/*
 * 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 J?rn 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);
  this.setTime(this.getTime() + (num*86400000) );
  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.substr(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 :(
 };
 
})();