// ── The grant/revoke flow (TEAMS.md §2.5 path 3) ───────────────────────────
//
// The RESOLVER lives in teamAccess.model.js and answers "may this account use the
// forum". This file is the WRITE half: who may hand that access out, to whom, and
// what stops a leader turning a Team forum into open hosting on the operator's
// site.
//
// **Two authorities, and they are not the same authority with different reach.**
//
//   staff  (admin | moderator) — any Team, no cap, may revoke anything
//   leader (path 2, on THIS Team) — own Team, capped, may not revoke a staff grant
//
// The last clause is the one worth stating: a leader who could revoke a
// staff-issued grant could undo a moderation decision, which is the whole reason
// `granted_by` is retained rather than collapsed into a boolean.
//
// **Nothing here writes `team_members`, in either direction, ever.** A grant is
// not a membership: it may name any Runic Gateway account, including one with no
// linked game identity at all — that is the point of it, since letting an unlinked
// guildmate into the forum must not be a staff ticket. `teams.model.js` keeps such
// an account off the roster and out of every membership count, and path 4 keeps it
// off external platforms.

const accessDb = require('./teamAccess.db')
const teamsDb = require('./teams.db')
const access = require('./teamAccess.model')
const usersDb = require('../users/users.db')
const settingsDb = require('../settings/settings.db')

// The per-Team ceiling on ACTIVE leader-issued grants. A leader admitting
// unlimited arbitrary accounts to a private space on the operator's host is a
// quiet way to turn a Team forum into free hosting; the cap is what makes it a
// decision the operator made rather than one a leader made for them.
const CAP_KEY = 'teams_max_grants_per_team'
const DEFAULT_CAP = 50

const STAFF_ROLES = ['admin', 'moderator']

async function grantCap() {
  const raw = await settingsDb.get(CAP_KEY)
  const n = Number.parseInt(raw, 10)
  return Number.isFinite(n) && n > 0 ? n : DEFAULT_CAP
}

const isStaff = (actor) => STAFF_ROLES.includes(actor?.role)

/**
 * What may this actor do with grants on this Team?
 *
 * Resolved once and returned whole, so the controller asks a question rather than
 * assembling the answer from three booleans — the shape that lets a leader check
 * and a staff check drift apart.
 */
async function authorityFor(teamId, actor) {
  if (isStaff(actor)) return { may: true, as: 'staff' }
  const leads = await access.isLeaderByUser(teamId, actor?.id)
  return { may: leads, as: leads ? 'leader' : null }
}

/**
 * Issue a grant. Returns the model result shape the Teams controllers translate:
 * `{ ok }` or `{ ok: false, status, error }`.
 *
 * `warning` on a staff grant past the cap is deliberate and is not an error:
 * staff are exempt, and silently exceeding a ceiling the operator configured is
 * worth saying out loud on the way past.
 */
async function grant({ team, actor, userId, username, reason }) {
  const authority = await authorityFor(team.id, actor)
  if (!authority.may) return { ok: false, status: 403, error: 'Not a leader of this Team' }

  const target = userId
    ? await usersDb.findById(userId)
    : await usersDb.findByUsername(username)
  if (!target) return { ok: false, status: 404, error: 'No such account' }

  const existing = await accessDb.activeGrant(team.id, target.id)
  if (existing) return { ok: false, status: 409, error: 'That account already has an active grant' }

  const cap = await grantCap()
  const count = await accessDb.activeGrantCount(team.id)
  let warning = null
  if (count >= cap) {
    if (authority.as === 'leader') {
      return { ok: false, status: 409, error: `This Team has reached its limit of ${cap} forum guests` }
    }
    warning = `This Team is past the configured limit of ${cap} forum guests`
  }

  await accessDb.insertGrant({
    teamId: team.id,
    userId: target.id,
    username: target.username,
    grantedBy: actor.id,
    grantedUsername: actor.username,
    reason,
  })
  return { ok: true, as: authority.as, grantee: target.username, ...(warning ? { warning } : {}) }
}

/**
 * Revoke a grant.
 *
 * The one asymmetry with `grant`: a leader may not revoke what staff issued.
 * Checked against `granted_by`'s role AT REVOKE TIME rather than against a stored
 * flag, so an account that has since lost its staff role stops protecting the
 * grants it made — which is the behaviour an operator demoting someone expects.
 */
async function revoke({ team, actor, userId, reason }) {
  const authority = await authorityFor(team.id, actor)
  if (!authority.may) return { ok: false, status: 403, error: 'Not a leader of this Team' }

  const existing = await accessDb.activeGrant(team.id, userId)
  if (!existing) return { ok: false, status: 404, error: 'No active grant for that account' }

  if (authority.as === 'leader' && existing.granted_by) {
    const issuer = await usersDb.findById(existing.granted_by)
    if (isStaff(issuer)) {
      return { ok: false, status: 403, error: 'That access was granted by staff and only staff may revoke it' }
    }
  }

  await accessDb.revokeGrant({
    teamId: team.id,
    userId,
    revokedBy: actor.id,
    revokedUsername: actor.username,
    reason,
  })
  return { ok: true, as: authority.as, grantee: existing.username }
}

/**
 * The Team's forum guests — active grants for accounts that are NOT members.
 *
 * The subtraction is the §3.2 "Forum guests" list: someone who is both a member
 * and a grantee is a member, listed on the roster, and appears here not at all.
 * Both facts stay true in the ledger; only the presentation picks one.
 */
async function forumGuests(teamId) {
  const [grants, members] = await Promise.all([
    accessDb.activeGrants(teamId),
    teamsDb.membersByTeam(teamId, { includeDeparted: false }),
  ])
  const memberUserIds = new Set(members.map((m) => m.user_id).filter((id) => id != null))
  return grants
    .filter((g) => g.user_id == null || !memberUserIds.has(g.user_id))
    .map((g) => ({
      userId: g.user_id,
      username: g.username,
      grantedBy: g.granted_username,
      grantedAt: g.granted_at,
      reason: g.reason,
    }))
}

module.exports = {
  CAP_KEY,
  DEFAULT_CAP,
  // Exported since phase 7: the Discord dispatcher's `access: 'staff'` has to
  // mean the same two roles every other Team surface means by it, and a second
  // copy of the list is a copy that drifts.
  STAFF_ROLES,
  grantCap,
  authorityFor,
  grant,
  revoke,
  forumGuests,
}