middleware.tsx

import { NextResponse, type NextRequest } from "next/server";
import { match } from "@formatjs/intl-localematcher";
import Negotiator from "negotiator";
import PageBaseConfiguration from "./configuration";

function getLocale(request: NextRequest) {
  const config = PageBaseConfiguration();

  try {
    const acceptedLanguage =
      request.headers.get("accept-language") ?? undefined;
    const headers = { "accept-language": acceptedLanguage };
    const languages = new Negotiator({ headers }).languages();

    return match(languages, config.supportedLocales, config.defaultLocale);
  } catch {
    return config.defaultLocale;
  }
}

function redirectToLocale(request: NextRequest, locale: string, path: string) {
  return NextResponse.redirect(new URL(`/${locale}${path}`, request.url));
}

export async function middleware(request: NextRequest) {
  const config = PageBaseConfiguration();
  const pathname = request.nextUrl.pathname;

  const pathLocale = config.supportedLocales.find(
    (locale) => pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`,
  );

  if (pathname === "/" && config.startRoute && config.startRoute !== "/") {
    const locale = getLocale(request);
    return redirectToLocale(
      request,
      locale,
      `/${config.startRoute}`.replaceAll("//", "/"),
    );
  }

  if (pathLocale == null) {
    const locale = getLocale(request);
    return redirectToLocale(request, locale, pathname);
  }

  const requestHeaders = new Headers(request.headers);
  requestHeaders.set("x-locale", pathLocale);

  return NextResponse.next({ request: { headers: requestHeaders } });
}

export const config = {
  matcher: [
    "/((?!api|_next|favicon.ico|robots.txt|sitemap.xml|appicons|backgrounds|favicons|flags|images|jumbotron|assets).*)",
  ],
};