/*
 * 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;

/**
 *  reference - any variable expression
 *
 *  @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
 *  @version $Id: ASTReference.java,v 1.4 2004/09/01 00:35:38 dion Exp $
 */
public class ASTReference extends SimpleNode
{
    SimpleNode root;

    public ASTReference(int id)
    {
        super(id);
    }

    public ASTReference(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
    {
        return  execute(null,jc);
    }

    public void jjtClose()
    {
        root = (SimpleNode) jjtGetChild(0);
    }

    public Object execute(Object obj, JexlContext jc)
             throws Exception
     {
         Object o = root.value(jc);

         /*
          * ignore the first child - it's our identifier
          */
         for(int i=1; i<jjtGetNumChildren(); i++)
         {
             o = ( (SimpleNode) jjtGetChild(i)).execute(o,jc);

             // check for a variable in the context named
             // child0.child1.child2 etc
             if(o == null) {
                 String varName = getIdentifierToDepth(i);
                 o = jc.getVars().get(varName);
             }
         }

         return o;
     }

    /**
     * This method returns a variable from this identifier and
     * it's children. For an expression like 'a.b.c', a is child
     * zero, b is child 1 and c is child 2.
     *  
     * @param i the depth of the child nodes to go to
     * @return the a dotted variable from this identifier and it's
     *    child nodes.
     */
    private String getIdentifierToDepth(int i) {
        StringBuffer varName = new StringBuffer();
         for (int j = 0; j <=i; j++) {
             SimpleNode node = (SimpleNode) jjtGetChild(j);
             if (node instanceof ASTIdentifier) {
               varName.append(((ASTIdentifier)node).getIdentifierString());
               if (j != i) varName.append('.');
             }
         }
        return varName.toString();
    }

    public String getRootString()
        throws Exception
    {
        if ( root instanceof ASTIdentifier)
            return ((ASTIdentifier) root).getIdentifierString();

        if (root instanceof ASTArrayAccess)
            return ((ASTArrayAccess) root).getIdentifierString();

        throw new Exception("programmer error : ASTReference : root not known"
                    + root );
    }
}