/** 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
}

async function run(ctx, argv) {
  const vfs = ctx.vfs
  let n = 10
  let start = 1
  if (argv[1] === '-n' && argv[2]) {
    n = parseInt(argv[2], 10) || 10
    start = 3
  } else if (argv[1] && /^-\d+$/.test(argv[1])) {
    n = parseInt(argv[1].slice(1), 10) || 10
    start = 2
  }
  const files = argv.slice(start).filter((a) => a !== '--')
  const take = (s) => {
    const lines = s.split('\n')
    const out = lines.slice(0, n).join('\n')
    ctx.console.log(
      out + (out && !out.endsWith('\n') && lines.length > n ? '\n' : '')
    )
  }
  if (!files.length) {
    take(bareStdin(ctx))
    return
  }
  for (const f of files) {
    const buf = await vfs.readFile(f)
    if (!buf) {
      ctx.console.error('head: ' + f + ': No such file')
      continue
    }
    if (files.length > 1) ctx.console.log('==> ' + f + ' <==')
    take(ctx.b4a.toString(buf))
  }
}