/*
    * 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.commons.monitoring.web.session;
  
  import org.apache.commons.monitoring.Role;
  import org.apache.commons.monitoring.counters.Counter;
  import org.apache.commons.monitoring.counters.Unit;
  import org.apache.commons.monitoring.repositories.Repository;
  import org.apache.commons.monitoring.stopwatches.StopWatch;
  
  import javax.servlet.http.HttpSessionEvent;
  import javax.servlet.http.HttpSessionListener;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  public class MonitoringSessionListener implements HttpSessionListener {
      private final Map<String, StopWatch> watches = new ConcurrentHashMap<String, StopWatch>();
  
      private final Counter counter;
  
      public MonitoringSessionListener() {
          counter = Repository.INSTANCE.getCounter(new Counter.Key(new Role("session", Unit.UNARY), "session"));
      }
  
      @Override
      public void sessionCreated(final HttpSessionEvent httpSessionEvent) {
          final StopWatch watch = Repository.INSTANCE.start(counter);
          watches.put(httpSessionEvent.getSession().getId(), watch);
      }
  
      @Override
      public void sessionDestroyed(final HttpSessionEvent httpSessionEvent) {
          final StopWatch watch = watches.remove(httpSessionEvent.getSession().getId());
          if (watch != null) {
              watch.stop();
          }
      }
  }