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;
    let headers = { "accept-language": acceptedLanguage };
    let languages = new Negotiator({ headers }).languages();

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

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

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

  if (pathname === "/" && config.startRoute && config.startRoute !== "/") {
    const locale = getLocale(request);

    return NextResponse.redirect(
      new URL(
        `/${locale}/${config.startRoute}`.replaceAll("//", "/"),
        request.url,
      ),
    );
  }

  // Redirect if there is no locale
  if (pathLocale == null) {
    const locale = getLocale(request);
    return NextResponse.redirect(new URL(`/${locale}${pathname}`, request.url));
  }

  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).*)",
  ],
};