import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";
import { SUPPORTED_LOCALES, DEFAULT_LOCALE, LOCALE_COOKIE, getPathWithoutLocale, buildLocalePath, isValidLocale } from "@/lib/i18n/locales";
import type { Locale } from "@/lib/i18n/locales";

const OLD_SERBIAN_PATHS = ["products", "about", "contact", "checkout"];

function detectLocale(cookieLocale: string | undefined, acceptLanguage: string): Locale {
  if (cookieLocale && isValidLocale(cookieLocale)) {
    return cookieLocale;
  }
  if (acceptLanguage.includes("en")) {
    return "en";
  }
  return DEFAULT_LOCALE;
}

export default function middleware(request: NextRequest) {
  const pathname = request.nextUrl.pathname;
  const cookieLocale = request.cookies.get(LOCALE_COOKIE)?.value;
  const acceptLanguage = request.headers.get("accept-language") || "";

  if (pathname === "/" || pathname === "") {
    const locale = detectLocale(cookieLocale, acceptLanguage);
    const url = request.nextUrl.clone();
    url.pathname = buildLocalePath(locale, "/");
    return NextResponse.redirect(url, 301);
  }

  const isOldSerbianPath = OLD_SERBIAN_PATHS.some(
    (path) => pathname === `/${path}` || pathname.startsWith(`/${path}/`)
  );

  if (isOldSerbianPath) {
    const locale = detectLocale(cookieLocale, acceptLanguage);
    const newPath = buildLocalePath(locale, pathname);
    const url = request.nextUrl.clone();
    url.pathname = newPath;
    return NextResponse.redirect(url, 301);
  }

  return NextResponse.next();
}

export const config = {
  matcher: [
    "/",
    `/${SUPPORTED_LOCALES.join("|")}/:path*`,
    "/((?!api|_next|_vercel|.*\\..*).*)",
  ],
};