/*
 * Copyright 1999-2004 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.
 */
/*
 * $Id: ExpressionVisitor.java,v 1.8 2005/01/23 00:10:05 mcnamara Exp $
 */
package org.apache.xalan.extensions;

import org.apache.xalan.templates.StylesheetRoot;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.functions.FuncExtFunction;
import org.apache.xpath.functions.FuncExtFunctionAvailable;
import org.apache.xpath.functions.Function;

/**
 * When {@link org.apache.xalan.processor.StylesheetHandler} creates 
 * an {@link org.apache.xpath.XPath}, the ExpressionVisitor
 * visits the XPath expression. For any extension functions it 
 * encounters, it instructs StylesheetRoot to register the
 * extension namespace. 
 * 
 * This mechanism is required to locate extension functions
 * that may be embedded within an expression.
 */
public class ExpressionVisitor extends XPathVisitor
{
  private StylesheetRoot m_sroot;
  
  /**
   * The constructor sets the StylesheetRoot variable which
   * is used to register extension namespaces.
   * @param sroot the StylesheetRoot that is being constructed.
   */
  public ExpressionVisitor (StylesheetRoot sroot)
  {
    m_sroot = sroot;
  }
  
  /**
   * If the function is an extension function, register the namespace.
   * 
   * @param owner The current XPath object that owns the expression.
   * @param func The function currently being visited.
   * 
   * @return true to continue the visit in the subtree, if any.
   */
  public boolean visitFunction(ExpressionOwner owner, Function func)
  {
    if (func instanceof FuncExtFunction)
    {
      String namespace = ((FuncExtFunction)func).getNamespace();
      m_sroot.getExtensionNamespacesManager().registerExtension(namespace);      
    }
    else if (func instanceof FuncExtFunctionAvailable)
    {
      String arg = ((FuncExtFunctionAvailable)func).getArg0().toString();
      if (arg.indexOf(":") > 0)
      {
      	String prefix = arg.substring(0,arg.indexOf(":"));
      	String namespace = this.m_sroot.getNamespaceForPrefix(prefix);
      	m_sroot.getExtensionNamespacesManager().registerExtension(namespace);
      }
    }
    return true;
  }

}