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

const SUPPORTED_LOCALES = ["en", "de"] as const;
type SupportedLocale = (typeof SUPPORTED_LOCALES)[number];

function pickLocaleFromHeader(acceptLanguage: string | null): SupportedLocale {
  if (!acceptLanguage) return "en";
  const lower = acceptLanguage.toLowerCase();
  // Very small parser: prefer de, then en
  if (lower.includes("de")) return "de";
  if (lower.includes("en")) return "en";
  return "en";
}

function hasLocalePrefix(pathname: string): boolean {
  return SUPPORTED_LOCALES.some((l) => pathname === `/${l}` || pathname.startsWith(`/${l}/`));
}

export function middleware(request: NextRequest) {
  const { pathname, search } = request.nextUrl;

  // If a locale-prefixed request hits a public asset path (e.g. /de/images/me.jpg),
  // redirect to the non-prefixed asset path.
  if (hasLocalePrefix(pathname)) {
    const rest = pathname.replace(/^\/(en|de)/, "") || "/";
    if (rest.includes(".")) {
      const responseUrl = request.nextUrl.clone();
      responseUrl.pathname = rest;
      const res = NextResponse.redirect(responseUrl);
      return addHeaders(request, res);
    }
  }

  // Do not locale-route public assets (anything with a dot), robots, sitemap, etc.
  if (pathname.includes(".")) {
    return addHeaders(request, NextResponse.next());
  }

  // Keep admin + APIs unlocalized for simplicity
  const isAdminOrApi =
    pathname.startsWith("/api/") ||
    pathname === "/api" ||
    pathname.startsWith("/manage") ||
    pathname.startsWith("/editor");

  // Locale routing for public site pages
  const responseUrl = request.nextUrl.clone();

  if (!isAdminOrApi) {
    if (hasLocalePrefix(pathname)) {
      // Persist locale preference
      const locale = pathname.split("/")[1] as SupportedLocale;
      const res = NextResponse.next();
      res.cookies.set("NEXT_LOCALE", locale, { path: "/" });

      // Continue below to add security headers
      // eslint-disable-next-line no-use-before-define
      return addHeaders(request, res);
    }

    // Redirect bare routes to locale-prefixed ones
    const preferred = pickLocaleFromHeader(request.headers.get("accept-language"));
    const redirectTarget =
      pathname === "/" ? `/${preferred}` : `/${preferred}${pathname}${search || ""}`;
    responseUrl.pathname = redirectTarget;
    const res = NextResponse.redirect(responseUrl);
    res.cookies.set("NEXT_LOCALE", preferred, { path: "/" });
    // eslint-disable-next-line no-use-before-define
    return addHeaders(request, res);
  }

  // Fix for 421 Misdirected Request with Nginx Proxy Manager
  // Ensure proper host header handling for reverse proxy
  const hostname = request.headers.get("host") || request.headers.get("x-forwarded-host") || "";
  
  // Add security headers to all responses
  const response = NextResponse.next();
  
  return addHeaders(request, response, hostname);
}

function addHeaders(request: NextRequest, response: NextResponse, hostnameOverride?: string) {
  const hostname =
    hostnameOverride ??
    request.headers.get("host") ??
    request.headers.get("x-forwarded-host") ??
    "";

  // Set proper headers for Nginx Proxy Manager
  if (hostname) {
    response.headers.set("X-Forwarded-Host", hostname);
    response.headers.set(
      "X-Real-IP",
      request.headers.get("x-real-ip") || request.headers.get("x-forwarded-for") || "",
    );
  }

  // Security headers (complementing next.config.ts headers)
  response.headers.set("X-DNS-Prefetch-Control", "on");
  response.headers.set("X-Frame-Options", "DENY");
  response.headers.set("X-Content-Type-Options", "nosniff");
  response.headers.set("X-XSS-Protection", "1; mode=block");
  response.headers.set("Referrer-Policy", "strict-origin-when-cross-origin");
  response.headers.set(
    "Permissions-Policy",
    "camera=(), microphone=(), geolocation=()",
  );

  // Rate limiting headers for API routes
  if (request.nextUrl.pathname.startsWith("/api/")) {
    response.headers.set("X-RateLimit-Limit", "100");
    response.headers.set("X-RateLimit-Remaining", "99");
  }

  return response;
}

export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - api (all API routes)
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico (favicon file)
     */
    "/((?!api|_next/static|_next/image|favicon.ico).*)",
  ],
};