001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.jxpath;
019
020import java.util.ArrayList;
021import java.util.Collections;
022import java.util.List;
023import java.util.stream.Collectors;
024
025/**
026 * A simple implementation of {@link NodeSet} that behaves as a collection of pointers.
027 */
028public class BasicNodeSet implements NodeSet {
029
030    private final List<Pointer> pointers = new ArrayList<>();
031    private List<Pointer> readOnlyPointers;
032    private List nodes;
033    private List values;
034
035    /**
036     * Constructs a new instance.
037     */
038    public BasicNodeSet() {
039        // empty
040    }
041
042    /**
043     * Add the specified NodeSet to this NodeSet.
044     *
045     * @param nodeSet to add
046     */
047    public void add(final NodeSet nodeSet) {
048        if (pointers.addAll(nodeSet.getPointers())) {
049            clear();
050        }
051    }
052
053    /**
054     * Add a pointer to this NodeSet.
055     *
056     * @param pointer to add
057     */
058    public void add(final Pointer pointer) {
059        if (pointers.add(pointer)) {
060            clear();
061        }
062    }
063
064    /**
065     * Clear cache list members.
066     */
067    private synchronized void clear() {
068        readOnlyPointers = null;
069        nodes = null;
070        values = null;
071    }
072
073    @Override
074    public synchronized List getNodes() {
075        if (nodes == null) {
076            nodes = Collections.unmodifiableList(pointers.stream().map(Pointer::getNode).collect(Collectors.toList()));
077        }
078        return nodes;
079    }
080
081    @Override
082    public synchronized List<Pointer> getPointers() {
083        if (readOnlyPointers == null) {
084            readOnlyPointers = Collections.unmodifiableList(pointers);
085        }
086        return readOnlyPointers;
087    }
088
089    @Override
090    public synchronized List getValues() {
091        if (values == null) {
092            values = Collections.unmodifiableList(pointers.stream().map(Pointer::getValue).collect(Collectors.toList()));
093        }
094        return values;
095    }
096
097    /**
098     * Remove a pointer from this NodeSet.
099     *
100     * @param pointer to remove
101     */
102    public void remove(final Pointer pointer) {
103        if (pointers.remove(pointer)) {
104            clear();
105        }
106    }
107
108    @Override
109    public String toString() {
110        return pointers.toString();
111    }
112}