// Deploy/restart warning banner, ported from mnw.js:578-652. Polls
// /api/restart-status; shows a countdown banner when a restart is scheduled.

/** Start polling for a scheduled restart and render the countdown banner. */
export function initRestartBanner(): void {
  let banner: HTMLElement | null = null;
  let countdownInterval: ReturnType<typeof setInterval> | null = null;
  let restartAt: number | null = null;

  function createBanner(): void {
    if (banner) return;
    banner = document.createElement('div');
    banner.id = 'restart-banner';
    banner.className = 'banner banner--warning';
    banner.setAttribute('role', 'alert');
    document.body.prepend(banner);
  }

  function removeBanner(): void {
    if (banner) {
      banner.remove();
      banner = null;
    }
    if (countdownInterval) {
      clearInterval(countdownInterval);
      countdownInterval = null;
    }
    restartAt = null;
  }

  function updateCountdown(): void {
    if (!banner || restartAt === null) return;
    const remaining = Math.max(0, Math.round(restartAt - Date.now() / 1000));
    if (remaining > 0) {
      banner.textContent = 'Update deploying — restarting in ' + remaining + 's';
    } else {
      banner.textContent = 'Restarting now...';
      if (countdownInterval) {
        clearInterval(countdownInterval);
        countdownInterval = null;
      }
    }
  }

  function startCountdown(ts: number): void {
    restartAt = ts;
    createBanner();
    updateCountdown();
    if (countdownInterval) clearInterval(countdownInterval);
    countdownInterval = setInterval(updateCountdown, 1000);
  }

  function poll(): void {
    fetch('/api/restart-status')
      .then((r) => r.json())
      .then((data: { restart_at?: number }) => {
        if (data.restart_at) {
          if (restartAt === null || restartAt !== data.restart_at) startCountdown(data.restart_at);
        } else {
          removeBanner();
        }
      })
      .catch(() => {
        // Already counting down and the poll failed: assume it's happening now.
        if (restartAt !== null) {
          if (banner) banner.textContent = 'Restarting now...';
          if (countdownInterval) {
            clearInterval(countdownInterval);
            countdownInterval = null;
          }
        }
      });
  }

  setTimeout(poll, 2000);
  setInterval(poll, 10000);
}