/*
 * Created on Jul 6, 2004
 */
package treeDraw;

/** A node suitable for use by linked lists, binary trees, general trees,
 * or any such structure characterized by a number of links to other
 * linked nodes.
 * <br />
 * Implementing classes should provide constructors of these forms:
 * <br />
 * public classname(type anObject);
 * <br />
 *
 * public classname(type anObject, ILink next); //set child(0)
 * <br />
 * public classname(type anObject, ILink left, ILink right); set child(0) and (1)
 * <br />
 * @author dickey
 */
public interface INode {
	
	/** A convenience method which should return the same as getChild(0)
	 * @return a node (which may be null)
	 */
	INode getLeft();	
	
	/** A convenience method which should return the same as getChild(1)
	 * @return a node (which may be null)
	 */
	INode getRight();
	
	/** Tells how many children this node may have.  For example, for a
	 * a binary tree, it would be a constant 2. 
	 * @return the maximum number of nodes allowed for this child, or
	 * -1 if there is no limit.
	 */
	int getMaxChildCount();
		
	/** Tells how many non-null children this node currently has. 
	 * @return number of non-null children, always >= 0.
	 */
	int getChildCount();
		
	/** Returns the node indicated, which may be null.  Nodes are
	 * numbered from 0 left to right.  In a binary tree, 
	 * getChild(0) should return the left node and getChild(1)
	 * should return the right node.
	 * @param childIndex a value >= and < getMaxChildCount.
	 * @return the node, which may be null.
	 */
	INode getChild(int childIndex);
	
	/** Convenience method for setChild(0, leftNode).
	 * 
	 * @param leftNode any node, which might be null.
	 */
	void setLeft(INode leftNode);
	
	/** Convenience method for setChild(1,rightNode).
	 * 
	 * @param rightNode any node, which might be null.
	 */
	void setRight(INode rightNode);
	
	/** Set the child to the given node value.  Nodes are numbered
	 * left to right from 0.  The node may be null.
	 * @param link
	 * @param childIndex
	 */
	void setChild(INode link, int childIndex);
	
	/** Set the element value of this node, replaced whatever
	 * was there.
	 * @param anObject any object, which may be null.
	 */
	void setValue(Object anObject);
	
	/** Get the element value of this node, which may be null.
	 * 
	 * @return the value currently stored at this node.  No changes
	 * are made to the node.
	 */
	Object getValue();
}