package binaryTree.visitor;

import binaryTree.*;
import ordering.*;

/**
* Removes the root of the host's parent. The host's parent and the calling deletion
* algorithm are passed to this IVisitor in the constructor.
*/
public class LeftDeleter implements IVisitor
{
   /**
   * The parent of the host.
   */
   private BiTree _hostParent;

   /**
   * The BSTDeleter algorithm that calls this IVisitor.
   */
   private IVisitor _deleter;

	public LeftDeleter (BiTree parent, IVisitor del)
	{
      _hostParent = parent;
      _deleter = del;
   }

	/**
    * Asks the _hostParent's right subtree to help delete _hostParent's root.
	 * @param host the left subtree of _hostParent.
	 * @param input not used
	 * @return null.
	 */
	public Object emptyCase (BiTree host, Object input)
	{
		return _hostParent.getRightSubTree ().execute (new RightDelDontAsk (_hostParent, _deleter), null);
      // EXERCISE FOR STUDENTS: Replace RightDelDontAsk with an anonymous inner class.
	}

	/**
    * Finds the maximum value in the host.
    * Asks the _hostParent to set its root to this maximum value, and removes
    * this maximum value from the host.
	 * @param host the left subtree of _hostParent.
	 * @param input not used.
	 * @return null.
	 */
	public Object nonEmptyCase (BiTree host, Object input)
	{
      BiTree maxTree = (BiTree)host.execute (MaxTreeFinder.Singleton, null);
      Object max = maxTree.getRootDat();
      _hostParent.setRootDat (max);
      maxTree.execute (_deleter, max);
		return null;
	}
}