/*
 * Copyright 2002,2004 The Apache Software Foundation.
 * 
 * Licensed 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 org.apache.commons.jexl.parser;

import org.apache.commons.jexl.JexlContext;

import java.util.Collection;
import java.util.Map;

/**
 *  function to see if reference doesn't exist in context
 *
 *  @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
 *  @author <a href="mailto:tobrien@apache.org">Tim O'Brien</a>
 *  @version $Id: ASTEmptyFunction.java,v 1.6 2004/08/23 13:30:36 dion Exp $
 */
public class ASTEmptyFunction extends SimpleNode
{
    public ASTEmptyFunction(int id)
    {
        super(id);
    }

    public ASTEmptyFunction(Parser p, int id)
    {
        super(p, id);
    }

    /** Accept the visitor. **/
    public Object jjtAccept(ParserVisitor visitor, Object data)
    {
        return visitor.visit(this, data);
    }

    public Object value(JexlContext jc)
        throws Exception
    {
        SimpleNode sn = (SimpleNode) jjtGetChild(0);

        /*
         * I can't believe this
         */

        Object o = sn.value(jc);

        if (o == null)
            return Boolean.TRUE;

        if (o instanceof String && "".equals((String) o))
            return Boolean.TRUE;

        if (o.getClass().isArray() && ((Object[])o).length == 0)
            return Boolean.TRUE;

        if (o instanceof Collection && ((Collection)o).isEmpty())
            return Boolean.TRUE;

        /*
         *  Map isn't a collection
         */
        if (o instanceof Map && ((Map)o).isEmpty())
            return Boolean.TRUE;

        return Boolean.FALSE;
    }
}