/* BARE_OS_BIN_API 1.0.0 — bump when staged /bin script semantics change (see developer guide). */
/** Shared helpers for drive-resident /bin scripts (prepended before each command). */
function bareStdin(ctx) {
  return typeof ctx.shellStdin === 'string' ? ctx.shellStdin : ''
}

/** @param {number} mode @param {'file' | 'directory' | 'symlink'} type */
function bareFormatModeString(mode, type) {
  const typeChar = type === 'directory' ? 'd' : type === 'symlink' ? 'l' : '-'
  const perm = mode & 0o777
  const r = (bit) => (perm & bit ? 'r' : '-')
  const w = (bit) => (perm & bit ? 'w' : '-')
  const x = (bit) => (perm & bit ? 'x' : '-')
  return (
    typeChar +
    r(0o400) +
    w(0o200) +
    x(0o100) +
    r(0o040) +
    w(0o020) +
    x(0o010) +
    r(0o004) +
    w(0o002) +
    x(0o001)
  )
}

/** @param {number} mtimeMs @param {number} [nowMs] */
function bareFormatLsMtime(mtimeMs, nowMs) {
  const now = nowMs != null ? nowMs : Date.now()
  const d = new Date(mtimeMs)
  const months = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec'
  ]
  const mon = months[d.getMonth()]
  const day = String(d.getDate()).padStart(2, ' ')
  const sixMo = 180 * 24 * 3600 * 1000
  if (Math.abs(now - mtimeMs) > sixMo) {
    const yr = String(d.getFullYear()).padStart(4, ' ')
    return mon + ' ' + day + '  ' + yr
  }
  const hh = String(d.getHours()).padStart(2, '0')
  const mm = String(d.getMinutes()).padStart(2, '0')
  return mon + ' ' + day + ' ' + hh + ':' + mm
}

/** @param {number} size */
function barePosixBlocks(size) {
  return Math.ceil(Number(size) / 512) || 0
}

/**
 * Raw stdout for NUL/binary when **`process.stdout.write`** is missing.
 * If **`ctx.bareOsBinWrite(Uint8Array|string)`** is set (tests / host), use it.
 * @param {Record<string, unknown>} ctx
 * @param {string | Uint8Array} chunk
 * @returns {boolean}
 */
function bareOsEmitRaw(ctx, chunk) {
  if (typeof ctx.bareOsBinWrite === 'function') {
    const b4 = ctx.b4a
    const u8 =
      typeof chunk === 'string'
        ? b4 && typeof b4.from === 'function'
          ? b4.from(chunk)
          : new TextEncoder().encode(chunk)
        : chunk
    ctx.bareOsBinWrite(u8 instanceof Uint8Array ? u8 : new Uint8Array(u8))
    return true
  }
  const w = globalThis.process?.stdout?.write
  if (typeof w === 'function') {
    w.call(globalThis.process.stdout, chunk)
    return true
  }
  return false
}

/** Map common failure tokens to documentation anchors (offline-friendly). */
var KERNEL_EXPLAIN_MAP = {
  boot_policy: 'docs/reference/kernel-extensions.md — BARE_OS_BOOT_POLICY',
  safe_mode: 'BARE_OS_BOOT_SAFE_MODE — skips rc.d, kernel.ext.d, onboot (developer-guide/giant-phase-kernel-program.md)',
  boot_journal:
    'BARE_OS_BOOT_TRANSACTION_JOURNAL — /run/bare-os/boot-transaction.ndjson',
  boot_checkpoint: 'BARE_OS_BOOT_CHECKPOINT — /run/bare-os/boot-checkpoint.json',
  kernel_ext:
    'kernel.ext.d — dependsOn, requires, after, before (stock kernel/init.js header)',
  giant_phase:
    '/proc/bare_os/giant_phase_program.json — giant-phase program snapshot',
  bare_module:
    'Use bare-module / bare-node mapping (Holepunch); never node:module in guest',
  bare_crypto:
    'Use bare-crypto / bare-node crypto shim; never node:crypto in guest',
  compat: 'docs/reference/compatibility-matrix.md',
  roadmap: 'docs/reference/feature-roadmap.md'
}

async function run(ctx, argv) {
  const key = String(argv[1] || '')
    .trim()
    .toLowerCase()
    .replace(/^bare_os_/, '')
    .replace(/-/g, '_')
  if (!key || argv[1] === '--help' || argv[1] === '-h') {
    ctx.console.log(
      'Usage: kernel-explain <topic>\nTopics: ' +
        Object.keys(KERNEL_EXPLAIN_MAP).sort().join(', ')
    )
    return
  }
  const hit = KERNEL_EXPLAIN_MAP[key]
  if (hit) {
    ctx.console.log(hit)
    return
  }
  for (const [k, v] of Object.entries(KERNEL_EXPLAIN_MAP)) {
    if (k.includes(key) || key.includes(k)) {
      ctx.console.log(k + ': ' + v)
      return
    }
  }
  ctx.console.error('kernel-explain: unknown topic: ' + argv[1])
  ctx.exitCode = 1
}