/**
 * Side-effect module: pins every Intl-based date/time display to East Africa
 * Time (UTC+3) so all users see the same wall-clock times no matter what
 * timezone their PC is set to. Import it FIRST in the app entry, before any
 * other app module, so no module-scope formatter is created unpatched:
 *
 *   import "@edr/ui-common/display-timezone";
 *
 * Call sites that pass an explicit `timeZone` option keep it. date-fns and
 * dayjs `format()` do NOT go through Intl and stay PC-local — don't use them
 * to display API timestamps.
 */
export const DISPLAY_TIME_ZONE = "Africa/Addis_Ababa";

type Locales = string | string[] | undefined;
type LocaleMethod = (
  this: Date,
  locales?: Locales,
  options?: Intl.DateTimeFormatOptions,
) => string;

function pinned(original: LocaleMethod): LocaleMethod {
  return function (locales, options) {
    return original.call(this, locales, {
      ...options,
      timeZone: options?.timeZone ?? DISPLAY_TIME_ZONE,
    });
  };
}

Date.prototype.toLocaleString = pinned(Date.prototype.toLocaleString);
Date.prototype.toLocaleDateString = pinned(Date.prototype.toLocaleDateString);
Date.prototype.toLocaleTimeString = pinned(Date.prototype.toLocaleTimeString);

const OriginalDateTimeFormat = Intl.DateTimeFormat;
function PinnedDateTimeFormat(
  locales?: Locales,
  options?: Intl.DateTimeFormatOptions,
): Intl.DateTimeFormat {
  return new OriginalDateTimeFormat(locales, {
    ...options,
    timeZone: options?.timeZone ?? DISPLAY_TIME_ZONE,
  });
}
// Keep `instanceof Intl.DateTimeFormat` and the static method working.
PinnedDateTimeFormat.prototype = OriginalDateTimeFormat.prototype;
PinnedDateTimeFormat.supportedLocalesOf = OriginalDateTimeFormat.supportedLocalesOf;
Intl.DateTimeFormat = PinnedDateTimeFormat as unknown as typeof Intl.DateTimeFormat;