/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.syncope.sra.security.oauth2;
  
  import java.net.URI;
  import java.nio.charset.StandardCharsets;
  import org.apache.syncope.sra.security.AbstractServerLogoutSuccessHandler;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.beans.factory.annotation.Qualifier;
  import org.springframework.security.core.Authentication;
  import org.springframework.security.oauth2.client.authentication.OAuth2AuthenticationToken;
  import org.springframework.security.oauth2.client.registration.ClientRegistration;
  import org.springframework.security.oauth2.client.registration.ReactiveClientRegistrationRepository;
  import org.springframework.security.oauth2.core.oidc.user.OidcUser;
  import org.springframework.security.web.server.WebFilterExchange;
  import org.springframework.security.web.server.authentication.logout.RedirectServerLogoutSuccessHandler;
  import org.springframework.util.Assert;
  import org.springframework.web.util.UriComponentsBuilder;
  import reactor.core.publisher.Mono;
  
  /**
   * A reactive logout success handler for initiating OIDC logout through the user agent.
   *
   * @see <a href="https://openid.net/specs/openid-connect-session-1_0.html#RPLogout">RP-Initiated Logout</a>
   * @see org.springframework.security.web.server.authentication.logout.ServerLogoutSuccessHandler
   */
  public class OidcClientInitiatedServerLogoutSuccessHandler extends AbstractServerLogoutSuccessHandler {
  
      @Autowired
      @Qualifier("oidcClientRegistrationRepository")
      private ReactiveClientRegistrationRepository clientRegistrationRepository;
  
      protected final RedirectServerLogoutSuccessHandler serverLogoutSuccessHandler =
              new RedirectServerLogoutSuccessHandler();
  
      /**
       * The URL to redirect to after successfully logging out when not originally an OIDC login
       *
       * @param logoutSuccessUrl the url to redirect to. Default is "/login?logout".
       */
      public void setLogoutSuccessUrl(final URI logoutSuccessUrl) {
          Assert.notNull(logoutSuccessUrl, "logoutSuccessUrl cannot be null");
          this.serverLogoutSuccessHandler.setLogoutSuccessUrl(logoutSuccessUrl);
      }
  
      @Override
      public Mono<Void> onLogoutSuccess(final WebFilterExchange exchange, final Authentication authentication) {
          return Mono.just(authentication).
                  filter(OAuth2AuthenticationToken.class::isInstance).
                  filter(token -> authentication.getPrincipal() instanceof OidcUser).
                  map(OAuth2AuthenticationToken.class::cast).
                  flatMap(this::endSessionEndpoint).
                  map(endSessionEndpoint -> endpointUri(exchange, endSessionEndpoint, authentication)).
                  switchIfEmpty(serverLogoutSuccessHandler.onLogoutSuccess(exchange, authentication).then(Mono.empty())).
                  flatMap(endpointUri -> redirectStrategy.sendRedirect(exchange.getExchange(), endpointUri));
      }
  
      private Mono<URI> endSessionEndpoint(final OAuth2AuthenticationToken token) {
          String registrationId = token.getAuthorizedClientRegistrationId();
          return clientRegistrationRepository.findByRegistrationId(registrationId).
                  map(ClientRegistration::getProviderDetails).
                  map(ClientRegistration.ProviderDetails::getConfigurationMetadata).
                  flatMap(configurationMetadata -> Mono.justOrEmpty(configurationMetadata.get("end_session_endpoint"))).
                  map(Object::toString).
                  map(URI::create);
      }
  
      private URI endpointUri(
              final WebFilterExchange exchange,
              final URI endSessionEndpoint,
              final Authentication authentication) {
  
          UriComponentsBuilder builder = UriComponentsBuilder.fromUri(endSessionEndpoint);
          builder.queryParam("id_token_hint", idToken(authentication));
  
          URI postLogout = getPostLogout(exchange);
          builder.queryParam("post_logout_redirect_uri", postLogout);
  
          return builder.encode(StandardCharsets.UTF_8).build().toUri();
      }
  
      private String idToken(final Authentication authentication) {
          return ((OidcUser) authentication.getPrincipal()).getIdToken().getTokenValue();
     }
 }