package org.apache.xalan.templates;

import java.util.Vector;

import org.apache.xml.utils.QName;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.operations.Variable;

/**
 * This class visits variable refs in an XPath and collects their QNames.
 */
public class VarNameCollector extends XPathVisitor
{
	Vector m_refs = new Vector();
	
	/**
	 * Reset the list for a fresh visitation and collection.
	 */
	public void reset()
	{
		m_refs.removeAllElements(); //.clear();
	}
	
	/**
	 * Get the number of variable references that were collected.
	 * @return the size of the list.
	 */
	public int getVarCount()
	{
		return m_refs.size();
	}
	
	/**
	 * Tell if the given qualified name occurs in 
	 * the list of qualified names collected.
	 * 
	 * @param refName Must be a valid qualified name.
	 * @return true if the list contains the qualified name.
	 */
	boolean doesOccur(QName refName)
	{
		return m_refs.contains(refName);
	}

	/**
	 * Visit a variable reference.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param var The variable reference object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitVariableRef(ExpressionOwner owner, Variable var)
	{
		m_refs.addElement(var.getQName());
		return true;
	}

}