/**
 * Bucket a week's event count into a 0–4 intensity level for the
 * sync-coverage heatmap, relative to the busiest week (`maxCount`).
 *
 * Pure view-model helper shared by the desktop and hub `SyncHeatmap`
 * components so the intensity thresholds have a single source of truth
 * (OPL-2525). The per-app colour treatment (cyan-glow on the hub,
 * GitHub-style on desktop) stays local — only the bucketing is shared.
 *
 * Kept in its own dependency-free module (exported at
 * `@scribe.cool/core/sync/activity-level`) so `"use client"` components can
 * import it without pulling the server-only sync engine (`node:zlib`) from
 * the `./sync` barrel into the client bundle.
 *
 * @returns 0 when there is no activity, otherwise 1–4 by quartile.
 */
export function getActivityLevel(count: number, maxCount: number): number {
  if (count === 0) return 0;
  const normalized = count / maxCount;
  if (normalized < 0.25) return 1;
  if (normalized < 0.5) return 2;
  if (normalized < 0.75) return 3;
  return 4;
}