/**
 * Copyright (C) 2009-2013 FoundationDB, LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.foundationdb.server.types.texpressions;

import com.foundationdb.qp.operator.Operator;
import com.foundationdb.qp.rowtype.RowType;
import com.foundationdb.server.explain.*;
import com.foundationdb.server.types.TInstance;
import com.foundationdb.server.types.aksql.aktypes.AkBool;
import com.foundationdb.server.types.value.ValueTarget;

public class ExistsSubqueryTExpression extends SubqueryTExpression
{
    private static final class InnerEvaluation extends SubqueryTEvaluateble
    {
        InnerEvaluation(Operator subquery,
                        RowType outerRowType, RowType innerRowType,
                        int bindingPosition)
        {
            super(subquery, outerRowType, innerRowType, bindingPosition, AkBool.INSTANCE.instance(true));
        }

        @Override
        protected void doEval(ValueTarget out)
        {   
            out.putBool(next() != null);
        }
    }

    public ExistsSubqueryTExpression(Operator subquery, RowType outerRowType, 
                                     RowType innerRowType, int bindingPosition)
    {
        super(subquery, outerRowType, innerRowType, bindingPosition);
    }
    
    @Override
    public TInstance resultType()
    {
        return AkBool.INSTANCE.instance(true);
    }

    @Override
    public TEvaluatableExpression build()
    {
        return new InnerEvaluation(subquery(),
                                   outerRowType(), innerRowType(),
                                   bindingPosition());
    }

    @Override
    public CompoundExplainer getExplainer(ExplainContext context) {
        CompoundExplainer explainer = super.getExplainer(context);
        explainer.addAttribute(Label.NAME, PrimitiveExplainer.getInstance("EXISTS"));
        return explainer;
    }

}