package list.dl;

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

class RightEndNode extends ANode
{
   final public static RightEndNode Singleton = new RightEndNode ();
	private RightEndNode ()
   {
   }

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

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

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

   /**
   * 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 parent the DLList that holds this ANode.
   */
   void setLeftRest (DLList dllist, DLList parent)
   {
      throw new IllegalStateException ("Should never call RightEnd.setLeftRest ()");
   }

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

   DLList rightRest (DLList parent)
   // Pre: this node is the right node of parent.
   {
      throw new NoSuchElementException ("RightEndNode.rightRest: 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 setLeftParent (DLList dllist)
   {
   }

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

   /**
   * 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 parent.
   * @param parent the DLList that holds this ANode.
   */
   void insertLeftFront (Object dat, DLList parent)
   {
      throw new IllegalStateException ("Should never call RightEnd.insertLeftFirst ()");
   }

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

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

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

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

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

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