package binaryTree;

import binaryTree.visitor.*;

/**
 * Models the binary tree structure using the state pattern and the visitor pattern.
 * Provides only structural behaviors and a hook to execute any visitor algorithm.
 * <Pre>
 * Exercise: Override the toString() method.  Use helper methods if necessary.
 * </Pre>
 * @author Dung X. Nguyen - Copyright 1999 - All rights reserved.
 * @since 11/10/99
 * @dependency binaryTree.visitor.IVisitor uses
 * @dependency binaryTree.IVisitor 
 */
public class BiTree
{
	/**
	 * the state of this BiTree.
	 * @SBGen Variable (,state,,64)
	 */
	private ANode _rootNode;

   /**
   * Initializes this BiTree to the empty state.
   */
   public BiTree ()
   {
      _rootNode = EmptyNode.Singleton;
   }
   
   /**
   * Gets the root data of this BiTree if it exists.
   * @return the root data element of this BiTree if it exists.
   * @exception NoSuchElementException if this BiTree is empty.
   */
	public Object getRootDat()
	{
      return _rootNode.getRootDat (this);
	}

	/**
    * Sets the root data element to a given object.
	 * @param dat
    * @exception NoSuchElementException if this BiTree is empty.
	 */
	public void setRootDat(Object dat)
	{
      _rootNode.setRootDat (dat, this);
	}

   /**
   * Gets the left subtree of this BiTree if it exists.
   * @return the left subtree of this BiTree if it exists.
   * @exception NoSuchElementException if this BiTree is empty.
   */
	public BiTree getLeftSubTree()
	{
      return _rootNode.getLeftSubTree (this);
	}

   /**
   * Gets the right subtree of this BiTree if it exsists.
   * @return the right subtree of this BiTree if it exists.
   * @exception NoSuchElementException if this BiTree is empty.
   */
	public BiTree getRightSubTree()
	{
      return _rootNode.getRightSubTree (this);
	}

	/**
    * Attaches a new left subtree to the left of this BiTree. Allowing this BiTree
    * to grow to the left.
	 * @param biTree
    * @exception NoSuchElementException if this BiTree is empty.
	 */
	public void setLeftSubTree(BiTree biTree)
	{
      _rootNode.setLeftSubTree(biTree, this);
	}

	/**
    * Attaches a new right subtree to the left of this BiTree, allowing this BiTree
    * to grow to the right.
	 * @param biTree
    * @exception NoSuchElementException if this BiTree is empty.
	 */
	public void setRightSubTree(BiTree biTree)
	{
      _rootNode.setRightSubTree(biTree, this);
	}

	/**
    * Inserts a root element to this BiTree.
    * Allows for state change from empty to non-empty.
	 * @param dat
    * @exception IllegalStateException if this BiTree has more than one element.
	 */
	public void insertRoot(Object dat)
	{
      _rootNode.insertRoot(dat, this);
	}

	/**
	 * Removes and returns the root data element of this BiTree.
    * @return the root data element of this BiTree.
    * @exception NoSuchElementException if this BiTree is empty.
	 */
	public Object remRoot()
	{
      return _rootNode.remRoot(this);
	}

	/**
    * Hook to execute any algorithm that presents itself as a visitor to this BiTree.
    * Applies the visitor pattern.
	 * @param algo a visitor to a BiTree.
	 * @param input the input for the algo visitor.
    * @return the output for the execution of algo.
	 */
	public Object execute(IVisitor algo, Object input)
	{
      return _rootNode.execute(algo, input, this);
	}

   public String toString ()
   {
      return (String)execute (ToString.Singleton, null);
      // EXERCISE FOR STUDENTS: The above line of code does not conform to the state
      // pattern because it does not forward the request to the state.  Rewrite the
      // code to conform to the state pattern.  You will need to add appropriate methods
      // to the states.  Review what we did for toString() in AListFW and other linear
      // recursive structures.
   }

	/**
    * Changes this BiTree to a given new state (i.e. node).
	 * @param node a new root node (i.e.state) for this BiTree.
	 */
	final void setRootNode(ANode node)
	{
      _rootNode = node;
	}

   /**
	 * Returns the current state of this BiTree.
	 * @return the current root node (state) of this BiTree.
	 */
	final ANode getRootNode()
	{
      return _rootNode;
	}

	/**
    * Helper method for <code>remRoot ()</code>. Removes and return the root element of
    * the parent of this Bitree, asking the sibbling tree to do it if necessary.
	 * @param sis the sibbling of this BiTree.
	 * @param dad the parent of this BiTree.
    * @return the root data of the parent of this BiTree.
	 */
	final Object remParent(BiTree sis, BiTree dad)
	{
      return _rootNode.remParent (sis, dad, this);
	}

	/**
    * Helper method for <code>remParent ()</code>. Removes and return the root element of
    * the parent of this Bitree, <I>knowing</I> the sibbling tree is empty.
	 * @param dad the parent of this BiTree.
    * @return the root data of the parent of this BiTree.
	 */
	final Object remParentNode (BiTree dad)
	{
      return _rootNode.remParentNode (dad, this);
	}
}