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

import { defaultLocale, locales } from "@/lib/i18n";

function getLocale(request: NextRequest): string {
  const accept = request.headers.get("accept-language") ?? "";
  const preferred = accept
    .split(",")
    .map((part) => part.split(";")[0].trim().slice(0, 2).toLowerCase());
  const match = preferred.find((code) =>
    (locales as readonly string[]).includes(code),
  );
  return match ?? defaultLocale;
}

export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;
  const pathnameHasLocale = locales.some(
    (locale) => pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`,
  );
  if (pathnameHasLocale) return;
  const locale = getLocale(request);
  request.nextUrl.pathname = `/${locale}${pathname}`;
  return NextResponse.redirect(request.nextUrl);
}

export const config = {
  // Exclude `api` (route handlers must not be locale-prefixed), `_next`
  // internals, and any path with a file extension (static assets).
  matcher: ["/((?!api|_next|.*\\..*).*)"],
};