import { useSyncExternalStore } from 'react';

/**
 * The score the open panel computes as the post is edited, for the toolbar
 * button: the stored score only changes when the post is saved.
 */
let current: number | null = null;
const listeners = new Set<() => void>();

export const setLiveScore = (score: number | null): void => {
  if (score === current) {
    return;
  }
  current = score;
  listeners.forEach(listener => listener());
};

export const getLiveScore = (): number | null => current;

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

export const useLiveScore = (): number | null =>
  useSyncExternalStore(subscribe, () => current);