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/*
   Copyright 2015 Tobias Schumacher

   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 de.tschumacher.sqsservice.consumer;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.amazonaws.services.sqs.model.Message;

import de.tschumacher.sqsservice.SQSQueue;
import de.tschumacher.sqsservice.supplier.SQSMessageFactory;

public class SQSMessageReceiver {

	private static final Logger logger = LoggerFactory
			.getLogger(SQSMessageReceiver.class);
	private static final int WORKER_COUNT = 5;
	protected static final int MAX_RETRYS = 5;
	protected static final int RETRY_SECONDS = 60 * 2;

	private final SQSMessageHandler handler;
	private final ExecutorService executorService;
	private boolean running = false;
	private final Runnable worker;
	final SQSMessageFactory factory;

	public SQSMessageReceiver(final SQSQueue queue,
			final SQSMessageHandler handler,
			final SQSMessageFactory factory) {
		super();
		this.handler = handler;
		this.worker = newWorker(queue);
		this.executorService = Executors.newFixedThreadPool(WORKER_COUNT);
		this.factory = factory;
		start();
	}

	public void start() {
		this.running = true;
		for (int i = 0; i < WORKER_COUNT; i++) {
			this.executorService.submit(this.worker);
		}
	}

	public void stop() throws InterruptedException {
		this.running = false;
	}

	private Runnable newWorker(final SQSQueue queue) {
		return new Runnable() {

			@Override
			public void run() {
				while (SQSMessageReceiver.this.running) {
					try {
						final Message receiveMessage = queue.receiveMessage();
						if (receiveMessage != null) {
							try {
								SQSMessageReceiver.this.handler
										.receivedMessage(
												queue,
												SQSMessageReceiver.this.factory
														.createMessage(receiveMessage
																.getBody()));
								queue.deleteMessage(receiveMessage
										.getReceiptHandle());
							} catch (final Throwable e) {
								logger.error("could not process message", e);
								queue.changeMessageVisibility(
										receiveMessage.getReceiptHandle(),
										RETRY_SECONDS);
							}
						}
					} catch (final Throwable e) {
						logger.error("could not handle message", e);
					}
				}

			}
		};
	}

	@Override
	protected void finalize() throws Throwable {
		stop();
		super.finalize();
	}

}