/**
 * Static utility class containing date-related functionality.
 * @static
 */
HD.util.Date = {
	/** The number of milliseconds in a day. */
	MILLISECONDS_PER_HOUR	: 60 * 60 * 1000,
	MILLISECONDS_PER_DAY	: 24 * 60 * 60 * 1000,
	MILLISECONDS_PER_YEAR	: 365 * 24 * 60 * 60 * 1000,
	
	CENTRAL_DAYTIME_TIME_OFFSET_FOR_DAYTIME : 5 * 60 * 60 * 1000 * -1,
	CENTRAL_DAYTIME_TIME_OFFSET_FOR_STANDARD : 6 * 60 * 60 * 1000 * -1,
	CENTRAL_STANDARD_TIME_OFFSET_FOR_DAYTIME : 5 * 60 * 60 * 1000 * -1,
	CENTRAL_STANDARD_TIME_OFFSET_FOR_STANDARD : 6 * 60 * 60 * 1000 * -1,
	
	getCentralTimeOffset : function(testDate) {
		var isTestDateStandard = testDate.toString().match(/Standard/);
		var isTodayStandard = new Date().toString().match(/Standard/);;
		
		if(!isTodayStandard && !isTestDateStandard) {
			return HD.util.Date.CENTRAL_DAYTIME_TIME_OFFSET_FOR_DAYTIME;
		} else if(!isTodayStandard && isTestDateStandard) {
			return HD.util.Date.CENTRAL_DAYTIME_TIME_OFFSET_FOR_STANDARD;
		} else if(isTodayStandard && !isTestDateStandard) {
			return HD.util.Date.CENTRAL_STANDARD_TIME_OFFSET_FOR_DAYTIME;
		} else if(isTodayStandard && isTestDateStandard) {
			return HD.util.Date.CENTRAL_STANDARD_TIME_OFFSET_FOR_STANDARD;
		}
		return 0;
	},
	
	/**
	 * Returns the number of days between two dates.
	 * 
	 * @param {Date} startDate the start date
	 * @param {Date} endDate the end date
	 * @return the number of days
	 */
	getNumberOfDays : function(startDate, endDate) {
		return Math.round((startDate.getTime() - endDate.getTime()) / this.MILLISECONDS_PER_DAY);
	},
	
	/**
	 * Constructs a date based on the provide time in milliseconds.
	 * 
	 * @param {int} timeInMillis the time expressed in milliseconds
	 * @return date object set to the provided time
	 */
	getDate : function(timeInMillis) {
		var date = new Date();
		date.setTime(timeInMillis);
		return date;
	},

	setDate : function(month, day, year) {
		var date = new Date();
		date.setFullYear(year, month - 1, day);
		return date;
	},
	
	isFuture : function(date) {
		return (new Date().getTime() - date.getTime()) < 0;
	},
	
	isPast : function(date) {
		return (new Date().getTime() - date.getTime()) > 0;
	},
	
	/**
	 * Formats a list of days.
	 * 
	 * @param {Array} days the list of days to format
	 * @param {String} format the date format
	 * @param {String} separator the separator between formatted days
	 * @return formatted dates string
	 */
	formatDaySpan : function(days, format, separator) {
		var formatted = [];
		for(var i = 0, len = days.length; i < len; i++) {
			formatted.push(this.format(days[i], format));
		}
		
		return formatted.join(separator);
	},
	
	/**
	 * Formats a range of days.
	 * 
	 * @param {Date} startDate the start date
	 * @param {Date} endDate the end date
	 * @param {String} format the format to use
	 * @return formatted dates string
	 */
	formatSpanList : function(startDate, endDate, format) {
		if(startDate == null || endDate == null || format == null) {
			return "";
		}
		var dates = [];
		
		var tempDate = this.getDate(startDate.getTime());
		
		dates.push(this.getDate(tempDate.getTime()));
		
		while(tempDate.getFullYear() != endDate.getFullYear() 
				|| tempDate.getMonth() != endDate.getMonth()
					|| tempDate.getDate() != endDate.getDate()) {
			tempDate.setTime(tempDate.getTime() + this.MILLISECONDS_PER_DAY);
			dates.push(this.getDate(tempDate.getTime()));
		}
		
		return this.formatList(dates, format);
	},
	
	/**
	 * Returns an array of dates formatted according to the provided format.
	 * 
	 * @param {Array} dates the list of dates to format
	 * @param {String} format the format to use
	 * @return list of formatted dates
	 */
	formatList : function(dates, format) {
    	var datesList = [];
    	
    	for(var i = 0, len = dates.length; i < len; i++) {
    		datesList.push(this.format(dates[i], format));
		}
    	
    	return datesList;
	},
	
	/**
	 * Formats date spans in 'mmm d, yyyy - mmm d, yyyy' format.
	 * 
	 * @param {Date} d1 starting date
	 * @param {Date} d2 ending date
	 */
	formatSpan : function(d1, d2) {
		if(d1 == null || d2 == null) {
			return "";
		}
		
		var date1 = d1.getDate();
		var month1 = d1.getMonth();
		var year1 = d1.getFullYear();
		
		var date2 = d2.getDate();
		var month2 = d2.getMonth();
		var year2 = d2.getFullYear();
		
		var dateString = "";
		
		if(date1 == date2 && month1 == month2 && year1 == year2) {
			dateString = this.format(d1, "mmm d',' yyyy");
		} else if(month1 == month2 && year1 == year2) {
			dateString = this.format(d1, "mmm d'-'");
			dateString += this.format(d2, "d',' yyyy");
		} else if(year1 == year2) {
			dateString = this.format(d1, "mmm d'-'");
			dateString += this.format(d2, "mmm d',' yyyy");
		} else {
			dateString = this.format(d1, "mmm d',' yyyy '-' ");
			dateString += this.format(d2, "mmm d',' yyyy");
		}
		
		return dateString;
	},
	
	/**
	 * Formats date objects.  Sample formats:
	 * 
	 *		default:      	"ddd mmm dd yyyy HH:MM:ss"
	 *		shortDate:      "m/d/yy"
	 *		mediumDate:     "mmm d, yyyy"
	 *		longDate:       "mmmm d, yyyy"
	 *		fullDate:       "dddd, mmmm d, yyyy"
	 *		shortTime:      "h:MM TT"
	 *		mediumTime:     "h:MM:ss TT"
	 *		longTime:       "h:MM:ss TT Z"
	 *		isoDate:        "yyyy-mm-dd"
	 *		isoTime:        "HH:MM:ss"
	 *		isoDateTime:    "yyyy-mm-dd'T'HH:MM:ss"
	 *		isoUtcDateTime: "UTC:yyyy-mm-dd'T'HH:MM:ss'Z'"
	 * 
	 * Original source code from http://blog.stevenlevithan.com/archives/date-time-format.
	 * 
	 * @param {Date} date the date object to format
	 * @param {String} format the format to use
	 * @return formatted date object
	 */
	format : function(date, format) {
		/*
		 *  ORIGINAL SOURCE FROM
		 *  http://blog.stevenlevithan.com/archives/date-time-format
		 *
		 * Date Format 1.2.2
		 * (c) 2007-2008 Steven Levithan <stevenlevithan.com>
		 * MIT license
		 * Includes enhancements by Scott Trenda <scott.trenda.net> and Kris Kowal <cixar.com/~kris.kowal/>
		 *
		 * Accepts a date, a mask, or a date and a mask.
		 * Returns a formatted version of the given date.
		 * The date defaults to the current date/time.
		 * The mask defaults to dateFormat.masks.default.
		 */
		var dateFormat = function () {
			var	token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[LloSZ]|"[^"]*"|'[^']*'/g,
				timezone = /\b(?:[PMCEA][SDP]T|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time|(?:GMT|UTC)(?:[-+]\d{4})?)\b/g,
				timezoneClip = /[^-+\dA-Z]/g,
				pad = function (val, len) {
					val = String(val);
					len = len || 2;
					while (val.length < len) val = "0" + val;
					return val;
				};
		
			// Regexes and supporting functions are cached through closure
			return function (date, mask, utc) {
				var dF = dateFormat;
		
				// You can't provide utc if you skip other args (use the "UTC:" mask prefix)
				if (arguments.length == 1 && (typeof date == "string" || date instanceof String) && !/\d/.test(date)) {
					mask = date;
					date = undefined;
				}
		
				// Passing date through Date applies Date.parse, if necessary
				date = date ? new Date(date) : new Date();
				if (isNaN(date)) throw new SyntaxError("invalid date");
		
				mask = String(dF.masks[mask] || mask || dF.masks["default"]);
		
				// Allow setting the utc argument via the mask
				if (mask.slice(0, 4) == "UTC:") {
					mask = mask.slice(4);
					utc = true;
				}
		
				var	_ = utc ? "getUTC" : "get",
					d = date[_ + "Date"](),
					D = date[_ + "Day"](),
					m = date[_ + "Month"](),
					y = date[_ + "FullYear"](),
					H = date[_ + "Hours"](),
					M = date[_ + "Minutes"](),
					s = date[_ + "Seconds"](),
					L = date[_ + "Milliseconds"](),
					o = utc ? 0 : date.getTimezoneOffset(),
					flags = {
						d:    d,
						dd:   pad(d),
						ddd:  dF.i18n.dayNames[D],
						dddd: dF.i18n.dayNames[D + 7],
						m:    m + 1,
						mm:   pad(m + 1),
						mmm:  dF.i18n.monthNames[m],
						mmmm: dF.i18n.monthNames[m + 12],
						yy:   String(y).slice(2),
						yyyy: y,
						h:    H % 12 || 12,
						hh:   pad(H % 12 || 12),
						H:    H,
						HH:   pad(H),
						M:    M,
						MM:   pad(M),
						s:    s,
						ss:   pad(s),
						l:    pad(L, 3),
						L:    pad(L > 99 ? Math.round(L / 10) : L),
						t:    H < 12 ? "a"  : "p",
						tt:   H < 12 ? "am" : "pm",
						T:    H < 12 ? "A"  : "P",
						TT:   H < 12 ? "AM" : "PM",
						Z:    utc ? "UTC" : (String(date).match(timezone) || [""]).pop().replace(timezoneClip, ""),
						o:    (o > 0 ? "-" : "+") + pad(Math.floor(Math.abs(o) / 60) * 100 + Math.abs(o) % 60, 4),
						S:    ["th", "st", "nd", "rd"][d % 10 > 3 ? 0 : (d % 100 - d % 10 != 10) * d % 10]
					};
		
				return mask.replace(token, function ($0) {
					return $0 in flags ? flags[$0] : $0.slice(1, $0.length - 1);
				});
			};
		}();
		
		// Some common format strings
		dateFormat.masks = {
			"default":      "ddd mmm dd yyyy HH:MM:ss",
			shortDate:      "m/d/yy",
			mediumDate:     "mmm d, yyyy",
			longDate:       "mmmm d, yyyy",
			fullDate:       "dddd, mmmm d, yyyy",
			shortTime:      "h:MM TT",
			mediumTime:     "h:MM:ss TT",
			longTime:       "h:MM:ss TT Z",
			isoDate:        "yyyy-mm-dd",
			isoTime:        "HH:MM:ss",
			isoDateTime:    "yyyy-mm-dd'T'HH:MM:ss",
			isoUtcDateTime: "UTC:yyyy-mm-dd'T'HH:MM:ss'Z'"
		};
		
		// Internationalization strings
		dateFormat.i18n = {
			dayNames: [
				"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
				"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
			],
			monthNames: [
				"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
				"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"
			]
		};
		
		return dateFormat(date, format);
	}
};