/** Coalesce pushes, serialize refreshes, and recover missed events after reconnect or tab activation. */
export function betaUpdates(load: () => Promise<unknown>, betaId?: () => number): () => void {
    let timer: ReturnType<typeof setTimeout> | undefined;
    let stopped = false,
        running = false,
        pending = false;
    const schedule = () => {
        pending = true;
        if (stopped || running || timer || document.hidden) return;
        timer = setTimeout(async () => {
            timer = undefined;
            if (stopped || document.hidden) return;
            running = true;
            pending = false;
            try {
                await load();
            } catch {
                /* The page owns its error state; later events can retry. */
            } finally {
                running = false;
                if (pending) schedule();
            }
        }, 200);
    };
    const changed = (event: Event) => {
        if (!betaId || (event as CustomEvent).detail?.betaId === betaId()) schedule();
    };
    const visible = () => {
        if (!document.hidden) schedule();
    };
    window.addEventListener('ec:beta-changed', changed);
    window.addEventListener('ec:pipeline-connected', schedule);
    window.addEventListener('ec:fleet-changed', schedule);
    document.addEventListener('visibilitychange', visible);
    return () => {
        stopped = true;
        clearTimeout(timer);
        window.removeEventListener('ec:beta-changed', changed);
        window.removeEventListener('ec:pipeline-connected', schedule);
        window.removeEventListener('ec:fleet-changed', schedule);
        document.removeEventListener('visibilitychange', visible);
    };
}