/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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: XPathVisitor.java 468655 2006-10-28 07:12:06Z minchau $
 */
package org.apache.xpath;

import org.apache.xpath.axes.LocPathIterator;
import org.apache.xpath.axes.UnionPathIterator;
import org.apache.xpath.functions.Function;
import org.apache.xpath.objects.XNumber;
import org.apache.xpath.objects.XString;
import org.apache.xpath.operations.Operation;
import org.apache.xpath.operations.UnaryOperation;
import org.apache.xpath.operations.Variable;
import org.apache.xpath.patterns.NodeTest;
import org.apache.xpath.patterns.StepPattern;
import org.apache.xpath.patterns.UnionPattern;

A derivation from this class can be passed to a class that implements 
the XPathVisitable interface, to have the appropriate method called 
for each component of the XPath.  Aside from possible other uses, the 
main intention is to provide a reasonable means to perform expression 
rewriting.
Each method has the form 
boolean visitComponentType(ExpressionOwner owner, ComponentType compType). 
The ExpressionOwner argument is the owner of the component, and can 
be used to reset the expression for rewriting.  If a method returns 
false, the sub hierarchy will not be traversed.
This class is meant to be a base class that will be derived by concrete classes, 
and doesn't much except return true for each method.
/**
 * A derivation from this class can be passed to a class that implements 
 * the XPathVisitable interface, to have the appropriate method called 
 * for each component of the XPath.  Aside from possible other uses, the 
 * main intention is to provide a reasonable means to perform expression 
 * rewriting.
 * 
 * <p>Each method has the form 
 * <code>boolean visitComponentType(ExpressionOwner owner, ComponentType compType)</code>. 
 * The ExpressionOwner argument is the owner of the component, and can 
 * be used to reset the expression for rewriting.  If a method returns 
 * false, the sub hierarchy will not be traversed.</p>
 * 
 * <p>This class is meant to be a base class that will be derived by concrete classes, 
 * and doesn't much except return true for each method.</p>
 */
public class XPathVisitor
{
	
Visit a LocationPath.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
path – The LocationPath object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a LocationPath.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param path The LocationPath object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitLocationPath(ExpressionOwner owner, LocPathIterator path)
	{
		return true;
	}

	
Visit a UnionPath.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
path – The UnionPath object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a UnionPath.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param path The UnionPath object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitUnionPath(ExpressionOwner owner, UnionPathIterator path)
	{
		return true;
	}
	
	
Visit a step within a location path.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
step – The Step object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a step within a location path.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param step The Step object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitStep(ExpressionOwner owner, NodeTest step)
	{
		return true;
	}
		
	
Visit a predicate within a location path.  Note that there isn't a 
proper unique component for predicates, and that the expression will 
be called also for whatever type Expression is.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
pred – The predicate object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a predicate within a location path.  Note that there isn't a 
	 * proper unique component for predicates, and that the expression will 
	 * be called also for whatever type Expression is.
	 * 
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param pred The predicate object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitPredicate(ExpressionOwner owner, Expression pred)
	{
		return true;
	}

	
Visit a binary operation.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
op – The operation object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a binary operation.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param op The operation object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitBinaryOperation(ExpressionOwner owner, Operation op)
	{
		return true;
	}

	
Visit a unary operation.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
op – The operation object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a unary operation.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param op The operation object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitUnaryOperation(ExpressionOwner owner, UnaryOperation op)
	{
		return true;
	}
	
	
Visit a variable reference.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
var – The variable reference object.
Returns:
true if the sub expressions should be traversed./**
	 * 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)
	{
		return true;
	}

	
Visit a function.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
func – The function reference object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a function.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param func The function reference object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitFunction(ExpressionOwner owner, Function func)
	{
		return true;
	}
	
	
Visit a match pattern.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
pattern – The match pattern object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a match pattern.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param pattern The match pattern object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitMatchPattern(ExpressionOwner owner, StepPattern pattern)
	{
		return true;
	}
	
	
Visit a union pattern.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
pattern – The union pattern object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a union pattern.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param pattern The union pattern object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitUnionPattern(ExpressionOwner owner, UnionPattern pattern)
	{
		return true;
	}
	
	
Visit a string literal.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
str – The string literal object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a string literal.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param str The string literal object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitStringLiteral(ExpressionOwner owner, XString str)
	{
		return true;
	}


	
Visit a number literal.
Params:
owner – The owner of the expression, to which the expression can 
             be reset if rewriting takes place.
num – The number literal object.
Returns:
true if the sub expressions should be traversed./**
	 * Visit a number literal.
	 * @param owner The owner of the expression, to which the expression can 
	 *              be reset if rewriting takes place.
	 * @param num The number literal object.
	 * @return true if the sub expressions should be traversed.
	 */
	public boolean visitNumberLiteral(ExpressionOwner owner, XNumber num)
	{
		return true;
	}


}