import Text.Pandoc.Definition
import qualified Data.Map.Strict as Map
import Text.Pandoc.JSON
import Data.Text (Text)
import Misc

main :: IO ()
main = toJSONFilter \(Pandoc (Meta m) body) -> do
  m' <- Map.alterF addSlugs "tags" m
  pure $ Pandoc (Meta m') body

addSlugs :: Maybe MetaValue -> IO (Maybe MetaValue)
addSlugs Nothing = pure Nothing
addSlugs (Just (toTextList -> Just tags)) =
  pure $ Just $ MetaList $ map addSlug1 tags
addSlugs (Just t) = fail $
  "'tags' is\n" <> show t <> "\nwanted a list of strings"

addSlug1 :: Text -> MetaValue
addSlug1 tag = MetaMap $ Map.fromList
  [("name", MetaString tag), ("slug", MetaString $ makeSlug tag)]