import { createServerClient } from '@supabase/ssr';
import { NextResponse, type NextRequest } from 'next/server';
import { supabaseAuthCookieName } from '@/lib/supabase/cookie-name';

// Path prefixes that are reachable without a completed MFA step-up. These are
// the auth flow itself, the MFA enrollment/challenge surface, their supporting
// APIs, and public email templates. Everything else (including the root path)
// requires aal2 once the user is authenticated.
const MFA_ALLOWLIST = [
  '/login',
  '/signup',
  '/auth',
  '/security',
  '/api/auth',
  '/api/security',
  '/email-templates',
];

function isMfaAllowlisted(path: string): boolean {
  return MFA_ALLOWLIST.some(
    (prefix) => path === prefix || path.startsWith(`${prefix}/`),
  );
}

export async function middleware(request: NextRequest) {
  let response = NextResponse.next({ request });

  const supabase = createServerClient(
    // Server-side requests reach Supabase directly over the Docker network
    // (SUPABASE_INTERNAL_URL, e.g. http://kong-prod:8000) so they bypass
    // Caddy's per-IP `/auth/*` rate limiter; all server traffic would
    // otherwise share a single NATed gateway IP and saturate that budget,
    // intermittently 429ing getUser() and bouncing users to /login. Falls
    // back to the public URL when the internal one is not configured.
    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      // Pin the cookie name to the public-URL-derived value so it matches the
      // browser client even though the API points at the internal host.
      cookieOptions: { name: supabaseAuthCookieName() },
      cookies: {
        getAll() {
          return request.cookies.getAll();
        },
        setAll(toSet) {
          toSet.forEach(({ name, value }) => request.cookies.set(name, value));
          response = NextResponse.next({ request });
          toSet.forEach(({ name, value, options }) =>
            response.cookies.set(name, value, options),
          );
        },
      },
    },
  );

  const {
    data: { user },
    error: userError,
  } = await supabase.auth.getUser();

  const path = request.nextUrl.pathname;

  // Carry any cookies Supabase rotated onto the working `response` over to a
  // deny/redirect response, so a refreshed session/refresh token is always
  // persisted — otherwise a fresh NextResponse would drop them and a
  // concurrent request could spuriously 401. Also stamp `no-store` so these
  // short-circuit responses are never cached by intermediaries or the browser.
  const withCookies = (res: NextResponse): NextResponse => {
    response.cookies.getAll().forEach((cookie) => res.cookies.set(cookie));
    res.headers.set('Cache-Control', 'no-store');
    return res;
  };

  const redirectTo = (pathname: string, search = ''): NextResponse => {
    const url = request.nextUrl.clone();
    url.pathname = pathname;
    url.search = search;
    return withCookies(NextResponse.redirect(url));
  };

  // If a session cookie is present but the auth server rejects it because the
  // underlying user or session no longer exists (a deleted account, or a stale
  // cookie that outlived its session), proactively clear the Supabase auth
  // cookies. Otherwise the browser keeps a token whose `sub` is gone, every
  // `getUser()` 403s with `user_not_found`, and the UI gets wedged in a
  // confusing "logged-out page that still shows a Sign out button" state.
  const INVALID_SESSION_CODES = new Set([
    'user_not_found',
    'session_not_found',
    'session_expired',
    'refresh_token_not_found',
    'bad_jwt',
  ]);
  const isAuthCookie = (name: string): boolean =>
    name.startsWith('sb-') && name.includes('-auth-token');
  if (
    !user &&
    userError &&
    INVALID_SESSION_CODES.has(userError.code ?? '') &&
    request.cookies.getAll().some((c) => isAuthCookie(c.name))
  ) {
    const clearStale = (res: NextResponse): NextResponse => {
      request.cookies.getAll().forEach((c) => {
        if (isAuthCookie(c.name)) {
          res.cookies.set(c.name, '', { maxAge: 0, path: '/' });
        }
      });
      res.headers.set('Cache-Control', 'no-store');
      return res;
    };
    if (path.startsWith('/api/')) {
      return clearStale(
        NextResponse.json({ error: 'unauthorized' }, { status: 401 }),
      );
    }
    if (!isMfaAllowlisted(path)) {
      const url = request.nextUrl.clone();
      url.pathname = '/login';
      url.search = '';
      return clearStale(NextResponse.redirect(url));
    }
    // Allowlisted pages (e.g. /login itself) render fine logged-out — just drop
    // the dead cookies so the nav is consistent on the next request.
    return clearStale(NextResponse.next({ request }));
  }

  // Defense-in-depth: guard the admin surface here in addition to the
  // per-route requireAdmin()/requireAdminApi() checks.
  if (path.startsWith('/admin') || path.startsWith('/api/admin')) {
    if (!user) {
      if (path.startsWith('/api/admin')) {
        return withCookies(
          NextResponse.json({ error: 'unauthorized' }, { status: 401 }),
        );
      }
      return redirectTo('/login');
    }
    if (user.app_metadata?.role !== 'admin') {
      if (path.startsWith('/api/admin')) {
        return withCookies(
          NextResponse.json({ error: 'forbidden' }, { status: 403 }),
        );
      }
      return redirectTo('/dashboard');
    }
  }

  // Mandatory MFA gate for every authenticated request outside the allowlist.
  if (user && !isMfaAllowlisted(path)) {
    const [{ data: aal }, { data: factors }] = await Promise.all([
      supabase.auth.mfa.getAuthenticatorAssuranceLevel(),
      supabase.auth.mfa.listFactors(),
    ]);
    const verifiedCount =
      factors?.all.filter((f) => f.status === 'verified').length ?? 0;

    if (verifiedCount === 0) {
      // No second factor at all → force enrollment.
      return redirectTo('/security/enroll');
    }
    if (aal?.nextLevel === 'aal2' && aal?.currentLevel === 'aal1') {
      // Has a factor but session is only aal1 → force step-up, preserving the
      // originally requested destination.
      const next = encodeURIComponent(`${path}${request.nextUrl.search}`);
      return redirectTo('/security/challenge', `?next=${next}`);
    }
  }

  return response;
}

export const config = {
  matcher: [
    '/((?!_next/static|_next/image|favicon.ico|api/tunnel/claim|api/device).*)',
    '/admin/:path*',
    '/api/admin/:path*',
  ],
};