///////////////////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
   // Copyright (C) 2001-2025 the original author or authors.
   //
   // This library is free software; you can redistribute it and/or
   // modify it under the terms of the GNU Lesser General Public
   // License as published by the Free Software Foundation; either
   // version 2.1 of the License, or (at your option) any later version.
   //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.xpath;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Optional;
  
  import com.puppycrawl.tools.checkstyle.xpath.iterators.DescendantIterator;
  import com.puppycrawl.tools.checkstyle.xpath.iterators.FollowingIterator;
  import com.puppycrawl.tools.checkstyle.xpath.iterators.PrecedingIterator;
  import com.puppycrawl.tools.checkstyle.xpath.iterators.ReverseListIterator;
  import net.sf.saxon.om.AxisInfo;
  import net.sf.saxon.om.NamespaceUri;
  import net.sf.saxon.om.NodeInfo;
  import net.sf.saxon.tree.iter.ArrayIterator;
  import net.sf.saxon.tree.iter.AxisIterator;
  import net.sf.saxon.tree.iter.EmptyIterator;
  import net.sf.saxon.tree.iter.SingleNodeIterator;
  import net.sf.saxon.tree.util.Navigator;
  import net.sf.saxon.type.Type;
  
  /**
   * Represents element node of Xpath-tree.
   */
  public abstract class AbstractElementNode extends AbstractNode {
  
      /** String literal for text attribute. */
      protected static final String TEXT_ATTRIBUTE_NAME = "text";
  
      /** Constant for optimization. */
      private static final AbstractNode[] EMPTY_ABSTRACT_NODE_ARRAY = new AbstractNode[0];
  
      /** Holder value for lazy creation of attribute node. */
      private static final AttributeNode ATTRIBUTE_NODE_UNINITIALIZED = new AttributeNode(null, null);
  
      /** The root node. */
      private final AbstractNode root;
  
      /** The parent of the current node. */
      private final AbstractNode parent;
  
      /** Depth of the node. */
      private final int depth;
  
      /** Represents index among siblings. */
      private final int indexAmongSiblings;
  
      /** The text attribute node. */
      private AttributeNode attributeNode = ATTRIBUTE_NODE_UNINITIALIZED;
  
      /**
       * Creates a new {@code AbstractElementNode} instance.
       *
       * @param root {@code Node} root of the tree
       * @param parent {@code Node} parent of the current node
       * @param depth the current node depth in the hierarchy
       * @param indexAmongSiblings the current node index among the parent children nodes
       */
      protected AbstractElementNode(AbstractNode root, AbstractNode parent,
              int depth, int indexAmongSiblings) {
          super(root.getTreeInfo());
          this.parent = parent;
          this.root = root;
          this.depth = depth;
          this.indexAmongSiblings = indexAmongSiblings;
      }
  
      /**
       * Creates {@code AttributeNode} object and returns it.
       *
       * @return attribute node if possible, otherwise the {@code null} value
       */
      protected abstract AttributeNode createAttributeNode();
  
      /**
       * Compares current object with specified for order.
       *
       * @param other another {@code NodeInfo} object
       * @return number representing order of current object to specified one
       */
      @Override
     public int compareOrder(NodeInfo other) {
         int result = 0;
         if (other instanceof AbstractNode node) {
             result = Integer.compare(depth, node.getDepth());
             if (result == 0) {
                 result = compareCommonAncestorChildrenOrder(this, other);
             }
         }
         return result;
     }
 
     /**
      * Walks up the hierarchy until a common ancestor is found.
      * Then compares topmost sibling nodes.
      *
      * @param first {@code NodeInfo} to compare
      * @param second {@code NodeInfo} to compare
      * @return the value {@code 0} if {@code first == second};
      *         a value less than {@code 0} if {@code first} should be first;
      *         a value greater than {@code 0} if {@code second} should be first.
      */
     private static int compareCommonAncestorChildrenOrder(NodeInfo first, NodeInfo second) {
         NodeInfo child1 = first;
         NodeInfo child2 = second;
         while (!child1.getParent().equals(child2.getParent())) {
             child1 = child1.getParent();
             child2 = child2.getParent();
         }
         final int index1 = ((AbstractElementNode) child1).indexAmongSiblings;
         final int index2 = ((AbstractElementNode) child2).indexAmongSiblings;
         return Integer.compare(index1, index2);
     }
 
     /**
      * Getter method for node depth.
      *
      * @return depth
      */
     @Override
     public int getDepth() {
         return depth;
     }
 
     /**
      * Returns attribute value.
      *
      * @param namespace namespace
      * @param localPart actual name of the attribute
      * @return attribute value or null if the attribute was not found
      */
     @Override
     public String getAttributeValue(NamespaceUri namespace, String localPart) {
         final String result;
         if (TEXT_ATTRIBUTE_NAME.equals(localPart)) {
             result = Optional.ofNullable(getAttributeNode())
                 .map(AttributeNode::getStringValue)
                 .orElse(null);
         }
         else {
             result = null;
         }
         return result;
     }
 
     /**
      * Returns type of the node.
      *
      * @return node kind
      */
     @Override
     public int getNodeKind() {
         return Type.ELEMENT;
     }
 
     /**
      * Returns parent.
      *
      * @return parent
      */
     @Override
     public NodeInfo getParent() {
         return parent;
     }
 
     /**
      * Returns root.
      *
      * @return root
      */
     @Override
     public AbstractNode getRoot() {
         return root;
     }
 
     /**
      * Determines axis iteration algorithm. Throws {@code UnsupportedOperationException} in case,
      * when there is no axis iterator for given axisNumber.
      *
      * <p>Reason of suppression for resource, IOResourceOpenedButNotSafelyClosed:
      * {@link AxisIterator} implements {@link java.io.Closeable} interface,
      * but none of the subclasses of the {@link AxisIterator}
      * class has non-empty {@code close()} method.
      *
      * @param axisNumber element from {@code AxisInfo}
      * @return {@code AxisIterator} object
      */
     @Override
     public AxisIterator iterateAxis(int axisNumber) {
         return switch (axisNumber) {
             case AxisInfo.ANCESTOR -> new Navigator.AncestorEnumeration(this, false);
             case AxisInfo.ANCESTOR_OR_SELF -> new Navigator.AncestorEnumeration(this, true);
             case AxisInfo.ATTRIBUTE -> SingleNodeIterator.makeIterator(getAttributeNode());
             case AxisInfo.CHILD -> {
                 if (hasChildNodes()) {
                     yield new ArrayIterator.OfNodes<>(
                             getChildren().toArray(EMPTY_ABSTRACT_NODE_ARRAY));
                 }
                 yield EmptyIterator.ofNodes();
             }
             case AxisInfo.DESCENDANT -> {
                 if (hasChildNodes()) {
                     yield new DescendantIterator(this, DescendantIterator.StartWith.CHILDREN);
                 }
                 yield EmptyIterator.ofNodes();
             }
             case AxisInfo.DESCENDANT_OR_SELF ->
                 new DescendantIterator(this, DescendantIterator.StartWith.CURRENT_NODE);
             case AxisInfo.PARENT -> SingleNodeIterator.makeIterator(parent);
             case AxisInfo.SELF -> SingleNodeIterator.makeIterator(this);
             case AxisInfo.FOLLOWING_SIBLING -> getFollowingSiblingsIterator();
             case AxisInfo.PRECEDING_SIBLING -> getPrecedingSiblingsIterator();
             case AxisInfo.FOLLOWING -> new FollowingIterator(this);
             case AxisInfo.PRECEDING -> new PrecedingIterator(this);
             default -> throw throwUnsupportedOperationException();
         };
     }
 
     /**
      * Returns preceding sibling axis iterator.
      *
      * <p>Reason of suppression for resource, IOResourceOpenedButNotSafelyClosed:
      * {@link AxisIterator} implements {@link java.io.Closeable} interface,
      * but none of the subclasses of the {@link AxisIterator}
      * class has non-empty {@code close()} method.
      *
      * @return iterator
      */
     private AxisIterator getPrecedingSiblingsIterator() {
         final AxisIterator result;
         if (indexAmongSiblings == 0) {
             result = EmptyIterator.ofNodes();
         }
         else {
             result = new ReverseListIterator(getPrecedingSiblings());
         }
         return result;
     }
 
     /**
      * Returns following sibling axis iterator.
      *
      * <p>Reason of suppression for resource, IOResourceOpenedButNotSafelyClosed:
      * {@link AxisIterator} implements {@link java.io.Closeable} interface,
      * but none of the subclasses of the {@link AxisIterator}
      * class has non-empty {@code close()} method.
      *
      * @return iterator
      */
     private AxisIterator getFollowingSiblingsIterator() {
         final AxisIterator result;
         if (indexAmongSiblings == parent.getChildren().size() - 1) {
             result = EmptyIterator.ofNodes();
         }
         else {
             result = new ArrayIterator.OfNodes<>(
                     getFollowingSiblings().toArray(EMPTY_ABSTRACT_NODE_ARRAY));
         }
         return result;
     }
 
     /**
      * Returns following siblings of the current node.
      *
      * @return siblings
      */
     private List<AbstractNode> getFollowingSiblings() {
         final List<AbstractNode> siblings = parent.getChildren();
         return siblings.subList(indexAmongSiblings + 1, siblings.size());
     }
 
     /**
      * Returns preceding siblings of the current node.
      *
      * @return siblings
      */
     private List<AbstractNode> getPrecedingSiblings() {
         final List<AbstractNode> siblings = parent.getChildren();
         return Collections.unmodifiableList(siblings.subList(0, indexAmongSiblings));
     }
 
     /**
      * Checks if token type supports {@code @text} attribute,
      * extracts its value, creates {@code AttributeNode} object and returns it.
      * Value can be accessed using {@code @text} attribute.
      *
      * @return attribute node if possible, otherwise the {@code null} value
      */
     private AttributeNode getAttributeNode() {
         if (attributeNode == ATTRIBUTE_NODE_UNINITIALIZED) {
             attributeNode = createAttributeNode();
         }
         return attributeNode;
     }
 
     /**
      * Returns UnsupportedOperationException exception.
      *
      * @return UnsupportedOperationException exception
      */
     private static UnsupportedOperationException throwUnsupportedOperationException() {
         return new UnsupportedOperationException("Operation is not supported");
     }
 }