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/*******************************************************************************
* Copyright (c) 2009, 2017 Cloudsmith Inc. and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Cloudsmith Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.p2.metadata.expression;
import java.util.*;
import org.eclipse.equinox.p2.metadata.expression.IEvaluationContext;
/**
* An expression that will collect items recursively based on a <code>rule</code>.
* The <code>rule</code> is applied for each item in the <code>collection</code> and
* is supposed to create a new collection. The <code>rule</code> is then applied for each item
* in the new collection. All items are collected into a set and items that are already
* in that set will not be perused again. The set becomes the result of the traversal.
*/
final class Traverse extends CollectionFilter {
Traverse(Expression collection, LambdaExpression lambda) {
super(collection, lambda);
}
@Override
public Object evaluate(IEvaluationContext context, Iterator<?> itor) {
return evaluateAsIterator(context, itor);
}
@Override
public Iterator<?> evaluateAsIterator(IEvaluationContext context, Iterator<?> iterator) {
HashSet<Object> collector = new HashSet<>();
while (iterator.hasNext())
traverse(collector, iterator.next(), context);
return collector.iterator();
}
@Override
public int getExpressionType() {
return TYPE_TRAVERSE;
}
@Override
public String getOperator() {
return KEYWORD_TRAVERSE;
}
void traverse(Set<Object> collector, Object parent, IEvaluationContext context) {
if (collector.add(parent)) {
Variable variable = lambda.getItemVariable();
context = EvaluationContext.create(context, variable);
variable.setValue(context, parent);
Iterator<?> subIterator = lambda.evaluateAsIterator(context);
while (subIterator.hasNext())
traverse(collector, subIterator.next(), context);
}
}
}
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