/**
 * Optional SCM_RIGHTS-style logical FD duplication for the POSIX socket FD bridge
 * (`BARE_OS_POSIX_SOCKET_SCM_RIGHTS=1`). See docs/reference/syscall-socket-contract.md.
 */

/**
 * @param {Record<string, string | undefined>} env
 */
export function wantPosixSocketScmRights(env) {
  const v = String(env?.BARE_OS_POSIX_SOCKET_SCM_RIGHTS ?? '')
    .trim()
    .toLowerCase()
  return v === '1' || v === 'true'
}

/**
 * @param {Record<string, string | undefined>} env
 */
export function bareOsScmRightsMaxFds(env) {
  const raw = String(env?.BARE_OS_POSIX_SOCKET_SCM_RIGHTS_MAX_FDS ?? '').trim()
  const n = Math.floor(Number(raw))
  if (Number.isFinite(n) && n > 0) return Math.min(16, n)
  return 4
}

/**
 * @param {unknown[]} arr
 * @returns {number[] | null}
 */
function collectFdsFromCmsgList(arr) {
  /** @type {number[]} */
  const fds = []
  for (const item of arr) {
    if (!item || typeof item !== 'object') return null
    const o = /** @type {Record<string, unknown>} */ (item)
    if (!Array.isArray(o.fds)) return null
    for (const f of o.fds) {
      const n = Number(f)
      if (!Number.isFinite(n) || n < 0) return null
      fds.push(n >>> 0)
    }
  }
  return fds
}

/**
 * @param {Record<string, unknown>} args
 * @param {boolean} scmOn
 * @param {number} maxFds
 * @returns {{ ok: true, fds: number[] } | { ok: false, reject: string }}
 */
export function bareOsParseSendmsgScmRights(args, scmOn, maxFds) {
  if (!args || typeof args !== 'object')
    return { ok: true, fds: [] }
  const ctl = args.control
  if (ctl instanceof Uint8Array && ctl.byteLength > 0)
    return { ok: false, reject: 'control' }
  const clen = Number(args.controllen)
  if (Number.isFinite(clen) && clen > 0)
    return { ok: false, reject: 'controllen' }
  const mh = args.msgHdr
  if (mh && typeof mh === 'object') {
    const mhc = /** @type {Record<string, unknown>} */ (mh).control
    if (mhc instanceof Uint8Array && mhc.byteLength > 0)
      return { ok: false, reject: 'msgHdr.control' }
  }

  /** @type {number[]} */
  let fds = []
  if (Array.isArray(args.cmsgs) && args.cmsgs.length > 0) {
    const r = collectFdsFromCmsgList(args.cmsgs)
    if (r === null) return { ok: false, reject: 'cmsgs' }
    fds = fds.concat(r)
  }
  if (mh && typeof mh === 'object') {
    const c2 = /** @type {Record<string, unknown>} */ (mh).cmsgs
    if (Array.isArray(c2) && c2.length > 0) {
      const r = collectFdsFromCmsgList(c2)
      if (r === null) return { ok: false, reject: 'msgHdr.cmsgs' }
      fds = fds.concat(r)
    }
  }

  if (fds.length > maxFds) return { ok: false, reject: 'cmsgs_cap' }
  if (!scmOn && fds.length > 0) return { ok: false, reject: 'cmsgs' }
  return { ok: true, fds }
}

/**
 * @param {unknown} slot
 * @param {string} k decimal fd string
 */
export function bareOsEnsureSocketSlotAliasKeys(slot, k) {
  if (!slot || typeof slot !== 'object') return
  const s = /** @type {{ aliasKeys?: Set<string> }} */ (slot)
  if (!s.aliasKeys || !(s.aliasKeys instanceof Set)) {
    s.aliasKeys = new Set()
  }
  s.aliasKeys.add(k)
}