jsonstuff.purs

type PlayPauseMessage =
  { play :: Boolean }

type SkipMessage =
  { skip :: Int }

data Message
  = PlayPause    PlayPauseMessage
  | Skip         SkipMessage

instance readForeignMessage :: ReadForeign Message where
  readImpl f = PlayPause <$> read' f <|> Skip <$> read' f
  
instance writeForeignMessage :: WriteForeign Message where
  writeImpl f = ???