/**
 * Decides whether the TUI should kick off a background `fetchAllFeeds` on
 * open. Pure: takes the latest fetch timestamp and the staleness threshold.
 *
 * Threshold semantics:
 *  - `> 0`  — auto-fetch when the latest fetch is older than the threshold,
 *             OR when there has never been a fetch.
 *  - `=== 0` — disabled (never auto-fetch). Lets users opt out via
 *              `RSS_AUTO_FETCH_HOURS=0`.
 */

const DEFAULT_AUTO_FETCH_HOURS = 1;
const HOUR_MS = 60 * 60 * 1000;

export function shouldAutoFetch(latest: Date | null, thresholdMs: number, now: Date): boolean {
  if (!Number.isFinite(thresholdMs) || thresholdMs <= 0) return false;
  if (!latest) return true;
  return now.getTime() - latest.getTime() > thresholdMs;
}

export function resolveAutoFetchThresholdMs(envValue: string | undefined): number {
  const fallback = DEFAULT_AUTO_FETCH_HOURS * HOUR_MS;
  if (envValue === undefined || envValue === '') return fallback;
  const value = envValue.trim();
  if (!/^\d+$/.test(value)) return fallback;
  const parsed = Number(value);
  const threshold = parsed * HOUR_MS;
  if (!Number.isSafeInteger(parsed) || !Number.isFinite(threshold)) return fallback;
  return threshold;
}