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/*
 * Copyright © 1996-2008 GlobalMentor, Inc. 
 *
 * 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 com.globalmentor.mail;

import java.util.concurrent.BlockingQueue;

import javax.mail.*;

import com.globalmentor.collections.AbstractRunnableBlockingQueueConsumer;
import com.globalmentor.log.Log;

import static com.globalmentor.java.Objects.*;

/**
 * A consumer that takes mail messages from a blocking queue and sends them. The given transport connection is opened and closed as needed. Errors are logged.
 * This runnable's interruption policy is to end execution.
 * @author Garret Wilson
 */
public class BlockingQueueMailSender extends AbstractRunnableBlockingQueueConsumer {

	/** The transport used for sending messages. */
	private final Transport transport;

	/** @return The transport used for sending messages. */
	protected Transport getTransport() {
		return transport;
	}

	/** The authentication user for sending the messages. */
	private final String user;

	/** @return The authentication user for sending the messages. */
	protected String getUser() {
		return user;
	}

	/** The authentication password for sending the messages. */
	private final String password;

	/** @return The authentication password for sending the messages. */
	protected String getPassword() {
		return password;
	}

	/**
	 * Blocking queue constructor.
	 * @param blockingQueue The blocking queue from which elements will be consumed.
	 * @param transport The transport to use for sending the messages.
	 * @param user The authentication user for sending the messages.
	 * @param password The authentication password for sending the messages.
	 * @throws NullPointerException if the given blocking queue, transport, user, and/or password is null.
	 */
	public BlockingQueueMailSender(final BlockingQueue blockingQueue, final Transport transport, final String user, final String password) {
		super(blockingQueue); //construct the parent class
		this.transport = checkInstance(transport, "Transport cannot be null.");
		this.user = checkInstance(user, "User cannot be null.");
		this.password = checkInstance(password, "Password cannot be null.");
	}

	/**
	 * Consumes an email message from the queue.
	 * @param message The email message to consume.
	 */
	public void consume(final Message message) {
		final Transport transport = getTransport(); //get the current transport
		try {
			if(!transport.isConnected()) { //if the transport is not connected
				transport.connect(getUser(), getPassword()); //connect to the transport
			}
			transport.sendMessage(message, message.getAllRecipients()); //send the message to all its recipients
			if(getBlockingQueue().isEmpty()) { //if there are currently no more elements in the queue
				transport.close(); //close the transport; we'll open it as needed
			}
		} catch(final MessagingException messagingException) { //if there is a messaging error
			Log.info(messagingException); //log the error
		}
	}

	/**
	 * Called when the consumer is stopped after processing ends. This version closes the transport.
	 */
	protected void stopped() {
		try {
			getTransport().close(); //close the transport
			super.stopped(); //do the default stopping
		} catch(final MessagingException messagingException) { //if there is a messaging error
			Log.info(messagingException); //log the error
		}
	}

}