Source code

001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.xpath;
021
022import com.puppycrawl.tools.checkstyle.xpath.iterators.DescendantIterator;
023import net.sf.saxon.Configuration;
024import net.sf.saxon.om.AxisInfo;
025import net.sf.saxon.om.GenericTreeInfo;
026import net.sf.saxon.om.NamespaceUri;
027import net.sf.saxon.om.NodeInfo;
028import net.sf.saxon.tree.iter.ArrayIterator;
029import net.sf.saxon.tree.iter.AxisIterator;
030import net.sf.saxon.tree.iter.EmptyIterator;
031import net.sf.saxon.tree.iter.SingleNodeIterator;
032import net.sf.saxon.type.Type;
033
034/**
035 * Represents root node of Xpath-tree.
036 */
037public abstract class AbstractRootNode extends AbstractNode {
038
039 /** Name of the root element. */
040 private static final String ROOT_NAME = "ROOT";
041
042 /** Constant for optimization. */
043 private static final AbstractNode[] EMPTY_ABSTRACT_NODE_ARRAY = new AbstractNode[0];
044
045 /**
046 * Creates a new {@code AbstractRootNode} instance.
047 */
048 protected AbstractRootNode() {
049 super(new GenericTreeInfo(Configuration.newConfiguration()));
050 }
051
052 /**
053 * Compares current object with specified for order.
054 * Throws {@code UnsupportedOperationException} because functionality not required here.
055 *
056 * @param nodeInfo another {@code NodeInfo} object
057 * @return number representing order of current object to specified one
058 */
059 @Override
060 public int compareOrder(NodeInfo nodeInfo) {
061 throw throwUnsupportedOperationException();
062 }
063
064 /**
065 * Returns attribute value. Throws {@code UnsupportedOperationException} because root node
066 * has no attributes.
067 *
068 * @param namespace namespace
069 * @param localPart actual name of the attribute
070 * @return attribute value
071 */
072 @Override
073 public String getAttributeValue(NamespaceUri namespace, String localPart) {
074 throw throwUnsupportedOperationException();
075 }
076
077 /**
078 * Returns local part.
079 *
080 * @return local part
081 */
082 @Override
083 public String getLocalPart() {
084 return ROOT_NAME;
085 }
086
087 /**
088 * Returns type of the node.
089 *
090 * @return node kind
091 */
092 @Override
093 public int getNodeKind() {
094 return Type.DOCUMENT;
095 }
096
097 /**
098 * Returns parent.
099 *
100 * @return parent
101 */
102 @Override
103 public NodeInfo getParent() {
104 return null;
105 }
106
107 /**
108 * Returns root of the tree.
109 *
110 * @return root of the tree
111 */
112 @Override
113 public NodeInfo getRoot() {
114 return this;
115 }
116
117 /**
118 * Determines axis iteration algorithm. Throws {@code UnsupportedOperationException} in case,
119 * when there is no axis iterator for given axisNumber.
120 *
121 * @param axisNumber element from {@code AxisInfo}
122 * @return {@code AxisIterator} object
123 */
124 @Override
125 public AxisIterator iterateAxis(int axisNumber) {
126 return switch (axisNumber) {
127 case AxisInfo.ANCESTOR,
128 AxisInfo.PARENT,
129 AxisInfo.FOLLOWING,
130 AxisInfo.FOLLOWING_SIBLING,
131 AxisInfo.PRECEDING,
132 AxisInfo.PRECEDING_SIBLING -> EmptyIterator.ofNodes();
133
134 case AxisInfo.ANCESTOR_OR_SELF,
135 AxisInfo.SELF -> SingleNodeIterator.makeIterator(this);
136
137 case AxisInfo.CHILD -> {
138 if (hasChildNodes()) {
139 yield new ArrayIterator.OfNodes<>(
140 getChildren().toArray(EMPTY_ABSTRACT_NODE_ARRAY));
141 }
142 yield EmptyIterator.ofNodes();
143 }
144
145 case AxisInfo.DESCENDANT -> {
146 if (hasChildNodes()) {
147 yield new DescendantIterator(this, DescendantIterator.StartWith.CHILDREN);
148 }
149 yield EmptyIterator.ofNodes();
150 }
151
152 case AxisInfo.DESCENDANT_OR_SELF ->
153 new DescendantIterator(this, DescendantIterator.StartWith.CURRENT_NODE);
154
155 default -> throw throwUnsupportedOperationException();
156 };
157 }
158
159 /**
160 * Getter method for node depth.
161 *
162 * @return always {@code 0}
163 */
164 @Override
165 public int getDepth() {
166 return 0;
167 }
168
169 /**
170 * Returns UnsupportedOperationException exception.
171 *
172 * @return UnsupportedOperationException exception
173 */
174 private static UnsupportedOperationException throwUnsupportedOperationException() {
175 return new UnsupportedOperationException("Operation is not supported");
176 }
177
178}