/**
 * 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.camel.processor.aggregate;

import org.apache.camel.Exchange;

/**
 * An {@link AggregationStrategy} which just uses the latest exchange which is useful
 * for status messages where old status messages have no real value. Another example is things
 * like market data prices, where old stock prices are not that relevant, only the current price is.
 *
 * @version $Revision: 885364 $
 */
public class UseLatestAggregationStrategy implements AggregationStrategy {

    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        if (newExchange == null) {
            return oldExchange;
        }
        newExchange.setException(checkException(oldExchange, newExchange));
        return newExchange;
    }
    
    protected Exception checkException(Exchange oldExchange, Exchange newExchange) {
        if (oldExchange == null) {
            return newExchange.getException();
        } else {
            return (newExchange != null && newExchange.getException() != null)
                ? newExchange.getException()
                : oldExchange.getException();
        }
    }

    @Override
    public String toString() {
        return "UseLatestAggregationStrategy";
    }
}
