src/main/java/org/apache/sling/scripting/sightly/impl/compiler/visitor/TrackingVisitor.java

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 * 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
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package org.apache.sling.scripting.sightly.impl.compiler.visitor;

import org.apache.sling.scripting.sightly.compiler.commands.Command;
import org.apache.sling.scripting.sightly.compiler.commands.Loop;
import org.apache.sling.scripting.sightly.compiler.commands.VariableBinding;
import org.apache.sling.scripting.sightly.compiler.util.VariableTracker;

/**
 * Command visitor which tracks variables in commands.
 */
public abstract class TrackingVisitor<T> extends UniformVisitor {

    protected final VariableTracker<T> tracker = new VariableTracker<>();

    @Override
    public void visit(VariableBinding.Start variableBindingStart) {
        super.visit(variableBindingStart);
        tracker.pushVariable(variableBindingStart.getVariableName(), assignDefault(variableBindingStart));
    }

    @Override
    public void visit(VariableBinding.End variableBindingEnd) {
        super.visit(variableBindingEnd);
        tracker.popVariable();
    }

    @Override
    public void visit(Loop.Start loopStart) {
        super.visit(loopStart);
        tracker.pushVariable(loopStart.getIndexVariable(), assignDefault(loopStart));
        tracker.pushVariable(loopStart.getItemVariable(), assignDefault(loopStart));
    }

    @Override
    public void visit(Loop.End loopEnd) {
        super.visit(loopEnd);
        tracker.popVariable();
        tracker.popVariable();
    }

    protected abstract T assignDefault(Command command);
}