/*
 * DomXPathExpression.java
 * Copyright (C) 2004 The Free Software Foundation
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU JAXP 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version. 
 */

package gnu.xml.dom;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.DOMException;
import org.w3c.dom.Node;
import org.w3c.dom.xpath.XPathException;
import org.w3c.dom.xpath.XPathNSResolver;
import org.w3c.dom.xpath.XPathResult;
import gnu.xml.xpath.DocumentOrderComparator;

/**
 * An XPath expression.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
class DomXPathExpression
implements org.w3c.dom.xpath.XPathExpression
{

  final DomDocument doc;
  final XPathExpression expression;
  final XPathNSResolver resolver;

  DomXPathExpression(DomDocument doc, String expression,
                     XPathNSResolver resolver)
    throws XPathException
  {
    this.doc = doc;
    this.resolver = resolver;
    
		XPathFactory factory = XPathFactory.newInstance();
		XPath xpath = factory.newXPath();
		if (resolver != null)
		  {
				xpath.setNamespaceContext(new DomNSResolverContext(resolver));
	 	  }
    try
      {
        this.expression = xpath.compile(expression);
      }
    catch (XPathExpressionException e)
      {
        throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,
						                     e.getMessage ());
      }
  }

  public Object evaluate(Node contextNode, short type, Object result)
    throws XPathException, DOMException
  {
		try
		  {
				QName typeName = null;
				switch (type)
				  {
						case XPathResult.BOOLEAN_TYPE:
							typeName = XPathConstants.BOOLEAN;
							break;
						case XPathResult.NUMBER_TYPE:
							typeName = XPathConstants.NUMBER;
							break;
						case XPathResult.STRING_TYPE:
							typeName = XPathConstants.STRING;
							break;
						case XPathResult.ANY_UNORDERED_NODE_TYPE:
						case XPathResult.FIRST_ORDERED_NODE_TYPE:
							typeName = XPathConstants.NODE;
							break;
						case XPathResult.UNORDERED_NODE_ITERATOR_TYPE:
						case XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE:
						case XPathResult.ORDERED_NODE_ITERATOR_TYPE:
						case XPathResult.ORDERED_NODE_SNAPSHOT_TYPE:
							typeName = XPathConstants.NODESET;
							break;
						default:
							throw new XPathException(XPathException.TYPE_ERR, null);
					}
				Object val = expression.evaluate(contextNode, typeName);
				switch (type)
				  {
						case XPathResult.ORDERED_NODE_ITERATOR_TYPE:
						case XPathResult.ORDERED_NODE_SNAPSHOT_TYPE:
							// Sort the nodes
							List ns = new ArrayList((Collection) val);
							Collections.sort(ns, new DocumentOrderComparator());
							val = ns;
					}
				return new DomXPathResult(val, type);
			}
		catch (javax.xml.xpath.XPathException e)
		  {
				throw new XPathException(XPathException.TYPE_ERR, e.getMessage());
			}
  }

  public String toString ()
  {
    return getClass ().getName () + "[expression=" + expression + "]";
  }
  
}
