/* 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
}

/** Session env map (`vfs.env`, then `ctx.env`). Never throws. */
function bareOsEnv(ctx) {
  const v = ctx && ctx.vfs && ctx.vfs.env
  if (v && typeof v === 'object') return v
  const e = ctx && ctx.env
  if (e && typeof e === 'object') return e
  return {}
}

/**
 * Strict POSIX-ish decimal integer (no octal, no exponent, no empty).
 * @param {unknown} s
 * @returns {number}
 */
function bareOsParseDecInt(s) {
  const t = String(s == null ? '' : s).trim()
  if (!/^[+-]?(?:0|[1-9][0-9]*)$/.test(t)) return NaN
  const n = Number.parseInt(t, 10)
  return Number.isSafeInteger(n) ? n : NaN
}

/** @param {unknown} s */
function bareOsParseNonNegInt(s) {
  const n = bareOsParseDecInt(s)
  return n >= 0 ? n : NaN
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {string} name
 * @param {number} fallback
 * @param {number} [min]
 * @param {number} [max]
 */
function bareOsEnvInt(ctx, name, fallback, min, max) {
  const raw = bareOsEnv(ctx)[name]
  if (raw == null || raw === '') return fallback
  const n = Number.parseInt(String(raw), 10)
  if (!Number.isFinite(n)) return fallback
  let v = n
  if (min != null && v < min) v = min
  if (max != null && v > max) v = max
  return v
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {string} msg
 * @param {number} [code]
 */
function bareOsFail(ctx, msg, code) {
  if (msg) ctx.console.error(msg)
  ctx.exitCode = code == null ? 1 : code
}

/** @param {unknown} e */
function bareOsIsNotFoundErr(e) {
  const code = e && typeof e === 'object' ? e.code : ''
  if (code === 'ENOENT') return true
  const msg = String((e && e.message) || e || '')
  return /ENOENT|No such file|not found/i.test(msg)
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {unknown} buf
 * @returns {Uint8Array}
 */
function bareOsToU8(ctx, buf) {
  if (!buf) return new Uint8Array(0)
  if (buf instanceof Uint8Array) return buf
  if (ctx && ctx.b4a && typeof ctx.b4a.from === 'function') return ctx.b4a.from(buf)
  return new Uint8Array(buf)
}

/** @param {string} dir @param {string} name */
function bareOsJoinPath(dir, name) {
  const d = String(dir || '').replace(/\/+$/, '')
  const n = String(name || '').replace(/^\/+/, '')
  if (!d || d === '/') return '/' + n
  return d + '/' + n
}

/** @param {string} p */
function bareOsBaseName(p) {
  const t = String(p || '').replace(/\/+$/, '')
  if (!t || t === '/') return t === '/' ? '/' : ''
  const i = t.lastIndexOf('/')
  return i < 0 ? t : t.slice(i + 1) || t
}

/** @param {string} p */
function bareOsParentDir(p) {
  const t = String(p || '').replace(/\/+$/, '') || '/'
  if (t === '/') return '/'
  const i = t.lastIndexOf('/')
  return i <= 0 ? '/' : t.slice(0, i) || '/'
}

/** @param {string} p */
function bareOsNormPath(p) {
  return String(p || '').replace(/\/+$/, '') || '/'
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {string} p
 */
function bareOsResolvePath(ctx, p) {
  if (ctx && ctx.vfs && typeof ctx.vfs.resolveLogical === 'function') {
    try {
      return String(ctx.vfs.resolveLogical(p) || p)
    } catch {
      /* fall through */
    }
  }
  return String(p || '')
}

/**
 * True when dest is src or lives under src (self-copy / self-move).
 * @param {Record<string, unknown>} ctx
 * @param {string} src
 * @param {string} dest
 */
function bareOsDestInsideSrc(ctx, src, dest) {
  const s = bareOsNormPath(bareOsResolvePath(ctx, src))
  const d = bareOsNormPath(bareOsResolvePath(ctx, dest))
  if (s === d) return true
  if (s === '/') return d !== '/'
  return d === s || d.startsWith(s + '/')
}

const BARE_OS_B64_ALPH =
  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

/** @param {Uint8Array} u8 */
function bareOsB64Encode(u8) {
  let out = ''
  let i = 0
  for (; i + 2 < u8.length; i += 3) {
    const n = (u8[i] << 16) | (u8[i + 1] << 8) | u8[i + 2]
    out +=
      BARE_OS_B64_ALPH[(n >> 18) & 63] +
      BARE_OS_B64_ALPH[(n >> 12) & 63] +
      BARE_OS_B64_ALPH[(n >> 6) & 63] +
      BARE_OS_B64_ALPH[n & 63]
  }
  const rest = u8.length - i
  if (rest === 1) {
    const n = u8[i] << 16
    out += BARE_OS_B64_ALPH[(n >> 18) & 63] + BARE_OS_B64_ALPH[(n >> 12) & 63] + '=='
  } else if (rest === 2) {
    const n = (u8[i] << 16) | (u8[i + 1] << 8)
    out +=
      BARE_OS_B64_ALPH[(n >> 18) & 63] +
      BARE_OS_B64_ALPH[(n >> 12) & 63] +
      BARE_OS_B64_ALPH[(n >> 6) & 63] +
      '='
  }
  return out
}

/**
 * RFC 4648 Base64 decode (also accepts URL-safe alphabet). Rejects junk.
 * @param {string} s
 * @returns {Uint8Array}
 */
function bareOsB64Decode(s) {
  const t = String(s).replace(/\s+/g, '')
  if (!t) return new Uint8Array(0)
  if (t.length % 4 === 1) throw new Error('invalid base64 length')
  let pad = 0
  if (t.endsWith('==')) pad = 2
  else if (t.endsWith('=')) pad = 1
  const body = pad ? t.slice(0, t.length - pad) : t
  const bytes = []
  let buf = 0
  let bits = 0
  for (let i = 0; i < body.length; i++) {
    const c = body[i]
    let v = BARE_OS_B64_ALPH.indexOf(c)
    if (v < 0) {
      if (c === '-') v = 62
      else if (c === '_') v = 63
      else throw new Error('invalid base64 character')
    }
    buf = (buf << 6) | v
    bits += 6
    if (bits >= 8) {
      bits -= 8
      bytes.push((buf >> bits) & 255)
    }
  }
  if (pad) {
    const want = Math.floor((body.length * 6) / 8)
    if (bytes.length > want) bytes.length = want
  }
  return new Uint8Array(bytes)
}

/**
 * @param {string} s
 * @returns {Uint8Array}
 */
function bareOsHexDecode(s) {
  const t = String(s).replace(/\s+/g, '')
  if (t.length % 2 !== 0) throw new Error('odd hex length')
  const out = new Uint8Array(t.length / 2)
  for (let i = 0; i < out.length; i++) {
    const pair = t.slice(i * 2, i * 2 + 2)
    if (!/^[0-9a-fA-F]{2}$/.test(pair)) throw new Error('invalid hex')
    out[i] = Number.parseInt(pair, 16)
  }
  return out
}

/** @param {Uint8Array} u8 */
function bareOsHexEncode(u8) {
  let s = ''
  for (let i = 0; i < u8.length; i++) s += u8[i].toString(16).padStart(2, '0')
  return s
}

/**
 * tail — last lines/bytes of files; -f/--follow with vfs.watch or poll.
 * Test/limit: BARE_OS_TAIL_F_POLL_MS, BARE_OS_TAIL_F_MAX_ROUNDS (empty = unlimited).
 */

function bareTailSleep(ms) {
  return new Promise((r) => setTimeout(r, ms))
}

function bareTailEnv(ctx) {
  return (ctx.vfs && ctx.vfs.env) || ctx.env || {}
}

function bareTailPollMs(env) {
  const n = Number.parseInt(String(env.BARE_OS_TAIL_F_POLL_MS || '1000'), 10)
  return Number.isFinite(n) && n >= 0 ? n : 1000
}

function bareTailMaxRounds(env) {
  const raw = env.BARE_OS_TAIL_F_MAX_ROUNDS
  if (raw == null || raw === '') return Number.POSITIVE_INFINITY
  const n = Number.parseInt(String(raw), 10)
  return Number.isFinite(n) && n >= 0 ? n : Number.POSITIVE_INFINITY
}

function bareTailUseWatch(ctx, vfs) {
  if (typeof vfs.watch !== 'function') return false
  const caps = ctx.bareOsRuntimeCaps
  if (caps && caps.features && caps.features.vfsWatch === false) return false
  return true
}

/** @param {string} s */
function bareTailSplitLines(s) {
  const lines = s.split('\n')
  if (s.endsWith('\n') && lines.length && lines[lines.length - 1] === '')
    lines.pop()
  return lines
}

/**
 * @param {Uint8Array} u8
 * @param {'end' | 'start'} which
 * @param {number} n count or 1-based start (+ mode)
 */
function bareTailBytesSlice(u8, which, n, fromPlus) {
  if (!u8 || !u8.byteLength) return new Uint8Array(0)
  if (which === 'end') {
    if (n <= 0) return new Uint8Array(0)
    const start = Math.max(0, u8.byteLength - n)
    return u8.subarray(start)
  }
  /* from start (+): GNU tail -c +K starts at byte K (1-based) */
  const idx = fromPlus ? Math.max(0, n - 1) : 0
  return idx >= u8.byteLength ? new Uint8Array(0) : u8.subarray(idx)
}

/**
 * @param {string} s
 * @param {'end' | 'start'} which
 * @param {number} n
 * @param {boolean} fromPlus
 * @param {*} b4a
 */
function bareTailLinesText(s, which, n, fromPlus, b4a) {
  const lines = bareTailSplitLines(s)
  if (which === 'end') {
    if (n <= 0) return ''
    const slice = lines.length <= n ? lines : lines.slice(-n)
    return slice.join('\n')
  }
  /* +N: from line N (1-based) */
  const start = fromPlus ? Math.max(0, n - 1) : 0
  const slice = lines.slice(start)
  return slice.join('\n')
}

/**
 * Emit follow chunks as full lines via console.log (tests capture log).
 * @param {string} chunk
 * @param {{ partial: string }} state
 */
function bareTailFollowEmit(ctx, chunk, state) {
  const combined = state.partial + chunk
  const lines = combined.split('\n')
  state.partial = lines.pop() || ''
  for (const ln of lines) ctx.console.log(ln)
}

function bareTailFollowFlush(ctx, state) {
  if (state.partial !== '') {
    ctx.console.log(state.partial)
    state.partial = ''
  }
}

/**
 * @param {*} ctx
 * @param {string} path
 * @param {*} vfs
 * @param {number} startOffset byte offset after initial read (next byte to emit)
 */
async function bareTailFollow(ctx, path, vfs, startOffset) {
  const env = bareTailEnv(ctx)
  const pollMs = bareTailPollMs(env)
  const maxRounds = bareTailMaxRounds(env)
  const state = { partial: '' }
  let offset = startOffset
  let rounds = 0

  const pumpOnce = async () => {
    const buf = await vfs.readFile(path)
    if (!buf) {
      offset = 0
      return
    }
    const u8 = buf instanceof Uint8Array ? buf : ctx.b4a.from(buf)
    if (u8.byteLength < offset) {
      offset = 0
    }
    if (u8.byteLength > offset) {
      const piece = u8.subarray(offset)
      offset = u8.byteLength
      bareTailFollowEmit(ctx, ctx.b4a.toString(piece), state)
    }
  }

  if (
    bareTailUseWatch(ctx, vfs) &&
    maxRounds === Number.POSITIVE_INFINITY
  ) {
    let handle = null
    try {
      handle = await vfs.watch(path)
    } catch {
      handle = null
    }
    if (handle && handle.watcher) {
      try {
        for await (const _ of handle.watcher) {
          await pumpOnce()
        }
      } finally {
        if (typeof handle.destroy === 'function') handle.destroy()
      }
      bareTailFollowFlush(ctx, state)
      return
    }
  }

  while (rounds < maxRounds) {
    await bareTailSleep(pollMs)
    await pumpOnce()
    rounds++
  }
  bareTailFollowFlush(ctx, state)
}

async function run(ctx, argv) {
  const vfs = ctx.vfs
  let follow = false
  /** @type {'lines' | 'bytes'} */
  let mode = 'lines'
  let count = 10
  let fromPlus = false
  let i = 1

  while (i < argv.length) {
    const a = argv[i]
    if (a === '--') {
      i++
      break
    }
    if (a === '-f' || a === '--follow') {
      follow = true
      i++
      continue
    }
    if (a === '-F') {
      follow = true
      i++
      continue
    }
    if (a === '-n' || a === '--lines') {
      const v = argv[i + 1]
      if (v == null) {
        ctx.console.error('tail: option requires an argument -- n')
        ctx.exitCode = 1
        return
      }
      i++
      mode = 'lines'
      if (v.startsWith('+')) {
        fromPlus = true
        count = bareOsParseNonNegInt(v.slice(1))
        if (!Number.isFinite(count) || count < 1) count = 1
      } else {
        fromPlus = false
        count = bareOsParseNonNegInt(v.startsWith('-') ? v.slice(1) : v)
        if (!Number.isFinite(count)) {
          ctx.console.error('tail: invalid number of lines: ' + v)
          ctx.exitCode = 1
          return
        }
      }
      i++
      continue
    }
    if (a.startsWith('-n') && a.length > 2) {
      const v = a.slice(2)
      mode = 'lines'
      if (v.startsWith('+')) {
        fromPlus = true
        count = bareOsParseNonNegInt(v.slice(1))
        if (!Number.isFinite(count) || count < 1) count = 1
      } else {
        fromPlus = false
        count = bareOsParseNonNegInt(v.startsWith('-') ? v.slice(1) : v)
        if (!Number.isFinite(count)) {
          ctx.console.error('tail: invalid number of lines: ' + v)
          ctx.exitCode = 1
          return
        }
      }
      i++
      continue
    }
    if (a === '-c' || a === '--bytes') {
      const v = argv[i + 1]
      if (v == null) {
        ctx.console.error('tail: option requires an argument -- c')
        ctx.exitCode = 1
        return
      }
      i++
      mode = 'bytes'
      if (v.startsWith('+')) {
        fromPlus = true
        count = bareOsParseNonNegInt(v.slice(1))
        if (!Number.isFinite(count) || count < 1) count = 1
      } else {
        fromPlus = false
        count = bareOsParseNonNegInt(v.startsWith('-') ? v.slice(1) : v)
        if (!Number.isFinite(count)) {
          ctx.console.error('tail: invalid number of bytes: ' + v)
          ctx.exitCode = 1
          return
        }
      }
      i++
      continue
    }
    if (a.startsWith('-c') && a.length > 2) {
      const v = a.slice(2)
      mode = 'bytes'
      if (v.startsWith('+')) {
        fromPlus = true
        count = bareOsParseNonNegInt(v.slice(1))
        if (!Number.isFinite(count) || count < 1) count = 1
      } else {
        fromPlus = false
        count = bareOsParseNonNegInt(v.startsWith('-') ? v.slice(1) : v)
        if (!Number.isFinite(count)) {
          ctx.console.error('tail: invalid number of bytes: ' + v)
          ctx.exitCode = 1
          return
        }
      }
      i++
      continue
    }
    if (a.startsWith('-') && /^-\d+$/.test(a)) {
      mode = 'lines'
      fromPlus = false
      count = Number.parseInt(a.slice(1), 10) || 10
      i++
      continue
    }
    if (a.startsWith('-')) {
      ctx.console.error('tail: unrecognized option: ' + a)
      ctx.exitCode = 1
      return
    }
    break
  }

  const files = argv.slice(i).filter((x) => x !== '--')

  if (follow && !files.length) {
    ctx.console.error(
      'tail: --follow is not supported for stdin on Bare OS (stdin is a captured string)'
    )
    ctx.exitCode = 1
    return
  }

  if (follow && files.length > 1) {
    ctx.console.error(
      'tail: following multiple files is not supported (use one path)'
    )
    ctx.exitCode = 1
    return
  }

  if (!files.length) {
    const s = bareStdin(ctx)
    if (mode === 'bytes') {
      const u8 = ctx.b4a.from(s, 'utf8')
      const slice = bareTailBytesSlice(
        u8,
        fromPlus ? 'start' : 'end',
        count,
        fromPlus
      )
      const out = ctx.b4a.toString(slice)
      if (out) ctx.console.log(out)
    } else {
      const out = bareTailLinesText(
        s,
        fromPlus ? 'start' : 'end',
        count,
        fromPlus,
        ctx.b4a
      )
      if (out) ctx.console.log(out)
    }
    return
  }

  for (const f of files) {
    const buf = await vfs.readFile(f)
    if (!buf) {
      ctx.console.error('tail: ' + f + ': No such file')
      ctx.exitCode = 1
      continue
    }
    if (files.length > 1) ctx.console.log('==> ' + f + ' <==')
    const u8 = buf instanceof Uint8Array ? buf : ctx.b4a.from(buf)
    const text = ctx.b4a.toString(u8)
    if (!follow) {
      if (mode === 'bytes') {
        const slice = bareTailBytesSlice(
          u8,
          fromPlus ? 'start' : 'end',
          count,
          fromPlus
        )
        const out = ctx.b4a.toString(slice)
        if (out) ctx.console.log(out)
      } else {
        const out = bareTailLinesText(
          text,
          fromPlus ? 'start' : 'end',
          count,
          fromPlus,
          ctx.b4a
        )
        if (out) ctx.console.log(out)
      }
      continue
    }
    if (mode === 'bytes') {
      const slice = bareTailBytesSlice(
        u8,
        fromPlus ? 'start' : 'end',
        count,
        fromPlus
      )
      const out = ctx.b4a.toString(slice)
      if (out) ctx.console.log(out)
      await bareTailFollow(ctx, f, vfs, u8.byteLength)
    } else {
      const out = bareTailLinesText(
        text,
        fromPlus ? 'start' : 'end',
        count,
        fromPlus,
        ctx.b4a
      )
      if (out) ctx.console.log(out)
      const startOffset = u8.byteLength
      await bareTailFollow(ctx, f, vfs, startOffset)
    }
  }
}