import { type NextRequest, NextResponse } from "next/server";
import { defaultLocale, isLocale } from "@/translations/config";

function getPreferredLocale(request: NextRequest) {
  const cookieLocale =
    request.cookies.get("HABIB_LANGUAGE")?.value ??
    request.cookies.get("habib_language")?.value;

  if (cookieLocale) {
    const normalizedCookie = cookieLocale.trim().toLowerCase();
    if (isLocale(normalizedCookie)) return normalizedCookie;
  }

  // Walk the full Accept-Language list (not only the first entry): some
  // devices send `fa-IR, fa;q=0.9, en;q=0.8` where the region subtag belongs
  // to the first entry but a bare supported language follows. Normalize
  // region/case (`fa-IR` → `fa`, `zh-Hans-CN` → `zh`) and skip wildcards.
  const acceptLanguage = request.headers.get("accept-language") ?? "";
  for (const part of acceptLanguage.split(",")) {
    const tag = part.split(";")[0]?.trim().toLowerCase();
    if (!tag || tag === "*") continue;
    const language = tag.split("-")[0];
    if (isLocale(language)) return language;
  }

  return defaultLocale;
}

export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;
  const pathnameLocale = pathname.split("/")[1];
  const pathnameHasLocale = isLocale(pathnameLocale);
  const cookieLocale =
    request.cookies.get("HABIB_LANGUAGE")?.value ??
    request.cookies.get("habib_language")?.value;
  const authoritativeLocale = isLocale(cookieLocale?.toLowerCase())
    ? cookieLocale.toLowerCase()
    : null;

  if (pathnameHasLocale) {
    if (authoritativeLocale && authoritativeLocale !== pathnameLocale) {
      const url = request.nextUrl.clone();
      const segments = pathname.split("/");
      segments[1] = authoritativeLocale;
      url.pathname = segments.join("/");
      return NextResponse.redirect(url);
    }
    const requestHeaders = new Headers(request.headers);
    requestHeaders.set("x-habib-locale", pathnameLocale);
    return NextResponse.next({ request: { headers: requestHeaders } });
  }

  const locale = getPreferredLocale(request);
  const url = request.nextUrl.clone();
  url.pathname = `/${locale}${pathname === "/" ? "" : pathname}`;

  return NextResponse.redirect(url);
}

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