/*
* 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 Jörn 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 = 'yyyy-mm-dd';
//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(this.getFullYear()+"-01-01" );
 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() {
 var r = Date.format;
 return r
 .split('yyyy').join(this.getFullYear())
 .split('yy').join((this.getFullYear() + '').substring(2))
 .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('1977-01-01');
var iY = f.indexOf('yyyy');
if (iY > -1) {
d.setFullYear(Number(s.substr(iY, 4)));
} else {
// 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 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);
}
d.setDate(Number(s.substr(f.indexOf('dd'), 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 :(
 };

})();