package binaryTree.visitor;

import binaryTree.*;

/**
* Replaces the root of the input tree with the maximum of the host, or the minimum of the
* input's right subtree, if any such values exists, otherwise removes the input's root.
*/
public class LeftDeleter implements IVisitor
{
	public final static LeftDeleter Singleton = new LeftDeleter ();

	private LeftDeleter()
	{
   }

	/**
    * Asks the input's right subtree to delete the input's root.
	 * @param host the left subtree of input.
	 * @param input a <code>BiTree</code> with the binary search property.
	 * @return null.
	 */
	public Object emptyCase(BiTree host, Object input)
	{
		return ((BiTree)input).getRightSubTree().execute(RightDelDontAsk.Singleton, input);
	}

	/**
    * Asks the input to set its root to the maximum value in the host, and removes
    * this maximum value from the host.
	 * @param host the left subtree of input.
	 * @param input a <code>BiTree</code> with the binary search property.
	 * @return null.
	 */
	public Object nonEmptyCase(BiTree host, Object input)
	{
      BiTree parent = (BiTree)input;
      BiTree maxTree = (BiTree)host.execute (MaxTreeFinder.Singleton, null);
      Object max = maxTree.getRootDat();
      parent.setRootDat (max);
      maxTree.execute (OOBSTDeleter.Singleton, max);
		return null;
	}
}