middleware.ts

import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";

import { i18n } from "./i18n-config";

import { match as matchLocale } from "@formatjs/intl-localematcher";
import Negotiator from "negotiator";

function getLocale(request: NextRequest): string | undefined {
  // Negotiator expects plain object so we need to transform headers
  const negotiatorHeaders: Record<string, string> = {};
  request.headers.forEach((value, key) => (negotiatorHeaders[key] = value));

  // @ts-ignore locales are readonly
  const locales: string[] = i18n.locales;

  // Use negotiator and intl-localematcher to get best locale
  let languages = new Negotiator({ headers: negotiatorHeaders }).languages(
    locales
  );

  const locale = matchLocale(languages, locales, i18n.defaultLocale);

  // Turn this on when english content is ready
  return "fi";
}

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

  if (
    [
      '/favicon.ico',
      '/favicon.png',
      '/manifest.json',
      '/admin',
      '/.netlify',
      '/.next',
      '#access_token'
    ].some(path => pathname.startsWith(path)) ||
    /\.(pdf|png|jpg|svg|ico|yml)$/.test(pathname)
  ) {
    return;
  }

  // Check if there is any supported locale in the pathname
  const pathnameIsMissingLocale = i18n.locales.every(
    (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`
  );

  // Redirect if there is no locale
  if (pathnameIsMissingLocale) {
    const locale = getLocale(request);

    return NextResponse.redirect(
      new URL(
        `/${locale}${pathname.startsWith("/") ? "" : "/"}${pathname}`,
        request.url
      )
    );
  }
}

export const config = {
  matcher: [
    // Skip all internal paths (_next)
    '/((?!_next|api|favicon.ico).*)',
    // Optional: Match all root level pages
    '/'
  ],
};