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 java.util.Stack;
020
021import org.apache.commons.jxpath.ri.EvalContext;
022import org.apache.commons.jxpath.ri.compiler.NodeTest;
023import org.apache.commons.jxpath.ri.model.NodeIterator;
024import org.apache.commons.jxpath.ri.model.NodePointer;
025
026/**
027 * EvalContext that walks the "preceding::" and "following::" axes.
028 *
029 * @author Dmitri Plotnikov
030 * @version $Revision: 670727 $ $Date: 2008-06-23 22:10:38 +0200 (Mo, 23 Jun 2008) $
031 */
032public class PrecedingOrFollowingContext extends EvalContext {
033    private NodeTest nodeTest;
034    private boolean setStarted = false;
035    private Stack stack = null;
036    private NodePointer currentNodePointer;
037    private NodePointer currentRootLocation;
038    private boolean reverse;
039
040    /**
041     * Create a new PrecedingOrFollowingContext.
042     * @param parentContext parent context
043     * @param nodeTest test
044     * @param reverse whether to iterate in reverse order
045     */
046    public PrecedingOrFollowingContext(
047        EvalContext parentContext,
048        NodeTest nodeTest,
049        boolean reverse) {
050        super(parentContext);
051        this.nodeTest = nodeTest;
052        this.reverse = reverse;
053    }
054
055    public NodePointer getCurrentNodePointer() {
056        return currentNodePointer;
057    }
058
059    public int getDocumentOrder() {
060        return reverse ? -1 : 1;
061    }
062
063    public void reset() {
064        super.reset();
065        setStarted = false;
066    }
067
068    public boolean setPosition(int position) {
069        if (position < this.position) {
070            reset();
071        }
072
073        while (this.position < position) {
074            if (!nextNode()) {
075                return false;
076            }
077        }
078        return true;
079    }
080
081    public boolean nextNode() {
082        if (!setStarted) {
083            setStarted = true;
084            if (stack == null) {
085                stack = new Stack();
086            }
087            else {
088                stack.clear();
089            }
090            currentRootLocation = parentContext.getCurrentNodePointer();
091            NodePointer parent = currentRootLocation.getParent();
092            if (parent != null) {
093                // TBD: check type
094                stack.push(
095                    parent.childIterator(null, reverse, currentRootLocation));
096            }
097        }
098
099        while (true) {
100            if (stack.isEmpty()) {
101                currentRootLocation = currentRootLocation.getParent();
102
103                if (currentRootLocation == null
104                    || currentRootLocation.isRoot()) {
105                    break;
106                }
107
108                NodePointer parent = currentRootLocation.getParent();
109                if (parent != null) {
110                    stack.push(
111                        parent.childIterator(
112                            null,
113                            reverse,
114                            currentRootLocation));
115                }
116            }
117
118            while (!stack.isEmpty()) {
119                if (!reverse) {
120                    NodeIterator it = (NodeIterator) stack.peek();
121                    if (it.setPosition(it.getPosition() + 1)) {
122                        currentNodePointer = it.getNodePointer();
123                        if (!currentNodePointer.isLeaf()) {
124                            stack.push(
125                                currentNodePointer.childIterator(
126                                    null,
127                                    reverse,
128                                    null));
129                        }
130                        if (currentNodePointer.testNode(nodeTest)) {
131                            super.setPosition(getCurrentPosition() + 1);
132                            return true;
133                        }
134                    }
135                    else {
136                        // We get here only if the name test failed
137                        // and the iterator ended
138                        stack.pop();
139                    }
140                }
141                else {
142                    NodeIterator it = (NodeIterator) stack.peek();
143                    if (it.setPosition(it.getPosition() + 1)) {
144                        currentNodePointer = it.getNodePointer();
145                        if (!currentNodePointer.isLeaf()) {
146                            stack.push(
147                                currentNodePointer.childIterator(
148                                    null,
149                                    reverse,
150                                    null));
151                        }
152                        else if (currentNodePointer.testNode(nodeTest)) {
153                            super.setPosition(getCurrentPosition() + 1);
154                            return true;
155                        }
156                    }
157                    else {
158                        stack.pop();
159                        if (!stack.isEmpty()) {
160                            it = (NodeIterator) stack.peek();
161                            currentNodePointer = it.getNodePointer();
162                            if (currentNodePointer.testNode(nodeTest)) {
163                                super.setPosition(getCurrentPosition() + 1);
164                                return true;
165                            }
166                        }
167                    }
168                }
169            }
170        }
171        return false;
172    }
173}