/*
 * Copyright 2015-2017 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.amqp.support.converter;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageProperties;

/**
 * A composite {@link MessageConverter} that delegates to an actual {@link MessageConverter}
 * based on the contentType header. Supports a default converter when no content type matches.
 * Note: the {@link MessageProperties} requires a content type header to select a converter
 * when used for outbound conversion, but the converter will (generally) override it to match
 * the actual conversion.
 *
 * @author Eric Rizzo
 * @author Gary Russell
 * @author Artem Bilan
 * @since 1.4.2
 */
public class ContentTypeDelegatingMessageConverter implements MessageConverter {

	private final Map<String, MessageConverter> delegates = new HashMap<String, MessageConverter>();

	private final MessageConverter defaultConverter;


	/**
	 * Constructs an instance using a default {@link SimpleMessageConverter}.
	 */
	public ContentTypeDelegatingMessageConverter() {
		this(new SimpleMessageConverter());
	}

	/**
	 * Constructs an instance using a the supplied default converter.
	 * May be null meaning a strict content-type match is required.
	 * @param defaultConverter the converter.
	 */
	public ContentTypeDelegatingMessageConverter(MessageConverter defaultConverter) {
		this.defaultConverter = defaultConverter;
	}

	public void setDelegates(Map<String, MessageConverter> delegatesByContentType) {
		this.delegates.clear();
		this.delegates.putAll(delegatesByContentType);
	}

	public Map<String, MessageConverter> getDelegates() {
		return Collections.unmodifiableMap(this.delegates);
	}


	/**
	 * Add a delegate converter for the content type.
	 * @param contentType the content type to check.
	 * @param messageConverter the {@link MessageConverter} for the content type.
	 * @since 1.6
	 */
	public void addDelegate(String contentType, MessageConverter messageConverter) {
		this.delegates.put(contentType, messageConverter);
	}

	/**
	 * Remove the delegate for the content type.
	 * @param contentType the content type key to remove {@link MessageConverter} from delegates.
	 * @return the remove {@link MessageConverter}.
	 */
	public MessageConverter removeDelegate(String contentType) {
		return this.delegates.remove(contentType);
	}

	@Override
	public Object fromMessage(Message message) throws MessageConversionException {
		String contentType = message.getMessageProperties().getContentType();
		return getConverterForContentType(contentType).fromMessage(message);
	}

	@Override
	public Message toMessage(Object object, MessageProperties messageProperties) {
		String contentType = messageProperties.getContentType();
		return getConverterForContentType(contentType).toMessage(object, messageProperties);
	}

	protected MessageConverter getConverterForContentType(String contentType) {
		MessageConverter delegate = getDelegates().get(contentType);
		if (delegate == null) {
			delegate = this.defaultConverter;
		}

		if (delegate == null) {
			throw new MessageConversionException("No delegate converter is specified for content type " + contentType);
		}
		else {
			return delegate;
		}
	}

}