// Reconnecting WebSocket shared by both frontends. A party laptop that sleeps,
// or a server restart, must not require reloading the tabs.

export function connect({ onMessage, onStatus } = {}) {
  let ws = null;
  let retry = 500;
  const outbox = [];

  function open() {
    const proto = location.protocol === 'https:' ? 'wss:' : 'ws:';
    ws = new WebSocket(`${proto}//${location.host}`);

    ws.addEventListener('open', () => {
      retry = 500;
      onStatus?.('online');
      while (outbox.length) ws.send(outbox.shift());
    });

    ws.addEventListener('message', (event) => {
      let msg;
      try {
        msg = JSON.parse(event.data);
      } catch {
        return;
      }
      onMessage?.(msg);
    });

    ws.addEventListener('close', () => {
      onStatus?.('offline');
      setTimeout(open, retry);
      retry = Math.min(retry * 2, 5000);
    });

    ws.addEventListener('error', () => ws.close());
  }

  open();

  return {
    send(message) {
      const payload = JSON.stringify(message);
      if (ws && ws.readyState === WebSocket.OPEN) ws.send(payload);
      else outbox.push(payload);
    },
  };
}

/** Seconds → H:MM:SS (or M:SS below an hour). */
export function formatDuration(seconds) {
  if (!Number.isFinite(seconds) || seconds < 0) return '?';
  const total = Math.round(seconds);
  const h = Math.floor(total / 3600);
  const m = Math.floor((total % 3600) / 60);
  const s = total % 60;
  return h > 0
    ? `${h}:${String(m).padStart(2, '0')}:${String(s).padStart(2, '0')}`
    : `${m}:${String(s).padStart(2, '0')}`;
}