middleware.ts

import { NextResponse } from 'next/server';
import { match } from '@formatjs/intl-localematcher';
import Negotiator from 'negotiator';

let locales = ['ru', 'en'];

function getLocale(request) {
  let languages = new Negotiator(request).languages(locales);
  let defaultLocale = 'ru';

  return match(languages, locales, defaultLocale);
}

export function middleware(request) {
  const pathname = request.nextUrl.pathname;
  const pathnameIsMissingLocale = locales.every(
    (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`,
  );
  const locale = getLocale(request);

  if (
    (pathname === '/' && locale !== 'ru') ||
    (pathname !== '/' && pathnameIsMissingLocale)
  ) {
    return NextResponse.redirect(
      new URL(`/${locale}${pathname}`, request.url),
    );
  }
}

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