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Convenient utility to build XML models by evaluating XPath expressions
/*
* Copyright 2017-2021 Alex Simkin
*
* 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 com.github.simy4.xpath.view;
import com.github.simy4.xpath.XmlBuilderException;
import com.github.simy4.xpath.navigator.Node;
import com.github.simy4.xpath.util.Function;
import com.github.simy4.xpath.util.Predicate;
import com.github.simy4.xpath.util.ReadOnlyIterator;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.NoSuchElementException;
import java.util.Set;
@SuppressWarnings("SameNameButDifferent")
public abstract class NodeSetView implements IterableNodeView, Serializable {
private static final long serialVersionUID = 1L;
private static final NodeSetView EMPTY_NODE_SET = new EmptyNodeSet();
@SuppressWarnings("unchecked")
public static NodeSetView empty() {
return (NodeSetView) EMPTY_NODE_SET;
}
public static NodeSetView of(
Iterable iterable, Predicate filter) {
return new IterableNodeSet(iterable, filter);
}
@Override
public int compareTo(View other) {
final Iterator> iterator = iterator();
if (iterator.hasNext()) {
return iterator.next().compareTo(other);
} else {
return other.toBoolean() ? -1 : 0;
}
}
@Override
public boolean toBoolean() {
return iterator().hasNext();
}
@Override
public double toNumber() {
final Iterator> iterator = iterator();
return iterator.hasNext() ? iterator.next().toNumber() : Double.NaN;
}
@Override
public String toString() {
final Iterator> iterator = iterator();
return iterator.hasNext() ? iterator.next().toString() : "";
}
@Override
public T visit(ViewVisitor visitor) throws XmlBuilderException {
return visitor.visit(this);
}
@Override
public IterableNodeView flatMap(
Function, ? extends IterableNodeView> fmap) {
return new FlatMapNodeSet(this, fmap);
}
private static final class EmptyNodeSet extends NodeSetView {
private static final long serialVersionUID = 1L;
@Override
public Iterator> iterator() {
return Collections.>emptyList().iterator();
}
}
private static final class IterableNodeSet extends NodeSetView {
private static final long serialVersionUID = 2L;
private final Set cache = new LinkedHashSet();
private final transient Iterable nodeSet;
private final transient Predicate filter;
private volatile boolean exhausted;
private IterableNodeSet(Iterable nodeSet, Predicate filter) {
this.nodeSet = nodeSet;
this.filter = filter;
}
@Override
public Iterator> iterator() {
return new IteratorImpl();
}
@SuppressWarnings({"StatementWithEmptyBody", "UnusedVariable"})
private void writeObject(ObjectOutputStream out) throws IOException {
for (NodeView ignored : this) {
// eagerly consume this node set to populate cache
}
out.defaultWriteObject();
}
private final class IteratorImpl extends PositionAwareIterator> {
private Iterator current = cache.iterator();
private boolean swapped;
@Override
public boolean hasNext() {
boolean hasNext = current.hasNext();
if (!hasNext && !swapped && !exhausted) {
current = new NodeSetIterator();
swapped = true;
hasNext = current.hasNext();
}
return hasNext;
}
@Override
public NodeView next(int position) {
return new NodeView(current.next(), position, hasNext());
}
}
private final class NodeSetIterator implements Iterator {
private final Iterator iterator = nodeSet.iterator();
private T nextElement;
private boolean hasNext;
private NodeSetIterator() {
nextMatch();
}
@Override
public boolean hasNext() {
return hasNext || !(exhausted = true);
}
@Override
public T next() {
return nextMatch();
}
@Override
public void remove() {
iterator.remove();
}
private T nextMatch() {
final T oldMatch = nextElement;
while (iterator.hasNext()) {
final T next = iterator.next();
if (filter.test(next) && cache.add(next)) {
hasNext = true;
nextElement = next;
return oldMatch;
}
}
hasNext = false;
return oldMatch;
}
}
}
private static final class FlatMapNodeSet extends NodeSetView {
private static final long serialVersionUID = 2L;
private final Set cache = new LinkedHashSet();
private final transient NodeSetView nodeSetView;
private final transient Function, ? extends IterableNodeView> fmap;
private volatile boolean exhausted;
private FlatMapNodeSet(
NodeSetView nodeSetView,
Function, ? extends IterableNodeView> fmap) {
this.nodeSetView = nodeSetView;
this.fmap = fmap;
}
@Override
public Iterator> iterator() {
return new IteratorImpl();
}
@SuppressWarnings({"StatementWithEmptyBody", "UnusedVariable"})
private void writeObject(ObjectOutputStream out) throws IOException {
for (NodeView ignored : this) {
// eagerly consume this node set to populate cache
}
out.defaultWriteObject();
}
private final class IteratorImpl extends PositionAwareIterator> {
private Iterator current = cache.iterator();
private boolean swapped;
@Override
public boolean hasNext() {
boolean hasNext = current.hasNext();
if (!hasNext && !swapped && !exhausted) {
current = new FlatMapIterator();
swapped = true;
hasNext = current.hasNext();
}
return hasNext;
}
@Override
@SuppressWarnings("unchecked")
public NodeView next(int position) {
return swapped
? ((NodeView) current.next()).copy(position, hasNext())
: new NodeView((T) current.next(), position, hasNext());
}
}
private final class FlatMapIterator extends ReadOnlyIterator> {
private final Iterator> nodeSetIterator = nodeSetView.iterator();
private Iterator> current =
Collections.>emptyList().iterator();
private NodeView nextElement;
private boolean hasNext;
private FlatMapIterator() {
nextMatch();
}
@Override
public boolean hasNext() {
return hasNext || !(exhausted = true);
}
@Override
public NodeView next() {
return nextMatch();
}
private NodeView nextMatch() {
final NodeView oldMatch = nextElement;
while (tryAdvance()) {
final NodeView next = current.next();
if (cache.add(next.getNode())) {
hasNext = true;
nextElement = next;
return oldMatch;
}
}
hasNext = false;
return oldMatch;
}
private boolean tryAdvance() {
boolean currentHasNext;
while (!(currentHasNext = current.hasNext()) && nodeSetIterator.hasNext()) {
current = fmap.apply(nodeSetIterator.next()).iterator();
}
return currentHasNext;
}
}
}
private abstract static class PositionAwareIterator extends ReadOnlyIterator {
private int position = 1;
@Override
public final T next() {
if (!hasNext()) {
throw new NoSuchElementException("No more elements");
}
return next(position++);
}
protected abstract T next(int position);
}
}
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