/*
* Date prototype extensions. Doesn't depend on any
* other code. Doens't overwrite existing methods.
*
* Adds dayNames, abbrDayNames, monthNames and abbrMonthNames static properties and isLeapYear,
* isWeekend, isWeekDay, getDaysInMonth, getDayName, getMonthName, getDayOfYear, getWeekOfYear,
* setDayOfYear, addYears, addMonths, addDays, addHours, addMinutes, addSeconds methods
*
* Copyright (c) 2006 JУЖrn Zaefferer and Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
*
* Additional methods and properties added by Kelvin Luck: firstDayOfWeek, dateFormat, zeroTime, asString, fromString -
* I've added my name to these methods so you know who to blame if they are broken!
* 
* Dual licensed under the MIT and GPL licenses:
*   http://www.opensource.org/licenses/mit-license.php
*   http://www.gnu.org/licenses/gpl.html
*
*/

/**
* An Array of day names starting with Sunday.
* 
* @example dayNames[0]
* @result 'Sunday'
*
* @name dayNames
* @type Array
* @cat Plugins/Methods/Date
*/
Date.dayNames = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];

/**
* An Array of abbreviated day names starting with Sun.
* 
* @example abbrDayNames[0]
* @result 'Sun'
*
* @name abbrDayNames
* @type Array
* @cat Plugins/Methods/Date
*/
Date.abbrDayNames = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];

/**
* An Array of month names starting with Janurary.
* 
* @example monthNames[0]
* @result 'January'
*
* @name monthNames
* @type Array
* @cat Plugins/Methods/Date
*/
Date.monthNames = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

/**
* An Array of abbreviated month names starting with Jan.
* 
* @example abbrMonthNames[0]
* @result 'Jan'
*
* @name monthNames
* @type Array
* @cat Plugins/Methods/Date
*/
Date.abbrMonthNames = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

/**
* The first day of the week for this locale.
*
* @name firstDayOfWeek
* @type Number
* @cat Plugins/Methods/Date
* @author Kelvin Luck
*/
Date.firstDayOfWeek = 1;

/**
* The format that string dates should be represented as (e.g. 'dd/mm/yyyy' for UK, 'mm/dd/yyyy' for US, 'yyyy-mm-dd' for Unicode etc).
*
* @name format
* @type String
* @cat Plugins/Methods/Date
* @author Kelvin Luck
*/
Date.format = 'dd/mm/yyyy';
//Date.format = 'mm/dd/yyyy';
//Date.format = 'yyyy-mm-dd';
//Date.format = 'dd mmm yy';

/**
* The first two numbers in the century to be used when decoding a two digit year. Since a two digit year is ambiguous (and date.setYear
* only works with numbers < 99 and so doesn't allow you to set years after 2000) we need to use this to disambiguate the two digit year codes.
*
* @name format
* @type String
* @cat Plugins/Methods/Date
* @author Kelvin Luck
*/
Date.fullYearStart = '20';

(function() {

	/**
	* Adds a given method under the given name 
	* to the Date prototype if it doesn't
	* currently exist.
	*
	* @private
	*/
	function add(name, method) {
		if (!Date.prototype[name]) {
			Date.prototype[name] = method;
		}
	};

	/**
	* Checks if the year is a leap year.
	*
	* @example var dtm = new Date("01/12/2008");
	* dtm.isLeapYear();
	* @result true
	*
	* @name isLeapYear
	* @type Boolean
	* @cat Plugins/Methods/Date
	*/
	add("isLeapYear", function() {
		var y = this.getFullYear();
		return (y % 4 == 0 && y % 100 != 0) || y % 400 == 0;
	});

	/**
	* Checks if the day is a weekend day (Sat or Sun).
	*
	* @example var dtm = new Date("01/12/2008");
	* dtm.isWeekend();
	* @result false
	*
	* @name isWeekend
	* @type Boolean
	* @cat Plugins/Methods/Date
	*/
	add("isWeekend", function() {
		return this.getDay() == 0 || this.getDay() == 6;
	});

	/**
	* Check if the day is a day of the week (Mon-Fri)
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.isWeekDay();
	* @result false
	* 
	* @name isWeekDay
	* @type Boolean
	* @cat Plugins/Methods/Date
	*/
	add("isWeekDay", function() {
		return !this.isWeekend();
	});

	/**
	* Gets the number of days in the month.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getDaysInMonth();
	* @result 31
	* 
	* @name getDaysInMonth
	* @type Number
	* @cat Plugins/Methods/Date
	*/
	add("getDaysInMonth", function() {
		return [31, (this.isLeapYear() ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][this.getMonth()];
	});

	/**
	* Gets the name of the day.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getDayName();
	* @result 'Saturday'
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getDayName(true);
	* @result 'Sat'
	* 
	* @param abbreviated Boolean When set to true the name will be abbreviated.
	* @name getDayName
	* @type String
	* @cat Plugins/Methods/Date
	*/
	add("getDayName", function(abbreviated) {
		return abbreviated ? Date.abbrDayNames[this.getDay()] : Date.dayNames[this.getDay()];
	});

	/**
	* Gets the name of the month.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getMonthName();
	* @result 'Janurary'
	*
	* @example var dtm = new Date("01/12/2008");
	* dtm.getMonthName(true);
	* @result 'Jan'
	* 
	* @param abbreviated Boolean When set to true the name will be abbreviated.
	* @name getDayName
	* @type String
	* @cat Plugins/Methods/Date
	*/
	add("getMonthName", function(abbreviated) {
		return abbreviated ? Date.abbrMonthNames[this.getMonth()] : Date.monthNames[this.getMonth()];
	});

	/**
	* Get the number of the day of the year.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getDayOfYear();
	* @result 11
	* 
	* @name getDayOfYear
	* @type Number
	* @cat Plugins/Methods/Date
	*/
	add("getDayOfYear", function() {
		var tmpdtm = new Date("1/1/" + this.getFullYear());
		return Math.floor((this.getTime() - tmpdtm.getTime()) / 86400000);
	});

	/**
	* Get the number of the week of the year.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.getWeekOfYear();
	* @result 2
	* 
	* @name getWeekOfYear
	* @type Number
	* @cat Plugins/Methods/Date
	*/
	add("getWeekOfYear", function() {
		return Math.ceil(this.getDayOfYear() / 7);
	});

	/**
	* Set the day of the year.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.setDayOfYear(1);
	* dtm.toString();
	* @result 'Tue Jan 01 2008 00:00:00'
	* 
	* @name setDayOfYear
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("setDayOfYear", function(day) {
		this.setMonth(0);
		this.setDate(day);
		return this;
	});

	/**
	* Add a number of years to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addYears(1);
	* dtm.toString();
	* @result 'Mon Jan 12 2009 00:00:00'
	* 
	* @name addYears
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addYears", function(num) {
		this.setFullYear(this.getFullYear() + num);
		return this;
	});

	/**
	* Add a number of months to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addMonths(1);
	* dtm.toString();
	* @result 'Tue Feb 12 2008 00:00:00'
	* 
	* @name addMonths
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addMonths", function(num) {
		var tmpdtm = this.getDate();

		this.setMonth(this.getMonth() + num);

		if (tmpdtm > this.getDate())
			this.addDays(-this.getDate());

		return this;
	});

	/**
	* Add a number of days to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addDays(1);
	* dtm.toString();
	* @result 'Sun Jan 13 2008 00:00:00'
	* 
	* @name addDays
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addDays", function(num) {
		this.setDate(this.getDate() + num);
		return this;
	});

	/**
	* Add a number of hours to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addHours(24);
	* dtm.toString();
	* @result 'Sun Jan 13 2008 00:00:00'
	* 
	* @name addHours
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addHours", function(num) {
		this.setHours(this.getHours() + num);
		return this;
	});

	/**
	* Add a number of minutes to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addMinutes(60);
	* dtm.toString();
	* @result 'Sat Jan 12 2008 01:00:00'
	* 
	* @name addMinutes
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addMinutes", function(num) {
		this.setMinutes(this.getMinutes() + num);
		return this;
	});

	/**
	* Add a number of seconds to the date object.
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.addSeconds(60);
	* dtm.toString();
	* @result 'Sat Jan 12 2008 00:01:00'
	* 
	* @name addSeconds
	* @type Date
	* @cat Plugins/Methods/Date
	*/
	add("addSeconds", function(num) {
		this.setSeconds(this.getSeconds() + num);
		return this;
	});

	/**
	* Sets the time component of this Date to zero for cleaner, easier comparison of dates where time is not relevant.
	* 
	* @example var dtm = new Date();
	* dtm.zeroTime();
	* dtm.toString();
	* @result 'Sat Jan 12 2008 00:01:00'
	* 
	* @name zeroTime
	* @type Date
	* @cat Plugins/Methods/Date
	* @author Kelvin Luck
	*/
	add("zeroTime", function() {
		this.setMilliseconds(0);
		this.setSeconds(0);
		this.setMinutes(0);
		this.setHours(0);
		return this;
	});

	/**
	* Returns a string representation of the date object according to Date.format.
	* (Date.toString may be used in other places so I purposefully didn't overwrite it)
	* 
	* @example var dtm = new Date("01/12/2008");
	* dtm.asString();
	* @result '12/01/2008' // (where Date.format == 'dd/mm/yyyy'
	* 
	* @name asString
	* @type Date
	* @cat Plugins/Methods/Date
	* @author Kelvin Luck
	*/
	add("asString", function(format) {
		var r = format || Date.format;
		return r
			.split('yyyy').join(this.getFullYear())
			.split('yy').join((this.getFullYear() + '').substring(2))
			.split('mmmm').join(this.getMonthName(false))
			.split('mmm').join(this.getMonthName(true))
			.split('mm').join(_zeroPad(this.getMonth() + 1))
			.split('dd').join(_zeroPad(this.getDate()));
	});

	/**
	* Returns a new date object created from the passed String according to Date.format or false if the attempt to do this results in an invalid date object
	* (We can't simple use Date.parse as it's not aware of locale and I chose not to overwrite it incase it's functionality is being relied on elsewhere)
	*
	* @example var dtm = Date.fromString("12/01/2008");
	* dtm.toString();
	* @result 'Sat Jan 12 2008 00:00:00' // (where Date.format == 'dd/mm/yyyy'
	* 
	* @name fromString
	* @type Date
	* @cat Plugins/Methods/Date
	* @author Kelvin Luck
	*/
	Date.fromString = function(s) {
		var f = Date.format;
		var d = new Date('01/01/1977');

		var mLength = 0;

		var iM = f.indexOf('mmmm');
		if (iM > -1) {
			for (var i = 0; i < Date.monthNames.length; i++) {
				var mStr = s.substrin(iM, Date.monthNames[i].length);
				if (Date.monthNames[i] == mStr) {
					mLength = Date.monthNames[i].length - 4;
					break;
				}
			}
			d.setMonth(i);
		} else {
			iM = f.indexOf('mmm');
			if (iM > -1) {
				var mStr = s.substr(iM, 3);
				for (var i = 0; i < Date.abbrMonthNames.length; i++) {
					if (Date.abbrMonthNames[i] == mStr) break;
				}
				d.setMonth(i);
			} else {
				d.setMonth(Number(s.substr(f.indexOf('mm'), 2)) - 1);
			}
		}

		var iY = f.indexOf('yyyy');

		if (iY > -1) {
			if (iM < iY) {
				iY += mLength;
			}
			d.setFullYear(Number(s.substr(iY, 4)));
		} else {
			if (iM < iY) {
				iY += mLength;
			}
			// TODO - this doesn't work very well - are there any rules for what is meant by a two digit year?
			d.setFullYear(Number(Date.fullYearStart + s.substr(f.indexOf('yy'), 2)));
		}
		var iD = f.indexOf('dd');
		if (iM < iD) {
			iD += mLength;
		}
		d.setDate(Number(s.substr(iD, 2)));
		if (isNaN(d.getTime())) {
			return false;
		}
		return d;
	};

	// utility method
	var _zeroPad = function(num) {
		var s = '0' + num;
		return s.substring(s.length - 2)
		//return ('0'+num).substring(-2); // doesn't work on IE :(
	};

})();