/**
 * 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.model;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;

import org.apache.camel.CamelContextAware;
import org.apache.camel.Expression;
import org.apache.camel.Predicate;
import org.apache.camel.Processor;
import org.apache.camel.builder.ExpressionClause;
import org.apache.camel.model.language.ExpressionDefinition;
import org.apache.camel.processor.CamelInternalProcessor;
import org.apache.camel.processor.aggregate.AggregateProcessor;
import org.apache.camel.processor.aggregate.AggregationStrategy;
import org.apache.camel.processor.aggregate.AggregationStrategyBeanAdapter;
import org.apache.camel.processor.aggregate.GroupedExchangeAggregationStrategy;
import org.apache.camel.processor.aggregate.OptimisticLockRetryPolicy;
import org.apache.camel.spi.AggregationRepository;
import org.apache.camel.spi.Metadata;
import org.apache.camel.spi.RouteContext;
import org.apache.camel.util.concurrent.SynchronousExecutorService;

/**
 * Aggregates many messages into a single message
 *
 * @version 
 */
@Metadata(label = "eip,routing")
@XmlRootElement(name = "aggregate")
@XmlAccessorType(XmlAccessType.FIELD)
public class AggregateDefinition extends ProcessorDefinition<AggregateDefinition> implements ExecutorServiceAwareDefinition<AggregateDefinition> {
    @XmlElement(name = "correlationExpression", required = true)
    private ExpressionSubElementDefinition correlationExpression;
    @XmlElement(name = "completionPredicate")
    private ExpressionSubElementDefinition completionPredicate;
    @XmlElement(name = "completionTimeout")
    private ExpressionSubElementDefinition completionTimeoutExpression;
    @XmlElement(name = "completionSize")
    private ExpressionSubElementDefinition completionSizeExpression;
    @XmlElement(name = "optimisticLockRetryPolicy")
    private OptimisticLockRetryPolicyDefinition optimisticLockRetryPolicyDefinition;
    @XmlTransient
    private ExpressionDefinition expression;
    @XmlTransient
    private AggregationStrategy aggregationStrategy;
    @XmlTransient
    private ExecutorService executorService;
    @XmlTransient
    private ScheduledExecutorService timeoutCheckerExecutorService;
    @XmlTransient
    private AggregationRepository aggregationRepository;
    @XmlTransient
    private OptimisticLockRetryPolicy optimisticLockRetryPolicy;
    @XmlAttribute
    private Boolean parallelProcessing;
    @XmlAttribute
    private Boolean optimisticLocking;
    @XmlAttribute
    private String executorServiceRef;
    @XmlAttribute
    private String timeoutCheckerExecutorServiceRef;
    @XmlAttribute
    private String aggregationRepositoryRef;
    @XmlAttribute
    private String strategyRef;
    @XmlAttribute
    private String strategyMethodName;
    @XmlAttribute
    private Boolean strategyMethodAllowNull;
    @XmlAttribute
    private Integer completionSize;
    @XmlAttribute
    private Long completionInterval;
    @XmlAttribute
    private Long completionTimeout;
    @XmlAttribute
    private Boolean completionFromBatchConsumer;
    @XmlAttribute
    @Deprecated
    private Boolean groupExchanges;
    @XmlAttribute
    private Boolean eagerCheckCompletion;
    @XmlAttribute
    private Boolean ignoreInvalidCorrelationKeys;
    @XmlAttribute
    private Integer closeCorrelationKeyOnCompletion;
    @XmlAttribute
    private Boolean discardOnCompletionTimeout;
    @XmlAttribute
    private Boolean forceCompletionOnStop;
    @XmlElementRef
    private List<ProcessorDefinition<?>> outputs = new ArrayList<ProcessorDefinition<?>>();

    public AggregateDefinition() {
    }

    public AggregateDefinition(Predicate predicate) {
        if (predicate != null) {
            setExpression(ExpressionNodeHelper.toExpressionDefinition(predicate));
        }
    }    
    
    public AggregateDefinition(Expression correlationExpression) {
        if (correlationExpression != null) {
            setExpression(ExpressionNodeHelper.toExpressionDefinition(correlationExpression));
        }
    }

    public AggregateDefinition(ExpressionDefinition correlationExpression) {
        this.expression = correlationExpression;
    }

    public AggregateDefinition(Expression correlationExpression, AggregationStrategy aggregationStrategy) {
        this(correlationExpression);
        this.aggregationStrategy = aggregationStrategy;
    }

    @Override
    public String toString() {
        return "Aggregate[" + description() + " -> " + getOutputs() + "]";
    }
    
    protected String description() {
        return getExpression() != null ? getExpression().getLabel() : "";
    }

    @Override
    public String getLabel() {
        return "aggregate[" + description() + "]";
    }

    @Override
    public Processor createProcessor(RouteContext routeContext) throws Exception {
        return createAggregator(routeContext);
    }

    protected AggregateProcessor createAggregator(RouteContext routeContext) throws Exception {
        Processor childProcessor = this.createChildProcessor(routeContext, true);

        String routeId = routeContext.getRoute().idOrCreate(routeContext.getCamelContext().getNodeIdFactory());

        // wrap the aggregate route in a unit of work processor
        CamelInternalProcessor internal = new CamelInternalProcessor(childProcessor);
        internal.addAdvice(new CamelInternalProcessor.UnitOfWorkProcessorAdvice(routeId));
        internal.addAdvice(new CamelInternalProcessor.RouteContextAdvice(routeContext));

        Expression correlation = getExpression().createExpression(routeContext);
        AggregationStrategy strategy = createAggregationStrategy(routeContext);

        boolean parallel = getParallelProcessing() != null && getParallelProcessing();
        boolean shutdownThreadPool = ProcessorDefinitionHelper.willCreateNewThreadPool(routeContext, this, parallel);
        ExecutorService threadPool = ProcessorDefinitionHelper.getConfiguredExecutorService(routeContext, "Aggregator", this, parallel);
        if (threadPool == null && !parallel) {
            // executor service is mandatory for the Aggregator
            // we do not run in parallel mode, but use a synchronous executor, so we run in current thread
            threadPool = new SynchronousExecutorService();
            shutdownThreadPool = true;
        }

        AggregateProcessor answer = new AggregateProcessor(routeContext.getCamelContext(), internal,
                correlation, strategy, threadPool, shutdownThreadPool);

        AggregationRepository repository = createAggregationRepository(routeContext);
        if (repository != null) {
            answer.setAggregationRepository(repository);
        }

        // this EIP supports using a shared timeout checker thread pool or fallback to create a new thread pool
        boolean shutdownTimeoutThreadPool = false;
        ScheduledExecutorService timeoutThreadPool = timeoutCheckerExecutorService;
        if (timeoutThreadPool == null && timeoutCheckerExecutorServiceRef != null) {
            // lookup existing thread pool
            timeoutThreadPool = routeContext.getCamelContext().getRegistry().lookupByNameAndType(timeoutCheckerExecutorServiceRef, ScheduledExecutorService.class);
            if (timeoutThreadPool == null) {
                // then create a thread pool assuming the ref is a thread pool profile id
                timeoutThreadPool = routeContext.getCamelContext().getExecutorServiceManager().newScheduledThreadPool(this,
                        AggregateProcessor.AGGREGATE_TIMEOUT_CHECKER, timeoutCheckerExecutorServiceRef);
                if (timeoutThreadPool == null) {
                    throw new IllegalArgumentException("ExecutorServiceRef " + timeoutCheckerExecutorServiceRef + " not found in registry or as a thread pool profile.");
                }
                shutdownTimeoutThreadPool = true;
            }
        }
        answer.setTimeoutCheckerExecutorService(timeoutThreadPool);
        answer.setShutdownTimeoutCheckerExecutorService(shutdownTimeoutThreadPool);

        // set other options
        answer.setParallelProcessing(parallel);
        if (getOptimisticLocking() != null) {
            answer.setOptimisticLocking(getOptimisticLocking());
        }
        if (getCompletionPredicate() != null) {
            Predicate predicate = getCompletionPredicate().createPredicate(routeContext);
            answer.setCompletionPredicate(predicate);
        } else if (strategy instanceof Predicate) {
            // if aggregation strategy implements predicate and was not configured then use as fallback
            log.debug("Using AggregationStrategy as completion predicate: {}", strategy);
            answer.setCompletionPredicate((Predicate) strategy);
        }
        if (getCompletionTimeoutExpression() != null) {
            Expression expression = getCompletionTimeoutExpression().createExpression(routeContext);
            answer.setCompletionTimeoutExpression(expression);
        }
        if (getCompletionTimeout() != null) {
            answer.setCompletionTimeout(getCompletionTimeout());
        }
        if (getCompletionInterval() != null) {
            answer.setCompletionInterval(getCompletionInterval());
        }
        if (getCompletionSizeExpression() != null) {
            Expression expression = getCompletionSizeExpression().createExpression(routeContext);
            answer.setCompletionSizeExpression(expression);
        }
        if (getCompletionSize() != null) {
            answer.setCompletionSize(getCompletionSize());
        }
        if (getCompletionFromBatchConsumer() != null) {
            answer.setCompletionFromBatchConsumer(getCompletionFromBatchConsumer());
        }
        if (getEagerCheckCompletion() != null) {
            answer.setEagerCheckCompletion(getEagerCheckCompletion());
        }
        if (getIgnoreInvalidCorrelationKeys() != null) {
            answer.setIgnoreInvalidCorrelationKeys(getIgnoreInvalidCorrelationKeys());
        }
        if (getCloseCorrelationKeyOnCompletion() != null) {
            answer.setCloseCorrelationKeyOnCompletion(getCloseCorrelationKeyOnCompletion());
        }
        if (getDiscardOnCompletionTimeout() != null) {
            answer.setDiscardOnCompletionTimeout(getDiscardOnCompletionTimeout());
        }
        if (getForceCompletionOnStop() != null) {
            answer.setForceCompletionOnStop(getForceCompletionOnStop());
        }
        if (optimisticLockRetryPolicy == null) {
            if (getOptimisticLockRetryPolicyDefinition() != null) {
                answer.setOptimisticLockRetryPolicy(getOptimisticLockRetryPolicyDefinition().createOptimisticLockRetryPolicy());
            }
        } else {
            answer.setOptimisticLockRetryPolicy(optimisticLockRetryPolicy);
        }
        return answer;
    }

    @Override
    public void configureChild(ProcessorDefinition<?> output) {
        if (expression != null && expression instanceof ExpressionClause) {
            ExpressionClause<?> clause = (ExpressionClause<?>) expression;
            if (clause.getExpressionType() != null) {
                // if using the Java DSL then the expression may have been set using the
                // ExpressionClause which is a fancy builder to define expressions and predicates
                // using fluent builders in the DSL. However we need afterwards a callback to
                // reset the expression to the expression type the ExpressionClause did build for us
                expression = clause.getExpressionType();
                // set the correlation expression from the expression type, as the model definition
                // would then be accurate
                correlationExpression = new ExpressionSubElementDefinition();
                correlationExpression.setExpressionType(clause.getExpressionType());
            }
        }
    }

    private AggregationStrategy createAggregationStrategy(RouteContext routeContext) {
        AggregationStrategy strategy = getAggregationStrategy();
        if (strategy == null && strategyRef != null) {
            Object aggStrategy = routeContext.lookup(strategyRef, Object.class);
            if (aggStrategy instanceof AggregationStrategy) {
                strategy = (AggregationStrategy) aggStrategy;
            } else if (aggStrategy != null) {
                AggregationStrategyBeanAdapter adapter = new AggregationStrategyBeanAdapter(aggStrategy, getAggregationStrategyMethodName());
                if (getStrategyMethodAllowNull() != null) {
                    adapter.setAllowNullNewExchange(getStrategyMethodAllowNull());
                    adapter.setAllowNullOldExchange(getStrategyMethodAllowNull());
                }
                strategy = adapter;
            } else {
                throw new IllegalArgumentException("Cannot find AggregationStrategy in Registry with name: " + strategyRef);
            }
        }

        if (groupExchanges != null && groupExchanges) {
            if (strategy != null || strategyRef != null) {
                throw new IllegalArgumentException("Options groupExchanges and AggregationStrategy cannot be enabled at the same time");
            }
            if (eagerCheckCompletion != null && !eagerCheckCompletion) {
                throw new IllegalArgumentException("Option eagerCheckCompletion cannot be false when groupExchanges has been enabled");
            }
            // set eager check to enabled by default when using grouped exchanges
            setEagerCheckCompletion(true);
            // if grouped exchange is enabled then use special strategy for that
            strategy = new GroupedExchangeAggregationStrategy();
        }

        if (strategy == null) {
            throw new IllegalArgumentException("AggregationStrategy or AggregationStrategyRef must be set on " + this);
        }

        if (strategy instanceof CamelContextAware) {
            ((CamelContextAware) strategy).setCamelContext(routeContext.getCamelContext());
        }

        return strategy;
    }

    private AggregationRepository createAggregationRepository(RouteContext routeContext) {
        AggregationRepository repository = getAggregationRepository();
        if (repository == null && aggregationRepositoryRef != null) {
            repository = routeContext.mandatoryLookup(aggregationRepositoryRef, AggregationRepository.class);
        }
        return repository;
    }

    public AggregationStrategy getAggregationStrategy() {
        return aggregationStrategy;
    }

    /**
     * The AggregationStrategy to use.
     * <p/>
     * Configuring an AggregationStrategy is required, and is used to merge the incoming Exchange with the existing already merged exchanges.
     * At first call the oldExchange parameter is null.
     * On subsequent invocations the oldExchange contains the merged exchanges and newExchange is of course the new incoming Exchange.
     */
    public void setAggregationStrategy(AggregationStrategy aggregationStrategy) {
        this.aggregationStrategy = aggregationStrategy;
    }

    public String getAggregationStrategyRef() {
        return strategyRef;
    }

    /**
     * A reference to lookup the AggregationStrategy in the Registry.
     * <p/>
     * Configuring an AggregationStrategy is required, and is used to merge the incoming Exchange with the existing already merged exchanges.
     * At first call the oldExchange parameter is null.
     * On subsequent invocations the oldExchange contains the merged exchanges and newExchange is of course the new incoming Exchange.
     */
    public void setAggregationStrategyRef(String aggregationStrategyRef) {
        this.strategyRef = aggregationStrategyRef;
    }

    public String getStrategyRef() {
        return strategyRef;
    }

    /**
     * A reference to lookup the AggregationStrategy in the Registry.
     * <p/>
     * Configuring an AggregationStrategy is required, and is used to merge the incoming Exchange with the existing already merged exchanges.
     * At first call the oldExchange parameter is null.
     * On subsequent invocations the oldExchange contains the merged exchanges and newExchange is of course the new incoming Exchange.
     */
    public void setStrategyRef(String strategyRef) {
        this.strategyRef = strategyRef;
    }

    public String getAggregationStrategyMethodName() {
        return strategyMethodName;
    }

    /**
     * This option can be used to explicit declare the method name to use, when using POJOs as the AggregationStrategy.
     */
    public void setAggregationStrategyMethodName(String strategyMethodName) {
        this.strategyMethodName = strategyMethodName;
    }

    public Boolean getStrategyMethodAllowNull() {
        return strategyMethodAllowNull;
    }

    public String getStrategyMethodName() {
        return strategyMethodName;
    }

    /**
     * This option can be used to explicit declare the method name to use, when using POJOs as the AggregationStrategy.
     */
    public void setStrategyMethodName(String strategyMethodName) {
        this.strategyMethodName = strategyMethodName;
    }

    /**
     * If this option is false then the aggregate method is not used for the very first aggregation.
     * If this option is true then null values is used as the oldExchange (at the very first aggregation),
     * when using POJOs as the AggregationStrategy.
     */
    public void setStrategyMethodAllowNull(Boolean strategyMethodAllowNull) {
        this.strategyMethodAllowNull = strategyMethodAllowNull;
    }

    /**
     * The expression used to calculate the correlation key to use for aggregation.
     * The Exchange which has the same correlation key is aggregated together.
     * If the correlation key could not be evaluated an Exception is thrown.
     * You can disable this by using the ignoreBadCorrelationKeys option.
     */
    public void setCorrelationExpression(ExpressionSubElementDefinition correlationExpression) {
        this.correlationExpression = correlationExpression;
    }

    public ExpressionSubElementDefinition getCorrelationExpression() {
        return correlationExpression;
    }

    public Integer getCompletionSize() {
        return completionSize;
    }

    public void setCompletionSize(Integer completionSize) {
        this.completionSize = completionSize;
    }

    public OptimisticLockRetryPolicyDefinition getOptimisticLockRetryPolicyDefinition() {
        return optimisticLockRetryPolicyDefinition;
    }

    public void setOptimisticLockRetryPolicyDefinition(OptimisticLockRetryPolicyDefinition optimisticLockRetryPolicyDefinition) {
        this.optimisticLockRetryPolicyDefinition = optimisticLockRetryPolicyDefinition;
    }

    public OptimisticLockRetryPolicy getOptimisticLockRetryPolicy() {
        return optimisticLockRetryPolicy;
    }

    public void setOptimisticLockRetryPolicy(OptimisticLockRetryPolicy optimisticLockRetryPolicy) {
        this.optimisticLockRetryPolicy = optimisticLockRetryPolicy;
    }

    public Long getCompletionInterval() {
        return completionInterval;
    }

    public void setCompletionInterval(Long completionInterval) {
        this.completionInterval = completionInterval;
    }

    public Long getCompletionTimeout() {
        return completionTimeout;
    }

    public void setCompletionTimeout(Long completionTimeout) {
        this.completionTimeout = completionTimeout;
    }

    public ExpressionSubElementDefinition getCompletionPredicate() {
        return completionPredicate;
    }

    public void setCompletionPredicate(ExpressionSubElementDefinition completionPredicate) {
        this.completionPredicate = completionPredicate;
    }

    public ExpressionSubElementDefinition getCompletionTimeoutExpression() {
        return completionTimeoutExpression;
    }

    public void setCompletionTimeoutExpression(ExpressionSubElementDefinition completionTimeoutExpression) {
        this.completionTimeoutExpression = completionTimeoutExpression;
    }

    public ExpressionSubElementDefinition getCompletionSizeExpression() {
        return completionSizeExpression;
    }

    public void setCompletionSizeExpression(ExpressionSubElementDefinition completionSizeExpression) {
        this.completionSizeExpression = completionSizeExpression;
    }

    public Boolean getGroupExchanges() {
        return groupExchanges;
    }

    public void setGroupExchanges(Boolean groupExchanges) {
        this.groupExchanges = groupExchanges;
    }

    public Boolean getCompletionFromBatchConsumer() {
        return completionFromBatchConsumer;
    }

    public void setCompletionFromBatchConsumer(Boolean completionFromBatchConsumer) {
        this.completionFromBatchConsumer = completionFromBatchConsumer;
    }

    public ExecutorService getExecutorService() {
        return executorService;
    }

    public void setExecutorService(ExecutorService executorService) {
        this.executorService = executorService;
    }

    public Boolean getOptimisticLocking() {
        return optimisticLocking;
    }

    public void setOptimisticLocking(boolean optimisticLocking) {
        this.optimisticLocking = optimisticLocking;
    }

    public Boolean getParallelProcessing() {
        return parallelProcessing;
    }

    public void setParallelProcessing(boolean parallelProcessing) {
        this.parallelProcessing = parallelProcessing;
    }

    public String getExecutorServiceRef() {
        return executorServiceRef;
    }

    public void setExecutorServiceRef(String executorServiceRef) {
        this.executorServiceRef = executorServiceRef;
    }

    public Boolean getEagerCheckCompletion() {
        return eagerCheckCompletion;
    }

    public void setEagerCheckCompletion(Boolean eagerCheckCompletion) {
        this.eagerCheckCompletion = eagerCheckCompletion;
    }

    public Boolean getIgnoreInvalidCorrelationKeys() {
        return ignoreInvalidCorrelationKeys;
    }

    public void setIgnoreInvalidCorrelationKeys(Boolean ignoreInvalidCorrelationKeys) {
        this.ignoreInvalidCorrelationKeys = ignoreInvalidCorrelationKeys;
    }

    public Integer getCloseCorrelationKeyOnCompletion() {
        return closeCorrelationKeyOnCompletion;
    }

    public void setCloseCorrelationKeyOnCompletion(Integer closeCorrelationKeyOnCompletion) {
        this.closeCorrelationKeyOnCompletion = closeCorrelationKeyOnCompletion;
    }

    public AggregationRepository getAggregationRepository() {
        return aggregationRepository;
    }

    public void setAggregationRepository(AggregationRepository aggregationRepository) {
        this.aggregationRepository = aggregationRepository;
    }

    public String getAggregationRepositoryRef() {
        return aggregationRepositoryRef;
    }

    public void setAggregationRepositoryRef(String aggregationRepositoryRef) {
        this.aggregationRepositoryRef = aggregationRepositoryRef;
    }

    public Boolean getDiscardOnCompletionTimeout() {
        return discardOnCompletionTimeout;
    }

    public void setDiscardOnCompletionTimeout(Boolean discardOnCompletionTimeout) {
        this.discardOnCompletionTimeout = discardOnCompletionTimeout;
    }
    
    public void setTimeoutCheckerExecutorService(ScheduledExecutorService timeoutCheckerExecutorService) {
        this.timeoutCheckerExecutorService = timeoutCheckerExecutorService;
    }

    public ScheduledExecutorService getTimeoutCheckerExecutorService() {
        return timeoutCheckerExecutorService;
    }

    public void setTimeoutCheckerExecutorServiceRef(String timeoutCheckerExecutorServiceRef) {
        this.timeoutCheckerExecutorServiceRef = timeoutCheckerExecutorServiceRef;
    }

    public String getTimeoutCheckerExecutorServiceRef() {
        return timeoutCheckerExecutorServiceRef;
    }

    public Boolean getForceCompletionOnStop() {
        return forceCompletionOnStop;
    }

    public void setForceCompletionOnStop(Boolean forceCompletionOnStop) {
        this.forceCompletionOnStop = forceCompletionOnStop;
    }

    // Fluent API
    //-------------------------------------------------------------------------

    /**
     * Use eager completion checking which means that the {{completionPredicate}} will use the incoming Exchange.
     * At opposed to without eager completion checking the {{completionPredicate}} will use the aggregated Exchange.
     *
     * @return builder
     */
    public AggregateDefinition eagerCheckCompletion() {
        setEagerCheckCompletion(true);
        return this;
    }

    /**
     * If a correlation key cannot be successfully evaluated it will be ignored by logging a {{DEBUG}} and then just
     * ignore the incoming Exchange.
     *
     * @return builder
     */
    public AggregateDefinition ignoreInvalidCorrelationKeys() {
        setIgnoreInvalidCorrelationKeys(true);
        return this;
    }

    /**
     * Closes a correlation key when its complete. Any <i>late</i> received exchanges which has a correlation key
     * that has been closed, it will be defined and a {@link org.apache.camel.processor.aggregate.ClosedCorrelationKeyException}
     * is thrown.
     *
     * @param capacity the maximum capacity of the closed correlation key cache.
     *                 Use <tt>0</tt> or negative value for unbounded capacity.
     * @return builder
     */
    public AggregateDefinition closeCorrelationKeyOnCompletion(int capacity) {
        setCloseCorrelationKeyOnCompletion(capacity);
        return this;
    }

    /**
     * Discards the aggregated message on completion timeout.
     * <p/>
     * This means on timeout the aggregated message is dropped and not sent out of the aggregator.
     *
     * @return builder
     */
    public AggregateDefinition discardOnCompletionTimeout() {
        setDiscardOnCompletionTimeout(true);
        return this;
    }

    /**
     * Enables the batch completion mode where we aggregate from a {@link org.apache.camel.BatchConsumer}
     * and aggregate the total number of exchanges the {@link org.apache.camel.BatchConsumer} has reported
     * as total by checking the exchange property {@link org.apache.camel.Exchange#BATCH_COMPLETE} when its complete.
     *
     * @return builder
     */
    public AggregateDefinition completionFromBatchConsumer() {
        setCompletionFromBatchConsumer(true);
        return this;
    }

    /**
     * Sets the completion size, which is the number of aggregated exchanges which would
     * cause the aggregate to consider the group as complete and send out the aggregated exchange.
     *
     * @param completionSize  the completion size
     * @return builder
     */
    public AggregateDefinition completionSize(int completionSize) {
        setCompletionSize(completionSize);
        return this;
    }

    /**
     * Sets the completion size, which is the number of aggregated exchanges which would
     * cause the aggregate to consider the group as complete and send out the aggregated exchange.
     *
     * @param completionSize  the completion size as an {@link org.apache.camel.Expression} which is evaluated as a {@link Integer} type
     * @return builder
     */
    public AggregateDefinition completionSize(Expression completionSize) {
        setCompletionSizeExpression(new ExpressionSubElementDefinition(completionSize));
        return this;
    }

    /**
     * Sets the completion interval, which would cause the aggregate to consider the group as complete
     * and send out the aggregated exchange.
     *
     * @param completionInterval  the interval in millis
     * @return the builder
     */
    public AggregateDefinition completionInterval(long completionInterval) {
        setCompletionInterval(completionInterval);
        return this;
    }

    /**
     * Sets the completion timeout, which would cause the aggregate to consider the group as complete
     * and send out the aggregated exchange.
     *
     * @param completionTimeout  the timeout in millis
     * @return the builder
     */
    public AggregateDefinition completionTimeout(long completionTimeout) {
        setCompletionTimeout(completionTimeout);
        return this;
    }

    /**
     * Sets the completion timeout, which would cause the aggregate to consider the group as complete
     * and send out the aggregated exchange.
     *
     * @param completionTimeout  the timeout as an {@link Expression} which is evaluated as a {@link Long} type
     * @return the builder
     */
    public AggregateDefinition completionTimeout(Expression completionTimeout) {
        setCompletionTimeoutExpression(new ExpressionSubElementDefinition(completionTimeout));
        return this;
    }

    /**
     * Sets the aggregate strategy to use
     *
     * @param aggregationStrategy  the aggregate strategy to use
     * @return the builder
     */
    public AggregateDefinition aggregationStrategy(AggregationStrategy aggregationStrategy) {
        setAggregationStrategy(aggregationStrategy);
        return this;
    }

    /**
     * Sets the aggregate strategy to use
     *
     * @param aggregationStrategyRef  reference to the strategy to lookup in the registry
     * @return the builder
     */
    public AggregateDefinition aggregationStrategyRef(String aggregationStrategyRef) {
        setAggregationStrategyRef(aggregationStrategyRef);
        return this;
    }

    /**
     * Sets the method name to use when using a POJO as {@link AggregationStrategy}.
     *
     * @param  methodName the method name to call
     * @return the builder
     */
    public AggregateDefinition aggregationStrategyMethodName(String methodName) {
        setAggregationStrategyMethodName(methodName);
        return this;
    }

    /**
     * Sets allowing null when using a POJO as {@link AggregationStrategy}.
     *
     * @return the builder
     */
    public AggregateDefinition aggregationStrategyMethodAllowNull() {
        setStrategyMethodAllowNull(true);
        return this;
    }

    /**
     * Sets the custom aggregate repository to use.
     * <p/>
     * Will by default use {@link org.apache.camel.processor.aggregate.MemoryAggregationRepository}
     *
     * @param aggregationRepository  the aggregate repository to use
     * @return the builder
     */
    public AggregateDefinition aggregationRepository(AggregationRepository aggregationRepository) {
        setAggregationRepository(aggregationRepository);
        return this;
    }

    /**
     * Sets the custom aggregate repository to use
     * <p/>
     * Will by default use {@link org.apache.camel.processor.aggregate.MemoryAggregationRepository}
     *
     * @param aggregationRepositoryRef  reference to the repository to lookup in the registry
     * @return the builder
     */
    public AggregateDefinition aggregationRepositoryRef(String aggregationRepositoryRef) {
        setAggregationRepositoryRef(aggregationRepositoryRef);
        return this;
    }

    /**
     * Enables grouped exchanges, so the aggregator will group all aggregated exchanges into a single
     * combined Exchange holding all the aggregated exchanges in a {@link java.util.List}.
     *
     * @deprecated use {@link GroupedExchangeAggregationStrategy} as aggregation strategy instead.
     */
    @Deprecated
    public AggregateDefinition groupExchanges() {
        setGroupExchanges(true);
        // must use eager check when using grouped exchanges
        setEagerCheckCompletion(true);
        return this;
    }

    /**
     * Sets the predicate used to determine if the aggregation is completed
     */
    public AggregateDefinition completionPredicate(Predicate predicate) {
        checkNoCompletedPredicate();
        setCompletionPredicate(new ExpressionSubElementDefinition(predicate));
        return this;
    }

    /**
     * Indicates to complete all current aggregated exchanges when the context is stopped
     */
    public AggregateDefinition forceCompletionOnStop() {
        setForceCompletionOnStop(true);
        return this;
    }

    /**
     * When aggregated are completed they are being send out of the aggregator.
     * This option indicates whether or not Camel should use a thread pool with multiple threads for concurrency.
     * If no custom thread pool has been specified then Camel creates a default pool with 10 concurrent threads.
     */
    public AggregateDefinition parallelProcessing() {
        setParallelProcessing(true);
        return this;
    }

    /**
     * Turns on using optimistic locking, which requires the aggregationRepository being used,
     * is supporting this by implementing {@link org.apache.camel.spi.OptimisticLockingAggregationRepository}.
     */
    public AggregateDefinition optimisticLocking() {
        setOptimisticLocking(true);
        return this;
    }

    /**
     * Allows to configure retry settings when using optimistic locking.
     */
    public AggregateDefinition optimisticLockRetryPolicy(OptimisticLockRetryPolicy policy) {
        setOptimisticLockRetryPolicy(policy);
        return this;
    }

    /**
     * If using parallelProcessing you can specify a custom thread pool to be used.
     * In fact also if you are not using parallelProcessing this custom thread pool is used to send out aggregated exchanges as well.
     */
    public AggregateDefinition executorService(ExecutorService executorService) {
        setExecutorService(executorService);
        return this;
    }

    /**
     * If using parallelProcessing you can specify a custom thread pool to be used.
     * In fact also if you are not using parallelProcessing this custom thread pool is used to send out aggregated exchanges as well.
     */
    public AggregateDefinition executorServiceRef(String executorServiceRef) {
        setExecutorServiceRef(executorServiceRef);
        return this;
    }

    /**
     * If using either of the completionTimeout, completionTimeoutExpression, or completionInterval options a
     * background thread is created to check for the completion for every aggregator.
     * Set this option to provide a custom thread pool to be used rather than creating a new thread for every aggregator.
     */
    public AggregateDefinition timeoutCheckerExecutorService(ScheduledExecutorService executorService) {
        setTimeoutCheckerExecutorService(executorService);
        return this;
    }

    /**
     * If using either of the completionTimeout, completionTimeoutExpression, or completionInterval options a
     * background thread is created to check for the completion for every aggregator.
     * Set this option to provide a custom thread pool to be used rather than creating a new thread for every aggregator.
     */
    public AggregateDefinition timeoutCheckerExecutorServiceRef(String executorServiceRef) {
        setTimeoutCheckerExecutorServiceRef(executorServiceRef);
        return this;
    }
    
    // Section - Methods from ExpressionNode
    // Needed to copy methods from ExpressionNode here so that I could specify the
    // correlation expression as optional in JAXB

    public ExpressionDefinition getExpression() {
        if (expression == null && correlationExpression != null) {
            expression = correlationExpression.getExpressionType();            
        }
        return expression;
    }

    public void setExpression(ExpressionDefinition expression) {
        this.expression = expression;
    }

    protected void checkNoCompletedPredicate() {
        if (getCompletionPredicate() != null) {
            throw new IllegalArgumentException("There is already a completionPredicate defined for this aggregator: " + this);
        }
    }

    @Override
    public List<ProcessorDefinition<?>> getOutputs() {
        return outputs;
    }

    public boolean isOutputSupported() {
        return true;
    }

    public void setOutputs(List<ProcessorDefinition<?>> outputs) {
        this.outputs = outputs;
    }

}