUSTOM_ID", s)])

emptyAttr :: Attr
emptyAttr = (pack "", [], []) 

filter' :: Block -> Block
filter' (Header _ _ _) = Null
filter' x = x