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YUI.add('yui2-datemath', function(Y) {

    var YAHOO    = Y.YUI2;

    /*

Copyright (c) 2011, Yahoo! Inc. All rights reserved.

Code licensed under the BSD License:

http://developer.yahoo.com/yui/license.html

version: 2.9.0

*/

/**

* The datemath module provides utility methods for basic JavaScript Date object manipulation and

* comparison.

*

* @module datemath

*/

/**

* YAHOO.widget.DateMath is used for simple date manipulation. The class is a static utility

* used for adding, subtracting, and comparing dates.

* @namespace YAHOO.widget

* @class DateMath

*/

YAHOO.widget.DateMath = {

    /**

    * Constant field representing Day

    * @property DAY

    * @static

    * @final

    * @type String

    */

    DAY : "D",

    /**

    * Constant field representing Week

    * @property WEEK

    * @static

    * @final

    * @type String

    */

    WEEK : "W",

    /**

    * Constant field representing Year

    * @property YEAR

    * @static

    * @final

    * @type String

    */

    YEAR : "Y",

    /**

    * Constant field representing Month

    * @property MONTH

    * @static

    * @final

    * @type String

    */

    MONTH : "M",

    /**

    * Constant field representing one day, in milliseconds

    * @property ONE_DAY_MS

    * @static

    * @final

    * @type Number

    */

    ONE_DAY_MS : 1000*60*60*24,

    /**

     * Constant field representing the date in first week of January

     * which identifies the first week of the year.

     * <p>

     * In the U.S, Jan 1st is normally used based on a Sunday start of week.

     * ISO 8601, used widely throughout Europe, uses Jan 4th, based on a Monday start of week.

     * </p>

     * @property WEEK_ONE_JAN_DATE

     * @static

     * @type Number

     */

    WEEK_ONE_JAN_DATE : 1,

    /**

    * Adds the specified amount of time to the this instance.

    * @method add

    * @param {Date} date The JavaScript Date object to perform addition on

    * @param {String} field The field constant to be used for performing addition.

    * @param {Number} amount The number of units (measured in the field constant) to add to the date.

    * @return {Date} The resulting Date object

    */

    add : function(date, field, amount) {

        var d = new Date(date.getTime());

        switch (field) {

            case this.MONTH:

                var newMonth = date.getMonth() + amount;

                var years = 0;

                if (newMonth < 0) {

                    while (newMonth < 0) {

                        newMonth += 12;

                        years -= 1;

                    }

                } else if (newMonth > 11) {

                    while (newMonth > 11) {

                        newMonth -= 12;

                        years += 1;

                    }

                }

                d.setMonth(newMonth);

                d.setFullYear(date.getFullYear() + years);

                break;

            case this.DAY:

                this._addDays(d, amount);

                // d.setDate(date.getDate() + amount);

                break;

            case this.YEAR:

                d.setFullYear(date.getFullYear() + amount);

                break;

            case this.WEEK:

                this._addDays(d, (amount * 7));

                // d.setDate(date.getDate() + (amount * 7));

                break;

        }

        return d;

    },

    /**

     * Private helper method to account for bug in Safari 2 (webkit < 420)

     * when Date.setDate(n) is called with n less than -128 or greater than 127.

     * <p>

     * Fix approach and original findings are available here:

     * http://brianary.blogspot.com/2006/03/safari-date-bug.html

     * </p>

     * @method _addDays

     * @param {Date} d JavaScript date object

     * @param {Number} nDays The number of days to add to the date object (can be negative)

     * @private

     */

    _addDays : function(d, nDays) {

        if (YAHOO.env.ua.webkit && YAHOO.env.ua.webkit < 420) {

            if (nDays < 0) {

                // Ensure we don't go below -128 (getDate() is always 1 to 31, so we won't go above 127)

                for(var min = -128; nDays < min; nDays -= min) {

                    d.setDate(d.getDate() + min);

                }

            } else {

                // Ensure we don't go above 96 + 31 = 127

                for(var max = 96; nDays > max; nDays -= max) {

                    d.setDate(d.getDate() + max);

                }

            }

            // nDays should be remainder between -128 and 96

        }

        d.setDate(d.getDate() + nDays);

    },

    /**

    * Subtracts the specified amount of time from the this instance.

    * @method subtract

    * @param {Date} date The JavaScript Date object to perform subtraction on

    * @param {Number} field The this field constant to be used for performing subtraction.

    * @param {Number} amount The number of units (measured in the field constant) to subtract from the date.

    * @return {Date} The resulting Date object

    */

    subtract : function(date, field, amount) {

        return this.add(date, field, (amount*-1));

    },

    /**

    * Determines whether a given date is before another date on the calendar.

    * @method before

    * @param {Date} date  The Date object to compare with the compare argument

    * @param {Date} compareTo The Date object to use for the comparison

    * @return {Boolean} true if the date occurs before the compared date; false if not.

    */

    before : function(date, compareTo) {

        var ms = compareTo.getTime();

        if (date.getTime() < ms) {

            return true;

        } else {

            return false;

        }

    },

    /**

    * Determines whether a given date is after another date on the calendar.

    * @method after

    * @param {Date} date  The Date object to compare with the compare argument

    * @param {Date} compareTo The Date object to use for the comparison

    * @return {Boolean} true if the date occurs after the compared date; false if not.

    */

    after : function(date, compareTo) {

        var ms = compareTo.getTime();

        if (date.getTime() > ms) {

            return true;

        } else {

            return false;

        }

    },

    /**

    * Determines whether a given date is between two other dates on the calendar.

    * @method between

    * @param {Date} date  The date to check for

    * @param {Date} dateBegin The start of the range

    * @param {Date} dateEnd  The end of the range

    * @return {Boolean} true if the date occurs between the compared dates; false if not.

    */

    between : function(date, dateBegin, dateEnd) {

        if (this.after(date, dateBegin) && this.before(date, dateEnd)) {

            return true;

        } else {

            return false;

        }

    },

    /**

    * Retrieves a JavaScript Date object representing January 1 of any given year.

    * @method getJan1

    * @param {Number} calendarYear  The calendar year for which to retrieve January 1

    * @return {Date} January 1 of the calendar year specified.

    */

    getJan1 : function(calendarYear) {

        return this.getDate(calendarYear,0,1);

    },

    /**

    * Calculates the number of days the specified date is from January 1 of the specified calendar year.

    * Passing January 1 to this function would return an offset value of zero.

    * @method getDayOffset

    * @param {Date} date The JavaScript date for which to find the offset

    * @param {Number} calendarYear The calendar year to use for determining the offset

    * @return {Number} The number of days since January 1 of the given year

    */

    getDayOffset : function(date, calendarYear) {

        var beginYear = this.getJan1(calendarYear); // Find the start of the year. This will be in week 1.

        // Find the number of days the passed in date is away from the calendar year start

        var dayOffset = Math.ceil((date.getTime()-beginYear.getTime()) / this.ONE_DAY_MS);

        return dayOffset;

    },

    /**

    * Calculates the week number for the given date. Can currently support standard

    * U.S. week numbers, based on Jan 1st defining the 1st week of the year, and

    * ISO8601 week numbers, based on Jan 4th defining the 1st week of the year.

    *

    * @method getWeekNumber

    * @param {Date} date The JavaScript date for which to find the week number

    * @param {Number} firstDayOfWeek The index of the first day of the week (0 = Sun, 1 = Mon ... 6 = Sat).

    * Defaults to 0

    * @param {Number} janDate The date in the first week of January which defines week one for the year

    * Defaults to the value of YAHOO.widget.DateMath.WEEK_ONE_JAN_DATE, which is 1 (Jan 1st).

    * For the U.S, this is normally Jan 1st. ISO8601 uses Jan 4th to define the first week of the year.

    *

    * @return {Number} The number of the week containing the given date.

    */

    getWeekNumber : function(date, firstDayOfWeek, janDate) {

        // Setup Defaults

        firstDayOfWeek = firstDayOfWeek || 0;

        janDate = janDate || this.WEEK_ONE_JAN_DATE;

        var targetDate = this.clearTime(date),

            startOfWeek,

            endOfWeek;

        if (targetDate.getDay() === firstDayOfWeek) {

            startOfWeek = targetDate;

        } else {

            startOfWeek = this.getFirstDayOfWeek(targetDate, firstDayOfWeek);

        }

        var startYear = startOfWeek.getFullYear();

        // DST shouldn't be a problem here, math is quicker than setDate();

        endOfWeek = new Date(startOfWeek.getTime() + 6*this.ONE_DAY_MS);

        var weekNum;

        if (startYear !== endOfWeek.getFullYear() && endOfWeek.getDate() >= janDate) {

            // If years don't match, endOfWeek is in Jan. and if the

            // week has WEEK_ONE_JAN_DATE in it, it's week one by definition.

            weekNum = 1;

        } else {

            // Get the 1st day of the 1st week, and

            // find how many days away we are from it.

            var weekOne = this.clearTime(this.getDate(startYear, 0, janDate)),

                weekOneDayOne = this.getFirstDayOfWeek(weekOne, firstDayOfWeek);

            // Round days to smoothen out 1 hr DST diff

            var daysDiff  = Math.round((targetDate.getTime() - weekOneDayOne.getTime())/this.ONE_DAY_MS);

            // Calc. Full Weeks

            var rem = daysDiff % 7;

            var weeksDiff = (daysDiff - rem)/7;

            weekNum = weeksDiff + 1;

        }

        return weekNum;

    },

    /**

     * Get the first day of the week, for the give date.

     * @param {Date} dt The date in the week for which the first day is required.

     * @param {Number} startOfWeek The index for the first day of the week, 0 = Sun, 1 = Mon ... 6 = Sat (defaults to 0)

     * @return {Date} The first day of the week

     */

    getFirstDayOfWeek : function (dt, startOfWeek) {

        startOfWeek = startOfWeek || 0;

        var dayOfWeekIndex = dt.getDay(),

            dayOfWeek = (dayOfWeekIndex - startOfWeek + 7) % 7;

        return this.subtract(dt, this.DAY, dayOfWeek);

    },

    /**

    * Determines if a given week overlaps two different years.

    * @method isYearOverlapWeek

    * @param {Date} weekBeginDate The JavaScript Date representing the first day of the week.

    * @return {Boolean} true if the date overlaps two different years.

    */

    isYearOverlapWeek : function(weekBeginDate) {

        var overlaps = false;

        var nextWeek = this.add(weekBeginDate, this.DAY, 6);

        if (nextWeek.getFullYear() != weekBeginDate.getFullYear()) {

            overlaps = true;

        }

        return overlaps;

    },

    /**

    * Determines if a given week overlaps two different months.

    * @method isMonthOverlapWeek

    * @param {Date} weekBeginDate The JavaScript Date representing the first day of the week.

    * @return {Boolean} true if the date overlaps two different months.

    */

    isMonthOverlapWeek : function(weekBeginDate) {

        var overlaps = false;

        var nextWeek = this.add(weekBeginDate, this.DAY, 6);

        if (nextWeek.getMonth() != weekBeginDate.getMonth()) {

            overlaps = true;

        }

        return overlaps;

    },

    /**

    * Gets the first day of a month containing a given date.

    * @method findMonthStart

    * @param {Date} date The JavaScript Date used to calculate the month start

    * @return {Date}  The JavaScript Date representing the first day of the month

    */

    findMonthStart : function(date) {

        var start = this.getDate(date.getFullYear(), date.getMonth(), 1);

        return start;

    },

    /**

    * Gets the last day of a month containing a given date.

    * @method findMonthEnd

    * @param {Date} date The JavaScript Date used to calculate the month end

    * @return {Date}  The JavaScript Date representing the last day of the month

    */

    findMonthEnd : function(date) {

        var start = this.findMonthStart(date);

        var nextMonth = this.add(start, this.MONTH, 1);

        var end = this.subtract(nextMonth, this.DAY, 1);

        return end;

    },

    /**

    * Clears the time fields from a given date, effectively setting the time to 12 noon.

    * @method clearTime

    * @param {Date} date The JavaScript Date for which the time fields will be cleared

    * @return {Date}  The JavaScript Date cleared of all time fields

    */

    clearTime : function(date) {

        date.setHours(12,0,0,0);

        return date;

    },

    /**

     * Returns a new JavaScript Date object, representing the given year, month and date. Time fields (hr, min, sec, ms) on the new Date object

     * are set to 0. The method allows Date instances to be created with the a year less than 100. "new Date(year, month, date)" implementations

     * set the year to 19xx if a year (xx) which is less than 100 is provided.

     * <p>

     * <em>NOTE:</em>Validation on argument values is not performed. It is the caller's responsibility to ensure

     * arguments are valid as per the ECMAScript-262 Date object specification for the new Date(year, month[, date]) constructor.

     * </p>

     * @method getDate

     * @param {Number} y Year.

     * @param {Number} m Month index from 0 (Jan) to 11 (Dec).

     * @param {Number} d (optional) Date from 1 to 31. If not provided, defaults to 1.

     * @return {Date} The JavaScript date object with year, month, date set as provided.

     */

    getDate : function(y, m, d) {

        var dt = null;

        if (YAHOO.lang.isUndefined(d)) {

            d = 1;

        }

        if (y >= 100) {

            dt = new Date(y, m, d);

        } else {

            dt = new Date();

            dt.setFullYear(y);

            dt.setMonth(m);

            dt.setDate(d);

            dt.setHours(0,0,0,0);

        }

        return dt;

    }

};

YAHOO.register("datemath", YAHOO.widget.DateMath, {version: "2.9.0", build: "2800"});

}, '2.9.0' ,{"requires": ["yui2-yahoo"]});