/*
    * 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;
  
  import java.util.Map;
  import java.util.Optional;
  import java.util.concurrent.ConcurrentHashMap;
  import org.apache.syncope.sra.RouteProvider;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.cloud.gateway.event.RefreshRoutesEvent;
  import org.springframework.cloud.gateway.route.Route;
  import org.springframework.cloud.gateway.route.RouteLocator;
  import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
  import org.springframework.context.ApplicationListener;
  import org.springframework.security.web.server.util.matcher.ServerWebExchangeMatcher;
  import org.springframework.web.server.ServerWebExchange;
  import reactor.core.publisher.Mono;
  
  public abstract class AbstractRouteMatcher
          implements ServerWebExchangeMatcher, ApplicationListener<RefreshRoutesEvent> {
  
      private static final Logger LOG = LoggerFactory.getLogger(AbstractRouteMatcher.class);
  
      protected static final Map<String, Map<String, Boolean>> CACHE = new ConcurrentHashMap<>();
  
      @Autowired
      private RouteLocator routeLocator;
  
      @Autowired
      protected RouteProvider routeProvider;
  
      protected abstract String getCacheName();
  
      protected abstract boolean routeBehavior(Route route);
  
      @Override
      public void onApplicationEvent(final RefreshRoutesEvent event) {
          Optional.ofNullable(CACHE.get(getCacheName())).ifPresent(Map::clear);
      }
  
      @Override
      public Mono<MatchResult> matches(final ServerWebExchange exchange) {
          // see org.springframework.cloud.gateway.handler.RoutePredicateHandlerMapping#lookupRoute
          return routeLocator.getRoutes().
                  // individually filter routes so that filterWhen error delaying is not a problem
                  concatMap(route -> Mono.just(route).filterWhen(r -> r.getPredicate().apply(exchange)).
                  // instead of immediately stopping main flux due to error, log and swallow it
                  doOnError(e -> LOG.error("Error applying predicate for route: {}", route.getId(), e)).
                  onErrorResume(e -> Mono.empty())).
                  next().
                  flatMap(route -> {
                      exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR, route.getId());
                      LOG.debug("[{}] Route found: {}", getClass().getName(), route);
  
                      boolean cond = Optional.ofNullable(CACHE.get(getCacheName()).get(route.getId())).orElseGet(() -> {
                          boolean result = routeBehavior(route);
                          CACHE.get(getCacheName()).put(route.getId(), result);
                          return result;
                      });
                      LOG.debug("[{}] Condition matched: {}", getClass().getName(), cond);
  
                      return cond ? MatchResult.match() : MatchResult.notMatch();
                  }).switchIfEmpty(Mono.defer(() -> {
              LOG.debug("[{}] No Route found", getClass().getName());
              return MatchResult.notMatch();
          }));
      }
  }