/*
    *  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.mina.filter.util;
  
  import org.apache.mina.core.filterchain.IoFilter;
  import org.apache.mina.core.filterchain.IoFilterAdapter;
  import org.apache.mina.core.filterchain.IoFilterChain;
  import org.apache.mina.core.session.IdleStatus;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.write.WriteRequest;
  
  /**
   * An {@link IoFilter}s wrapper that keeps track of the number of usages of this filter and will call init/destroy
   * when the filter is not in use.
   *
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   * @org.apache.xbean.XBean
   */
  public class ReferenceCountingFilter extends IoFilterAdapter {
      private final IoFilter filter;
  
      private int count = 0;
  
      /**
       * Creates a new ReferenceCountingFilter instance
       * 
       * @param filter the filter we are counting references on
       */
      public ReferenceCountingFilter(IoFilter filter) {
          this.filter = filter;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public synchronized void onPreAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
          if (0 == count) {
              filter.init();
          }
  
          ++count;
  
          filter.onPreAdd(parent, name, nextFilter);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public synchronized void onPostRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
          filter.onPostRemove(parent, name, nextFilter);
  
          --count;
  
          if (0 == count) {
              filter.destroy();
          }
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void exceptionCaught(NextFilter nextFilter, IoSession session, Throwable cause) throws Exception {
          filter.exceptionCaught(nextFilter, session, cause);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void filterClose(NextFilter nextFilter, IoSession session) throws Exception {
          filter.filterClose(nextFilter, session);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
          filter.filterWrite(nextFilter, session, writeRequest);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws Exception {
         filter.messageReceived(nextFilter, session, message);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
         filter.messageSent(nextFilter, session, writeRequest);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void onPostAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
         filter.onPostAdd(parent, name, nextFilter);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void onPreRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
         filter.onPreRemove(parent, name, nextFilter);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void sessionClosed(NextFilter nextFilter, IoSession session) throws Exception {
         filter.sessionClosed(nextFilter, session);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void sessionCreated(NextFilter nextFilter, IoSession session) throws Exception {
         filter.sessionCreated(nextFilter, session);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void sessionIdle(NextFilter nextFilter, IoSession session, IdleStatus status) throws Exception {
         filter.sessionIdle(nextFilter, session, status);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void sessionOpened(NextFilter nextFilter, IoSession session) throws Exception {
         filter.sessionOpened(nextFilter, session);
     }
 }