import { useCallback, useRef } from 'react';
import { defineChannel } from 'hooks/usePanelChannel';

/**
 * "Something on the fofos site changed — anyone reading it should read it again."
 *
 * ── Why a channel and not the URL ──
 *
 * `docs/navigation-audit.md` draws the line: anything ADDRESSABLE goes in the URL, and a channel is
 * only for a signal. Nobody wants to link to "the moment after the connection was saved", and there is
 * nothing to select — this is the second kind.
 *
 * ── The nonce is a plain counter, and that is not an accident ──
 *
 * Copied deliberately from `plugins/proxy-manager/web/channel.ts`, which records why.
 * `setSignal(n => n + 1)` is WRONG: the functional setter applies against the value captured at
 * render, so two bumps inside one render window both compute `snapshot + 1` and the second silently
 * overwrites the first — nobody re-reads. `Date.now()` has the same flaw in miniature, two bumps in
 * one millisecond being one number. A module counter never reads React state, so it cannot be wrong
 * however often it is called.
 */
const useFofosChangedChannel = defineChannel<number>('fofos-admin:changed', 0);

let nonce = 0;

export const useFofosChanged = () => {
  const [signal, setSignal] = useFofosChangedChannel();

  // The setter is a fresh closure every render and this `bump` goes into dependency lists, so it is
  // read through a ref — stable identity without freezing the first render's setter.
  const setRef = useRef(setSignal);
  setRef.current = setSignal;
  const bump = useCallback(() => setRef.current(++nonce), []);

  return [signal, bump] as const;
};