package edu.umaine.cs.cos226;

import java.util.List;

/**
 * Represents a single node in a tree.
 */
public interface TreeNode<E> {

	/**
	 * @return This node's element
	 */
	public E getElement();

	/**
	 * Set this node's element to the argument.
	 * 
	 * @param elem
	 *            The element encapsulated by this node.
	 */
	public void setElement(E elem);

	/**
	 * Makes the given node a child of this node.
	 * 
	 * @param child
	 *            The node to add as a child; it must not be null.
	 */
	public void setChild(TreeNode<E> child);

	/**
	 * @return The child that is directly below this node or null if none
	 *         exists.
	 */
	public TreeNode<E> getFirstChild();
	
	/**
	 * @return All of this node's descendents that are directly below this node
	 *         in the tree's hierarchy. Children in the list should be ordered
	 *         according to the next sibling relationship.
	 */
	public List<TreeNode<E>> getChildren();

	/**
	 * Makes the known next sibling of this node <code>sibling</code>.
	 * 
	 * @param sibling
	 *            Will become this node's sibling; it must not be null.
	 */
	public void setNextSibling(TreeNode<E> sibling);

	/**
	 * @return The sibling of this node or null if none exists.
	 */
	public TreeNode<E> getNextSibling();

	/**
	 * @return The number of nodes belonging to this node's subtree, including
	 *         this node.
	 */
	public int size();

	/**
	 * The height of any node is 1 more than the height of its maximum-height
	 * child.
	 * 
	 * @return The height of this node in the tree.
	 */
	public int height();

	/**
	 * @return The elements in the subtree rooted at this node in an order that
	 *         ensures parents occur before any of their children.
	 */
	public List<TreeNode<E>> getPreOrder();

	/**
	 * @return The elements in the subtree rooted at this node in an order that
	 *         ensures parents occur after all of their children.
	 */
	public List<TreeNode<E>> getPostOrder();

}