io.prestosql.sql.tree.StackableAstVisitor Maven / Gradle / Ivy
/*
* 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.
*/
package io.prestosql.sql.tree;
import java.util.LinkedList;
import java.util.Optional;
public class StackableAstVisitor
extends AstVisitor>
{
public R process(Node node, StackableAstVisitorContext context)
{
context.push(node);
try {
return node.accept(this, context);
}
finally {
context.pop();
}
}
public static class StackableAstVisitorContext
{
private final LinkedList stack = new LinkedList<>();
private final C context;
public StackableAstVisitorContext(C context)
{
this.context = context;
}
public C getContext()
{
return context;
}
private void pop()
{
stack.pop();
}
void push(Node node)
{
stack.push(node);
}
public Optional getPreviousNode()
{
if (stack.size() > 1) {
return Optional.of(stack.get(1));
}
return Optional.empty();
}
}
}