/**
 * 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.component.jms;

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.Session;

import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.Exchange;
import org.apache.camel.ExchangePattern;
import org.apache.camel.Processor;
import org.apache.camel.RollbackExchangeException;
import org.apache.camel.RuntimeCamelException;
import org.apache.camel.util.AsyncProcessorConverterHelper;
import org.apache.camel.util.ObjectHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jms.core.JmsOperations;
import org.springframework.jms.core.MessageCreator;
import org.springframework.jms.listener.SessionAwareMessageListener;

import static org.apache.camel.util.ObjectHelper.wrapRuntimeCamelException;

/**
 * A JMS {@link MessageListener} which can be used to delegate processing to a
 * Camel endpoint.
 *
 * Note that instance of this object has to be thread safe (reentrant)
 *
 * @version 
 */
public class EndpointMessageListener implements SessionAwareMessageListener {
    private static final Logger LOG = LoggerFactory.getLogger(EndpointMessageListener.class);
    private final JmsEndpoint endpoint;
    private final AsyncProcessor processor;
    private JmsBinding binding;
    private boolean eagerLoadingOfProperties;
    private Object replyToDestination;
    private JmsOperations template;
    private boolean disableReplyTo;
    private boolean async;

    public EndpointMessageListener(JmsEndpoint endpoint, Processor processor) {
        this.endpoint = endpoint;
        this.processor = AsyncProcessorConverterHelper.convert(processor);
    }

    @Override
    public void onMessage(Message message, Session session) throws JMSException {
        LOG.trace("onMessage START");

        LOG.debug("{} consumer received JMS message: {}", endpoint, message);

        boolean sendReply;
        RuntimeCamelException rce;
        try {
            Object replyDestination = getReplyToDestination(message);
            // we can only send back a reply if there was a reply destination configured
            // and disableReplyTo hasn't been explicit enabled
            sendReply = replyDestination != null && !disableReplyTo;

            // we should also not send back reply to ourself if this destination and replyDestination is the same
            Destination destination = JmsMessageHelper.getJMSDestination(message);
            if (destination != null && sendReply && !endpoint.isReplyToSameDestinationAllowed() && destination.equals(replyDestination)) {
                LOG.debug("JMSDestination and JMSReplyTo is the same, will skip sending a reply message to itself: {}", destination);
                sendReply = false;
            }

            final Exchange exchange = createExchange(message, session, replyDestination);
            if (eagerLoadingOfProperties) {
                exchange.getIn().getBody();
                exchange.getIn().getHeaders();
            }
            String correlationId = message.getJMSCorrelationID();
            if (correlationId != null) {
                LOG.debug("Received Message has JMSCorrelationID [{}]", correlationId);
            }

            // process the exchange either asynchronously or synchronous
            LOG.trace("onMessage.process START");
            AsyncCallback callback = new EndpointMessageListenerAsyncCallback(message, exchange, endpoint, sendReply, replyDestination);

            // async is by default false, which mean we by default will process the exchange synchronously
            // to keep backwards compatible, as well ensure this consumer will pickup messages in order
            // (eg to not consume the next message before the previous has been fully processed)
            // but if end user explicit configure consumerAsync=true, then we can process the message
            // asynchronously (unless endpoint has been configured synchronous, or we use transaction)
            boolean forceSync = endpoint.isSynchronous() || endpoint.isTransacted();
            if (forceSync || !isAsync()) {
                // must process synchronous if transacted or configured to do so
                if (LOG.isTraceEnabled()) {
                    LOG.trace("Processing exchange {} synchronously", exchange.getExchangeId());
                }
                try {
                    processor.process(exchange);
                } catch (Exception e) {
                    exchange.setException(e);
                } finally {
                    callback.done(true);
                }
            } else {
                // process asynchronous using the async routing engine
                if (LOG.isTraceEnabled()) {
                    LOG.trace("Processing exchange {} asynchronously", exchange.getExchangeId());
                }
                boolean sync = processor.process(exchange, callback);
                if (!sync) {
                    // will be done async so return now
                    return;
                }
            }
            // if we failed processed the exchange from the async callback task, then grab the exception
            rce = exchange.getException(RuntimeCamelException.class);

        } catch (Exception e) {
            rce = wrapRuntimeCamelException(e);
        }

        // an exception occurred so rethrow to trigger rollback on JMS listener
        // the JMS listener will use the error handler to handle the uncaught exception
        if (rce != null) {
            LOG.trace("onMessage END throwing exception: {}", rce.getMessage());
            // Spring message listener container will handle uncaught exceptions
            // being thrown from this onMessage, and will us the ErrorHandler configured
            // on the JmsEndpoint to handle the exception
            throw rce;
        }

        LOG.trace("onMessage END");
    }

    /**
     * Callback task that is performed when the exchange has been processed
     */
    private final class EndpointMessageListenerAsyncCallback implements AsyncCallback {

        private final Message message;
        private final Exchange exchange;
        private final JmsEndpoint endpoint;
        private final boolean sendReply;
        private final Object replyDestination;

        private EndpointMessageListenerAsyncCallback(Message message, Exchange exchange, JmsEndpoint endpoint,
                                                     boolean sendReply, Object replyDestination) {
            this.message = message;
            this.exchange = exchange;
            this.endpoint = endpoint;
            this.sendReply = sendReply;
            this.replyDestination = replyDestination;
        }

        @Override
        public void done(boolean doneSync) {
            LOG.trace("onMessage.process END");

            // now we evaluate the processing of the exchange and determine if it was a success or failure
            // we also grab information from the exchange to be used for sending back a reply (if we are to do so)
            // so the following logic seems a bit complicated at first glance

            // if we send back a reply it can either be the message body or transferring a caused exception
            org.apache.camel.Message body = null;
            Exception cause = null;
            RuntimeCamelException rce = null;

            if (exchange.isFailed() || exchange.isRollbackOnly()) {
                if (exchange.isRollbackOnly()) {
                    // rollback only so wrap an exception so we can rethrow the exception to cause rollback
                    rce = wrapRuntimeCamelException(new RollbackExchangeException(exchange));
                } else if (exchange.getException() != null) {
                    // an exception occurred while processing
                    if (endpoint.isTransferException()) {
                        // send the exception as reply, so null body and set the exception as the cause
                        body = null;
                        cause = exchange.getException();
                    } else {
                        // only throw exception if endpoint is not configured to transfer exceptions back to caller
                        // do not send a reply but wrap and rethrow the exception
                        rce = wrapRuntimeCamelException(exchange.getException());
                    }
                } else {
                    org.apache.camel.Message msg = exchange.hasOut() ? exchange.getOut() : exchange.getIn();
                    if (msg.isFault()) {
                        // a fault occurred while processing
                        body = msg;
                        cause = null;
                    }
                }
            } else {
                // process OK so get the reply body if we are InOut and has a body
                // If the ppl don't want to send the message back, he should use the InOnly
                if (sendReply && exchange.getPattern().isOutCapable()) {
                    if (exchange.hasOut()) {
                        body = exchange.getOut();
                    } else {
                        body = exchange.getIn();
                    }
                    cause = null;
                }
            }

            // send back reply if there was no error and we are supposed to send back a reply
            if (rce == null && sendReply && (body != null || cause != null)) {
                LOG.trace("onMessage.sendReply START");
                if (replyDestination instanceof Destination) {
                    sendReply((Destination)replyDestination, message, exchange, body, cause);
                } else {
                    sendReply((String)replyDestination, message, exchange, body, cause);
                }
                LOG.trace("onMessage.sendReply END");
            }

            // if an exception occurred
            if (rce != null) {
                if (doneSync) {
                    // we were done sync, so put exception on exchange, so we can grab it in the onMessage
                    // method and rethrow it
                    exchange.setException(rce);
                } else {
                    // we were done async, so use the endpoint error handler
                    if (endpoint.getErrorHandler() != null) {
                        endpoint.getErrorHandler().handleError(rce);
                    }
                }
            }
        }
    }

    public Exchange createExchange(Message message, Session session, Object replyDestination) {
        Exchange exchange = endpoint.createExchange();
        JmsBinding binding = getBinding();
        exchange.setProperty(Exchange.BINDING, binding);
        exchange.setIn(new JmsMessage(message, session, binding));

        // lets set to an InOut if we have some kind of reply-to destination
        if (replyDestination != null && !disableReplyTo) {
            // only change pattern if not already out capable
            if (!exchange.getPattern().isOutCapable()) {
                exchange.setPattern(ExchangePattern.InOut);
            }
        }
        return exchange;
    }

    // Properties
    // -------------------------------------------------------------------------
    public JmsBinding getBinding() {
        if (binding == null) {
            binding = endpoint.getBinding();
        }
        return binding;
    }

    /**
     * Sets the binding used to convert from a Camel message to and from a JMS
     * message
     *
     * @param binding the binding to use
     */
    public void setBinding(JmsBinding binding) {
        this.binding = binding;
    }

    public boolean isEagerLoadingOfProperties() {
        return eagerLoadingOfProperties;
    }

    public void setEagerLoadingOfProperties(boolean eagerLoadingOfProperties) {
        this.eagerLoadingOfProperties = eagerLoadingOfProperties;
    }

    public synchronized JmsOperations getTemplate() {
        if (template == null) {
            template = endpoint.createInOnlyTemplate();
        }
        return template;
    }

    public void setTemplate(JmsOperations template) {
        this.template = template;
    }

    public boolean isDisableReplyTo() {
        return disableReplyTo;
    }

    /**
     * Allows the reply-to behaviour to be disabled
     */
    public void setDisableReplyTo(boolean disableReplyTo) {
        this.disableReplyTo = disableReplyTo;
    }

    public Object getReplyToDestination() {
        return replyToDestination;
    }

    /**
     * Provides an explicit reply to destination which overrides
     * any incoming value of {@link Message#getJMSReplyTo()}
     *
     * @param replyToDestination the destination that should be used to send replies to
     * as either a String or {@link javax.jms.Destination} type.
     */
    public void setReplyToDestination(Object replyToDestination) {
        this.replyToDestination = replyToDestination;
    }

    public boolean isAsync() {
        return async;
    }

    /**
     * Sets whether asynchronous routing is enabled.
     * <p/>
     * By default this is <tt>false</tt>. If configured as <tt>true</tt> then
     * this listener will process the {@link org.apache.camel.Exchange} asynchronous.
     */
    public void setAsync(boolean async) {
        this.async = async;
    }

    // Implementation methods
    //-------------------------------------------------------------------------

    /**
     * Strategy to determine which correlation id to use among <tt>JMSMessageID</tt> and <tt>JMSCorrelationID</tt>.
     *
     * @param message the JMS message
     * @return the correlation id to use
     * @throws JMSException can be thrown
     */
    protected String determineCorrelationId(final Message message) throws JMSException {
        final String messageId = message.getJMSMessageID();
        final String correlationId = message.getJMSCorrelationID();

        if (endpoint.getConfiguration().isUseMessageIDAsCorrelationID()) {
            return messageId;
        } else if (ObjectHelper.isEmpty(correlationId)) {
            // correlation id is empty so fallback to message id
            return messageId;
        } else {
            return correlationId;
        }
    }

    protected void sendReply(Destination replyDestination, final Message message, final Exchange exchange,
                             final org.apache.camel.Message out, final Exception cause) {
        if (replyDestination == null) {
            LOG.debug("Cannot send reply message as there is no replyDestination for: {}", out);
            return;
        }
        getTemplate().send(replyDestination, new MessageCreator() {
            public Message createMessage(Session session) throws JMSException {
                Message reply = endpoint.getBinding().makeJmsMessage(exchange, out, session, cause);
                final String correlationID = determineCorrelationId(message);
                reply.setJMSCorrelationID(correlationID);

                if (LOG.isDebugEnabled()) {
                    LOG.debug("{} sending reply JMS message [correlationId:{}]: {}", new Object[]{endpoint, correlationID, reply});
                }
                return reply;
            }
        });
    }

    protected void sendReply(String replyDestination, final Message message, final Exchange exchange,
                             final org.apache.camel.Message out, final Exception cause) {
        if (replyDestination == null) {
            LOG.debug("Cannot send reply message as there is no replyDestination for: {}", out);
            return;
        }
        getTemplate().send(replyDestination, new MessageCreator() {
            public Message createMessage(Session session) throws JMSException {
                Message reply = endpoint.getBinding().makeJmsMessage(exchange, out, session, cause);
                final String correlationID = determineCorrelationId(message);
                reply.setJMSCorrelationID(correlationID);

                if (LOG.isDebugEnabled()) {
                    LOG.debug("{} sending reply JMS message [correlationId:{}]: {}", new Object[]{endpoint, correlationID, reply});
                }
                return reply;
            }
        });
    }

    protected Object getReplyToDestination(Message message) throws JMSException {
        // lets send a response back if we can
        Object destination = getReplyToDestination();
        if (destination == null) {
            destination = JmsMessageHelper.getJMSReplyTo(message);
        }
        return destination;
    }

    @Override
    public String toString() {
        return "EndpointMessageListener[" + endpoint + "]";
    }
}