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

const locales = ["fa", "en"] as const;
const defaultLocale = "fa";

function pickLocale(req: NextRequest): string {
  const accept = req.headers.get("accept-language") ?? "";
  const preferred = accept
    .split(",")
    .map((p) => p.trim().split(";")[0]!.toLowerCase().split("-")[0])
    .find((tag) => (locales as readonly string[]).includes(tag));
  return preferred ?? defaultLocale;
}

export function proxy(req: NextRequest) {
  const { pathname } = req.nextUrl;
  const hasLocale = locales.some(
    (loc) => pathname === `/${loc}` || pathname.startsWith(`/${loc}/`),
  );
  if (hasLocale) return;

  const locale = pickLocale(req);
  const url = req.nextUrl.clone();
  url.pathname = `/${locale}${pathname === "/" ? "" : pathname}`;
  return NextResponse.redirect(url);
}

export const config = {
  matcher: ["/((?!_next|api|favicon.ico|.*\\..*).*)"],
};