/*
    * 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.filters;
  
  import java.util.Objects;
  import java.util.Optional;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.syncope.sra.SessionConfig;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.cache.CacheManager;
  import org.springframework.cloud.gateway.filter.GatewayFilter;
  import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
  import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory.NameConfig;
  import org.springframework.security.core.context.SecurityContext;
  import org.springframework.security.oauth2.core.oidc.StandardClaimNames;
  import org.springframework.security.oauth2.core.oidc.user.OidcUser;
  import org.springframework.security.oauth2.core.user.OAuth2User;
  import org.springframework.security.web.server.context.WebSessionServerSecurityContextRepository;
  import org.springframework.session.Session;
  import reactor.core.publisher.Mono;
  
  public class PrincipalToRequestHeaderFilterFactory extends AbstractGatewayFilterFactory<NameConfig> {
  
      @Autowired
      private CacheManager cacheManager;
  
      public PrincipalToRequestHeaderFilterFactory() {
          super(NameConfig.class);
      }
  
      @Override
      public GatewayFilter apply(final NameConfig config) {
          return (exchange, chain) -> exchange.getSession().
                  flatMap(session -> Mono.justOrEmpty(Optional.ofNullable(
                  cacheManager.getCache(SessionConfig.DEFAULT_CACHE).get(session.getId(), Session.class)).
                  map(cachedSession -> {
                      String principal = null;
  
                      SecurityContext ctx = cachedSession.getAttribute(
                              WebSessionServerSecurityContextRepository.DEFAULT_SPRING_SECURITY_CONTEXT_ATTR_NAME);
                      if (ctx != null && ctx.getAuthentication() != null) {
                          if (ctx.getAuthentication().getPrincipal() instanceof OidcUser) {
                              principal = ((OidcUser) ctx.getAuthentication().getPrincipal()).
                                      getIdToken().getTokenValue();
                          } else if (ctx.getAuthentication().getPrincipal() instanceof OAuth2User) {
                              principal = Objects.toString(((OAuth2User) ctx.getAuthentication().getPrincipal()).
                                      getAttributes().get(StandardClaimNames.PREFERRED_USERNAME), null);
                          } else {
                              principal = ctx.getAuthentication().getName();
                          }
                      }
  
                      return principal;
                  }))).
                  transform(principal -> principal.flatMap(p -> StringUtils.isEmpty(p)
                  ? chain.filter(exchange)
                  : chain.filter(exchange.mutate().
                          request(exchange.getRequest().mutate().
                                  headers(headers -> headers.add(config.getName(), p)).build()).
                          build()))).
                  switchIfEmpty(chain.filter(exchange));
      }
  }