/* 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 diff(1) for Bare OS: compares two text files (VFS paths).
 * Supports -q (quiet, exit status only), -s (report when identical), -u (single-hunk unified).
 */

/**
 * @param {string} a
 * @param {string} b
 */
function splitLines(a) {
  const s = a.replace(/\r\n/g, '\n')
  const parts = s.split('\n')
  if (parts.length && parts[parts.length - 1] === '') parts.pop()
  return parts
}

/**
 * @param {string} pathA
 * @param {string} pathB
 * @param {string} sa
 * @param {string} sb
 * @returns {string | null} unified hunk or null if identical
 */
function unifiedOneHunk(pathA, pathB, sa, sb) {
  const la = splitLines(sa)
  const lb = splitLines(sb)
  let i = 0
  const n = Math.min(la.length, lb.length)
  while (i < n && la[i] === lb[i]) i++
  if (i === la.length && i === lb.length) return null
  const oldLine = la[i] != null ? la[i] : ''
  const newLine = lb[i] != null ? lb[i] : ''
  return (
    `--- ${pathA}\n+++ ${pathB}\n@@ -${i + 1},1 +${i + 1},1 @@\n-${oldLine}\n+${newLine}\n`
  )
}

async function run(ctx, argv) {
  let quiet = false
  let sameReport = false
  let unified = false
  /** @type {string[]} */
  const files = []
  for (let i = 1; i < argv.length; i++) {
    const a = argv[i]
    if (a === '--') {
      files.push(...argv.slice(i + 1))
      break
    }
    if (a === '-q') {
      quiet = true
      continue
    }
    if (a === '-s') {
      sameReport = true
      continue
    }
    if (a === '-u' || a === '-U0' || a === '--unified') {
      unified = true
      continue
    }
    if (a.startsWith('-')) {
      ctx.console.error('diff: unsupported option ' + a)
      ctx.exitCode = 2
      return
    }
    files.push(a)
  }
  if (files.length !== 2) {
    ctx.console.error('usage: diff [-q] [-s] [-u] FILE1 FILE2')
    ctx.exitCode = 2
    return
  }
  const [f1, f2] = files
  let b1
  let b2
  try {
    b1 = await ctx.vfs.readFile(f1)
    b2 = await ctx.vfs.readFile(f2)
  } catch (e) {
    ctx.console.error('diff: ' + ((e && e.message) || String(e)))
    ctx.exitCode = 2
    return
  }
  const s1 = b1 ? ctx.b4a.toString(b1) : ''
  const s2 = b2 ? ctx.b4a.toString(b2) : ''
  if (s1 === s2) {
    if (sameReport) ctx.console.log(`Files ${f1} and ${f2} are identical`)
    ctx.exitCode = 0
    return
  }
  if (quiet) {
    ctx.exitCode = 1
    return
  }
  if (unified) {
    const u = unifiedOneHunk(f1, f2, s1, s2)
    if (u) ctx.console.log(u.replace(/\n$/, ''))
  } else {
    const la = splitLines(s1)
    const lb = splitLines(s2)
    let i = 0
    const n = Math.min(la.length, lb.length)
    while (i < n && la[i] === lb[i]) i++
    ctx.console.log(`${i + 1}c${i + 1}`)
    ctx.console.log(`< ${la[i] != null ? la[i] : ''}`)
    ctx.console.log('---')
    ctx.console.log(`> ${lb[i] != null ? lb[i] : ''}`)
  }
  ctx.exitCode = 1
}