AviatorNil.java

/**
 *  Copyright (C) 2010 dennis zhuang (killme2008@gmail.com)
 *
 *  This library is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published
 *  by the Free Software Foundation; either version 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  This library 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 **/
package com.googlecode.aviator.runtime.type;

import java.util.Map;

import com.googlecode.aviator.utils.TypeUtils;


/**
 * Aviator nil object
 * 
 * @author dennis
 * 
 */
public class AviatorNil extends AviatorObject {
    public static final AviatorNil NIL = new AviatorNil();


    private AviatorNil() {

    }


    @Override
    public AviatorObject add(AviatorObject other, Map<String, Object> env) {
        switch (other.getAviatorType()) {
        case String:
            return new AviatorString("null" + other.getValue(env));
        case JavaType:
            final Object otherValue = other.getValue(env);
            if (TypeUtils.isString(otherValue)) {
                return new AviatorString("null" + otherValue);
            }
            else {
                return super.add(other, env);
            }
        default:
            return super.add(other, env);
        }
    }


    @Override
    public int compare(AviatorObject other, Map<String, Object> env) {
        if (this == other)
            return 0;
        switch (other.getAviatorType()) {
        case Nil:
            return 0;
        case JavaType:
            if (other.getValue(env) == null) {
                return 0;
            }
        }
        // Any object is greater than nil except nil
        return -1;
    }


    @Override
    public AviatorType getAviatorType() {
        return AviatorType.Nil;
    }


    @Override
    public Object getValue(Map<String, Object> env) {
        return null;
    }

}