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 */
017package org.apache.commons.jxpath.ri.axes;
018
019import org.apache.commons.jxpath.Pointer;
020import org.apache.commons.jxpath.ri.EvalContext;
021import org.apache.commons.jxpath.ri.compiler.NodeTest;
022import org.apache.commons.jxpath.ri.model.NodeIterator;
023import org.apache.commons.jxpath.ri.model.NodePointer;
024
025/**
026 * EvalContext that can walk the "child::", "following-sibling::" and
027 * "preceding-sibling::" axes.
028 *
029 * @author Dmitri Plotnikov
030 * @version $Revision: 652903 $ $Date: 2008-05-02 22:46:32 +0200 (Fr, 02 Mai 2008) $
031 */
032public class ChildContext extends EvalContext {
033    private NodeTest nodeTest;
034    private boolean startFromParentLocation;
035    private boolean reverse;
036    private NodeIterator iterator;
037
038    /**
039     * Create a new ChildContext.
040     * @param parentContext parent EvalContext
041     * @param nodeTest NodeTest
042     * @param startFromParentLocation whether to start from parent location
043     * @param reverse whether to iterate in reverse
044     */
045    public ChildContext(EvalContext parentContext, NodeTest nodeTest,
046            boolean startFromParentLocation, boolean reverse) {
047        super(parentContext);
048        this.nodeTest = nodeTest;
049        this.startFromParentLocation = startFromParentLocation;
050        this.reverse = reverse;
051    }
052
053    public NodePointer getCurrentNodePointer() {
054        if (position == 0 && !setPosition(1)) {
055            return null;
056        }
057        return iterator == null ? null : iterator.getNodePointer();
058    }
059
060    /**
061     * This method is called on the last context on the path when only
062     * one value is needed.  Note that this will return the whole property,
063     * even if it is a collection. It will not extract the first element
064     * of the collection.  For example, "books" will return the collection
065     * of books rather than the first book from that collection.
066     * @return Pointer
067     */
068    public Pointer getSingleNodePointer() {
069        if (position == 0) {
070            while (nextSet()) {
071                prepare();
072                if (iterator == null) {
073                    return null;
074                }
075                // See if there is a property there, singular or collection
076                NodePointer pointer = iterator.getNodePointer();
077                if (pointer != null) {
078                    return pointer;
079                }
080            }
081            return null;
082        }
083        return getCurrentNodePointer();
084    }
085
086    public boolean nextNode() {
087        return setPosition(getCurrentPosition() + 1);
088    }
089
090    public void reset() {
091        super.reset();
092        iterator = null;
093    }
094
095    public boolean setPosition(int position) {
096        int oldPosition = getCurrentPosition();
097        super.setPosition(position);
098        if (oldPosition == 0) {
099            prepare();
100        }
101        return iterator == null ? false : iterator.setPosition(position);
102    }
103
104    /**
105     * Allocates a PropertyIterator.
106     */
107    private void prepare() {
108        NodePointer parent = parentContext.getCurrentNodePointer();
109        if (parent == null) {
110            return;
111        }
112        NodePointer useParent = startFromParentLocation ? parent.getParent() : parent;
113        iterator = useParent.childIterator(nodeTest, reverse,
114                startFromParentLocation ? parent : null);
115    }
116}