import { Link } from 'react-router';
import { Bell } from 'lucide-react';
import { useUnreadCount } from '../api/queries/alerts';
import { useSelectedEnv } from '../api/queries/alertMeta';
import css from './NotificationBell.module.css';

/**
 * Global notification bell shown in the layout header. Links to the alerts
 * inbox and renders a badge with the unread-alert count for the currently
 * selected environment.
 *
 * Polling pause when the tab is hidden is handled by `useUnreadCount`'s
 * `refetchIntervalInBackground: false`; no separate visibility subscription
 * is needed. If per-severity coloring (spec §13) is re-introduced, the
 * backend `UnreadCountResponse` must grow a `bySeverity` map.
 */
export function NotificationBell() {
  const env = useSelectedEnv();
  const { data } = useUnreadCount();

  const count = data?.count ?? 0;

  if (!env) return null;

  return (
    <Link
      to="/alerts/inbox"
      role="button"
      aria-label={`Notifications (${count} unread)`}
      className={css.bell}
    >
      <Bell size={16} />
      {count > 0 && (
        <span className={css.badge} aria-hidden>
          {count > 99 ? '99+' : count}
        </span>
      )}
    </Link>
  );
}