worldmonitor/api/mcp/freshness.ts

import type { FreshnessCheck } from './types';

function parseFiniteRecordCount(raw: unknown): number | null {
  if (typeof raw === 'number') return Number.isFinite(raw) ? raw : null;
  if (typeof raw === 'string' && raw.trim() !== '') {
    const parsed = Number(raw);
    return Number.isFinite(parsed) ? parsed : null;
  }
  return null;
}

export function evaluateFreshness(checks: FreshnessCheck[], metas: unknown[], now = Date.now()): { cached_at: string | null; stale: boolean } {
  let stale = false;
  let oldestFetchedAt = Number.POSITIVE_INFINITY;
  let hasAnyValidMeta = false;
  let hasAllValidMeta = true;

  for (const [i, check] of checks.entries()) {
    const meta = metas[i];
    const fetchedAt = meta && typeof meta === 'object' && 'fetchedAt' in meta
      ? Number((meta as { fetchedAt: unknown }).fetchedAt)
      : Number.NaN;

    if (!Number.isFinite(fetchedAt) || fetchedAt <= 0) {
      hasAllValidMeta = false;
      stale = true;
      continue;
    }

    hasAnyValidMeta = true;
    oldestFetchedAt = Math.min(oldestFetchedAt, fetchedAt);
    stale ||= (now - fetchedAt) / 60_000 > check.maxStaleMin;

    if (check.minRecordCount != null) {
      const recordCount = meta && typeof meta === 'object' && 'recordCount' in meta
        ? parseFiniteRecordCount((meta as { recordCount: unknown }).recordCount)
        : null;
      stale ||= recordCount == null || recordCount < check.minRecordCount;
    }
  }

  return {
    cached_at: hasAnyValidMeta && hasAllValidMeta ? new Date(oldestFetchedAt).toISOString() : null,
    stale,
  };
}