/**
 * Optional peer admission gate from **`BARE_OS_PEER_ALLOWLIST_HEX`**
 * (comma-separated hex public keys; empty = deny unless explicit allow-all).
 *
 * **`BARE_OS_PEER_DENYLIST_HEX`** — comma-separated hex keys; if the peer matches,
 * verdict is **`deny`** before allowlist evaluation (denylist wins).
 *
 * **`BARE_OS_PEER_REQUIRE_CAPS_JSON`** — JSON array of capability strings; when set,
 * **`meta.caps`** must include every required token (hosts pass peer caps when known).
 *
 * When **`BARE_OS_DHT_ADDRESS_CLASS_ALLOWLIST`** is set and callers pass
 * **`dhtAddressClass`** (hyperdht-address–style hint), the class must appear in
 * the allow list after the key gate passes.
 *
 * Admission results use **`schema: 2`** (v1 was **`schema: 1`** only).
 *
 * @param {Record<string, unknown> | null | undefined} env
 * @param {string} peerKeyHex
 * @param {{ dhtAddressClass?: string, caps?: string[] } | null | undefined} [meta]
 */
const ADMISSION_SCHEMA = 2

/**
 * @param {Record<string, unknown> | null | undefined} env
 */
function zeroTrustStrictProfile(env) {
  const p = String(env?.BARE_OS_ZERO_TRUST_PROFILE || '')
    .trim()
    .toLowerCase()
  return p === 'strict' || p === 'security'
}

/** @param {string} s */
function normKeyHex(s) {
  return String(s || '')
    .trim()
    .toLowerCase()
    .replace(/^0x/, '')
}

/** @param {string} raw */
function keySetFromCommaHex(raw) {
  return new Set(
    raw
      .split(/[\s,]+/)
      .map((s) => normKeyHex(s))
      .filter(Boolean)
  )
}

/**
 * @param {Record<string, unknown> | null | undefined} env
 * @returns {string[] | null}
 */
function parseRequireCaps(env) {
  const raw = String(env?.BARE_OS_PEER_REQUIRE_CAPS_JSON || '').trim()
  if (!raw) return null
  try {
    const j = JSON.parse(raw)
    if (!Array.isArray(j)) return null
    const caps = j
      .map((x) => String(x).trim())
      .filter(Boolean)
      .slice(0, 32)
    return caps.length ? caps : null
  } catch {
    return null
  }
}

export function evaluateBareOsPeerAdmission(env, peerKeyHex, meta = undefined) {
  const want = normKeyHex(peerKeyHex)
  const atMs = () => Date.now()

  const denyRaw = String(env?.BARE_OS_PEER_DENYLIST_HEX || '').trim()
  if (denyRaw) {
    const denySet = keySetFromCommaHex(denyRaw)
    if (want && denySet.has(want)) {
      return {
        schema: ADMISSION_SCHEMA,
        verdict: 'deny',
        reason: 'peer_denylist',
        denylistSize: denySet.size,
        atMs: atMs()
      }
    }
  }

  const requireCaps = parseRequireCaps(env)
  if (requireCaps && requireCaps.length > 0) {
    const peerCapsRaw = meta && Array.isArray(meta.caps) ? meta.caps : []
    const peerSet = new Set(
      peerCapsRaw.map((c) => String(c).trim()).filter(Boolean)
    )
    for (const c of requireCaps) {
      if (!peerSet.has(c)) {
        return {
          schema: ADMISSION_SCHEMA,
          verdict: 'deny',
          reason: 'peer_missing_cap',
          requiredCaps: [...requireCaps],
          atMs: atMs()
        }
      }
    }
  }

  const raw = String(env?.BARE_OS_PEER_ALLOWLIST_HEX || '').trim()
  const strict =
    env?.BARE_OS_PEER_ALLOWLIST_STRICT === '1' ||
    env?.BARE_OS_PEER_ALLOWLIST_STRICT === 'true' ||
    zeroTrustStrictProfile(env)
  const allowAll =
    env?.BARE_OS_PEER_ALLOW_ALL === '1' || env?.BARE_OS_PEER_ALLOW_ALL === 'true'
  /** @type {{ schema: number, verdict: string, note?: string, allowlistSize?: number, strictProfile?: boolean, atMs?: number, dhtAddressClassGate?: Record<string, unknown> }} */
  let base
  if (!raw) {
    if (strict || !allowAll) {
      base = {
        schema: ADMISSION_SCHEMA,
        verdict: 'deny',
        reason: 'peer_allowlist_empty',
        note:
          'Peer allowlist is empty; admission denied unless BARE_OS_PEER_ALLOW_ALL=1.'
      }
    } else {
      base = {
        schema: ADMISSION_SCHEMA,
        verdict: 'allow',
        note: 'No allowlist and BARE_OS_PEER_ALLOW_ALL=1; peers admitted.'
      }
    }
  } else {
    const set = keySetFromCommaHex(raw)
    const ok = want && set.has(want)
    base = {
      schema: ADMISSION_SCHEMA,
      verdict: ok ? 'allow' : 'deny',
      allowlistSize: set.size,
      strictProfile: strict || undefined,
      atMs: atMs()
    }
  }

  const classRaw = String(env?.BARE_OS_DHT_ADDRESS_CLASS_ALLOWLIST || '').trim()
  if (!classRaw) {
    if (base.atMs == null) base.atMs = atMs()
    return base
  }

  const allowClasses = new Set(
    classRaw.split(',').map((s) => s.trim().toLowerCase()).filter(Boolean)
  )
  if (allowClasses.size === 0) {
    if (base.atMs == null) base.atMs = atMs()
    return base
  }

  const cls = String(meta?.dhtAddressClass || '')
    .trim()
    .toLowerCase()
  if (!cls) {
    return {
      ...base,
      atMs: base.atMs ?? atMs(),
      dhtAddressClassGate: {
        schema: 1,
        mode: 'no_peer_class_hint',
        note: 'BARE_OS_DHT_ADDRESS_CLASS_ALLOWLIST is set but caller did not supply dhtAddressClass — stock Hyperswarm path does not classify peers; allow key verdict only.'
      }
    }
  }

  if (!allowClasses.has(cls)) {
    return {
      schema: ADMISSION_SCHEMA,
      verdict: 'deny',
      reason: 'dht_address_class',
      dhtAddressClass: cls,
      allowedClasses: [...allowClasses],
      note: 'Peer DHT address class not listed in BARE_OS_DHT_ADDRESS_CLASS_ALLOWLIST.',
      atMs: atMs()
    }
  }

  if (base.verdict === 'deny') return base

  return {
    ...base,
    atMs: base.atMs ?? atMs(),
    dhtAddressClassGate: { schema: 1, mode: 'allow', class: cls }
  }
}

/**
 * Build an event-bus row for **`peer_admission`** audit (**never** includes full peer keys).
 *
 * @param {string} peerKeyHex
 * @param {{ verdict: string, reason?: string, schema: number }} result
 * @param {{ dhtAddressClass?: string } | null | undefined} [meta]
 */
export function bareOsFormatPeerAdmissionAuditEvent(peerKeyHex, result, meta) {
  const norm = String(peerKeyHex || '')
    .trim()
    .toLowerCase()
    .replace(/^0x/, '')
  const keyShort = norm ? norm.slice(0, 16) : ''
  return {
    type: 'peer_admission',
    verdict: result.verdict,
    reason: result.reason,
    peerKeyHexPrefix: keyShort || undefined,
    admissionSchema: result.schema,
    dhtAddressClass:
      meta && typeof meta === 'object'
        ? String(meta.dhtAddressClass || '').trim() || undefined
        : undefined
  }
}

/**
 * Per-bucket rate gate for admission audit (**mutates** **`lastMap`** on allow).
 *
 * @param {string} bucket
 * @param {number} now
 * @param {number} rateMs
 * @param {Map<string, number>} lastMap
 */
export function bareOsPeerAdmissionAuditRateAllow(bucket, now, rateMs, lastMap) {
  if (rateMs <= 0) return true
  const last = lastMap.get(bucket) ?? 0
  if (now - last < rateMs) return false
  lastMap.set(bucket, now)
  return true
}