/*
    * 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.cas;
  
  import java.net.URI;
  import org.apache.syncope.sra.security.web.server.DoNothingIfCommittedServerRedirectStrategy;
  import org.apache.syncope.sra.session.SessionUtils;
  import org.jasig.cas.client.Protocol;
  import org.jasig.cas.client.validation.Assertion;
  import org.jasig.cas.client.validation.TicketValidationException;
  import org.jasig.cas.client.validation.TicketValidator;
  import org.jasig.cas.client.validation.json.Cas30JsonServiceTicketValidator;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.security.authentication.BadCredentialsException;
  import org.springframework.security.authentication.ReactiveAuthenticationManager;
  import org.springframework.security.core.Authentication;
  import org.springframework.security.web.server.ServerRedirectStrategy;
  import org.springframework.security.web.server.WebFilterExchange;
  import org.springframework.security.web.server.authentication.AuthenticationWebFilter;
  import org.springframework.security.web.server.authentication.ServerAuthenticationConverter;
  import org.springframework.security.web.server.authentication.ServerAuthenticationSuccessHandler;
  import org.springframework.security.web.server.util.matcher.AndServerWebExchangeMatcher;
  import org.springframework.security.web.server.util.matcher.NegatedServerWebExchangeMatcher;
  import reactor.core.publisher.Mono;
  
  public class CASAuthenticationWebFilter extends AuthenticationWebFilter {
  
      private static final Logger LOG = LoggerFactory.getLogger(CASAuthenticationWebFilter.class);
  
      private final Protocol protocol;
  
      private final TicketValidator ticketValidator;
  
      public CASAuthenticationWebFilter(
              final ReactiveAuthenticationManager authenticationManager,
              final Protocol protocol,
              final String casServerUrlPrefix) {
  
          super(authenticationManager);
  
          this.protocol = protocol;
          this.ticketValidator = new Cas30JsonServiceTicketValidator(casServerUrlPrefix);
  
          setRequiresAuthenticationMatcher(new AndServerWebExchangeMatcher(
                  CASUtils.ticketAvailable(protocol),
                  new NegatedServerWebExchangeMatcher(SessionUtils.authInSession())));
  
          setServerAuthenticationConverter(validateAssertion());
  
          setAuthenticationSuccessHandler(redirectToInitialRequestURI());
      }
  
      private ServerAuthenticationConverter validateAssertion() {
          return exchange -> CASUtils.retrieveTicketFromRequest(exchange, protocol).
                  flatMap(ticket -> {
                      try {
                          String serviceUrl = CASUtils.constructServiceUrl(exchange, protocol);
                          LOG.debug("Constructed service url: {}", serviceUrl);
  
                          Assertion assertion = ticketValidator.validate(
                                  ticket,
                                  CASUtils.constructServiceUrl(exchange, protocol));
                          return Mono.just(new CASAuthenticationToken(assertion));
                      } catch (TicketValidationException e) {
                          LOG.error("Could not validate {}", ticket, e);
                          throw new BadCredentialsException("Could not validate " + ticket);
                      }
                  });
      }
  
      private ServerAuthenticationSuccessHandler redirectToInitialRequestURI() {
          return new ServerAuthenticationSuccessHandler() {
  
              private final ServerRedirectStrategy redirectStrategy = new DoNothingIfCommittedServerRedirectStrategy();
  
              @Override
              public Mono<Void> onAuthenticationSuccess(
                      final WebFilterExchange webFilterExchange, final Authentication authentication) {
  
                  return webFilterExchange.getExchange().getSession().
                          flatMap(session -> redirectStrategy.sendRedirect(
                          webFilterExchange.getExchange(),
                         session.<URI>getRequiredAttribute(SessionUtils.INITIAL_REQUEST_URI)));
             }
         };
     }
 }