let headers = { 'accept-language': 'en-US,en;q=0.5' };
let languages = new Negotiator({ headers }).languages();
let locales = ['en', 'de'];
let defaultLocale = 'en';

match(languages, locales, defaultLocale);

function getLocale(request) {
    // Extract the language from the request headers
    const acceptLanguage = request.headers.get('accept-language');

    // Parse the accept language header to get the preferred languages
    const preferredLanguages = acceptLanguage
        ? acceptLanguage.split(',').map((language) => {
              const [locale, q] = language.trim().split(';q=');
              return { locale, q: parseFloat(q || '1') };
          })
        : [];

    // Sort the preferred languages by quality (q) in descending order
    preferredLanguages.sort((a, b) => b.q - a.q);

    // Find the first supported language from the preferred languages
    const supportedLanguage = preferredLanguages.find((language) =>
        locales.includes(language.locale),
    );

    // Return the supported language or the default locale if none found
    return supportedLanguage ? supportedLanguage.locale : defaultLocale;
}

export function middleware(request) {
    // Check if there is any supported locale in the pathname
    const { pathname } = request.nextUrl;
    const pathnameHasLocale = locales.some(
        (locale) =>
            pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`,
    );

    if (pathnameHasLocale) return;

    // Redirect if there is no locale
    const locale = getLocale(request);
    const newPathname = locale === 'en' ? pathname : `/${locale}${pathname}`;
    request.nextUrl.pathname = newPathname;
    // e.g. incoming request is /products
    // The new URL is now /en/products if locale is not 'en'
    return Response.redirect(request.nextUrl);
}

export const config = {
    matcher: [
     (_next)
        '/((?!_next).*)',
        // Optional: only run on root (/) URL
        // '/'
    ],
};