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

/**
 * "Something at NPM changed — anyone reading it should read it again."
 *
 * Two publishers, and naming it after the second one would have been wrong the other way round. The
 * connection being saved or removed is one. **A chat turn that ran tools is the other**, and it is the
 * bigger one: an agent that deletes a proxy host leaves every list on the screen describing a world that
 * no longer exists, and nothing else would ever tell them.
 *
 * ── 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 — "something changed, re-read it". This is the second kind. Nobody wants to link to "the
 * moment after the connection was saved", and there is nothing to select.
 *
 * ── Why it is needed at all ──
 *
 * The panels are siblings in a workspace layout. None of them can call into another and none should try —
 * they are mounted independently and no one owns the rest. Before this, saving a connection left every
 * panel showing whatever it had failed to load a minute earlier, and the only fix a person had was a
 * manual refresh. Reported on 2026-08-25 the first time a connection was saved through the form; the chat
 * publisher was added the same day, after an agent deleted two hosts that stayed on screen.
 *
 * ── The nonce is a plain counter, and that is not an accident ──
 *
 * Copied deliberately from `officerdev/src/channels.ts`, which records why. `setSignal(n => n + 1)` is
 * WRONG here: 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 useNpmChangedChannel = defineChannel<number>('proxy-manager:npm-changed', 0);

let nonce = 0;

export const useNpmChanged = () => {
  const [signal, setSignal] = useNpmChangedChannel();

  // 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;
};