import { useEffect, useSyncExternalStore } from 'react';

/**
 * Screens whose own buttons sit bottom-right, where the Copilot's reminder
 * bubble would cover them (Save changes, Save and continue). While one is
 * mounted the launcher keeps its button and count but shows no bubble.
 */
let screens = 0;
const listeners = new Set<() => void>();

const notify = (): void => listeners.forEach(listener => listener());

const subscribe = (listener: () => void): (() => void) => {
  listeners.add(listener);
  return () => listeners.delete(listener);
};

const isQuiet = (): boolean => screens > 0;

/**
 * Keeps the launcher's bubble away while the calling screen is mounted.
 *
 * @param active - Whether the screen has its buttons on screen now.
 */
export const useQuietLauncher = (active = true): void => {
  useEffect(() => {
    if (!active) {
      return undefined;
    }
    screens += 1;
    notify();
    return () => {
      screens -= 1;
      notify();
    };
  }, [active]);
};

/**
 * @return Whether a mounted screen asked the launcher to keep its bubble away.
 */
export const useLauncherQuiet = (): boolean =>
  useSyncExternalStore(subscribe, isQuiet, isQuiet);