/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.commons.jxpath.ri.model.jdom;
  
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.commons.jxpath.ri.compiler.NodeTest;
  import org.apache.commons.jxpath.ri.model.NodeIterator;
  import org.apache.commons.jxpath.ri.model.NodePointer;
  import org.jdom.Document;
  import org.jdom.Element;
  
  /**
   * An iterator of children of a JDOM Node.
   */
  public class JDOMNodeIterator implements NodeIterator {
  
      private final NodePointer parent;
      private final NodeTest nodeTest;
      private final boolean reverse;
      private int position;
      private int index;
      private List children;
      private Object child;
  
      /**
       * Constructs a new JDOMNodeIterator.
       *
       * @param parent    pointer
       * @param nodeTest  test
       * @param reverse   whether to iterate in reverse
       * @param startWith starting pointer
       */
      public JDOMNodeIterator(final NodePointer parent, final NodeTest nodeTest, final boolean reverse, final NodePointer startWith) {
          this.parent = parent;
          if (startWith != null) {
              this.child = startWith.getNode();
          }
          // TBD: optimize me for different node tests
          final Object node = parent.getNode();
          if (node instanceof Document) {
              this.children = ((Document) node).getContent();
          } else if (node instanceof Element) {
              this.children = ((Element) node).getContent();
          } else {
              this.children = Collections.EMPTY_LIST;
          }
          this.nodeTest = nodeTest;
          this.reverse = reverse;
      }
  
      @Override
      public NodePointer getNodePointer() {
          if (child == null) {
              if (!setPosition(1)) {
                  return null;
              }
              position = 0;
          }
          return new JDOMNodePointer(parent, child);
      }
  
      @Override
      public int getPosition() {
          return position;
      }
  
      /**
       * Iterate to next pointer.
       *
       * @return whether valid
       */
      private boolean next() {
          position++;
          if (!reverse) {
              if (position == 1) {
                  index = 0;
                  if (child != null) {
                      index = children.indexOf(child) + 1;
                  }
              } else {
                  index++;
              }
             for (; index < children.size(); index++) {
                 child = children.get(index);
                 if (testChild()) {
                     return true;
                 }
             }
             return false;
         }
         if (position == 1) {
             index = children.size() - 1;
             if (child != null) {
                 index = children.indexOf(child) - 1;
             }
         } else {
             index--;
         }
         for (; index >= 0; index--) {
             child = children.get(index);
             if (testChild()) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * This is actually never invoked during the normal evaluation of xpaths - an iterator is always going forward, never backwards. So, this is implemented
      * only for completeness and perhaps for those who use these iterators outside of XPath evaluation.
      *
      * @return boolean
      */
     private boolean previous() {
         position--;
         if (!reverse) {
             while (--index >= 0) {
                 child = children.get(index);
                 if (testChild()) {
                     return true;
                 }
             }
         } else {
             for (; index < children.size(); index++) {
                 child = children.get(index);
                 if (testChild()) {
                     return true;
                 }
             }
         }
         return false;
     }
 
     @Override
     public boolean setPosition(final int position) {
         while (this.position < position) {
             if (!next()) {
                 return false;
             }
         }
         while (this.position > position) {
             if (!previous()) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Test a child node.
      *
      * @return whether test passes.
      */
     private boolean testChild() {
         return JDOMNodePointer.testNode(parent, child, nodeTest);
     }
 }