jsbeans

/*!
 * Copyright (c) 2009 Francesco Mele jsbeans@francescomele.com
 *
 * This Software is licenced under the LGPL Licence (GNU Lesser General 
 * Public License).
 * In addition to the LGPL Licence the Software is subject to the 
 * following conditions:
 * 
 * 	i	every modification must be public and comunicated to the Author
 * 	ii	every "jsbean" added to this library must be self consistent 
 * 		except for the dependence from jsbeans-x.x.x.js
 * 	iii	copyright notice and this permission notice shall be included 
 * 		in all copies or substantial portions of the Software
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
/**
 * A collection of utilities for date
 * @namespace jsbeans
 * @class date
 * @static
 */
jsbeans.date = {
	/**
	 * @property YEAR
	 * @type Integer
	 * @default 1
	 * @static
	 * @final
	 * */
	YEAR: 1,
	/**
	 * @property MONTH
	 * @type Integer
	 * @default 2
	 * @static
	 * @final
	 * */
	MONTH: 2,
	/**
	 * @property DATE
	 * @type Integer
	 * @default 3
	 * @static
	 * @final
	 * */
	DATE: 3,
	/**
	 * @property HOUR
	 * @type Integer
	 * @default 4
	 * @static
	 * @final
	 * */
	HOUR: 4,
	/**
	 * @property MINUTE
	 * @type Integer
	 * @default 5
	 * @static
	 * @final
	 * */
	MINUTE: 5,
	/**
	 * @property SECOND
	 * @type Integer
	 * @default 6
	 * @static
	 * @final
	 * */
	SECOND: 6,
	/**
	 * @property MILLIS
	 * @type Integer
	 * @default 7
	 * @static
	 * @final
	 * */
	MILLIS: 7,
	/**
	 * @property OFFSET
	 * @type Integer
	 * @default new Date().getTimezoneOffset() / 60
	 * @static
	 * @final
	 * */
	OFFSET: new Date().getTimezoneOffset() / 60,
	/**
	 * Starting by a date it let you go up or down in calendar for the chosen item (year, month, ..) by the step of your choice (1 by default). 
	 * @method add
	 * @param date {Date} a starting date
	 * @param rollerType {Integer} use <code class="prop">jsbeans.date.YEAR</code>, <code class="prop">jsbeans.date.MONTH</code>, <code class="prop">jsbeans.date.DATE</code>, ...
	 * @param [amount] {Integer} how much to roll. May be negative. Default 1
	 * @return {Date} a new date that differs from <code class="param">date</code> in <code class="param">rollerType</code> by <code class="param">amount</code>
	 * @static
	 * */
	add: function(d, rollerType /*, amount*/) {
		var amount = arguments[2] || 1;
		switch (rollerType) {
		case 1 /*year*/ :
			var next = d.getFullYear() + amount;
			return new Date(Date.UTC(
					next, 
					d.getMonth(), 
					d.getDate(), 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds(), 
					d.getMilliseconds()));
		case 2 /*month*/ :
			var next = d.getMonth() + amount;
			return new Date(Date.UTC(
					d.getFullYear(), 
					next, 
					d.getDate(), 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds(), 
					d.getMilliseconds()));
		case 3 /*date*/ :
			return new Date(Date.UTC(
					d.getFullYear(), 
					d.getMonth(), 
					d.getDate() + amount, 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds(), 
					d.getMilliseconds()));
		case 4 /*hour*/ :
			return new Date(Date.UTC(
					d.getFullYear(), 
					d.getMonth(), 
					d.getDate(), 
					d.getHours() + amount + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds(), 
					d.getMilliseconds()));
		case 5 /*minute*/ :
			return new Date(Date.UTC(
					d.getFullYear(), 
					d.getMonth(), 
					d.getDate(), 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes() + amount, 
					d.getSeconds(), 
					d.getMilliseconds()));
		case 6 /*second*/ :
			return new Date(Date.UTC(
					d.getFullYear(), 
					d.getMonth(), 
					d.getDate(), 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds() + amount, 
					d.getMilliseconds()));
		case 7 /*milliseconds*/ :
			return new Date(Date.UTC(
					d.getFullYear(), 
					d.getMonth(), 
					d.getDate(), 
					d.getHours() + jsbeans.date.OFFSET, 
					d.getMinutes(), 
					d.getSeconds(), 
					d.getMilliseconds() + amount));
		}
	},
	/**
	 * Formula taken from <a href="http://en.wikipedia.org/wiki/Leap_year#Algorithm">Wikipedia</a>.<br/>
	 * If {@param} <code class="param">object</code> is an Integer it will be treated as year.
	 * @method isLeapYear
	 * @param object {Date | Integer}
	 * @return {boolean}
	 * @static
	 * */
	isLeapYear: function(o) {
		var y = null;
		if (typeof o == "number") {
			y = o;
		} 
		else if (o.constructor && (""+o.constructor).indexOf("Date") != -1) {
			y = o.getFullYear();
		} 
		else {
			return false;
		}
		if ((y % 400 == 0) || ((y % 4 == 0) && (y % 100 != 0)) ) {
	       return true;
		} 
		else {
	       return false;
		}
	},
	/**
	 * Returns how many days has the month in given {@param} <code class="param">date</code>
	 * @method getDaysInMonth
	 * @param date {Date}
	 * @return {Integer}
	 * @static
	 * */
	getDaysInMonth: function(d) {
		var m = d.getMonth();
		if (m == 3 || m == 5 || m == 8 || m == 10) {
			return 30;
		} 
		else if (m == 1) {
			if (jsbeans.date.isLeapYear(d)) {
				return 29;
			} 
			else {
				return 28;
			}
		} 
		else {
			return 31;
		}
	}
};