/*
 * 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.loadbalancer;

import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.Exchange;

/**
 * A base class for {@link LoadBalancer} implementations which choose a single destination for each exchange (rather
 * like JMS Queues)
 */
public abstract class QueueLoadBalancer extends LoadBalancerSupport {

    @Override
    public boolean process(final Exchange exchange, final AsyncCallback callback) {
        AsyncProcessor[] list = doGetProcessors();
        if (list.length > 0) {
            AsyncProcessor processor = chooseProcessor(list, exchange);
            if (processor == null) {
                Exception e = new IllegalStateException("No processors could be chosen to process " + exchange);
                exchange.setException(e);
            } else {
                processor.process(exchange, callback);
                return false;
            }
        }
        // no processors but indicate we are done
        callback.done(false);
        return false;
    }

    protected abstract AsyncProcessor chooseProcessor(AsyncProcessor[] processors, Exchange exchange);
}
