/**
 * 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.impl;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

import org.apache.camel.Consumer;
import org.apache.camel.Endpoint;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.processor.Logger;
import org.apache.camel.spi.ExceptionHandler;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * A default implementation of the {@link org.apache.camel.PollingConsumer} which uses the normal
 * asynchronous consumer mechanism along with a {@link BlockingQueue} to allow
 * the caller to pull messages on demand.
 *
 * @version $Revision: 789550 $
 */
public class EventDrivenPollingConsumer extends PollingConsumerSupport implements Processor {
    private static final transient Log LOG = LogFactory.getLog(EventDrivenPollingConsumer.class);
    private BlockingQueue<Exchange> queue;
    private ExceptionHandler interuptedExceptionHandler = new LoggingExceptionHandler(new Logger(LOG));
    private Consumer consumer;

    public EventDrivenPollingConsumer(Endpoint endpoint) {
        this(endpoint, new ArrayBlockingQueue<Exchange>(1000));
    }

    public EventDrivenPollingConsumer(Endpoint endpoint, BlockingQueue<Exchange> queue) {
        super(endpoint);
        this.queue = queue;
    }

    public Exchange receiveNoWait() {
        return receive(0);
    }

    public Exchange receive() {
        while (isRunAllowed()) {
            try {
                return queue.take();
            } catch (InterruptedException e) {
                handleInteruptedException(e);
            }
        }
        if (LOG.isTraceEnabled()) {
            LOG.trace("Consumer is not running, so returning null");
        }
        return null;
    }

    public Exchange receive(long timeout) {
        try {
            return queue.poll(timeout, TimeUnit.MILLISECONDS);
        } catch (InterruptedException e) {
            handleInteruptedException(e);
            return null;
        }
    }

    public void process(Exchange exchange) throws Exception {
        queue.offer(exchange);
    }

    public ExceptionHandler getInteruptedExceptionHandler() {
        return interuptedExceptionHandler;
    }

    public void setInteruptedExceptionHandler(ExceptionHandler interuptedExceptionHandler) {
        this.interuptedExceptionHandler = interuptedExceptionHandler;
    }

    protected void handleInteruptedException(InterruptedException e) {
        getInteruptedExceptionHandler().handleException(e);
    }

    protected void doStart() throws Exception {
        // lets add ourselves as a consumer
        consumer = getEndpoint().createConsumer(this);
        consumer.start();
    }

    protected void doStop() throws Exception {
        if (consumer != null) {
            try {
                consumer.stop();
            } finally {
                consumer = null;
            }
        }
    }
}
