////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code for adherence to a set of rules.
   // Copyright (C) 2001-2019 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 com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import net.sf.saxon.Configuration;
  import net.sf.saxon.om.AxisInfo;
  import net.sf.saxon.om.GenericTreeInfo;
  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 root node of Xpath-tree.
   *
   */
  public class RootNode extends AbstractNode {
  
      /** Name of the root element. */
      private static final String ROOT_NAME = "ROOT";
  
      /** Constant for optimization. */
      private static final AbstractNode[] EMPTY_ABSTRACT_NODE_ARRAY = new AbstractNode[0];
  
      /** The ast node. */
      private final DetailAST detailAst;
  
      /**
       * Creates a new {@code RootNode} instance.
       *
       * @param detailAst reference to {@code DetailAST}
       */
      public RootNode(DetailAST detailAst) {
          super(new GenericTreeInfo(Configuration.newConfiguration()));
          this.detailAst = detailAst;
  
          createChildren();
      }
  
      /**
       * Iterates siblings of the current node and
       * recursively creates new Xpath-nodes.
       */
      private void createChildren() {
          DetailAST currentChild = detailAst;
          while (currentChild != null) {
              final ElementNode child = new ElementNode(this, this, currentChild);
              addChild(child);
              currentChild = currentChild.getNextSibling();
          }
      }
  
      /**
       * Returns attribute value. Throws {@code UnsupportedOperationException} because root node
       * has no attributes.
       * @param namespace namespace
       * @param localPart actual name of the attribute
       * @return attribute value
       */
      @Override
      public String getAttributeValue(String namespace, String localPart) {
          throw throwUnsupportedOperationException();
      }
  
      /**
       * Returns local part.
       * @return local part
       */
      // -@cs[SimpleAccessorNameNotation] Overrides method from the base class.
      // Issue: https://github.com/sevntu-checkstyle/sevntu.checkstyle/issues/166
      @Override
      public String getLocalPart() {
          return ROOT_NAME;
      }
  
      /**
       * Returns type of the node.
      * @return node kind
      */
     @Override
     public int getNodeKind() {
         return Type.DOCUMENT;
     }
 
     /**
      * Returns parent.
      * @return parent
      */
     @Override
     public NodeInfo getParent() {
         return null;
     }
 
     /**
      * Returns root of the tree.
      * @return root of the tree
      */
     @Override
     public NodeInfo getRoot() {
         return this;
     }
 
     /**
      * Returns string value.
      * @return string value
      */
     // -@cs[SimpleAccessorNameNotation] Overrides method from the base class.
     // Issue: https://github.com/sevntu-checkstyle/sevntu.checkstyle/issues/166
     @Override
     public String getStringValue() {
         return ROOT_NAME;
     }
 
     /**
      * Determines axis iteration algorithm. Throws {@code UnsupportedOperationException} in case,
      * when there is no axis iterator for given axisNumber.
      * @param axisNumber element from {@code AxisInfo}
      * @return {@code AxisIterator} object
      */
     @Override
     public AxisIterator iterateAxis(byte axisNumber) {
         final AxisIterator result;
         switch (axisNumber) {
             case AxisInfo.ANCESTOR:
             case AxisInfo.ATTRIBUTE:
             case AxisInfo.PARENT:
                 result = EmptyIterator.OfNodes.THE_INSTANCE;
                 break;
             case AxisInfo.ANCESTOR_OR_SELF:
             case AxisInfo.SELF:
                 try (AxisIterator iterator = SingleNodeIterator.makeIterator(this)) {
                     result = iterator;
                 }
                 break;
             case AxisInfo.CHILD:
                 if (hasChildNodes()) {
                     try (AxisIterator iterator = new ArrayIterator.OfNodes(
                             getChildren().toArray(EMPTY_ABSTRACT_NODE_ARRAY))) {
                         result = iterator;
                     }
                 }
                 else {
                     result = EmptyIterator.OfNodes.THE_INSTANCE;
                 }
                 break;
             case AxisInfo.DESCENDANT:
                 if (hasChildNodes()) {
                     try (AxisIterator iterator =
                                  new Navigator.DescendantEnumeration(this, false, true)) {
                         result = iterator;
                     }
                 }
                 else {
                     result = EmptyIterator.OfNodes.THE_INSTANCE;
                 }
                 break;
             case AxisInfo.DESCENDANT_OR_SELF:
                 try (AxisIterator iterator =
                              new Navigator.DescendantEnumeration(this, true, true)) {
                     result = iterator;
                 }
                 break;
             default:
                 throw throwUnsupportedOperationException();
         }
         return result;
     }
 
     /**
      * Returns line number.
      * @return line number
      */
     @Override
     public int getLineNumber() {
         return detailAst.getLineNo();
     }
 
     /**
      * Returns column number.
      * @return column number
      */
     @Override
     public int getColumnNumber() {
         return detailAst.getColumnNo();
     }
 
     /**
      * Getter method for token type.
      * @return token type
      */
     @Override
     public int getTokenType() {
         return TokenTypes.EOF;
     }
 
     /**
      * Returns underlying node.
      * @return underlying node
      */
     // -@cs[SimpleAccessorNameNotation] Overrides method from the base class.
     // Issue: https://github.com/sevntu-checkstyle/sevntu.checkstyle/issues/166
     @Override
     public DetailAST getUnderlyingNode() {
         return detailAst;
     }
 
     /**
      * Returns UnsupportedOperationException exception.
      * @return UnsupportedOperationException exception
      */
     private static UnsupportedOperationException throwUnsupportedOperationException() {
         return new UnsupportedOperationException("Operation is not supported");
     }
 
 }