/*
 * 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 = ['日', '一', '二', '三', '四', '五', '六'];

/**
 * 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 = ['一月', '二月', '三月', '四月', '五月', '六月', '七月', '八月', '九月', '十月', '十一月', '十二月'];

/**
 * An Array of abbreviated month names starting with Jan.
 * 
 * @example abbrMonthNames[0]
 * @result 'Jan'
 *
 * @name monthNames
 * @type Array
 * @cat Plugins/Methods/Date
 */
Date.abbrMonthNames = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12'];

/**
 * 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()))
            .split('hh').join(_zeroPad(this.getHours()))
            .split('min').join(_zeroPad(this.getMinutes()))
            .split('ss').join(_zeroPad(this.getSeconds()));
    });
    
    /**
     * 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, format)
    {
        var f = format || 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 :(
    };
    
})();