// ── What the bridge can say, and who may hear it ──────────────────────────
//
// One file, because these two questions have to be answered together or the
// second one rots: which frame kinds exist, and which of them a member of the
// public may see.
//
// ── The boundary ──────────────────────────────────────────────────────────
//
// Protocol 2's catalogue includes frames carrying **IP addresses** (a login
// attempt, an approval, a ban) and **one player's complaint about another** (a
// report), and one — a destroyed structure — that names where somebody lives.
// They are stored, because an operator chasing ban evasion needs them and
// because the sidecar persists what it is told. They must never reach a public
// page.
//
// **The boundary is enforced HERE, on the side that serves, and not on the wire.**
// The plugin could have stamped a `class` on every frame and saved this file the
// trouble; it deliberately does not (PROTOCOL.md §8.5). A boundary declared by
// the sender is a boundary a compromised — or merely out-of-date — game host can
// widen. Core's own shard fan-out works the same way: a public stream with an
// allowlist of kinds, and an admin stream that adds the rest.
//
// ── Default deny, and why it is not paranoia ──────────────────────────────
//
// `isPublic` answers `false` for a kind it has never heard of. That matters
// because of the shape of the mistake it prevents: the next protocol version
// adds a kind, this module ingests it happily (`rust_events` stores what it is
// given), and a page that filtered by a DENY list would publish it the day it
// first arrived — before anybody had decided whether it should be public. With
// an allowlist the new kind is invisible until somebody adds it here, which is
// the same moment they think about it.
//
// The test holds this list against `docs/rust-link/PROTOCOL.md` §8.4's table, so
// adding a kind to the spec without classifying it fails a build rather than
// shipping an address to a public page.

/**
 * Kinds a public, signed-out visitor may see.
 *
 * Each entry is a decision. `player.chat` is here because a shard's chat is
 * public by the same logic that makes a killfeed public — it happened in front
 * of everyone who was on the server — and an operator who disagrees turns the
 * feature off rather than relying on this list being wrong.
 */
const PUBLIC_KINDS = Object.freeze([
  'player.connected',
  'player.disconnected',
  'player.respawned',
  'player.death',
  'player.chat',
  'player.tally',
  'server.wipe',
  'server.initialized',
  'server.shutdown',
])

/**
 * Kinds an admin may see and nobody else.
 *
 * Listed rather than implied by absence, so that "we know about this kind and it
 * is restricted" is distinguishable from "nobody has classified this kind" — the
 * second is a finding, and a bare allowlist cannot tell you which you are
 * looking at.
 */
const STAFF_KINDS = Object.freeze([
  'entity.destroyed',
  'player.reported',
  'player.banned',
  'player.unbanned',
  'player.login.attempt',
  'player.approved',
])

/** Every kind protocol 2 defines. */
const ALL_KINDS = Object.freeze([...PUBLIC_KINDS, ...STAFF_KINDS])

const PUBLIC = new Set(PUBLIC_KINDS)
const STAFF = new Set(STAFF_KINDS)

/**
 * May a signed-out visitor see this kind?
 *
 * Default deny: an unknown kind is not public. Callers pass whatever arrived on
 * the wire, including a kind from a newer protocol this build has never seen.
 */
function isPublic(kind) {
  return PUBLIC.has(kind)
}

/** Is this a kind this build knows about at all? */
function isKnown(kind) {
  return PUBLIC.has(kind) || STAFF.has(kind)
}

/**
 * Narrows a list of requested kinds to the ones a viewer may have.
 *
 * Returning the allowlist itself when nothing was requested is what makes the
 * public route safe by construction rather than by remembering to filter: there
 * is no code path where "no filter" means "everything".
 */
function kindsFor({ admin = false, requested = null } = {}) {
  const permitted = admin ? ALL_KINDS : PUBLIC_KINDS

  if (!requested || requested.length === 0) return [...permitted]

  const allowed = new Set(permitted)
  return requested.filter((k) => allowed.has(k))
}

module.exports = {
  PUBLIC_KINDS,
  STAFF_KINDS,
  ALL_KINDS,
  isPublic,
  isKnown,
  kindsFor,
}