/*
    * 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.beans;
  
  import org.apache.commons.jxpath.JXPathContext;
  import org.apache.commons.jxpath.ri.QName;
  import org.apache.commons.jxpath.ri.model.NodePointer;
  
  /**
   * Used when there is a need to construct a Pointer for a collection element
   * that does not exist.  For example, if the path is "foo[3]", but the
   * collection "foo" only has one element or is empty or is null, the
   * NullElementPointer can be used to capture this situation without putting a
   * regular NodePointer into an invalid state.  Just create a NullElementPointer
   * with index 2 (= 3 - 1) and a "foo" pointer as the parent.
   *
   * @author Dmitri Plotnikov
   * @version $Revision: 652884 $ $Date: 2008-05-02 22:02:00 +0200 (Fr, 02 Mai 2008) $
   */
  public class NullElementPointer extends CollectionPointer {
  
      private static final long serialVersionUID = 8714236818791036721L;
  
      /**
       * Create a new NullElementPointer.
       * @param parent parent pointer
       * @param index int
       */
      public NullElementPointer(NodePointer parent, int index) {
          super(parent, (Object) null);
          this.index = index;
      }
  
      public QName getName() {
          return null;
      }
  
      public Object getBaseValue() {
          return null;
      }
  
      public Object getImmediateNode() {
          return null;
      }
  
      public boolean isLeaf() {
          return true;
      }
  
      public boolean isCollection() {
          return false;
      }
  
      /**
       * Get the property pointer for this.
       * @return PropertyPointer
       */
      public PropertyPointer getPropertyPointer() {
          return new NullPropertyPointer(this);
      }
  
      public NodePointer getValuePointer() {
          return new NullPointer(this, getName());
      }
  
      public void setValue(Object value) {
          throw new UnsupportedOperationException(
              "Collection element does not exist: " + this);
      }
  
      public boolean isActual() {
          return false;
      }
  
      public boolean isContainer() {
          return true;
      }
  
      public NodePointer createPath(JXPathContext context) {
          return parent.createChild(context, null, index);
      }
  
      public NodePointer createPath(JXPathContext context, Object value) {
          return parent.createChild(context, null, index, value);
      }
 
     public int hashCode() {
         return getImmediateParentPointer().hashCode() + index;
     }
 
     public boolean equals(Object object) {
         if (object == this) {
             return true;
         }
 
         if (!(object instanceof NullElementPointer)) {
             return false;
         }
 
         NullElementPointer other = (NullElementPointer) object;
         return getImmediateParentPointer() == other.getImmediateParentPointer()
                 && index == other.index;
     }
 
     public int getLength() {
         return 0;
     }
 
     public String asPath() {
         StringBuffer buffer = new StringBuffer();
         NodePointer parent = getImmediateParentPointer();
         if (parent != null) {
             buffer.append(parent.asPath());
         }
         if (index != WHOLE_COLLECTION) {
             // Address the list[1][2] case
             if (parent != null && parent.getIndex() != WHOLE_COLLECTION) {
                 buffer.append("/.");
             }
             else if (parent != null
                     && parent.getImmediateParentPointer() != null
                     && parent.getImmediateParentPointer().getIndex() != WHOLE_COLLECTION) {
                 buffer.append("/.");
             }
             buffer.append("[").append(index + 1).append(']');
         }
 
         return buffer.toString();
     }
 }