// Taken from MDC @ Core_JavaScript_1.5_Reference/Objects/Date.
function dateToISO8601(d) {
  function pad(n) { return n < 10 ? '0' + n : n; }

  return (d.getUTCFullYear() + '-' +
          pad(d.getUTCMonth() + 1) + '-' +
          pad(d.getUTCDate()) + 'T' + 
          pad(d.getUTCHours()) + ':' +
          pad(d.getUTCMinutes()) + ':' +
          pad(d.getUTCSeconds()) + 'Z');
}

// Taken from http://delete.me.uk/2005/03/iso8601.html
function dateFromISO8601(string) {
    var regexp = "([0-9]{4})(-([0-9]{2})(-([0-9]{2})" +
        "(T([0-9]{2}):([0-9]{2})(:([0-9]{2})(\.([0-9]+))?)?" +
        "(Z|(([-+])([0-9]{2}):([0-9]{2})))?)?)?)?";
    var d = string.match(new RegExp(regexp));

    var offset = 0;
    var date = new Date(d[1], 0, 1);

    if (d[3]) { date.setMonth(d[3] - 1); }
    if (d[5]) { date.setDate(d[5]); }
    if (d[7]) { date.setHours(d[7]); }
    if (d[8]) { date.setMinutes(d[8]); }
    if (d[10]) { date.setSeconds(d[10]); }
    if (d[12]) { date.setMilliseconds(Number("0." + d[12]) * 1000); }
    if (d[14]) {
        offset = (Number(d[16]) * 60) + Number(d[17]);
        offset *= ((d[15] == '-') ? 1 : -1);
    }

    offset -= date.getTimezoneOffset();
    var time = (Number(date) + (offset * 60 * 1000));
    date.setTime(Number(time));
    return date;
}

/*
 * JavaScript Pretty Date
 * Copyright (c) 2008 John Resig (jquery.com)
 * Licensed under the MIT license.
 */

// Takes an ISO time and returns a string representing how
// long ago the date represents.
function prettyDate(time){
	var date = dateFromISO8601(time),
		diff = (((new Date()).getTime() - date.getTime()) / 1000),
		day_diff = Math.floor(diff / 86400);
			
	if ( isNaN(day_diff) || day_diff < 0 || day_diff >= 31 )
		return;
			
	return day_diff == 0 && (
			diff < 60 && "just now" ||
			diff < 120 && "1 minute ago" ||
			diff < 3600 && Math.floor( diff / 60 ) + " minutes ago" ||
			diff < 7200 && "1 hour ago" ||
			diff < 86400 && Math.floor( diff / 3600 ) + " hours ago") ||
		day_diff == 1 && "Yesterday" ||
		day_diff < 7 && day_diff + " days ago" ||
		day_diff < 31 && Math.ceil( day_diff / 7 ) + " weeks ago";
}

// If jQuery is included in the page, adds a jQuery plugin to handle it as well
if ( typeof jQuery != "undefined" )
	jQuery.fn.prettyDate = function(){
		return this.each(function(){
			var date = prettyDate(this.title);
			if ( date )
				jQuery(this).text( date );
		});
	};