/*
 ***************************************************************************************
 *  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.epl.expression.core;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.type.CronOperatorEnum;
import com.espertech.esper.type.CronParameter;
import com.espertech.esper.util.JavaClassHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.StringWriter;

/**
 * Expression for a parameter within a crontab.
 * <p>
 * May have one subnode depending on the cron parameter type.
 */
public class ExprNumberSetCronParam extends ExprNodeBase implements ExprEvaluator {
    private static final Logger log = LoggerFactory.getLogger(ExprNumberSetCronParam.class);

    private final CronOperatorEnum cronOperator;
    private transient ExprEvaluator evaluator;
    private static final long serialVersionUID = -1315999998249935318L;

    /**
     * Ctor.
     *
     * @param cronOperator type of cron parameter
     */
    public ExprNumberSetCronParam(CronOperatorEnum cronOperator) {
        this.cronOperator = cronOperator;
    }

    public ExprEvaluator getExprEvaluator() {
        return this;
    }

    /**
     * Returns the cron parameter type.
     *
     * @return type of cron parameter
     */
    public CronOperatorEnum getCronOperator() {
        return cronOperator;
    }


    public void toPrecedenceFreeEPL(StringWriter writer) {
        if (this.getChildNodes().length != 0) {
            this.getChildNodes()[0].toEPL(writer, getPrecedence());
            writer.append(" ");
        }
        writer.append(cronOperator.getSyntax());
    }

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

    public boolean isConstantResult() {
        if (this.getChildNodes().length == 0) {
            return true;
        }
        return this.getChildNodes()[0].isConstantResult();
    }

    public boolean equalsNode(ExprNode node, boolean ignoreStreamPrefix) {
        if (!(node instanceof ExprNumberSetCronParam)) {
            return false;
        }
        ExprNumberSetCronParam other = (ExprNumberSetCronParam) node;
        return other.cronOperator.equals(this.cronOperator);
    }

    public ExprNode validate(ExprValidationContext validationContext) throws ExprValidationException {
        if (this.getChildNodes().length == 0) {
            return null;
        }
        evaluator = this.getChildNodes()[0].getExprEvaluator();
        Class type = evaluator.getType();
        if (!(JavaClassHelper.isNumericNonFP(type))) {
            throw new ExprValidationException("Frequency operator requires an integer-type parameter");
        }
        return null;
    }

    public Class getType() {
        return CronParameter.class;
    }

    public Object evaluate(EventBean[] eventsPerStream, boolean isNewData, ExprEvaluatorContext exprEvaluatorContext) {
        if (this.getChildNodes().length == 0) {
            return new CronParameter(cronOperator, null);
        }
        Object value = evaluator.evaluate(eventsPerStream, isNewData, exprEvaluatorContext);
        if (value == null) {
            log.warn("Null value returned for cron parameter");
            return new CronParameter(cronOperator, null);
        } else {
            int intValue = ((Number) value).intValue();
            return new CronParameter(cronOperator, intValue);
        }
    }
}