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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.document.annotation;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.ListIterator;
import java.util.NoSuchElementException;
/**
* ListIterator implementation which performs a depth-first traversal of SpanNodes.
*
* @author <a href="mailto:einarmr@yahoo-inc.com">Einar M R Rosenvinge</a>
*/
class RecursiveNodeIterator implements ListIterator<SpanNode> {
protected Deque<PeekableListIterator<SpanNode>> stack = new ArrayDeque<>();
protected ListIterator<SpanNode> iteratorFromLastCallToNext = null;
RecursiveNodeIterator(ListIterator<SpanNode> it) {
stack.push(new PeekableListIterator<>(it));
}
protected RecursiveNodeIterator() {
}
@Override
public boolean hasNext() {
if (stack.isEmpty()) {
return false;
}
PeekableListIterator<SpanNode> iterator = stack.peek();
if (!iterator.hasNext()) {
stack.pop();
return hasNext();
}
SpanNode node = iterator.peek();
if (!iterator.traversed) {
//we set the traversed flag on our way down
iterator.traversed = true;
stack.push(new PeekableListIterator<>(node.childIterator()));
return hasNext();
}
return true;
}
@Override
public SpanNode next() {
if (stack.isEmpty() || !hasNext()) {
iteratorFromLastCallToNext = null;
throw new NoSuchElementException("No next element available.");
}
stack.peek().traversed = false;
iteratorFromLastCallToNext = stack.peek();
return stack.peek().next();
}
@Override
public boolean hasPrevious() {
throw new UnsupportedOperationException();
}
@Override
public SpanNode previous() {
throw new UnsupportedOperationException();
}
@Override
public int nextIndex() {
throw new UnsupportedOperationException();
}
@Override
public int previousIndex() {
throw new UnsupportedOperationException();
}
@Override
public void remove() {
if (stack.isEmpty()) {
throw new IllegalStateException();
}
if (iteratorFromLastCallToNext != null) {
iteratorFromLastCallToNext.remove();
} else {
throw new IllegalStateException();
}
}
@Override
public void set(SpanNode spanNode) {
if (stack.isEmpty()) {
throw new IllegalStateException();
}
if (iteratorFromLastCallToNext != null) {
iteratorFromLastCallToNext.set(spanNode);
} else {
throw new IllegalStateException();
}
}
@Override
public void add(SpanNode spanNode) {
throw new UnsupportedOperationException();
}
}
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