import type { Locale } from "date-fns";
import type { AppDateFormat, AppLocale, AppRequestHeaders, AppTimeFormat, AppTimezone } from "./types.js";
/**
 * THE PER-REQUEST HOME OF EVERYTHING A NON-REACT CALLER READS (v32, gh#1219).
 *
 * Locale, timezone, the date/time formats and the request headers used to be three module-level
 * variables (`translate.ts`, `request-headers.ts`, `lib/datetime/sync.ts`). In a browser that is
 * one user and harmless. On a server it is every request at once: the last `AppProvider` to render
 * wrote them, so a `translateCurrent` / `formatDate` / `getAppRequestHeaders` call in request A
 * answered with request B's language and zone — measured in `ssr-request-isolation.test.tsx`.
 *
 * Now each of those modules keeps its slot in ONE `AppSettingsState` object, and which object is
 * "current" depends on where the call runs:
 *
 * 1. inside `runWithAppSettings(settings, fn)` → that call's own object. On a server it is carried
 *    by `AsyncLocalStorage`, so it survives every `await` inside `fn`; where no AsyncLocalStorage
 *    exists it covers the synchronous part of `fn` only.
 * 2. otherwise → one module-level object, which is the browser's single-user case.
 *
 * React components do not need this: they read `AppProvider`'s context, which is per tree by
 * construction. The scope is for code that has no React context to read.
 */
export type AppSettings = {
    locale: AppLocale;
    fallbackLocale: AppLocale;
    timezone: AppTimezone;
    timeFormat: AppTimeFormat;
    dateFormat: AppDateFormat;
};
/** @internal Each module owns one slot; an unset slot means "nothing chose it — use the default". */
export type AppSettingsState = {
    i18n?: Partial<Pick<AppSettings, "locale" | "fallbackLocale">>;
    datetime?: Partial<Pick<AppSettings, "locale" | "timezone" | "timeFormat" | "dateFormat">> & {
        dateFnsLocale?: Locale;
    };
    headers?: Partial<AppRequestHeaders>;
};
/** @internal The state object the current call belongs to. Mutated in place by the `sync*` writers. */
export declare function getAppSettingsState(): AppSettingsState;
/**
 * Run `fn` with its own locale / timezone / format / header state — one call per server request.
 *
 * Everything `fn` reaches without a React context (`translateCurrent`, `formatDate` with no
 * options, `getAppRequestHeaders`, and an `AppProvider` rendered inside it syncing its values for
 * those callers) reads and writes THIS call's state, never another request's. Unset fields keep
 * the neutral defaults (`<html lang>`/`en`, UTC on a server, formats from `Intl`).
 *
 * ```ts
 * const html = await runWithAppSettings({ locale: "de", timezone: "Europe/Berlin" }, () =>
 *   renderToString(<App />),
 * );
 * ```
 */
export declare function runWithAppSettings<R>(settings: Partial<AppSettings>, fn: () => R): R;