package list.dl;

import java.util.NoSuchElementException;
import list.dl.algo.IAlgoLeft;
import list.dl.algo.IAlgoRight;

/**
* Singleton pattern representing the right end node of a doubly-linked list.
 * @author DXN
 * @version 3.2
 * @since 10/17/00
*/
class RightEndNode extends ANode
{
   final static RightEndNode Singleton = new RightEndNode ();
	private RightEndNode ()
   {
   }

   /**
   * Throws IllegalStateException.
   * @param owner
   * @return
   */
   Object getFirst (DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.getFirst ()");
   }

   /**
   * Throws IllegalStateException.  Can never be a the left node of a DLList
   * @param owner
   * @return
   */
   DLList getLeftRest (DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.getLeftRest ()");
   }

   /**
   * Throws IllegalStateException.
   * @param dat the element that is to replace the current first element on the left/right of the owner list.
   * @param owner the DLList that holds this ANode.
   */
   void setFirst (Object dat, DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.setFirst ()");
   }

   /**
   * Throws IllegalStateException.  Can never be a the left node of a DLList
   * @param dllist the new tail that is to replace the current one.
   * @param owner the DLList that holds this ANode.
   */
   void setLeftRest (DLList dllist, DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.setLeftRest ()");
   }

   DLList getRightRest (DLList owner)
   // Pre: this node is the right node of owner.
   {
      throw new NoSuchElementException ("RightEndNode.getRightRest: right end has no right tail.");
   }

   /**
   * Does nothing.  The right node is dessigned a singleton to be shared.  There is no left link.
   * @param dllist
   */
   void setLeftOwner (DLList dllist)
   {
   }

   /**
   * Throws IllegalStateException.
   * @param dllist
   */
   void setRightOwner (DLList dllist)
   {
      throw new IllegalStateException ("Should never call RightEnd.setRightOwner ()");
   }

   /**
   * Throws IllegalStateException.  Can never be a the left node of a DLList
   * @param dat the element to be inserted to the left front of the owner.
   * @param owner the DLList that holds this ANode.
   */
   void insertLeftFront (Object dat, DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.insertLeftFirst ()");
   }

   /**
   * Throws IllegalStateException.  Can never be a the left node of a DLList
   * @param owner the DLList that holds this ANode.
   * @return
   */
   Object remLeftFront (DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.remLeftFront ()");
   }

   /**
   * @param dat
   */
   void insertRightFront (Object dat, DLList owner)
   // Pre: this node is the right node of owner.
   // Post: this node is the right node of owner.getRightRest ().
   {
      new DataNode (dat, owner, new DLList ());
         /* old style:
         DLList newList = new DLList ();
         DataNode newNode = new DataNode (dat, owner, newList);
         newList.setLeftNode (newNode);
         owner.setRightNode (newNode);
         */
   }

   Object remRightFront (DLList owner)
   // Pre: this node is the right node of owner.
   {
      throw new NoSuchElementException ("RightEndNode.remRightFront: Right end has no data.");
   }

   /**
   * Throws new NoSuchElementException.
   * @param dat
   */
   void setRightFirst (Object dat, DLList owner)
   // Pre: this node is the right node of owner.
   {
      throw new NoSuchElementException ("RightEndNode.setRightFirst: Right end has no data.");
   }

   /**
   * Throws new NoSuchElementException.
   * @param dllist
   */
   void setRightRest (DLList dllist, DLList owner)
   // Pre: this node is the right node of owner.
   {
      throw new NoSuchElementException ("RightEndNode.setRightRest: Right end has no right tail.");
   }

   /**
   * @param algo
   * @param input
   * @param owner
   */
   Object executeRight (IAlgoRight algo, Object input, DLList owner)
   // Pre: this node is the right node of ownerList.
   {
      return algo.rightEndCase (owner, input);
   }
   
   /**
   * Throws IllegalStateException.  Can never be a the left node of a DLList
   * @param algo
   * @param input
   * @param owner
   * @return
   */
   Object executeLeft (IAlgoLeft algo, Object input, DLList owner)
   {
      throw new IllegalStateException ("Should never call RightEnd.executeLeft ()");
   }
}