import type { AbstractIntlMessages } from "next-intl";

/**
 * Client-side message scoping.
 *
 * `getMessages()` hands back the whole catalogue, and the root layout feeds all
 * of it to `NextIntlClientProvider`, which serialises every message into the RSC
 * payload of every page. The catalogue is ~235 KB of which `pages.admin` and
 * `admin` together are ~177 KB — and no public page ever reads either.
 *
 * Nested `NextIntlClientProvider`s REPLACE the parent's messages rather than
 * merging them (see use-intl's IntlProvider: `messages ?? parent.messages`), so
 * a segment cannot ask for "just my part". Instead the public layout installs a
 * provider seeded with the public subset, which shrinks the payload for every
 * public page while leaving /admin, /mod, /client and /admin-next on the full set.
 */

/** Top-level namespaces plus `pages.*` sub-namespaces reserved for staff tools. */
const ADMIN_ONLY_NAMESPACES = new Set(["admin"]);
const ADMIN_ONLY_PAGE_NAMESPACES = new Set(["admin"]);

/**
 * Drop the staff-tool namespaces from a full catalogue.
 *
 * A denylist rather than an allowlist on purpose: a new public page should work
 * immediately rather than silently 500 on a missing namespace, and the only
 * namespaces that must never reach a public client are the two admin ones. A
 * guard test asserts that no component under `app/(site)` references them.
 */
export function publicClientMessages(
	messages: AbstractIntlMessages,
): AbstractIntlMessages {
	const result: AbstractIntlMessages = {};

	for (const [key, value] of Object.entries(messages)) {
		if (ADMIN_ONLY_NAMESPACES.has(key)) continue;
		if (key !== "pages") {
			result[key] = value;
			continue;
		}

		const pages: AbstractIntlMessages = {};
		for (const [pageKey, pageValue] of Object.entries(
			value as AbstractIntlMessages,
		)) {
			if (ADMIN_ONLY_PAGE_NAMESPACES.has(pageKey)) continue;
			pages[pageKey] = pageValue;
		}
		result.pages = pages;
	}

	return result;
}