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

/* 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 tokens = argv.slice(1)
  if (!tokens.length || tokens[0] === '--help' || tokens[0] === '-h') {
    ctx.console.log(
      'usage: expr EXPRESSION\nInteger arithmetic (+ - * / %), comparisons, and string = / !=.'
    )
    return
  }
  let i = 0
  const peek = () => tokens[i]
  const take = () => tokens[i++]
  function parsePrimary() {
    const t = take()
    if (t === '(') {
      const v = parseAdd()
      if (take() !== ')') throw new Error('syntax error')
      return v
    }
    if (/^-?\d+$/.test(t)) return { kind: 'n', v: parseInt(t, 10) }
    return { kind: 's', v: t }
  }
  function parseMul() {
    let left = parsePrimary()
    while (peek() === '*' || peek() === '/' || peek() === '%') {
      const op = take()
      const right = parsePrimary()
      if (left.kind !== 'n' || right.kind !== 'n') throw new Error('non-numeric')
      if (op === '*') left = { kind: 'n', v: left.v * right.v }
      else if (op === '/') {
        if (right.v === 0) throw new Error('division by zero')
        left = { kind: 'n', v: Math.trunc(left.v / right.v) }
      } else {
        if (right.v === 0) throw new Error('division by zero')
        left = { kind: 'n', v: left.v % right.v }
      }
    }
    return left
  }
  function parseAdd() {
    let left = parseMul()
    while (peek() === '+' || peek() === '-') {
      const op = take()
      const right = parseMul()
      if (left.kind !== 'n' || right.kind !== 'n') throw new Error('non-numeric')
      left = {
        kind: 'n',
        v: op === '+' ? left.v + right.v : left.v - right.v
      }
    }
    return left
  }
  function parseCmp() {
    let left = parseAdd()
    const op = peek()
    if (
      op === '=' ||
      op === '==' ||
      op === '!=' ||
      op === '<' ||
      op === '<=' ||
      op === '>' ||
      op === '>='
    ) {
      take()
      const right = parseAdd()
      if (op === '=' || op === '==') {
        const eq =
          left.kind === right.kind &&
          (left.kind === 'n' ? left.v === right.v : left.v === right.v)
        return { kind: 'n', v: eq ? 1 : 0 }
      }
      if (op === '!=') {
        const eq =
          left.kind === right.kind &&
          (left.kind === 'n' ? left.v === right.v : left.v === right.v)
        return { kind: 'n', v: eq ? 0 : 1 }
      }
      if (left.kind !== 'n' || right.kind !== 'n') throw new Error('non-numeric')
      let ok = false
      if (op === '<') ok = left.v < right.v
      else if (op === '<=') ok = left.v <= right.v
      else if (op === '>') ok = left.v > right.v
      else if (op === '>=') ok = left.v >= right.v
      return { kind: 'n', v: ok ? 1 : 0 }
    }
    return left
  }
  try {
    const r = parseCmp()
    if (i < tokens.length) throw new Error('syntax error')
    ctx.console.log(String(r.kind === 'n' ? r.v : r.v))
  } catch (e) {
    ctx.console.error('expr: ' + (e.message || e))
    ctx.exitCode = 2
  }
}