// proxy.ts  (was middleware.ts)
import { NextRequest, NextResponse } from "next/server";
import { defaultLocale, isValidLocale } from "@/lib/dictionaries";

// RENAMED: middleware → proxy (Next.js 16 convention)
export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;

  // Skip static files, API routes, Next.js internals
  if (
    pathname.startsWith("/_next") ||
    pathname.startsWith("/api") ||
    pathname.startsWith("/favicon") ||
    pathname.includes(".")
  ) {
    return NextResponse.next();
  }

  // Check if path already has a valid locale prefix
  const pathLocale = pathname.split("/")[1];
  if (isValidLocale(pathLocale)) {
    // Serve directly — NEVER redirect locale-prefixed URLs.
    // Forward the URL locale as a request header so server components
    // without params access (e.g. not-found.tsx) can read it.
    const requestHeaders = new Headers(request.headers);
    requestHeaders.set("x-locale", pathLocale);
    requestHeaders.set("x-preferred-locale", detectPreferredLocale(request));
    return NextResponse.next({ request: { headers: requestHeaders } });
  }

  // No locale prefix — redirect to default (or cookie preference)
  const cookieLocale = request.cookies.get("NEXT_LOCALE")?.value;
  const targetLocale =
    cookieLocale && isValidLocale(cookieLocale) ? cookieLocale : defaultLocale;

  const url = request.nextUrl.clone();
  url.pathname = `/${targetLocale}${pathname}`;
  return NextResponse.redirect(url, 307);
}

function detectPreferredLocale(request: NextRequest): string {
  const acceptLang = request.headers.get("accept-language") || "";

  const segments = acceptLang
    .split(",")
    .map((part) => {
      const [lang, q] = part.trim().split(";q=");
      return {
        lang: lang.toLowerCase().trim(),
        quality: q ? parseFloat(q) : 1.0,
      };
    })
    .sort((a, b) => b.quality - a.quality);

  for (const { lang } of segments) {
    const base = lang.split("-")[0];
    if (["sr", "bs", "hr"].includes(base)) return "sr";
    if (base === "en") return "en";
  }

  return defaultLocale;
}

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