/**
 * Persist an operator-facing snapshot of HDMS mounts.
 * Writes `/.bare/os/mounts_last.json` on the personal drive first, then best-effort
 * `/etc/bare-os/mounts.json` when the system image is writable (often not for guest sessions).
 * Source of truth remains `/.bare/hdms/registry.json` on the personal drive.
 */

import b4a from 'b4a'

/**
 * @param {{ writeFile?: Function, mkdir?: Function } | null | undefined} vfs
 * @param {import('./hdms-manager.js').HdmsController | null | undefined} hdms
 * @param {{ console?: { warn?: (msg: string) => void } }} [opts] Guest session console; omit to stay silent on failure (tests / minimal VFS).
 */
export async function persistBareOsMountsSnapshot(vfs, hdms, opts = {}) {
  if (!vfs || typeof vfs.writeFile !== 'function') return
  if (!hdms?.active || !hdms.registry) return

  /** @type {{ label: string, target: string, mode: string, readOnly: boolean, key?: string, ns?: string }[]} */
  const mounts = []
  for (const d of hdms.registry.drives) {
    mounts.push({
      label: d.label,
      target: `/mnt/${d.label}`,
      mode: d.mode,
      readOnly: d.mode === 'readonly',
      ...(d.key ? { key: d.key } : {}),
      ...(d.ns ? { ns: d.ns } : {})
    })
  }

  const doc = {
    schemaVersion: 1,
    updatedAt: new Date().toISOString(),
    note: 'Snapshot for operators; authoritative registry is /.bare/hdms/registry.json on the personal drive. When writable, the same JSON is mirrored at /.bare/os/mounts_last.json for multi-drive tooling.',
    mounts
  }
  const body = JSON.stringify(doc, null, 2) + '\n'
  const buf = b4a.from(body, 'utf8')

  /** Personal-drive mirror (always preferred; VFS allows writes here for normal sessions). */
  let personalOk = false
  try {
    await vfs.mkdir('/.bare/os', { recursive: true })
    await vfs.writeFile('/.bare/os/mounts_last.json', buf)
    personalOk = true
  } catch {
    /* personal tree may be unavailable in minimal tests */
  }

  /** Optional system-drive copy for operators when the system image is writable. */
  let systemOk = false
  try {
    await vfs.mkdir('/etc/bare-os', { recursive: true })
    await vfs.writeFile('/etc/bare-os/mounts.json', buf)
    systemOk = true
  } catch {
    /* expected for guests: /etc is on the system drive and not under $HOME */
  }

  if (!personalOk && !systemOk) {
    const msg =
      '[bare-os] mounts snapshot persist failed: could not write /.bare/os/mounts_last.json or /etc/bare-os/mounts.json'
    const w = opts.console && typeof opts.console.warn === 'function'
    if (w) opts.console.warn(msg)
  }
}