/*
 * Created on Jul 14, 2003
 */
/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 2002, International
 * Business Machines Corporation., http://www.ibm.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xpath;

import org.apache.xpath.expression.Expr;
import org.apache.xpath.expression.OperatorExpr;
import org.apache.xpath.expression.PathExpr;
import org.apache.xpath.impl.ExprImpl;
import org.apache.xpath.impl.StepExprImpl;

/**
 * A collection of utility methods for XPath.
 * @author <a href="mailto:villard@us.ibm.com">Lionel Villard</a>
 * @version $Id$
 */
public class XPath20Utilities
{

	/**
	 * Return true whether the specified expression might select the document node.
	 * The test is performed statically, therefore there is no guarantee
	 * that the expression will indeed match the document node at runtime.
	 * @param Expr
	 * @return boolean 		
	 */
	static public boolean isMatchDocumentNode(Expr expr)
	{
		boolean result;
		try
		{
			switch (expr.getExprType())
			{
				case Expr.SEQUENCE_EXPR :
					OperatorExpr op = (OperatorExpr) expr;
					switch (op.getOperatorType())
					{
						case OperatorExpr.COMMA :
			
							if (op.getOperandCount() == 1)
							{
								result = isMatchDocumentNode(op.getOperand(0));
							} else
							{
								result = false;
							}
							break;
						case OperatorExpr.UNION_COMBINE :
							result = false;
							for (int i = op.getOperandCount() - 1; i >= 0; i--)
							{
								if (isMatchDocumentNode(op.getOperand(i)))
								{
									result = true;
									break;
								}
							}
							break;
						default :
							result = false;
					}
					break;
				case Expr.PATH_EXPR :
					PathExpr p = (PathExpr) expr;
						result =
							(p.isAbsolute() && p.getOperandCount() == 1); // '/'
			
					break;
				case Expr.STEP_EXPR :
				 	// single step
					result = ((StepExprImpl) expr).isRootOnSelfNode();
					break;
			
				default :
					result = false;
			}
		} catch (XPath20Exception e)
		{
			// Bug
			e.printStackTrace();
			result = false;
		}
		return result;
	}
	
	/**
	 * Returns true whenever the specified expression is a
	 * <em>singleton sequence</em> (a sequence with only one item).
	 */
	public static boolean isSingletonSequence(Expr e)
	{
		return e != null && e.getExprType() == Expr.SEQUENCE_EXPR
		&& ((OperatorExpr) e).getOperandCount() == 1;
	}
	
	/**
	 * Return true whenever the specified expression is a 
	 * absolute path, eventually embedded in a singleton sequence
	 * @param e
	 * @return
	 */
	public static boolean isAbsolutePath(Expr e)
	{
		try
		{
			return (e.getExprType() == Expr.PATH_EXPR && ((PathExpr) e).isAbsolute())
			|| (isSingletonSequence(e) && isAbsolutePath(((OperatorExpr) e).getOperand(0)));
		} catch (XPath20Exception e1)
		{
			e1.printStackTrace();
			return false;
		}
	} 
	
	/**
	 * Returns true whether the specified {@link Expr} is
	 * <code>fn:root(self::node())</code>
	 * @param expr
	 * @return
	 */
	public static boolean isRootOnSelfNode(Expr expr)
	{
		return ((ExprImpl) expr).isRootOnSelfNode();
	}

}