/*
 * 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 = '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;
    if (r.split('mm').length>1) { // ugly workaround to make sure we don't replace the m's in e.g. noveMber
      r = r.split('mmmm').join(this.getMonthName(false))
        .split('mmm').join(this.getMonthName(true))
        .split('mm').join(_zeroPad(this.getMonth()+1))
    } else {
      r = r.split('m').join(this.getMonth()+1);
    }
    r = r.split('yyyy').join(this.getFullYear())
      .split('yy').join((this.getFullYear() + '').substring(2))
      .split('dd').join(_zeroPad(this.getDate()))
      .split('d').join(this.getDate());
    return r;
  });
  
  /**
   * 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('01/01/1970');
    
    if (s == '') return d;

    s = s.toLowerCase();
    var matcher = '';
    var order = [];
    var r = /(dd?d?|mm?m?|yy?yy?)+([^(m|d|y)])?/g;
    var results;
    while ((results = r.exec(f)) != null)
    {
      switch (results[1]) {
        case 'd':
        case 'dd':
        case 'm':
        case 'mm':
        case 'yy':
        case 'yyyy':
          matcher += '(\\d+\\d?\\d?\\d?)+';
          order.push(results[1].substr(0, 1));
          break;
        case 'mmm':
          matcher += '([a-z]{3})';
          order.push('M');
          break;
      }
      if (results[2]) {
        matcher += results[2];
      }
      
    }
    var dm = new RegExp(matcher);
    var result = s.match(dm);
    for (var i=0; i<order.length; i++) {
      var res = result[i+1];
      switch(order[i]) {
        case 'd':
          d.setDate(res);
          break;
        case 'm':
          d.setMonth(Number(res)-1);
          break;
        case 'M':
          for (var j=0; j<Date.abbrMonthNames.length; j++) {
            if (Date.abbrMonthNames[j].toLowerCase() == res) break;
          }
          d.setMonth(j);
          break;
        case 'y':
          d.setYear(res);
          break;
      }
    }

    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 :(
  };
  
})();