bare-operating-system/packages/bare-os-seeder/kernel/bin/tsort

/* 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
}

async function run(ctx, argv) {
  const paths = []
  for (let i = 1; i < argv.length; i++) {
    const a = argv[i]
    if (a === '-h' || a === '--help') {
      ctx.console.log(
        'usage: tsort [FILE]\nTopological sort of directed edges (one pair per line: A B).'
      )
      return
    }
    if (a.startsWith('-')) {
      ctx.console.error('tsort: unsupported option ' + a)
      ctx.exitCode = 1
      return
    }
    paths.push(a)
  }
  const b4 = ctx.b4a
  let text
  if (!paths.length || paths[0] === '-') text = bareStdin(ctx)
  else {
    const b = await ctx.vfs.readFile(paths[0])
    if (!b) {
      ctx.console.error('tsort: cannot read ' + paths[0])
      ctx.exitCode = 1
      return
    }
    text = b4.toString(b)
  }
  const edges = []
  const nodes = new Set()
  for (const line of text.split('\n')) {
    const t = line.trim()
    if (!t) continue
    const parts = t.split(/\s+/)
    if (parts.length < 2) continue
    const u = parts[0]
    const v = parts[1]
    edges.push([u, v])
    nodes.add(u)
    nodes.add(v)
  }
  const indeg = new Map()
  const adj = new Map()
  for (const n of nodes) {
    indeg.set(n, 0)
    adj.set(n, [])
  }
  for (const [u, v] of edges) {
    indeg.set(v, (indeg.get(v) || 0) + 1)
    adj.get(u).push(v)
  }
  const q = []
  for (const [n, d] of indeg) {
    if (d === 0) q.push(n)
  }
  q.sort()
  const out = []
  while (q.length) {
    const u = q.shift()
    out.push(u)
    for (const v of adj.get(u) || []) {
      indeg.set(v, indeg.get(v) - 1)
      if (indeg.get(v) === 0) {
        q.push(v)
        q.sort()
      }
    }
  }
  if (out.length !== nodes.size) {
    ctx.console.error('tsort: cycle in input')
    ctx.exitCode = 1
    return
  }
  for (const n of out) ctx.console.log(n)
}