export const SUBJECTS = {
  STATEMENT_GET: 'verae.billing.statement.get',
  BALANCE_ADJUST: 'verae.billing.balance.adjust',
  AUTHZ_CHECK: 'verae.access.authz.check',
};
const PLANE = 'staff';

async function authz(subject, payload) {
  const http = process.env.AUTHZ_URL;
  if (!http && !process.env.NATS_URL) return { allow: true, subject };
  if (http) {
    const r = await fetch(`${http.replace(/\/$/, '')}/check`, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify({ plane: PLANE, subject, kind: payload?.kind, payload, principal: payload?.agent }),
    });
    return r.json();
  }
  return { allow: true, subject };
}

export async function billingRequest(subject, payload) {
  const decision = await authz(subject, payload);
  if (decision && decision.allow === false) {
    const err = new Error(decision.reason || 'denied');
    err.status = 403;
    err.decision = decision;
    throw err;
  }
  const url = process.env.NATS_URL;
  if (!url) return null;
  try {
    const { connect, StringCodec } = await import('nats');
    const nc = await connect({ servers: url.split(','), name: 'zappier-customer-service' });
    const sc = StringCodec();
    const m = await nc.request(subject, sc.encode(JSON.stringify({ ...payload, plane: PLANE })), { timeout: 2000 });
    const out = JSON.parse(sc.decode(m.data) || '{}');
    await nc.close();
    return out;
  } catch (err) {
    if (err.status === 403) throw err;
    return null;
  }
}