login :: RS.Connection -> T.Text -> T.Text -> IO (Maybe BS.ByteString)
login conn username password = do
    let user = userFormat username
    let pass = T.encodeUtf8 password
    canlogin <- runMaybeT $
        do
          uuid <- getID conn user
          [(_,salt), (_,hash)] <- getSaltAndHash conn (useridFormat uuid)
          let Right rehash = ARG.hash ARG.defaultHashOptions pass salt
          if rehash == hash
              then return (Just uuid)
              else return Nothing
    return (asum canlogin)