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/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.esodata;
import java.util.*;
import bjc.data.*;
final class FlatNestIterator<Element> implements ListIterator<Element>
{
private Deque<ListIterator<Either<Element, NestList<Element>>>> iterators;
public FlatNestIterator(ListIterator<Either<Element, NestList<Element>>> iterator)
{
this.iterators = new ArrayDeque<>();
this.iterators.add(iterator);
}
@Override
public boolean hasNext() {
boolean result = false;
do {
result = iterators.peek().hasNext();
if (result == false) iterators.pop();
} while (result == false && iterators.isEmpty() == false);
return result;
}
@Override
public Element next() {
Holder<Element> element = Holder.of(null);
do {
element = iterators.peek().next().extract((ele) -> {
return Holder.of(ele);
}, (lst) -> {
// Ignore empty sublists.
if (lst.size() != 0) iterators.push(lst.listIterator());
return null;
});
} while (element == null && hasNext());
if (element == null) throw new NoSuchElementException();
return element.getValue();
}
@Override
public boolean hasPrevious() {
boolean result = false;
do {
result = iterators.peek().hasPrevious();
if (result == false) iterators.pop();
} while (result == false && iterators.isEmpty() == false);
return result;
}
@Override
public Element previous() {
Holder<Element> element = Holder.of(null);
do {
element = iterators.peek().previous().extract((ele) -> {
return Holder.of(ele);
}, (lst) -> {
// Ignore empty sublists.
if (lst.size() != 0) iterators.push(lst.listIterator());
return null;
});
} while (element == null && hasPrevious());
if (element == null) throw new NoSuchElementException();
return element.getValue();
}
@Override
public int nextIndex() {
return iterators.peek().nextIndex();
}
@Override
public int previousIndex() {
return iterators.peek().previousIndex();
}
@Override
public void remove() {
iterators.peek().remove();
}
@Override
public void set(Element e) {
iterators.peek().set(Either.left(e));
}
@Override
public void add(Element e) {
iterators.peek().add(Either.left(e));
}
}
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