const BASE = process.env.PROMETHEUS_URL ?? 'http://prometheus:9090';

interface PromResponse {
  status: string;
  data: { result: Array<{ value: [number, string] }> };
}

/** Run an instant query and return the scalar value, or null on error. */
export async function scalar(q: string): Promise<number | null> {
  try {
    const url = `${BASE}/api/v1/query?query=${encodeURIComponent(q)}`;
    const res = await fetch(url, { signal: AbortSignal.timeout(6_000) });
    const json = await res.json() as PromResponse;
    if (json.status === 'success' && json.data.result.length > 0) {
      return parseFloat(json.data.result[0].value[1]);
    }
  } catch { /* unreachable */ }
  return null;
}