/* eslint-disable eslint-comments/no-unlimited-disable */
/* eslint-disable */
// @ts-nocheck

import { getDefaultOptions, type Locale } from '../../../date-fns/index.ts';
import type { FormatOptionsWithTZ } from '../../index.ts';

/**
 * Returns the formatted time zone name of the provided `timeZone` or the current
 * system time zone if omitted, accounting for DST according to the UTC value of
 * the date.
 */
export function tzIntlTimeZoneName(
  length: Intl.DateTimeFormatOptions['timeZoneName'],
  date: Date,
  options: FormatOptionsWithTZ,
): string | undefined {
  const defaultOptions = getDefaultOptions();
  const dtf = getDTF(length, options.timeZone, options.locale ?? defaultOptions.locale);
  return 'formatToParts' in dtf ? partsTimeZone(dtf, date) : hackyTimeZone(dtf, date);
}

function partsTimeZone(dtf: Intl.DateTimeFormat, date: Date): string | undefined {
  const formatted = dtf.formatToParts(date);

  for (let i = formatted.length - 1; i >= 0; --i) {
    if (formatted[i].type === 'timeZoneName') {
      return formatted[i].value;
    }
  }
  return undefined;
}

function hackyTimeZone(dtf: Intl.DateTimeFormat, date: Date) {
  const formatted = dtf.format(date).replace(/\u200E/g, '');
  const tzNameMatch = / [\w-+ ]+$/.exec(formatted);
  return tzNameMatch ? tzNameMatch[0].substr(1) : '';
}

// If a locale has been provided `en-US` is used as a fallback in case it is an
// invalid locale, otherwise the locale is left undefined to use the system locale.
function getDTF(
  length: Intl.DateTimeFormatOptions['timeZoneName'],
  timeZone: string | undefined,
  locale: Pick<Locale, 'code'> | undefined,
) {
  return new Intl.DateTimeFormat(locale ? [locale.code, 'en-US'] : undefined, {
    timeZone: timeZone,
    timeZoneName: length,
  });
}

/* eslint-enable */