0pt/middleware.ts

/**
 * `middleware.ts` -- Next.js request middleware = 0pt's framework-level auth
 * seam (the Next analog of a Fastify `onRequest` hook).
 *
 * This runs the Zitadel verification (src/auth/context.ts ->
 * src/auth/zitadel.ts) in front of every 0pt capability route (/api/0pt/*).
 * It does NOT touch the v0-generated UI routes or the unrelated
 * payment/order APIs (see the matcher below and the note in the PR that
 * introduced the fail-closed default).
 *
 *   AUTH_ENFORCE unset, or anything except "false" (DEFAULT, enforced):
 *     a valid verified token is required; 401 on missing/invalid, 403 when
 *     X-Tenant-Id disagrees with the token tenant. On success the verified
 *     principal is forwarded to the handler as `x-0pt-verified-sub` /
 *     `x-0pt-verified-tenant` request headers.
 *   AUTH_ENFORCE == "false" (explicit local-dev escape hatch): never rejects.
 *     REFUSED in production -- `assertAuthConfigSafe()` below throws at module
 *     load, so a production instance cannot boot with auth switched off.
 *
 * Health/metrics are exempt (they are also outside the matcher below, but the
 * exemption is kept explicit for robustness).
 */

import { NextResponse, type NextRequest } from 'next/server';
import { assertAuthConfigSafe, resolveAuthContext } from '@/src/auth/context';

// STARTUP GATE: fail to boot rather than serve /api/0pt/* openly in production.
assertAuthConfigSafe();

// Only guard the 0pt capability surface. The matcher keeps this middleware off
// the UI, auth, and payment routes entirely.
export const config = {
  matcher: ['/api/0pt/:path*'],
};

const EXEMPT_PATTERNS: RegExp[] = [
  /^\/api\/health(\/|$)/,
  /^\/api\/ready(\/|$)/,
  /^\/api\/admin\/metrics(\/|$)/,
];

export async function middleware(req: NextRequest): Promise<NextResponse> {
  const path = req.nextUrl.pathname;
  if (EXEMPT_PATTERNS.some((re) => re.test(path))) {
    return NextResponse.next();
  }

  const decision = await resolveAuthContext(req.headers);

  if (!decision.ok) {
    return NextResponse.json(
      { error: decision.code, message: decision.message, ...(decision.details ? { details: decision.details } : {}) },
      { status: decision.status },
    );
  }

  const principal = decision.ctx.principal;
  if (principal) {
    const forwarded = new Headers(req.headers);
    forwarded.set('x-0pt-verified-sub', principal.sub);
    forwarded.set('x-0pt-verified-tenant', principal.tenantId);
    return NextResponse.next({ request: { headers: forwarded } });
  }

  return NextResponse.next();
}