svelte-kit-vice/src/lib/util/dias/_vendor/calendars/BuddhistCalendar.ts

/*
 * Copyright 2020 Adobe. All rights reserved.
 * This file is licensed to you 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 REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

// Portions of the code in this file are based on code from ICU.
// Original licensing can be found in the NOTICE file in the root directory of this source tree.

import type { AnyCalendarDate, CalendarIdentifier } from '../core/types';
import { CalendarDate } from '../core/CalendarDate';
import { fromExtendedYear, getExtendedYear, GregorianCalendar } from './GregorianCalendar';

const BUDDHIST_ERA_START = -543;

/**
 * The Buddhist calendar is the same as the Gregorian calendar, but counts years
 * starting from the birth of Buddha in 543 BC (Gregorian). It supports only one
 * era, identified as 'BE'.
 */
export class BuddhistCalendar extends GregorianCalendar {
	identifier: CalendarIdentifier = 'buddhist';

	fromJulianDay(jd: number): CalendarDate {
		let gregorianDate = super.fromJulianDay(jd);
		let year = getExtendedYear(gregorianDate.era, gregorianDate.year);
		return new CalendarDate(
			this,
			year - BUDDHIST_ERA_START,
			gregorianDate.month,
			gregorianDate.day
		);
	}

	toJulianDay(date: AnyCalendarDate): number {
		return super.toJulianDay(toGregorian(date));
	}

	getEras(): string[] {
		return ['BE'];
	}

	getDaysInMonth(date: AnyCalendarDate): number {
		return super.getDaysInMonth(toGregorian(date));
	}

	balanceDate(): void {}
}

function toGregorian(date: AnyCalendarDate) {
	let [era, year] = fromExtendedYear(date.year + BUDDHIST_ERA_START);
	return new CalendarDate(era, year, date.month, date.day);
}