/* 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
}

/**
 * Minimal patch(1): applies a single unified diff from stdin (ctx.shellStdin).
 * Supports -pNUM strip, --dry-run. Intended for diffs emitted by Bare OS diff -u.
 */

/**
 * @param {string} path
 * @param {number} p
 */
function stripPath(path, p) {
  const segs = path.replace(/\\/g, '/').split('/').filter(Boolean)
  const rest = segs.slice(Math.min(p, segs.length))
  return rest.length ? rest.join('/') : segs[segs.length - 1] || path
}

async function run(ctx, argv) {
  let p = 0
  let dry = false
  /** @type {string | null} */
  let overrideFile = null
  for (let i = 1; i < argv.length; i++) {
    const a = argv[i]
    if (a === '--dry-run' || a === '--check') {
      dry = true
      continue
    }
    if (a === '-p' || a === '--strip') {
      const n = argv[i + 1]
      if (n == null || !/^\d+$/.test(n)) {
        ctx.console.error('patch: -p requires a number')
        ctx.exitCode = 2
        return
      }
      p = Number(n)
      i++
      continue
    }
    if (a.startsWith('-p') && a.length > 2 && /^\d+$/.test(a.slice(2))) {
      p = Number(a.slice(2))
      continue
    }
    if (a.startsWith('-')) {
      ctx.console.error('patch: unsupported option ' + a)
      ctx.exitCode = 2
      return
    }
    overrideFile = a
    break
  }

  const raw = bareStdin(ctx) || ''
  const lines = raw.replace(/\r\n/g, '\n').split('\n')
  let minus = ''
  let plus = ''
  for (let i = 0; i < lines.length; i++) {
    const ln = lines[i]
    if (ln.startsWith('--- ')) {
      minus = ln.slice(4).trim().split(/\s+/)[0]
      continue
    }
    if (ln.startsWith('+++ ')) {
      plus = ln.slice(4).trim().split(/\s+/)[0]
      continue
    }
  }
  const targetRaw = overrideFile || plus || minus
  if (!targetRaw) {
    ctx.console.error('patch: could not determine path from patch')
    ctx.exitCode = 2
    return
  }
  const target = stripPath(targetRaw.replace(/^b\//, ''), p)

  let hunkStart = lines.findIndex((l) => /^@@/.test(l))
  if (hunkStart < 0) {
    ctx.console.error('patch: missing @@ hunk')
    ctx.exitCode = 2
    return
  }

  /** @type {string[]} */
  const oldParts = []
  /** @type {string[]} */
  const newParts = []
  for (let i = hunkStart + 1; i < lines.length; i++) {
    const l = lines[i]
    if (l.startsWith('@@')) break
    if (l.startsWith('-')) oldParts.push(l.slice(1))
    else if (l.startsWith('+')) newParts.push(l.slice(1))
    else if (l.startsWith(' ')) {
      const body = l.slice(1)
      oldParts.push(body)
      newParts.push(body)
    }
  }

  let cur = ''
  try {
    const buf = await ctx.vfs.readFile(target)
    cur = buf ? ctx.b4a.toString(buf) : ''
  } catch (e) {
    ctx.console.error('patch: ' + ((e && e.message) || String(e)))
    ctx.exitCode = 2
    return
  }

  const cl = splitLinesKeep(cur)
  const expectOld = oldParts.join('\n')
  const gotOld = cl.join('\n')
  if (expectOld !== gotOld) {
    ctx.console.error('patch: file content does not match hunk (try correct -p)')
    ctx.exitCode = 1
    return
  }

  const out = newParts.join('\n') + (newParts.length ? '\n' : '')
  if (!dry) await ctx.vfs.writeFile(target, ctx.b4a.from(out))
  ctx.exitCode = 0
}

/** @param {string} s */
function splitLinesKeep(s) {
  const t = s.replace(/\r\n/g, '\n')
  const parts = t.split('\n')
  if (parts.length && parts[parts.length - 1] === '') parts.pop()
  return parts
}