example.hs

webRoute
  :: (MonadWidget t m, WR.PathInfo a)
  => T.Text     -- ^ The part of the URL not related to SPA routing, starting with '/'
  -> Event t a
  -> m (Dynamic t (Either T.Text a))
webRoute pathBase aUpdates = do
  route' encoder decoder aUpdates
 where
   -- x = WR.fromPathInfo :: _
   encoder u a = u & U.pathL .~ T.encodeUtf8 (pathBase <> WR.toPathInfo a)
   decoder u = first T.pack . WR.fromPathInfo =<<
     note (pathBase <> " is a Bad prefix for " <> T.decodeUtf8 (U.serializeURIRef' u))
     (BS.stripPrefix (T.encodeUtf8 pathBase) (u ^. U.pathL))