/**
* Copyright (c) 2008-2009 Apple Inc. All rights reserved.
* Copyright (C) 2012 FuseSource, Inc.
* http://fusesource.com
*
* 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.fusesource.hawtdispatch;
/**
* <p>
* The EventAggregator interface is used by the {@link CustomDispatchSource} objects to handle
* coalescing data before passing it to the application. Implementations of this class should
* be stateless to remain thread-safe. You can also use one of several built in implementations:
* </p>
*
* <ul>
* <li>{@link EventAggregators#INTEGER_ADD}</li>
* <li>{@link EventAggregators#INTEGER_OR}</li>
* <li>{@link EventAggregators#LONG_ADD}</li>
* <li>{@link EventAggregators#LONG_OR}</li>
* </ul>
*
* @author <a href="http://hiramchirino.com">Hiram Chirino</a>
*/
public interface EventAggregator<Event, MergedEvent> {
/**
* <p>
* Merge the given event with the previous event values.
* </p>
*
* @param previous may be null
* @param event the value that should be merged
* @return a newly merged result
*/
public MergedEvent mergeEvent(MergedEvent previous, Event event);
/**
* <p>
* Merge the given events with the previous event values.
* </p>
*
* @param previous the value of previous merges
* @param events the value of more merges
* @return a newly merged result
*/
public MergedEvent mergeEvents(MergedEvent previous, MergedEvent events);
}