/**
 * Live Hyperdrive / core length hints for `/proc/bare_os/replication` and
 * `metrics_live.replicationLive` (non-secret progress; not full per-peer throughput).
 *
 * @param {{ drive?: unknown, personalDrive?: unknown } | null | undefined} disk
 * @param {number} peerCount
 */
export function buildBareOsReplicationLiveSketch(disk, peerCount) {
  let systemCoreLength = null
  let personalCoreLength = null
  try {
    const c =
      disk &&
      disk.drive &&
      /** @type {{ core?: { length?: number } }} */ (disk.drive).core
    if (c && typeof c.length === 'number') systemCoreLength = c.length
  } catch {
    systemCoreLength = null
  }
  try {
    const c =
      disk &&
      disk.personalDrive &&
      /** @type {{ core?: { length?: number } }} */ (disk.personalDrive).core
    if (c && typeof c.length === 'number') personalCoreLength = c.length
  } catch {
    personalCoreLength = null
  }
  let auxiliaryDriveCount = 0
  try {
    if (disk && Array.isArray(disk.auxiliaryDrives))
      auxiliaryDriveCount = disk.auxiliaryDrives.length
  } catch {
    auxiliaryDriveCount = 0
  }
  const stallHint =
    peerCount === 0
      ? 'no_peers'
      : systemCoreLength == null
        ? 'length_unavailable'
        : 'ok'
  return {
    schema: 2,
    systemCoreLength,
    personalCoreLength,
    auxiliaryDriveCount,
    stallHint,
    note: 'Schema 2 adds auxiliaryDriveCount (read-only mirror Hyperdrives under /mirror/aux*). Append-only core lengths are non-secret progress hints; aligns with corestore-snapshot / multi-drive replication operator workflows — not a full telemetry plane.'
  }
}