GregorianCal.js

/*
 * GregorianCal.js - Represent a Gregorian calendar object.
 *
 * Copyright © 2012-2018, JEDLSoft
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


var Utils = require("./Utils.js");
var MathUtils = require("./MathUtils.js");
var Calendar = require("./Calendar.js");

/**
 * @class
 * Construct a new Gregorian calendar object. This class encodes information about
 * a Gregorian calendar.<p>
 *
 *
 * @constructor
 * @param {{noinstance:boolean}=} options
 * @extends Calendar
 */
var GregorianCal = function(options) {
    if (!options || !options.noinstance) {
        this.type = "gregorian";
    }

    if (options && typeof(options.onLoad) === "function") {
        options.onLoad(this);
    }
};

/**
 * the lengths of each month
 * @private
 * @const
 * @type Array.<number>
 */
GregorianCal.monthLengths = [
    31,  /* Jan */
    28,  /* Feb */
    31,  /* Mar */
    30,  /* Apr */
    31,  /* May */
    30,  /* Jun */
    31,  /* Jul */
    31,  /* Aug */
    30,  /* Sep */
    31,  /* Oct */
    30,  /* Nov */
    31   /* Dec */
];

/**
 * Return the number of months in the given year. The number of months in a year varies
 * for some luni-solar calendars because in some years, an extra month is needed to extend the
 * days in a year to an entire solar year. The month is represented as a 1-based number
 * where 1=first month, 2=second month, etc.
 *
 * @param {number} year a year for which the number of months is sought
 * @return {number} The number of months in the given year
 */
GregorianCal.prototype.getNumMonths = function(year) {
    return 12;
};

/**
 * Return the number of days in a particular month in a particular year. This function
 * can return a different number for a month depending on the year because of things
 * like leap years.
 *
 * @param {number} month the month for which the length is sought
 * @param {number} year the year within which that month can be found
 * @return {number} the number of days within the given month in the given year
 */
GregorianCal.prototype.getMonLength = function(month, year) {
    if (month !== 2 || !this.isLeapYear(year)) {
        return GregorianCal.monthLengths[month-1];
    } else {
        return 29;
    }
};

/**
 * Return true if the given year is a leap year in the Gregorian calendar.
 * The year parameter may be given as a number, or as a GregDate object.
 * @param {number|GregorianDate} year the year for which the leap year information is being sought
 * @return {boolean} true if the given year is a leap year
 */
GregorianCal.prototype.isLeapYear = function(year) {
    var y = (typeof(year) === 'number' ? year : year.getYears());
    var centuries = MathUtils.mod(y, 400);
    return (MathUtils.mod(y, 4) === 0 && centuries !== 100 && centuries !== 200 && centuries !== 300);
};

/**
 * Return the type of this calendar.
 *
 * @return {string} the name of the type of this calendar
 */
GregorianCal.prototype.getType = function() {
    return this.type;
};

/* register this calendar for the factory method */
Calendar._constructors["gregorian"] = GregorianCal;

module.exports = GregorianCal;