{
  "success": false,
  "error": {
    "code": "ERROR_CODE",
    "message": "Human-readable error description."
  }
}

async function zetApiCall(endpoint, body) {
  const response = await fetch(`https://api.zet.money/v1${endpoint}`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': process.env.ZET_API_KEY,
    },
    body: JSON.stringify(body),
  });

  const result = await response.json();

  if (!result.success) {
    const { code, message } = result.error;

    switch (code) {
      case 'RATE_LIMITED':
        // Retry after delay
        const retryAfter = response.headers.get('X-RateLimit-Reset');
        await sleep(retryAfter * 1000 - Date.now());
        return zetApiCall(endpoint, body);

      case 'QUOTE_EXPIRED':
        // Get a new quote
        throw new Error('Quote expired, please request a new one');

      case 'INSUFFICIENT_BALANCE':
        // Show user-friendly message
        throw new Error('Not enough balance for this transaction');

      default:
        throw new Error(`Zet API Error [${code}]: ${message}`);
    }
  }

  return result.data;
}