private OAuth2AccessTokenEntity fetchValidRegistrationToken(
      OAuth2Authentication auth, ClientDetailsEntity client) {

    OAuth2AuthenticationDetails details = (OAuth2AuthenticationDetails) auth.getDetails();
    OAuth2AccessTokenEntity token = tokenService.readAccessToken(details.getTokenValue());

    if (config.getRegTokenLifeTime() != null) {

      try {
        // Re-issue the token if it has been issued before [currentTime - validity]
        Date validToDate =
            new Date(System.currentTimeMillis() - config.getRegTokenLifeTime() * 1000);
        if (token.getJwt().getJWTClaimsSet().getIssueTime().before(validToDate)) {
          logger.info("Rotating the registration access token for " + client.getClientId());
          tokenService.revokeAccessToken(token);
          OAuth2AccessTokenEntity newToken = connectTokenService.createResourceAccessToken(client);
          tokenService.saveAccessToken(newToken);
          return newToken;
        } else {
          // it's not expired, keep going
          return token;
        }
      } catch (ParseException e) {
        logger.error("Couldn't parse a known-valid token?", e);
        return token;
      }
    } else {
      // tokens don't expire, just return it
      return token;
    }
  }
  /**
   * Get the meta information for a client.
   *
   * @param clientId
   * @param m
   * @param auth
   * @return
   */
  @PreAuthorize(
      "hasRole('ROLE_CLIENT') and #oauth2.hasScope('"
          + OAuth2AccessTokenEntity.REGISTRATION_TOKEN_SCOPE
          + "')")
  @RequestMapping(value = "/{id}", method = RequestMethod.GET, produces = "application/json")
  public String readClientConfiguration(
      @PathVariable("id") String clientId, Model m, OAuth2Authentication auth) {

    ClientDetailsEntity client = clientService.loadClientByClientId(clientId);

    if (client != null && client.getClientId().equals(auth.getOAuth2Request().getClientId())) {

      // we return the token that we got in
      OAuth2AuthenticationDetails details = (OAuth2AuthenticationDetails) auth.getDetails();
      OAuth2AccessTokenEntity token = tokenService.readAccessToken(details.getTokenValue());

      // TODO: urlencode the client id for safety?
      RegisteredClient registered =
          new RegisteredClient(
              client, token.getValue(), config.getIssuer() + "register/" + client.getClientId());

      // send it all out to the view
      m.addAttribute("client", registered);
      m.addAttribute("code", HttpStatus.OK); // http 200

      return "clientInformationResponseView";
    } else {
      // client mismatch
      logger.error(
          "readClientConfiguration failed, client ID mismatch: "
              + clientId
              + " and "
              + auth.getOAuth2Request().getClientId()
              + " do not match.");
      m.addAttribute("code", HttpStatus.FORBIDDEN); // http 403

      return "httpCodeView";
    }
  }
  /**
   * Update the metainformation for a given client.
   *
   * @param clientId
   * @param jsonString
   * @param m
   * @param auth
   * @return
   */
  @PreAuthorize(
      "hasRole('ROLE_CLIENT') and #oauth2.hasScope('"
          + OAuth2AccessTokenEntity.REGISTRATION_TOKEN_SCOPE
          + "')")
  @RequestMapping(
      value = "/{id}",
      method = RequestMethod.PUT,
      produces = "application/json",
      consumes = "application/json")
  public String updateClient(
      @PathVariable("id") String clientId,
      @RequestBody String jsonString,
      Model m,
      OAuth2Authentication auth) {

    ClientDetailsEntity newClient = ClientDetailsEntityJsonProcessor.parse(jsonString);
    ClientDetailsEntity oldClient = clientService.loadClientByClientId(clientId);

    if (newClient != null
        && oldClient != null // we have an existing client and the new one parsed
        && oldClient
            .getClientId()
            .equals(
                auth.getOAuth2Request()
                    .getClientId()) // the client passed in the URI matches the one in the auth
        && oldClient
            .getClientId()
            .equals(
                newClient.getClientId()) // the client passed in the body matches the one in the URI
    ) {

      // a client can't ask to update its own client secret to any particular value
      newClient.setClientSecret(oldClient.getClientSecret());

      // we need to copy over all of the local and SECOAUTH fields
      newClient.setAccessTokenValiditySeconds(oldClient.getAccessTokenValiditySeconds());
      newClient.setIdTokenValiditySeconds(oldClient.getIdTokenValiditySeconds());
      newClient.setRefreshTokenValiditySeconds(oldClient.getRefreshTokenValiditySeconds());
      newClient.setDynamicallyRegistered(true); // it's still dynamically registered
      newClient.setAllowIntrospection(oldClient.isAllowIntrospection());
      newClient.setAuthorities(oldClient.getAuthorities());
      newClient.setClientDescription(oldClient.getClientDescription());
      newClient.setCreatedAt(oldClient.getCreatedAt());
      newClient.setReuseRefreshToken(oldClient.isReuseRefreshToken());

      // set of scopes that are OK for clients to dynamically register for
      Set<SystemScope> dynScopes = scopeService.getDynReg();

      // scopes that the client is asking for
      Set<SystemScope> requestedScopes = scopeService.fromStrings(newClient.getScope());

      // the scopes that the client can have must be a subset of the dynamically allowed scopes
      Set<SystemScope> allowedScopes = Sets.intersection(dynScopes, requestedScopes);

      // make sure that the client doesn't ask for scopes it can't have
      newClient.setScope(scopeService.toStrings(allowedScopes));

      try {
        // save the client
        ClientDetailsEntity savedClient = clientService.updateClient(oldClient, newClient);

        // we return the token that we got in
        // TODO: rotate this after some set amount of time
        OAuth2AuthenticationDetails details = (OAuth2AuthenticationDetails) auth.getDetails();
        OAuth2AccessTokenEntity token = tokenService.readAccessToken(details.getTokenValue());

        // TODO: urlencode the client id for safety?
        RegisteredClient registered =
            new RegisteredClient(
                savedClient,
                token.getValue(),
                config.getIssuer() + "register/" + savedClient.getClientId());

        // send it all out to the view
        m.addAttribute("client", registered);
        m.addAttribute("code", HttpStatus.OK); // http 200

        return "clientInformationResponseView";
      } catch (IllegalArgumentException e) {
        logger.error("Couldn't save client", e);
        m.addAttribute("code", HttpStatus.BAD_REQUEST);

        return "httpCodeView";
      }
    } else {
      // client mismatch
      logger.error(
          "readClientConfiguration failed, client ID mismatch: "
              + clientId
              + " and "
              + auth.getOAuth2Request().getClientId()
              + " do not match.");
      m.addAttribute("code", HttpStatus.FORBIDDEN); // http 403

      return "httpCodeView";
    }
  }