/**************************************************************************************
* Copyright (C) 2008 EsperTech, Inc. All rights reserved. *
* http://esper.codehaus.org *
* 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;
import com.espertech.esper.client.EventBean;
import com.espertech.esper.view.window.RandomAccessByIndex;
import com.espertech.esper.view.window.RandomAccessByIndexGetter;
import com.espertech.esper.view.window.RelativeAccessByEventNIndex;
import com.espertech.esper.view.window.RelativeAccessByEventNIndexMap;
import java.util.Collection;
import java.util.Collections;
public class ExprPreviousEvalStrategyPrev implements ExprPreviousEvalStrategy
{
private final int streamNumber;
private final ExprEvaluator indexNode;
private final ExprEvaluator evalNode;
private final RandomAccessByIndexGetter randomAccessGetter;
private final RelativeAccessByEventNIndexMap relativeAccessGetter;
private final boolean isConstantIndex;
private final Integer constantIndexNumber;
private final boolean isTail;
public ExprPreviousEvalStrategyPrev(int streamNumber, ExprEvaluator indexNode, ExprEvaluator evalNode, RandomAccessByIndexGetter randomAccessGetter, RelativeAccessByEventNIndexMap relativeAccessGetter, boolean constantIndex, Integer constantIndexNumber, boolean tail)
{
this.streamNumber = streamNumber;
this.indexNode = indexNode;
this.evalNode = evalNode;
this.randomAccessGetter = randomAccessGetter;
this.relativeAccessGetter = relativeAccessGetter;
isConstantIndex = constantIndex;
this.constantIndexNumber = constantIndexNumber;
isTail = tail;
}
public Object evaluate(EventBean[] eventsPerStream, ExprEvaluatorContext exprEvaluatorContext)
{
EventBean substituteEvent = getSubstitute(eventsPerStream, exprEvaluatorContext);
if (substituteEvent == null)
{
return null;
}
// Substitute original event with prior event, evaluate inner expression
EventBean originalEvent = eventsPerStream[streamNumber];
eventsPerStream[streamNumber] = substituteEvent;
Object evalResult = evalNode.evaluate(eventsPerStream, true, exprEvaluatorContext);
eventsPerStream[streamNumber] = originalEvent;
return evalResult;
}
public EventBean evaluateGetEventBean(EventBean[] eventsPerStream, ExprEvaluatorContext context) {
return getSubstitute(eventsPerStream, context);
}
public Collection<EventBean> evaluateGetCollEvents(EventBean[] eventsPerStream, ExprEvaluatorContext context) {
return null;
}
public Collection evaluateGetCollScalar(EventBean[] eventsPerStream, ExprEvaluatorContext context) {
Object result = evaluate(eventsPerStream, context);
if (result == null) {
return null;
}
return Collections.singletonList(result);
}
private EventBean getSubstitute(EventBean[] eventsPerStream, ExprEvaluatorContext exprEvaluatorContext) {
// Use constant if supplied
Integer index;
if (isConstantIndex)
{
index = constantIndexNumber;
}
else
{
// evaluate first child, which returns the index
Object indexResult = indexNode.evaluate(eventsPerStream, true, exprEvaluatorContext);
if (indexResult == null)
{
return null;
}
index = ((Number) indexResult).intValue();
}
// access based on index returned
EventBean substituteEvent;
if (randomAccessGetter != null)
{
RandomAccessByIndex randomAccess = randomAccessGetter.getAccessor();
if (!isTail) {
substituteEvent = randomAccess.getNewData(index);
}
else {
substituteEvent = randomAccess.getNewDataTail(index);
}
}
else
{
EventBean evalEvent = eventsPerStream[streamNumber];
RelativeAccessByEventNIndex relativeAccess = relativeAccessGetter.getAccessor(evalEvent);
if (!isTail) {
substituteEvent = relativeAccess.getRelativeToEvent(evalEvent, index);
}
else {
substituteEvent = relativeAccess.getRelativeToEnd(evalEvent, index);
}
}
return substituteEvent;
}
}