/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * Licensed 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.executor;

import java.util.EventListener;

import org.apache.mina.core.session.IoEvent;

/**
 * Listens and filters all event queue operations occurring in
 * {@link OrderedThreadPoolExecutor} and {@link UnorderedThreadPoolExecutor}.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
public interface IoEventQueueHandler extends EventListener {

    /**
     * A dummy handler which always accepts event doing nothing particular.
     */
    IoEventQueueHandler NOOP = new IoEventQueueHandler() {
        public boolean accept(Object source, IoEvent event) {
            return true;
        }
        public void offered(Object source, IoEvent event) {
            // NOOP
        }
        public void polled(Object source, IoEvent event) {
            // NOOP
        }
    };

    /**
     * Returns <tt>true</tt> if and only if the specified <tt>event</tt> is
     * allowed to be offered to the event queue.  The <tt>event</tt> is dropped
     * if <tt>false</tt> is returned.
     */
    boolean accept(Object source, IoEvent event);

    /**
     * Invoked after the specified <tt>event</tt> has been offered to the
     * event queue.
     */
    void offered(Object source, IoEvent event);

    /**
     * Invoked after the specified <tt>event</tt> has been polled from the
     * event queue.
     */
    void polled(Object source, IoEvent event);
}
