/**
 * Shows a date as the time since it, beside every dump, comment, message and
 * notification.
 *
 * @module
 */

import { i18n } from "@lingui/core";

/**
 * Returns how long ago `date` was, as "3 minutes ago", in the current locale.
 * It is computed at render, so the text only moves on when the caller
 * re-renders. A month counts 30 days and a year 365. Every date shown is of
 * something that happened, so one in the future, which only a clock ahead of
 * this one can give, reads as "now".
 */
export function relativeTime(date: Date): string {
  const rtf = new Intl.RelativeTimeFormat(i18n.locale, { numeric: "auto" });
  const abs = Math.max(0, Date.now() - date.getTime()) / 1000;

  if (abs < 60) return rtf.format(-Math.round(abs), "second");
  if (abs < 3600) return rtf.format(-Math.round(abs / 60), "minute");
  if (abs < 86400) return rtf.format(-Math.round(abs / 3600), "hour");
  if (abs < 7 * 86400) return rtf.format(-Math.round(abs / 86400), "day");
  if (abs < 30 * 86400) return rtf.format(-Math.round(abs / 7 / 86400), "week");
  if (abs < 365 * 86400) {
    return rtf.format(-Math.round(abs / 30 / 86400), "month");
  }
  return rtf.format(-Math.round(abs / 365 / 86400), "year");
}