import { NextRequest, NextResponse } from "next/server";
import { verifyToken, COOKIE_NAME } from "@/lib/auth-edge";

const CSRF_COOKIE_NAME = "bh-csrf-token";
const CSRF_HEADER_NAME = "x-csrf-token";
const STATE_CHANGING_METHODS = new Set(["POST", "PUT", "DELETE", "PATCH"]);

function generateCsrfToken(): string {
  const array = new Uint8Array(32);
  crypto.getRandomValues(array);
  let binary = "";
  for (const b of array) binary += String.fromCharCode(b);
  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

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

  // Allow login page and login API
  if (pathname === "/admin/login" || pathname === "/api/auth/login") {
    return NextResponse.next();
  }

  // Protect /admin/* and /api/admin/*
  const token = request.cookies.get(COOKIE_NAME)?.value;
  const valid = token ? await verifyToken(token) : false;

  if (!valid) {
    if (pathname.startsWith("/api/")) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }
    return NextResponse.redirect(new URL("/admin/login", request.url));
  }

  // Auto-issue CSRF cookie if missing (e.g. session from before CSRF was added)
  const hasCsrf = request.cookies.has(CSRF_COOKIE_NAME);
  if (!hasCsrf) {
    const csrfToken = generateCsrfToken();
    const response = NextResponse.next();
    response.cookies.set(CSRF_COOKIE_NAME, csrfToken, {
      httpOnly: false,
      secure: process.env.NODE_ENV === "production",
      sameSite: "strict",
      path: "/",
      maxAge: 60 * 60 * 24,
    });
    return response;
  }

  // CSRF check on state-changing API requests
  if (pathname.startsWith("/api/admin/") && STATE_CHANGING_METHODS.has(request.method)) {
    const csrfCookie = request.cookies.get(CSRF_COOKIE_NAME)?.value;
    const csrfHeader = request.headers.get(CSRF_HEADER_NAME);

    if (!csrfCookie || !csrfHeader || csrfCookie !== csrfHeader) {
      return NextResponse.json({ error: "CSRF token mismatch" }, { status: 403 });
    }
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/admin/:path*", "/api/admin/:path*"],
};