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Complex event processing and event series analysis component

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/**************************************************************************************
 * Copyright (C) 2006-2015 EsperTech Inc. All rights reserved.                        *
 * http://www.espertech.com/esper                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.epl.expression.prior;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.epl.expression.core.ExprEvaluator;
import com.espertech.esper.epl.expression.core.ExprEvaluatorContext;

/**
 * Represents the 'prior' prior event function in an expression node tree.
 */
public abstract class ExprPriorEvalStrategyBase implements ExprPriorEvalStrategy
{
    public abstract EventBean getSubstituteEvent(EventBean originalEvent, boolean isNewData, int constantIndexNumber);

    public Object evaluate(EventBean[] eventsPerStream, boolean isNewData, ExprEvaluatorContext exprEvaluatorContext, int streamNumber, ExprEvaluator evaluator, int constantIndexNumber)
    {
        EventBean originalEvent = eventsPerStream[streamNumber];

        EventBean substituteEvent = getSubstituteEvent(originalEvent, isNewData, constantIndexNumber);

        // Substitute original event with prior event, evaluate inner expression
        eventsPerStream[streamNumber] = substituteEvent;
        Object evalResult = evaluator.evaluate(eventsPerStream, isNewData, exprEvaluatorContext);
        eventsPerStream[streamNumber] = originalEvent;

        return evalResult;
    }
}