/***********************************************************************************************************************************************************************
 * File Name: datetime.util.js
 * Type of Program: Utility
 * Description: Pure date/time formatting helpers for backend use (emails, crons, notifications).
 *
 * All functions accept an optional options object: { timezone, locale }
 *   timezone — 'UTC' (default) | 'local'  (server's local timezone)
 *   locale   — BCP 47 tag, defaults to 'en-US'
 *
 * UTC is the default because emails and cron output must be unambiguous regardless
 * of where the server runs. Pass { timezone: 'local' } only when displaying times
 * relative to the server's configured locale (e.g. admin dashboards, server logs).
 ***********************************************************************************************************************************************************************/

function tzOpt(timezone) {
  return timezone === 'local' ? {} : { timeZone: 'UTC' };
}

function loc(locale) {
  return locale ?? 'en-US';
}

/** "June 27, 2026" */
function fmtDate(value, { timezone = 'UTC', locale } = {}) {
  if (!value) return '—';
  return new Date(value).toLocaleDateString(loc(locale), {
    month: 'long', day: 'numeric', year: 'numeric',
    ...tzOpt(timezone),
  });
}

/** "June 27, 2026, 3:45 PM UTC" */
function fmtDateTime(value, { timezone = 'UTC', locale } = {}) {
  if (!value) return '—';
  return new Date(value).toLocaleString(loc(locale), {
    month: 'long', day: 'numeric', year: 'numeric',
    hour: 'numeric', minute: '2-digit',
    timeZoneName: 'short',
    ...tzOpt(timezone),
  });
}

/** "3:45 PM UTC" */
function fmtTime(value, { timezone = 'UTC', locale } = {}) {
  if (!value) return '—';
  return new Date(value).toLocaleTimeString(loc(locale), {
    hour: 'numeric', minute: '2-digit',
    timeZoneName: 'short',
    ...tzOpt(timezone),
  });
}

module.exports = { fmtDate, fmtDateTime, fmtTime };