/**
 * Countdown from a given number.
 *
 * Usage:
 * 	var c = new Countdown(display,ondone,options);
 * 	c.start(10);
 * 	if (c.isRunning()) c.stop();
 * 	c.resume();
 *
 * Parameters:
 * 	display -- function to execute to display the count
 * 	        or DOM element ID where count is to appear
 *	        or DOM element
 * 	ondone -- function to execute when countdown reaches 0
 *	       or URL to redirect the browser when countdown is done
 * 	options -- optional options map
 *
 * Version 2.1
 * Copyright 2006,2010,  Mack Pexton, mackpexton.com
 * License http://www.opensource.org/licenses/mit-license.php
 */
(function(){
	var default_options = {
		prefix: '',		// prefix added to counter display
		suffix: '',		// suffix added to counter display
		frequency: 1000,	// 1 second in milliseconds
	};

	var countdown = function(display,ondone,options) {
		if (typeof display == 'function') { this.display = display; }
		else { this.el = (typeof display == 'string') ? document.getElementById(display) : display; }

		this.ondone = ondone;

		this.options = {};
		for (var p in default_options) { this.options[p] = default_options[p]; }
		if (options) { for (var p in options) { this.options[p] = options[p]; } }

		this.counter = 10;	// arbitrary default for safety
	}

	countdown.prototype = {
		start: function(n) {
			if (this.timerID) this.stop();
			if (n) this.counter = parseInt(n);
			var obj = this;
			var timer = function() {
				if (obj.display) obj.display(obj.counter);
				if (obj.el) obj.el.innerHTML = (obj.options.prefix ? obj.options.prefix : '') + obj.counter + (obj.options.suffix ? obj.options.suffix : '');
				if (obj.counter <= 0) {
					obj.timerID = null;
					if (typeof obj.ondone == 'function') obj.ondone(obj.el);
					if (typeof obj.ondone == 'string') window.location.href = obj.ondone;
					return;
				}
				obj.timerID = setTimeout(arguments.callee,obj.options.frequency);
				obj.counter -= 1;
			}
			timer();	// start countdown
		},
		stop: function() { if (this.timerID) { clearTimeout(this.timerID); this.timerID = null; } },
		resume: function() { this.start(); },
		isRunning: function() { return !!this.timerID; },
	};

	// Expose 
	window.Countdown = countdown;
})();