/*
* JBoss, Home of Professional Open Source.
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership. Some portions may be licensed
* to Red Hat, Inc. under one or more contributor license agreements.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA.
*/
package org.teiid.query.optimizer.xml;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedList;
import org.teiid.query.function.FunctionLibrary;
import org.teiid.query.sql.LanguageObject;
import org.teiid.query.sql.navigator.PreOrderNavigator;
import org.teiid.query.sql.symbol.Expression;
import org.teiid.query.sql.symbol.Function;
import org.teiid.query.sql.visitor.ExpressionMappingVisitor;
/**
* <p>Walk a tree of language objects and replaces any usage of 'context' syntax
* (implemented as a Function) with it's right argument. The stripped-off
* 'context' Functions can be gotten as a Collection afterward.</p>
*/
class ContextReplacerVisitor extends ExpressionMappingVisitor {
private Collection contextFunctions = new LinkedList(); //contains Function objects
/**
* Construct a new visitor
*/
ContextReplacerVisitor() {
super(Collections.EMPTY_MAP);
}
/**
* Get the Collection of Function objects representing context operators
* which were stripped out of the language object by this visitor
* @return Collection of Function
*/
Collection getContextFunctions(){
return this.contextFunctions;
}
/**
* @see org.teiid.query.sql.visitor.ExpressionMappingVisitor#replaceExpression(org.teiid.query.sql.symbol.Expression)
*/
public Expression replaceExpression(Expression exp) {
if (exp instanceof Function){
Function function = (Function)exp;
if (function.getName().equalsIgnoreCase(FunctionLibrary.CONTEXT)){
this.contextFunctions.add(function);
//return 2nd argument to 'context'
return function.getArg(1);
}
}
return exp;
}
/**
* Helper to quickly replace 'context'
* @param obj Language object
*/
static final Collection replaceContextFunctions(LanguageObject obj) {
if (obj == null){
return Collections.EMPTY_SET;
}
ContextReplacerVisitor visitor = new ContextReplacerVisitor();
PreOrderNavigator.doVisit(obj, visitor);
return visitor.getContextFunctions();
}
}