// One tab polls for every open DevDesk tab (devdesk#8): whoever fetches the
// session list or the alerts broadcasts the result, and a tab that heard a fresh
// result recently skips its own poll. Each poll costs a ttyd client and a PTY.

const channel = typeof BroadcastChannel === 'function' ? new BroadcastChannel('devdesk') : null;
const heard = new Map();
const handlers = new Map();

channel?.addEventListener('message', (event) => {
  const { key, data } = event.data ?? {};
  const handler = handlers.get(key);
  if (!handler) return;
  heard.set(key, Date.now());
  handler(data);
});

export function onShared(key, handler) {
  handlers.set(key, handler);
}

export function share(key, data) {
  try {
    channel?.postMessage({ key, data });
  } catch {
    // Not cloneable or channel closed: the other tabs just poll themselves.
  }
}

export function heardWithin(key, ms) {
  return Date.now() - (heard.get(key) ?? 0) < ms;
}