Gestione degli errori

async function callWithRetry(fn, { maxAttempts = 3, baseDelay = 500 } = {}) {
  // Safe codes to retry: 429, 500, 502, 503
  const RETRYABLE = new Set([429, 500, 502, 503]);

  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    const res = await fn();

    if (res.ok) return res;

    const { status } = res;

    // Non-retryable — surface error immediately
    if (!RETRYABLE.has(status)) {
      const body = await res.json().catch(() => ({}));
      throw Object.assign(new Error(body.error ?? 'API error'), { status, body });
    }

    if (attempt === maxAttempts) {
      throw Object.assign(new Error('Max retries reached'), { status });
    }

    // Exponential backoff: 500ms, 1000ms, 2000ms …
    const delay = baseDelay * 2 ** (attempt - 1);
    await new Promise(r => setTimeout(r, delay));
  }
}

// Usage
const res = await callWithRetry(() =>
  fetch('https://api.novauth.com/api/v1/connect-hub/call/flash', {
    method: 'POST',
    headers: {
      'x-api-key':    process.env.BETATEL_API_KEY,
      'x-account-id': process.env.BETATEL_ACCOUNT_ID,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ callee: '+14155552671' })
  })
);

async function sendWithFallback(phone, otp) {
  // 1. Try Verify Call first
  try {
    const flash = await fetch('.../call/flash', {
      method: 'POST',
      headers,
      body: JSON.stringify({ callee: phone })
    });
    if (flash.ok) return { channel: 'flash', ...(await flash.json()) };
  } catch {}

  // 2. Flash failed — fall back to Telegram if user has it
  try {
    const tg = await fetch('.../telegram', {
      method: 'POST',
      headers,
      body: JSON.stringify({ to: phone, code: otp, ttl: 120 })
    });
    if (tg.ok) return { channel: 'telegram', ...(await tg.json()) };
  } catch {}

  // 3. Final fallback: SMS (widest global reach)
  const sms = await fetch('.../sms', {
    method: 'POST',
    headers,
    body: JSON.stringify({ to: phone, text: `Your code: ${otp}` })
  });
  if (!sms.ok) throw new Error('All channels failed');
  return { channel: 'sms', ...(await sms.json()) };
}

const res = await fetch(url, { method: 'POST', headers, body });

if (res.status === 429) {
  const retryAfter = Number(res.headers.get('Retry-After') ?? 1);
  console.warn(`Rate limited — waiting ${retryAfter}s`);
  await new Promise(r => setTimeout(r, retryAfter * 1000));
  // retry the request
}