//
// This work is licensed under the Creative Commons Attribution 2.5 License. To 
// view a copy of this license, visit
// http://creativecommons.org/licenses/by/2.5/
// or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San
// Francisco, California, 94105, USA.
//
// All copies and derivatives of this source must contain the license statement 
// above and the following attribution:
//
// Author: Kyle Scholz      http://kylescholz.com/
// Copyright: 2006
//

/**
 * A very shallow extend() method. Simply inherit properties of the indicated class
 * when they don't conflict with anything already in our prototype.
 */
Function.prototype.extend = function( inheritFrom ) {
	for( property in inheritFrom.prototype ) {
		if ( !( property in this.prototype ) ) {
			this.prototype[property] = inheritFrom.prototype[property];
		}
	}
}

/**
 * GraphModel:
 * 
 * Defines a prototype for GraphModel implementations.
 * 
 * TODO: @extends TimerListener
 */
var GraphModel = function(){};
GraphModel.prototype = {
	
	// A collection of GraphModelListeners that want to receive updates from this graph
	subscribers: new Array(),
	
	// A collection  of root nodes
	updateQueue: new Array(),
	
	//
	nextUID: 0,
	
	/*
	 * Initialize the instance.
	 */
	initialize: function( frameWidth, frameHeight ) {
		this['frameWidth'] = frameWidth;
		this['frameHeight'] = frameHeight;
	},

	/*
	 * Update nodes in updateQueue.
	 * 
	 * @overrides TimerListener.update
	 */		
	update: function() {
		throw( "update: Method not implemented.")
	},

	/*
	 * Add a subscriber.
	 * 
	 * TODO: verify that listener conforms to interface
	 */
	subscribe: function( graphModelListener ) {
		this['subscribers'].push( graphModelListener );
	},
	
	/*
	 * Add a node to the Graph. This method must be overriden.
	 * 
	 * @throws "Method not implemented."
	 */
	addNode: function() {
		throw( "addNode: Method not implemented.")
	},
	
	/*
	 * Add a new edge to the Graph. This method must be overriden.
	 * 
	 * @throws "Method not implemented."
	 */
	addEdge: function() {
		throw( "addEdge: Method not implemented.")
	}
	
}