/*
    * 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.
   */
  public class NullElementPointer extends CollectionPointer {
  
      private static final long serialVersionUID = 8714236818791036721L;
  
      /**
       * Constructs a new NullElementPointer.
       *
       * @param parent parent pointer
       * @param index  int
       */
      public NullElementPointer(final NodePointer parent, final int index) {
          super(parent, (Object) null);
          this.index = index;
      }
  
      @Override
      public String asPath() {
          final StringBuilder buffer = new StringBuilder();
          final 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();
      }
  
      @Override
      public NodePointer createPath(final JXPathContext context) {
          return parent.createChild(context, null, index);
      }
  
      @Override
      public NodePointer createPath(final JXPathContext context, final Object value) {
          return parent.createChild(context, null, index, value);
      }
  
      @Override
      public boolean equals(final Object object) {
          if (object == this) {
              return true;
          }
          if (!(object instanceof NullElementPointer)) {
              return false;
          }
          final NullElementPointer other = (NullElementPointer) object;
          return getImmediateParentPointer() == other.getImmediateParentPointer() && index == other.index;
      }
  
      @Override
      public Object getBaseValue() {
          return null;
      }
  
      @Override
      public Object getImmediateNode() {
          return null;
      }
  
      @Override
      public int getLength() {
          return 0;
      }
  
     @Override
     public QName getName() {
         return null;
     }
 
     /**
      * Gets the property pointer for this.
      *
      * @return PropertyPointer
      */
     public PropertyPointer getPropertyPointer() {
         return new NullPropertyPointer(this);
     }
 
     @Override
     public NodePointer getValuePointer() {
         return new NullPointer(this, getName());
     }
 
     @Override
     public int hashCode() {
         return getImmediateParentPointer().hashCode() + index;
     }
 
     @Override
     public boolean isActual() {
         return false;
     }
 
     @Override
     public boolean isCollection() {
         return false;
     }
 
     @Override
     public boolean isContainer() {
         return true;
     }
 
     @Override
     public boolean isLeaf() {
         return true;
     }
 
     @Override
     public void setValue(final Object value) {
         throw new UnsupportedOperationException("Collection element does not exist: " + this);
     }
 }