/**
 * 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.processor;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;

import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.Endpoint;
import org.apache.camel.EndpointAware;
import org.apache.camel.Exchange;
import org.apache.camel.ExchangePattern;
import org.apache.camel.Expression;
import org.apache.camel.Message;
import org.apache.camel.Processor;
import org.apache.camel.StreamCache;
import org.apache.camel.Traceable;
import org.apache.camel.impl.DefaultExchange;
import org.apache.camel.support.ServiceSupport;
import org.apache.camel.util.AsyncProcessorHelper;
import org.apache.camel.util.EventHelper;
import org.apache.camel.util.ExchangeHelper;
import org.apache.camel.util.ObjectHelper;
import org.apache.camel.util.ServiceHelper;
import org.apache.camel.util.StopWatch;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Processor for wire tapping exchanges to an endpoint destination.
 *
 * @version 
 */
public class WireTapProcessor extends ServiceSupport implements AsyncProcessor, Traceable, EndpointAware {
    private static final Logger LOG = LoggerFactory.getLogger(WireTapProcessor.class);
    private final Endpoint destination;
    private final Processor processor;
    private final ExchangePattern exchangePattern;
    private final ExecutorService executorService;
    private volatile boolean shutdownExecutorService;

    // expression or processor used for populating a new exchange to send
    // as opposed to traditional wiretap that sends a copy of the original exchange
    private Expression newExchangeExpression;
    private List<Processor> newExchangeProcessors;
    private boolean copy;
    private Processor onPrepare;

    public WireTapProcessor(Endpoint destination, Processor processor, ExchangePattern exchangePattern,
                            ExecutorService executorService, boolean shutdownExecutorService) {
        this.destination = destination;
        this.processor = processor;
        this.exchangePattern = exchangePattern;
        ObjectHelper.notNull(executorService, "executorService");
        this.executorService = executorService;
        this.shutdownExecutorService = shutdownExecutorService;
    }

    @Override
    public String toString() {
        return "WireTap[" + destination + "]";
    }

    @Override
    public String getTraceLabel() {
        return "wireTap(" + destination + ")";
    }

    public Endpoint getEndpoint() {
        return destination;
    }

    public void process(Exchange exchange) throws Exception {
        AsyncProcessorHelper.process(this, exchange);
    }

    public boolean process(final Exchange exchange, final AsyncCallback callback) {
        if (!isStarted()) {
            throw new IllegalStateException("WireTapProcessor has not been started: " + this);
        }

        // must configure the wire tap beforehand
        Exchange target;
        try {
            target = configureExchange(exchange, exchangePattern);
        } catch (Exception e) {
            exchange.setException(e);
            callback.done(true);
            return true;
        }

        final Exchange wireTapExchange = target;

        // send the exchange to the destination using an executor service
        executorService.submit(new Callable<Exchange>() {
            public Exchange call() throws Exception {
                final StopWatch watch = new StopWatch();
                try {
                    EventHelper.notifyExchangeSending(wireTapExchange.getContext(), wireTapExchange, destination);
                    LOG.debug(">>>> (wiretap) {} {}", destination, wireTapExchange);
                    processor.process(wireTapExchange);
                } catch (Throwable e) {
                    LOG.warn("Error occurred during processing " + wireTapExchange + " wiretap to " + destination + ". This exception will be ignored.", e);
                } finally {
                    // emit event that the exchange was sent to the endpoint
                    long timeTaken = watch.stop();
                    EventHelper.notifyExchangeSent(wireTapExchange.getContext(), wireTapExchange, destination, timeTaken);
                }
                return wireTapExchange;
            }
        });

        // continue routing this synchronously
        callback.done(true);
        return true;
    }


    protected Exchange configureExchange(Exchange exchange, ExchangePattern pattern) throws IOException {
        Exchange answer;
        if (copy) {
            // use a copy of the original exchange
            answer = configureCopyExchange(exchange);
        } else {
            // use a new exchange
            answer = configureNewExchange(exchange);
        }

        // set property which endpoint we send to
        answer.setProperty(Exchange.TO_ENDPOINT, destination.getEndpointUri());

        // prepare the exchange
        if (newExchangeExpression != null) {
            Object body = newExchangeExpression.evaluate(answer, Object.class);
            if (body != null) {
                answer.getIn().setBody(body);
            }
        }

        if (newExchangeProcessors != null) {
            for (Processor processor : newExchangeProcessors) {
                try {
                    processor.process(answer);
                } catch (Exception e) {
                    throw ObjectHelper.wrapRuntimeCamelException(e);
                }
            }
        }

        // if the body is a stream cache we must use a copy of the stream in the wire tapped exchange
        Message msg = answer.hasOut() ? answer.getOut() : answer.getIn();
        if (msg.getBody() instanceof StreamCache) {
            // in parallel processing case, the stream must be copied, therefore get the stream
            StreamCache cache = (StreamCache) msg.getBody();
            StreamCache copied = cache.copy();
            if (copied != null) {
                msg.setBody(copied);
            }
        }

        // invoke on prepare on the exchange if specified
        if (onPrepare != null) {
            try {
                onPrepare.process(answer);
            } catch (Exception e) {
                throw ObjectHelper.wrapRuntimeCamelException(e);
            }
        }

        return answer;
    }

    private Exchange configureCopyExchange(Exchange exchange) {
        // must use a copy as we dont want it to cause side effects of the original exchange
        Exchange copy = ExchangeHelper.createCorrelatedCopy(exchange, false);
        // set MEP to InOnly as this wire tap is a fire and forget
        copy.setPattern(ExchangePattern.InOnly);
        return copy;
    }

    private Exchange configureNewExchange(Exchange exchange) {
        return new DefaultExchange(exchange.getFromEndpoint(), ExchangePattern.InOnly);
    }

    public List<Processor> getNewExchangeProcessors() {
        return newExchangeProcessors;
    }

    public void setNewExchangeProcessors(List<Processor> newExchangeProcessors) {
        this.newExchangeProcessors = newExchangeProcessors;
    }

    public Expression getNewExchangeExpression() {
        return newExchangeExpression;
    }

    public void setNewExchangeExpression(Expression newExchangeExpression) {
        this.newExchangeExpression = newExchangeExpression;
    }

    public void addNewExchangeProcessor(Processor processor) {
        if (newExchangeProcessors == null) {
            newExchangeProcessors = new ArrayList<Processor>();
        }
        newExchangeProcessors.add(processor);
    }

    public boolean isCopy() {
        return copy;
    }

    public void setCopy(boolean copy) {
        this.copy = copy;
    }

    public Processor getOnPrepare() {
        return onPrepare;
    }

    public void setOnPrepare(Processor onPrepare) {
        this.onPrepare = onPrepare;
    }

    @Override
    protected void doStart() throws Exception {
        ServiceHelper.startService(processor);
    }

    @Override
    protected void doStop() throws Exception {
        ServiceHelper.stopService(processor);
    }

    @Override
    protected void doShutdown() throws Exception {
        ServiceHelper.stopAndShutdownService(processor);
        if (shutdownExecutorService) {
            destination.getCamelContext().getExecutorServiceManager().shutdownNow(executorService);
        }
    }
}