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

// ---------------------------------------------------------------------------
// Simple in-memory rate limiter (resets on cold start / per-instance)
// For production use a Redis-backed store via @upstash/ratelimit or similar.
// ---------------------------------------------------------------------------
interface RateLimitEntry {
  count: number;
  resetAt: number;
}

const rateLimitMap = new Map<string, RateLimitEntry>();
const RATE_LIMIT_MAX = 100; // requests per window
const RATE_LIMIT_WINDOW_MS = 60_000; // 1 minute

function checkRateLimit(ip: string): boolean {
  const now = Date.now();
  const entry = rateLimitMap.get(ip);

  if (!entry || now > entry.resetAt) {
    rateLimitMap.set(ip, { count: 1, resetAt: now + RATE_LIMIT_WINDOW_MS });
    return true; // allowed
  }

  if (entry.count >= RATE_LIMIT_MAX) {
    return false; // blocked
  }

  entry.count++;
  return true; // allowed
}

// ---------------------------------------------------------------------------
// Paths that bypass middleware entirely
// ---------------------------------------------------------------------------
const PUBLIC_PATH_PREFIXES = [
  "/api/auth",
  "/_next",
  "/favicon.ico",
  "/public",
];

const STATIC_EXTENSIONS = /\.(png|jpe?g|gif|svg|ico|webp|woff2?|ttf|otf|eot|css|js\.map)$/i;

function isPublicPath(pathname: string): boolean {
  if (STATIC_EXTENSIONS.test(pathname)) return true;
  return PUBLIC_PATH_PREFIXES.some((prefix) => pathname.startsWith(prefix));
}

// ---------------------------------------------------------------------------
// Security headers applied to every response
// ---------------------------------------------------------------------------
function buildCSP(nonce: string): string {
  return [
    "default-src 'self'",
    `script-src 'self' 'nonce-${nonce}'`,
    "style-src 'self' 'unsafe-inline' https://fonts.googleapis.com",
    "font-src 'self' https://fonts.gstatic.com data:",
    "img-src 'self' data: blob: https://crafatar.com https://mc-heads.net https://visage.surgeplay.com https://minotar.net",
    "connect-src 'self' ws: wss:",
    "frame-src 'self'",
    "frame-ancestors 'self'",
    "worker-src 'self' blob:",
    "media-src 'self'",
    "object-src 'none'",
    "base-uri 'self'",
    "form-action 'self'",
  ].join("; ");
}

function applySecurityHeaders(response: NextResponse, nonce: string): void {
  const csp = buildCSP(nonce);
  response.headers.set("Content-Security-Policy", csp);
  response.headers.set("X-Frame-Options", "SAMEORIGIN");
  response.headers.set("X-Content-Type-Options", "nosniff");
  response.headers.set("Referrer-Policy", "strict-origin-when-cross-origin");
  response.headers.set(
    "Permissions-Policy",
    "camera=(), microphone=(), geolocation=(), browsing-topics=()"
  );
  // Pass the nonce to pages so they can inject it into inline scripts
  response.headers.set("x-nonce", nonce);
}

// ---------------------------------------------------------------------------
// Middleware
// ---------------------------------------------------------------------------
export async function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;

  // Skip middleware for public/static paths
  if (isPublicPath(pathname)) {
    return NextResponse.next();
  }

  // Generate a fresh nonce for this request
  const nonce = crypto.randomBytes(16).toString("base64");

  // ---------------------------------------------------------------------------
  // Rate limiting for API routes
  // ---------------------------------------------------------------------------
  if (pathname.startsWith("/api/")) {
    const ip =
      request.headers.get("x-forwarded-for")?.split(",")[0]?.trim() ??
      request.headers.get("x-real-ip") ??
      "unknown";

    if (!checkRateLimit(ip)) {
      return new NextResponse(
        JSON.stringify({ error: "Too many requests. Please slow down." }),
        {
          status: 429,
          headers: {
            "Content-Type": "application/json",
            "Retry-After": "60",
            "X-RateLimit-Limit": String(RATE_LIMIT_MAX),
            "X-RateLimit-Window": "60",
          },
        }
      );
    }
  }

  // ---------------------------------------------------------------------------
  // Auth guard for dashboard routes
  // ---------------------------------------------------------------------------
  if (pathname.startsWith("/(dashboard)") || isDashboardRoute(pathname)) {
    try {
      // Dynamically import auth to avoid circular deps at module init
      const { auth } = await import("@/lib/auth/index");
      const session = await auth.api.getSession({
        headers: request.headers,
      });

      if (!session) {
        const loginUrl = new URL("/login", request.url);
        loginUrl.searchParams.set("callbackUrl", pathname);
        const redirectResponse = NextResponse.redirect(loginUrl);
        applySecurityHeaders(redirectResponse, nonce);
        return redirectResponse;
      }
    } catch {
      // If auth module is not yet available (during initial setup), allow through
      // In production this should not happen
      console.error("[middleware] Auth check failed – denying access");
      const loginUrl = new URL("/login", request.url);
      const redirectResponse = NextResponse.redirect(loginUrl);
      applySecurityHeaders(redirectResponse, nonce);
      return redirectResponse;
    }
  }

  // ---------------------------------------------------------------------------
  // Allow the request through, attach security headers
  // ---------------------------------------------------------------------------
  const response = NextResponse.next();
  applySecurityHeaders(response, nonce);
  return response;
}

/**
 * Checks whether the pathname maps to a dashboard route.
 * Next.js route groups (dashboard) don't appear in the URL, so we protect
 * all non-auth, non-api routes that would render inside the dashboard layout.
 */
function isDashboardRoute(pathname: string): boolean {
  const AUTH_ROUTES = ["/login", "/register", "/forgot-password", "/reset-password", "/verify"];
  if (AUTH_ROUTES.some((r) => pathname.startsWith(r))) return false;
  if (pathname.startsWith("/api/")) return false;
  if (pathname === "/") return true;

  const DASHBOARD_SEGMENTS = [
    "/dashboard",
    "/console",
    "/monitoring",
    "/scheduler",
    "/players",
    "/map",
    "/plugins",
    "/files",
    "/backups",
    "/settings",
    "/updates",
    "/team",
    "/audit",
  ];
  return DASHBOARD_SEGMENTS.some((seg) => pathname.startsWith(seg));
}

export const config = {
  matcher: [
    /*
     * Match all request paths except:
     * - _next/static (static files)
     * - _next/image (image optimisation)
     * - favicon.ico
     */
    "/((?!_next/static|_next/image|favicon.ico).*)",
  ],
};