/*
    *  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.session.IoEventType;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.write.WriteRequest;
  import org.apache.mina.core.write.WriteRequestWrapper;
  
  /**
   * An abstract {@link IoFilter} that simplifies the implementation of
   * an {@link IoFilter} that filters an {@link IoEventType#WRITE} event.
   *
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   *
   */
  public abstract class WriteRequestFilter extends IoFilterAdapter {
      @Override
      public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
          Object filteredMessage = doFilterWrite(nextFilter, session, writeRequest);
          if (filteredMessage != null && filteredMessage != writeRequest.getMessage()) {
              nextFilter.filterWrite(session, new FilteredWriteRequest(filteredMessage, writeRequest));
          } else {
              nextFilter.filterWrite(session, writeRequest);
          }
      }
  
      @Override
      public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
          if (writeRequest instanceof FilteredWriteRequest) {
              FilteredWriteRequest req = (FilteredWriteRequest) writeRequest;
              if (req.getParent() == this) {
                  nextFilter.messageSent(session, req.getParentRequest());
                  return;
              }
          }
  
          nextFilter.messageSent(session, writeRequest);
      }
  
      protected abstract Object doFilterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest)
              throws Exception;
  
      private class FilteredWriteRequest extends WriteRequestWrapper {
          private final Object filteredMessage;
  
          public FilteredWriteRequest(Object filteredMessage, WriteRequest writeRequest) {
              super(writeRequest);
  
              if (filteredMessage == null) {
                  throw new IllegalArgumentException("filteredMessage");
              }
              this.filteredMessage = filteredMessage;
          }
  
          public WriteRequestFilter getParent() {
              return WriteRequestFilter.this;
          }
  
          @Override
          public Object getMessage() {
              return filteredMessage;
          }
      }
  }