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package oracle.toplink.essentials.internal.parsing;

import oracle.toplink.essentials.queryframework.ObjectLevelReadQuery;
import oracle.toplink.essentials.queryframework.ReportQuery;
import oracle.toplink.essentials.expressions.Expression;

/**
 * INTERNAL
 * <p><b>Purpose</b>: Model a AVG
 * <p><b>Responsibilities</b>:<ul>
 * <li> Apply itself to a query correctly
 * </ul>
 */
public class AvgNode extends AggregateNode {

    /**
     * INTERNAL
     * Apply this node to the passed query
     */
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext context) {
        if (theQuery.isReportQuery()) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            reportQuery.addAttribute(resolveAttribute(), 
                                     generateExpression(context), Double.class);
        }
    }

    /**
     * INTERNAL
     * Validate node and calculate its type.
     */
    public void validate(ParseTreeContext context) {
        if (left != null) {
            left.validate(context);
        }
        TypeHelper typeHelper = context.getTypeHelper();
        setType(typeHelper.getDoubleClassType());
    }

    /**
     * INTERNAL
     */
    protected Expression addAggregateExression(Expression expr) {
        return expr.average();
    }

    /**
     * INTERNAL
     * Get the string representation of this node.
     */
    public String getAsString() {
        return "AVG(" + left.getAsString() + ")";
    }
}