/**
 * 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'
  /** @type {{ schema: number, download?: number, upload?: number, peers?: number, source?: string } | null} */
  let monitorProgress = null
  try {
    const m = disk && disk.drive && typeof disk.drive.monitor === 'function'
      ? disk.drive.monitor()
      : null
    if (m && typeof m === 'object') {
      const dl =
        typeof m.downloadedBlocks === 'number'
          ? m.downloadedBlocks
          : typeof m.download === 'number'
            ? m.download
            : null
      const ul =
        typeof m.uploadedBlocks === 'number'
          ? m.uploadedBlocks
          : typeof m.upload === 'number'
            ? m.upload
            : null
      const peers = typeof m.peers === 'number' ? m.peers : null
      if (dl != null || ul != null || peers != null) {
        monitorProgress = {
          schema: 1,
          ...(dl != null ? { download: dl } : {}),
          ...(ul != null ? { upload: ul } : {}),
          ...(peers != null ? { peers } : {}),
          source: 'hyperdrive.monitor'
        }
      }
    }
  } catch {
    monitorProgress = null
  }
  return {
    schema: 4,
    systemCoreLength,
    personalCoreLength,
    auxiliaryDriveCount,
    stallHint,
    ...(monitorProgress ? { monitorProgress } : {}),
    corestoreSnapshotSurface: {
      schema: 1,
      operatorWorkflow:
        'Pause or quiesce writers → replicate cores → export snapshot (corestore-snapshot style). Guest **`guestSuspendResume`** remains **ENOTSUP** unless the host registers Corestore suspend/resume hooks.',
      readOnly: true
    },
    note: 'Schema 4 keeps schema 3 fields and optionally exposes monitorProgress when Hyperdrive monitor() returns counters (download/upload/peers).'
  }
}