Positional.java

/**
 * Copyright 2015 Santhosh Kumar Tekuri
 *
 * The JLibs authors license this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package jlibs.xml.sax.dog.expr.nodset;

import jlibs.core.lang.ImpossibleException;
import jlibs.xml.sax.dog.DataType;
import jlibs.xml.sax.dog.Scope;
import jlibs.xml.sax.dog.expr.Evaluation;
import jlibs.xml.sax.dog.expr.Expression;
import jlibs.xml.sax.dog.sniff.Event;


/**
 * @author Santhosh Kumar T
 */
public abstract class Positional extends Expression{
    public final boolean position;
    public Expression predicate;

    public Positional(boolean position){
        this(DataType.NUMBER, position);
    }

    public Positional(DataType resultType, boolean position){
        super(Scope.LOCAL, resultType);
        this.position = position;
    }

    @Override
    public final Object getResult(){
        throw new ImpossibleException();
    }

    @Override
    public Object getResult(Event event){
        return new PositionalEvaluation(this, event.order(), event.positionTrackerStack.peekFirst());
    }

    protected Object translate(Double result){
        return result;
    }
}

final class PositionalEvaluation extends Evaluation<Positional>{
    public PositionalEvaluation previous, next;

    private PositionTracker locationEval;
    protected PositionalEvaluation(Positional expression, long order, PositionTracker locationEval){
        super(expression, order);
        this.locationEval = locationEval;
    }

    @Override
    public void start(){
        if(expression.position)
            locationEval.addPositionListener(this);
        else
            locationEval.addLastLitener(this);
    }

    private Object result;

    @Override
    public Object getResult(){
        return result;
    }

    public void setResult(Double result){
        this.result = expression.translate(result);
        fireFinished();
    }

    @Override
    public void finished(Evaluation evaluation){}

    @Override
    protected void dispose(){
        if(expression.position)
            locationEval.removePositionListener(this);
        else
            locationEval.removeLastLitener(this);
    }
}