PersianAlgoCal.js

/*
 * PersianAlgoCal.js - Represent a Persian algorithmic calendar object.
 *
 * Copyright © 2014-2015,2018, 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 MathUtils = require("./MathUtils.js");
var Calendar = require("./Calendar.js");
/**
 * @class
 * Construct a new Persian algorithmic calendar object. This class encodes information about
 * a Persian algorithmic calendar.<p>
 *
 * @param {Object=} options Options governing the construction of this instance
 * @constructor
 * @extends Calendar
 */
var PersianAlgoCal = function(options) {
    this.type = "persian-algo";
    if (options && typeof(options.onLoad) === "function") {
        options.onLoad(this);
    }
};
/**
 * the lengths of each month
 * @private
 * @const
 * @type Array.<number>
 */
PersianAlgoCal.monthLengths = [
    31,  // Farvardin
    31,  // Ordibehesht
    31,  // Khordad
    31,  // Tir
    31,  // Mordad
    31,  // Shahrivar
    30,  // Mehr
    30,  // Aban
    30,  // Azar
    30,  // Dey
    30,  // Bahman
    29   // Esfand
];
/**
 * 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
 */
PersianAlgoCal.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
 */
PersianAlgoCal.prototype.getMonLength = function(month, year) {
    if (month !== 12 || !this.isLeapYear(year)) {
        return PersianAlgoCal.monthLengths[month-1];
    } else {
        // Month 12, Esfand, has 30 days instead of 29 in leap years
        return 30;
    }
};
/**
 * Return the equivalent year in the 2820 year cycle that begins on
 * Far 1, 474. This particular cycle obeys the cycle-of-years formula
 * whereas the others do not specifically. This cycle can be used as
 * a proxy for other years outside of the cycle by shifting them into
 * the cycle.
 * @param {number} year year to find the equivalent cycle year for
 * @returns {number} the equivalent cycle year
 */
PersianAlgoCal.prototype.equivalentCycleYear = function(year) {
    var y = year - (year >= 0 ? 474 : 473);
    return MathUtils.mod(y, 2820) + 474;
};
/**
 * Return true if the given year is a leap year in the Persian calendar.
 * The year parameter may be given as a number, or as a PersAlgoDate object.
 * @param {number} year the year for which the leap year information is being sought
 * @return {boolean} true if the given year is a leap year
 */
PersianAlgoCal.prototype.isLeapYear = function(year) {
    return (MathUtils.mod((this.equivalentCycleYear(year) + 38) * 682, 2816) < 682);
};
/**
 * Return the type of this calendar.
 *
 * @return {string} the name of the type of this calendar
 */
PersianAlgoCal.prototype.getType = function() {
    return this.type;
};
/* register this calendar for the factory method */
Calendar._constructors["persian-algo"] = PersianAlgoCal;
module.exports = PersianAlgoCal;