// ── Who may see who is online ─────────────────────────────────────────────
//
// The org lead's rule, settled 2026-09-22: **nothing tells who is online by
// default.** It is always the lowest blast radius — staff — unless an operator
// deliberately widens it, and a COUNT of players is fine where a list of names
// is not.
//
// "Who is online" is wider than the Online tab. Every frame that says a named
// player was on the server at a given moment says it: a connect, a respawn, a
// death, a chat line, a gather tally (`catalogue.PRESENCE_KINDS`), and a
// leaderboard row's `lastSeen`, which a tally refreshes every minute while
// somebody plays. All of them sit behind this one setting.
//
// ── The audiences ─────────────────────────────────────────────────────────
//
//   staff       an admin or a moderator — the two roles every Team surface in
//               core also means by "staff"
//   signed_in   any active website account
//   public      anybody, signed in or not
//
// Ordered, each rung implying the ones below it. The names line up with phase
// 14's map-layer switches (public / players / admin) so that one layer can take
// this over rather than sit beside it.
//
// ── Two fallbacks, deliberately asymmetric ────────────────────────────────
//
// An unrecognised VIEWER reads as the bottom rung and an unrecognised
// REQUIREMENT reads as the top one, so a value nobody expected always loses.
// One shared fallback cannot do that: whichever way it points, it fails open on
// one side. module-uo's shard visibility learned this the hard way; the rule is
// copied here rather than rediscovered.

const core = require('../../core')

const db = require('./visibility.db')

const log = core.logger('visibility')

const AUDIENCES = Object.freeze(['public', 'signed_in', 'staff'])
const RANK = new Map(AUDIENCES.map((a, i) => [a, i]))

/** The narrowest rung, and the default wherever nothing has been chosen. */
const DEFAULT_PRESENCE = 'staff'

/** The `rust_settings` key the fleet default lives under. */
const PRESENCE_KEY = 'presence.audience'

const isAudience = (value) => RANK.has(value)

const viewerRank = (level) => RANK.get(level) ?? 0
const requiredRank = (level) => RANK.get(level) ?? RANK.get('staff')

/** Does a viewer at `viewer` satisfy a requirement of `required`? */
const meets = (viewer, required) => viewerRank(viewer) >= requiredRank(required)

/**
 * The viewer's rung, re-read from the database.
 *
 * `getUserFromRequest` decodes a token and nothing more — the role in it is the
 * role the account had when it signed in. For a gate on who may see who is
 * online, that is not good enough: a moderator demoted this morning would keep
 * the roll call until their token expired, and a banned account would keep
 * reading it too. So the token only says WHO; the row says what they are now.
 *
 * Any failure resolves to `public` — the bottom rung — because an unanswerable
 * question about somebody's standing must grant nothing.
 */
async function viewerLevel(req) {
  try {
    const claimed = req.user || core.auth.getUserFromRequest(req)
    if (!claimed || claimed.id == null) return 'public'

    const user = await core.users.getById(claimed.id)
    if (!user) return 'public'
    if (user.status && user.status !== 'active') return 'public'

    if (user.role === 'admin' || user.role === 'moderator') return 'staff'
    return 'signed_in'
  } catch (err) {
    log.warn('could not resolve the viewer; treating them as anonymous', { error: err.message })
    return 'public'
  }
}

/** A stored value as an audience, narrowing anything this build does not recognise. */
function normalise(value) {
  return isAudience(value) ? value : DEFAULT_PRESENCE
}

/** The fleet default. */
async function fleetPresence() {
  const stored = await db.getSetting(PRESENCE_KEY)
  return stored == null ? DEFAULT_PRESENCE : normalise(stored)
}

/**
 * The audience that applies to one server: its override if it has one, the
 * fleet default otherwise.
 *
 * A server that does not exist gets the fleet default, which is the right answer
 * for the routes that call this: they answer an empty list for an unknown id,
 * and an empty list is empty at every rung.
 */
async function presenceFor(serverId) {
  const override = await db.getServerPresence(serverId)
  if (override != null) return normalise(override)
  return fleetPresence()
}

/**
 * Everything a public route needs in one call: may this viewer see who is on
 * this server?
 *
 * Throws nothing. A setting that cannot be read resolves to "no" — the routes
 * that ask would otherwise have to choose between a 500 and publishing names.
 */
async function canSeePresence(req, serverId) {
  try {
    const [level, required] = await Promise.all([viewerLevel(req), presenceFor(serverId)])
    return { visible: meets(level, required), level, required }
  } catch (err) {
    log.warn('could not resolve presence visibility; withholding it', { server: serverId, error: err.message })
    return { visible: false, level: 'public', required: DEFAULT_PRESENCE }
  }
}

/** The admin screen's read: the fleet default and every server beside it. */
async function describe() {
  const [fleet, servers] = await Promise.all([fleetPresence(), db.listServerPresence()])
  return {
    audiences: [...AUDIENCES],
    presence: {
      fleet,
      servers: servers.map((s) => {
        const override = s.presence == null ? null : normalise(s.presence)
        return {
          id: s.id,
          name: s.name,
          enabled: Boolean(s.enabled),
          override,
          effective: override || fleet,
        }
      }),
    },
  }
}

/**
 * The admin screen's write.
 *
 * `fleet` is optional; `servers` maps an id to an audience, or to `null` to
 * clear its override. Validated whole before anything is written, so a request
 * naming one unknown server changes nothing rather than half of what it asked.
 *
 * Resolves `{ ok, changed }`, or `{ ok: false, status, message }` — a refusal is a
 * sentence the page can show.
 */
async function update({ fleet, servers } = {}, actor = null) {
  if (fleet !== undefined && !isAudience(fleet)) {
    return { ok: false, status: 400, message: `"${fleet}" is not an audience. Choose one of: ${AUDIENCES.join(', ')}.` }
  }

  const changes = Object.entries(servers || {})
  for (const [id, value] of changes) {
    if (value !== null && !isAudience(value)) {
      return { ok: false, status: 400, message: `"${value}" is not an audience for server ${id}.` }
    }
    // eslint-disable-next-line no-await-in-loop
    if ((await db.getServerPresence(id)) === undefined) {
      return { ok: false, status: 404, message: `There is no server called ${id}.` }
    }
  }

  const userId = actor && actor.id != null ? actor.id : null

  if (fleet !== undefined) await db.setSetting(PRESENCE_KEY, fleet, userId)
  for (const [id, value] of changes) {
    // eslint-disable-next-line no-await-in-loop
    await db.setServerPresence(id, value)
  }

  // What was written, for the controller's audit row. Recorded there rather than
  // here because the activity log takes the REQUEST (who, from where), and a
  // model that took a request would be a model that could only be called by one.
  return {
    ok: true,
    changed: {
      ...(fleet !== undefined ? { fleet } : {}),
      servers: Object.fromEntries(changes.map(([id, value]) => [id, value === null ? 'inherit' : value])),
    },
  }
}

module.exports = {
  AUDIENCES,
  DEFAULT_PRESENCE,
  PRESENCE_KEY,
  isAudience,
  meets,
  normalise,
  viewerLevel,
  fleetPresence,
  presenceFor,
  canSeePresence,
  describe,
  update,
}