package list.dl;

import list.dl.algo.IAlgoLeft;
import list.dl.algo.IAlgoRight;

   /**
   * Models a node in a doubly-linked list.  Represents the state of the owner list.
 * @author DXN
 * @version 3.2
 * @since 10/17/00
   */
abstract class ANode
{
      /**
	   * Returns the first element of the owner left (or right) list.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract Object getFirst(DLList owner);

	   abstract DLList getLeftRest(DLList owner);

   	abstract DLList getRightRest(DLList owner);

      /**
	   * Replaces the first element of the owner left (or right) list with the given data element.
	   * @param dat the element that is to replace the first element on the left (or right) of the owner list.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract void setFirst(Object dat, DLList owner);

	   /**
	   * Replaces the left list with the given list.
	   * @param dllist the new tail that is to replace the current one.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract void setLeftRest(DLList dllist, DLList owner);

	   /**
	   * Replaces the right list with the given list.
	   * @param dllist the new tail that is to replace the current one.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract void setRightRest(DLList dllist, DLList owner);

      /**
      * Sets the left owner link.
      */
      abstract void setLeftOwner (DLList dllist);

      /**
      * Sets the right owner link.
      */
      abstract void setRightOwner (DLList dllist);

	   /**
	   * Inserts a data element to the left front of the owner list.
	   * @param dat the element to be inserted to the left front of the owner.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract void insertLeftFront(Object dat, DLList owner);

	   /**
	   * Inserts a data element to the right front of the owner list.
	   * @param dat the element to be inserted to the right front of the owner.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract void insertRightFront(Object dat, DLList owner);


	   /**
	   * Removes and returns the first element on the left of the owner DLList.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract Object remLeftFront(DLList owner);

	   /**
	   * Removes and returns the first element on the right of the owner DLList.
      * @param owner the DLList that holds this ANode.
	   */
	   abstract Object remRightFront(DLList owner);

	   /**
	   * @param algo
	   * @param input
	   * @param owner
	   */
	   abstract Object executeLeft(IAlgoLeft algo, Object input, DLList owner);

	   /**
	   * @param algo
	   * @param inputParam
	   * @param owner
	   */
	   abstract Object executeRight(IAlgoRight algo, Object input, DLList owner);
}