Reflex file loader

FileLoader.hs

fileLoader :: MonadWidget t m => FileInputConfig t -> m (Event t Text)
fileLoader cfg = do
    fls <- fmapMaybe listToMaybe . updated . value <$> fileInput cfg
    reader <- liftIO newFileReader
    performEvent_ $ ffor fls $ \f -> liftIO $
      readAsDataURL reader (Just f)
    wrapDomEvent reader (`on` load) $ do
      res <- liftIO $ fromJSValUnchecked =<< getResult reader
      let Right contents = decodeUtf8 <$> B64.decode
            (encodeUtf8 $ snd $ T.breakOnEnd "base64," res)
      return contents