import b4a from 'b4a'
/**
 * POSIX-like stat metadata stored in Hyperdrive entry value.metadata.bareOs (JSON).
 */

/** @typedef {{ mode: number, uid: number, gid: number, uname: string, gname: string, mtimeMs: number, ctimeMs: number }} BareOsMeta */

export const S_IFDIR = 0o040000
export const S_IFREG = 0o100000
export const S_IFLNK = 0o120000

const DEFAULT_UMASK = 0o022

/**
 * @param {Record<string, string>} env
 */
export function parseUmask(env) {
  const raw = env.UMASK
  if (raw == null || raw === '') return DEFAULT_UMASK
  const s = String(raw).trim()
  const m = /^0?([0-7]{1,3})$/.exec(s)
  if (m) return Number.parseInt(m[1], 8) & 0o777
  return DEFAULT_UMASK
}

/**
 * @param {Record<string, string>} env
 */
export function parseUidGid(env) {
  const uid = Number.parseInt(String(env.UID ?? '0'), 10)
  const gid = Number.parseInt(String(env.GID ?? '0'), 10)
  return {
    uid: Number.isFinite(uid) ? uid : 0,
    gid: Number.isFinite(gid) ? gid : 0
  }
}

/**
 * @param {Record<string, string>} env
 */
export function identityNames(env) {
  const user = env.USER || env.LOGNAME || 'root'
  const group = env.GROUP || user
  return { user, group }
}

/**
 * @param {unknown} value Hyperdrive entry .value
 * @returns {BareOsMeta | null}
 */
export function extractBareOs(value) {
  if (!value || typeof value !== 'object') return null
  const md = /** @type {Record<string, unknown>} */ (value).metadata
  if (!md || typeof md !== 'object') return null
  const b = /** @type {Record<string, unknown>} */ (md).bareOs
  if (!b || typeof b !== 'object') return null
  const mode = Number(b.mode)
  const uid = Number(b.uid)
  const gid = Number(b.gid)
  if (!Number.isFinite(mode)) return null
  return {
    mode: mode & 0xffff,
    uid: Number.isFinite(uid) ? uid : 0,
    gid: Number.isFinite(gid) ? gid : 0,
    uname: typeof b.uname === 'string' ? b.uname : 'root',
    gname: typeof b.gname === 'string' ? b.gname : 'root',
    mtimeMs:
      typeof b.mtimeMs === 'number' && Number.isFinite(b.mtimeMs)
        ? b.mtimeMs
        : Date.now(),
    ctimeMs:
      typeof b.ctimeMs === 'number' && Number.isFinite(b.ctimeMs)
        ? b.ctimeMs
        : Date.now()
  }
}

/**
 * @param {Record<string, unknown> | null | undefined} existingMetadata
 * @param {BareOsMeta} bareOs
 */
export function mergeEntryMetadata(existingMetadata, bareOs) {
  const base =
    existingMetadata && typeof existingMetadata === 'object'
      ? { ...existingMetadata }
      : {}
  return { ...base, bareOs }
}

/**
 * @param {Record<string, string>} env
 * @param {{ executable?: boolean }} [opts]
 * @returns {BareOsMeta}
 */
export function newBareOsForFile(env, opts = {}) {
  const umask = parseUmask(env)
  const { uid, gid } = parseUidGid(env)
  const { user, group } = identityNames(env)
  const now = Date.now()
  let mode = S_IFREG | (0o666 & ~umask)
  if (opts.executable) mode |= 0o111
  return {
    mode,
    uid,
    gid,
    uname: user,
    gname: group,
    mtimeMs: now,
    ctimeMs: now
  }
}

/**
 * @param {BareOsMeta | null} prev
 * @param {Record<string, string>} env
 * @param {{ executable?: boolean, bumpMtime?: boolean, touchCtime?: boolean, legacyExecutable?: boolean }} [opts]
 * @returns {BareOsMeta}
 */
export function mergeBareOsOnWrite(prev, env, opts = {}) {
  const now = Date.now()
  if (!prev) {
    const umask = parseUmask(env)
    const { uid, gid } = parseUidGid(env)
    const { user, group } = identityNames(env)
    const legacyEx = !!opts.legacyExecutable
    const wantEx =
      opts.executable !== undefined ? opts.executable : legacyEx
    let mode = S_IFREG | (0o666 & ~umask)
    if (wantEx) mode |= 0o111
    return {
      mode,
      uid,
      gid,
      uname: user,
      gname: group,
      mtimeMs: now,
      ctimeMs: now
    }
  }
  const executable =
    opts.executable !== undefined ? opts.executable : !!(prev.mode & 0o111)
  let mode = prev.mode
  if (opts.executable !== undefined) {
    if (executable) mode |= 0o111
    else mode &= ~0o111
  }
  return {
    mode,
    uid: prev.uid,
    gid: prev.gid,
    uname: prev.uname,
    gname: prev.gname,
    mtimeMs: opts.bumpMtime !== false ? now : prev.mtimeMs,
    ctimeMs: opts.touchCtime ? now : prev.ctimeMs
  }
}

/**
 * @param {Record<string, string>} env
 * @returns {BareOsMeta}
 */
export function newBareOsForSymlink(env) {
  const { uid, gid } = parseUidGid(env)
  const { user, group } = identityNames(env)
  const now = Date.now()
  return {
    mode: S_IFLNK | 0o777,
    uid,
    gid,
    uname: user,
    gname: group,
    mtimeMs: now,
    ctimeMs: now
  }
}

/**
 * @param {import('hyperdrive').default} personalDrive
 * @param {{ drive: import('hyperdrive').default, virtualHomeDir?: boolean, virtualMntRoot?: boolean, virtualVarRoot?: boolean }} r
 */
export function isPersonalRoute(personalDrive, r) {
  if (
    r.virtualHomeDir ||
    r.virtualMntRoot ||
    r.virtualVarRoot ||
    r.virtualPseudo
  ) {
    return false
  }
  return r.drive === personalDrive
}

/**
 * @param {string} abs absolute logical path
 * @param {boolean} personal
 * @param {Record<string, string>} env
 * @param {'file' | 'directory' | 'symlink'} type
 * @param {{ executable?: boolean, linkname?: string }} [entryHints]
 */
export function synthesizeStat(
  abs,
  personal,
  env,
  type,
  entryHints = {}
) {
  const now = Date.now()
  const nlink = 1
  if (type === 'symlink') {
    const linkname = entryHints.linkname || ''
    const size = b4a.from(linkname, 'utf8').length
    const { uid, gid } = personal ? parseUidGid(env) : { uid: 0, gid: 0 }
    const { user, group } = personal
      ? identityNames(env)
      : { user: 'root', group: 'root' }
    return {
      type: 'symlink',
      path: abs,
      size,
      mode: S_IFLNK | 0o777,
      uid,
      gid,
      user,
      group,
      mtimeMs: now,
      ctimeMs: now,
      nlink,
      linkname
    }
  }
  if (type === 'directory') {
    const mode = personal ? S_IFDIR | (0o777 & ~parseUmask(env)) : S_IFDIR | 0o755
    const { uid, gid } = personal ? parseUidGid(env) : { uid: 0, gid: 0 }
    const { user, group } = personal
      ? identityNames(env)
      : { user: 'root', group: 'root' }
    return {
      type: 'directory',
      path: abs,
      size: 0,
      mode,
      uid,
      gid,
      user,
      group,
      mtimeMs: now,
      ctimeMs: now,
      nlink
    }
  }
  // file
  let mode = S_IFREG | 0o644
  if (!personal) {
    if (abs.startsWith('/bin/') || abs.startsWith('/boot/')) mode = S_IFREG | 0o555
    else if (abs.startsWith('/etc/')) mode = S_IFREG | 0o644
    else mode = S_IFREG | 0o644
    return {
      type: 'file',
      path: abs,
      size: 0,
      mode,
      uid: 0,
      gid: 0,
      user: 'root',
      group: 'root',
      mtimeMs: now,
      ctimeMs: now,
      nlink
    }
  }
  const umask = parseUmask(env)
  let fm = S_IFREG | (0o666 & ~umask)
  if (entryHints.executable) fm |= 0o111
  const { uid, gid } = parseUidGid(env)
  const { user, group } = identityNames(env)
  return {
    type: 'file',
    path: abs,
    size: 0,
    mode: fm,
    uid,
    gid,
    user,
    group,
    mtimeMs: now,
    ctimeMs: now,
    nlink
  }
}

/**
 * @param {BareOsMeta} bo
 * @param {'file' | 'directory' | 'symlink'} type
 * @param {number} size
 * @param {string} abs
 * @param {string} [linkname]
 */
export function statFromBareOs(bo, type, size, abs, linkname) {
  const o = {
    type,
    path: abs,
    size,
    mode: bo.mode,
    uid: bo.uid,
    gid: bo.gid,
    user: bo.uname,
    group: bo.gname,
    mtimeMs: bo.mtimeMs,
    ctimeMs: bo.ctimeMs,
    nlink: 1
  }
  if (linkname != null) o.linkname = linkname
  return o
}

/**
 * @param {string} abs
 */
export function isVirtualMountPoint(abs) {
  const n = abs.replace(/\/+$/, '') || '/'
  return (
    abs === '/' ||
    abs === '/home' ||
    abs === '/mnt' ||
    abs === '/var' ||
    abs === '/home/' ||
    abs === '/mnt/' ||
    abs === '/var/' ||
    n === '/proc' ||
    n === '/proc/self' ||
    n === '/sys' ||
    n === '/sys/fs' ||
    n === '/sys/fs/bare_os' ||
    n === '/run' ||
    n === '/run/bare-os' ||
    n === '/dev'
  )
}

/**
 * @param {number} mode
 * @param {'file' | 'directory' | 'symlink'} type
 */
export function formatModeString(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]
 */
export function formatLsMtime(mtimeMs, 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(nowMs - 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
 */
export function posixBlocks(size) {
  return Math.ceil(Number(size) / 512) || 0
}

/**
 * @param {{ uid: number, gid: number, mode: number }} st
 * @param {number} euid
 * @param {number} egid
 * @param {'r' | 'w' | 'x'} op
 * @param {'file' | 'directory'} kind
 */
export function modeAllows(st, euid, egid, op, kind) {
  const mode = st.mode & 0o777
  const bit =
    op === 'r' ? 0o444 : op === 'w' ? 0o222 : 0o111
  let masked = 0
  if (euid === st.uid) masked = (mode >> 6) & 7
  else if (egid === st.gid) masked = (mode >> 3) & 7
  else masked = mode & 7
  const need = op === 'r' ? 4 : op === 'w' ? 2 : 1
  return (masked & need) === need
}