/*
 * Copyright 2002-2014 the original author or authors.
 *
 * 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 org.springframework.integration.mail.transformer;

import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.integration.mail.support.MailUtils;
import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
import org.springframework.integration.support.DefaultMessageBuilderFactory;
import org.springframework.integration.support.MessageBuilderFactory;
import org.springframework.integration.support.utils.IntegrationUtils;
import org.springframework.integration.transformer.MessageTransformationException;
import org.springframework.integration.transformer.Transformer;
import org.springframework.messaging.Message;

/**
 * Base class for Transformers that convert from a JavaMail Message to a
 * Spring Integration Message.
 *
 * @author Mark Fisher
 * @author Gary Russell
 * @author Artem Bilan
 */
public abstract class AbstractMailMessageTransformer<T> implements Transformer,
		BeanFactoryAware {

	protected final Log logger = LogFactory.getLog(this.getClass());

	private volatile BeanFactory beanFactory;

	private volatile MessageBuilderFactory messageBuilderFactory = new DefaultMessageBuilderFactory();

	private volatile boolean messageBuilderFactorySet;


	@Override
	public final void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
	}

	protected MessageBuilderFactory getMessageBuilderFactory() {
		if (!this.messageBuilderFactorySet) {
			if (this.beanFactory != null) {
				this.messageBuilderFactory = IntegrationUtils.getMessageBuilderFactory(this.beanFactory);
			}
			this.messageBuilderFactorySet = true;
		}
		return this.messageBuilderFactory;
	}

	@Override
	public Message<?> transform(Message<?> message) {
		Object payload = message.getPayload();
		if (!(payload instanceof javax.mail.Message)) {
			throw new MessageTransformationException(message, this.getClass().getSimpleName()
					+ " requires a javax.mail.Message payload");
		}
		javax.mail.Message mailMessage = (javax.mail.Message) payload;
		AbstractIntegrationMessageBuilder<T> builder = null;
		try {
			builder = this.doTransform(mailMessage);
		}
		catch (Exception e) {
			throw new MessageTransformationException(message, "failed to transform mail message", e);
		}
		if (builder == null) {
			throw new MessageTransformationException(message, "failed to transform mail message");
		}
		builder.copyHeaders(this.extractHeaderMapFromMailMessage(mailMessage));
		return builder.build();
	}

	protected abstract AbstractIntegrationMessageBuilder<T> doTransform(javax.mail.Message mailMessage) throws Exception;


	private Map<String, Object> extractHeaderMapFromMailMessage(javax.mail.Message mailMessage) {
		return MailUtils.extractStandardHeaders(mailMessage);
	}

}