import { createAction } from '@reduxjs/toolkit';

/*
 * Tier 2 offline support contract. RTK Query can seed its cache from a
 * persisted snapshot via `extractRehydrationInfo` (see `api/index.ts`). We use
 * a single action whose payload is the previously-saved api slice state; the
 * api reducer pulls `queries`/`mutations` out of it on startup so last-seen
 * library data renders read-only while the backend is unreachable.
 *
 * The type string lives here (not in the store) so `api/index.ts` can match it
 * without importing from the store layer (which would create a cycle).
 */
export const REHYDRATE_API = 'api/rehydrate';

export interface RehydrateApiPayload {
  queries: Record<string, unknown>;
  mutations: Record<string, unknown>;
  // RTKQ's invalidation slice reads `provided.tags`/`provided.keys` during
  // rehydration (it does `Object.entries(provided.tags ?? {})`), so `provided`
  // must be an object — a bare `{ queries, mutations }` makes it crash on
  // `provided.tags` of undefined. Always present; empty objects are valid.
  provided: { tags: Record<string, unknown>; keys: Record<string, unknown> };
}

export const rehydrateApi = createAction<RehydrateApiPayload>(REHYDRATE_API);