Hijri Days Adjustments

This example demonstrates an approach to customize the display of Hijri dates in Temporal by implementing an AdjustableHijriTemporal class. This class allows for shifting Hijri dates forward or backward by a specified number of days.

The code below showcases how to:

1. Synchronize displayed Hijri dates with local Hijri calendars
2. Facilitate the use of alternative Hijri calendar epochs

Key features of this implementation:

• Adjusts the display of Hijri dates without modifying the underlying calendar system
• Applies a simple day shift without altering month lengths or other calendar rules
• Provides visual alignment for different Hijri calendar variants

NOTE: This example is intended for basic Hijri date adjustments and visual alignment. It does not implement comprehensive calendar customization or detailed Hijri calendar variants. For more complex Hijri calendar adjustments or variants, a more sophisticated implementation would be necessary.

/* eslint-disable no-console */
import * as Temporal from '../../polyfill/lib/temporal.mjs';

/**
 * AdjustableHijriTemporal: A class for customizing Hijri date display.
 *
 * This class allows for adjustment of Hijri dates by shifting days forward or backward.
 * It's designed to:
 * 1. Help users synchronize displayed Hijri dates with their local Hijri calendar.
 * 2. Facilitate the use of alternative Hijri calendar epochs.
 *
 * Key points:
 * - It adjusts the display of Hijri dates without modifying the underlying calendar system.
 * - The adjustment is a simple day shift and does not alter month lengths or other calendar rules.
 * - This approach is useful for visual alignment but does not implement comprehensive
 *   calendar customization or detailed Hijri calendar variants.
 *
 * Note: For more complex Hijri calendar adjustments or variants, a more sophisticated
 * implementation would be necessary.
 */

class AdjustableHijriTemporal {
  #temporal;
  #daysToShift;
  #adjustedDate;

  constructor(temporal, calendar = 'islamic-umalqura', daysToShift = 0) {
    this.#temporal = temporal.withCalendar(calendar);
    this.#daysToShift = daysToShift;
    this.#adjustedDate = this.#temporal.add({ days: this.#daysToShift });
  }

  get day() {
    return this.#adjustedDate.day;
  }
  get dayOfWeek() {
    return this.#temporal.dayOfWeek;
  }
  get dayOfYear() {
    return this.#adjustedDate.dayOfYear;
  }
  get daysInMonth() {
    return this.#adjustedDate.daysInMonth;
  }
  get daysInYear() {
    return this.#adjustedDate.daysInYear;
  }
  get month() {
    return this.#adjustedDate.month;
  }
  get monthCode() {
    return this.#adjustedDate.monthCode;
  }
  get monthsInYear() {
    return this.#adjustedDate.monthsInYear;
  }
  get year() {
    return this.#adjustedDate.year;
  }
  get inLeapYear() {
    return this.#adjustedDate.inLeapYear;
  }

  toString(options) {
    return this.#adjustedDate.toString(options);
  }

  toJSON() {
    return this.#adjustedDate.toJSON();
  }

  toLocaleString(locales, options) {
    const formatter = new Intl.DateTimeFormat(locales, options);
    const originalParts = formatter.formatToParts(this.#temporal);
    const adjustedParts = formatter.formatToParts(this.#adjustedDate);
    for (let i = 0; i < adjustedParts.length; i++) {
      if (adjustedParts[i].type === 'weekday') {
        adjustedParts[i].value = originalParts[i].value;
        break;
      }
    }
    return adjustedParts.map((part) => part.value).join('');
  }

  add(durationLike, options) {
    return this.#adjustedDate.add(durationLike, options);
  }

  subtract(durationLike, options) {
    return this.#adjustedDate.subtract(durationLike, options);
  }

  until(other, options) {
    return this.#adjustedDate.until(other, options);
  }

  since(other, options) {
    return this.#adjustedDate.since(other, options);
  }

  with(dateLike, options) {
    return this.#adjustedDate.with(dateLike, options);
  }

  withCalendar(calendar) {
    return this.#adjustedDate.withCalendar(calendar);
  }

  equals(other) {
    if (other instanceof AdjustableHijriTemporal) return this.#adjustedDate.equals(other.#adjustedDate);

    return this.#adjustedDate.equals(other);
  }
}

const Hdate = new Temporal.PlainDate(2024, 7, 6, 'islamic-umalqura');
const AHdate = new AdjustableHijriTemporal(Hdate, 'islamic-umalqura', 1);

console.log(
  Hdate.day,
  Hdate.dayOfWeek,
  Hdate.month,
  Hdate.year,
  Hdate.toLocaleString('en-SG', {
    dateStyle: 'full',
    calendar: 'islamic-umalqura'
  })
); // 30 6 12 1445 Saturday, 30 Dhuʻl-Hijjah 1445 AH
console.log(
  AHdate.day,
  AHdate.dayOfWeek,
  AHdate.month,
  AHdate.year,
  AHdate.toLocaleString('en-SG', {
    dateStyle: 'full',
    calendar: 'islamic-umalqura'
  })
); // 1 6 1 1446 Saturday, 1 Muharram 1446 AH