/*
 ***************************************************************************************
 *  Copyright (C) 2006 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.client.soda;

import java.io.StringWriter;

/**
 * Average of the (distinct) values returned by an expression.
 * <p>
 * Expects a single child expression providing the values to aggregate.
 */
public class AvgProjectionExpression extends ExpressionBase {
    private boolean distinct;
    private static final long serialVersionUID = 8608818096433764685L;

    /**
     * Ctor.
     */
    public AvgProjectionExpression() {
    }

    /**
     * Ctor - for use to create an expression tree, without inner expression
     *
     * @param isDistinct true if distinct
     */
    public AvgProjectionExpression(boolean isDistinct) {
        this.distinct = isDistinct;
    }

    /**
     * Ctor - adds the expression to project.
     *
     * @param expression returning values to project
     * @param isDistinct true if distinct
     */
    public AvgProjectionExpression(Expression expression, boolean isDistinct) {
        this.distinct = isDistinct;
        this.getChildren().add(expression);
    }

    public ExpressionPrecedenceEnum getPrecedence() {
        return ExpressionPrecedenceEnum.UNARY;
    }

    public void toPrecedenceFreeEPL(StringWriter writer) {
        ExpressionBase.renderAggregation(writer, "avg", distinct, this.getChildren());
    }

    /**
     * Returns true if the projection considers distinct values only.
     *
     * @return true if distinct
     */
    public boolean isDistinct() {
        return distinct;
    }

    /**
     * Returns true if the projection considers distinct values only.
     *
     * @return true if distinct
     */
    public boolean getDistinct() {
        return distinct;
    }

    /**
     * Set the distinct flag indicating the projection considers distinct values only.
     *
     * @param distinct true for distinct, false for not distinct
     */
    public void setDistinct(boolean distinct) {
        this.distinct = distinct;
    }
}