// ── module-uo's registered audiences ───────────────────────────────────────
//
// ENGAGEMENT.md §5.1a, and this module's first three. An audience is a NAMED SET
// OF PEOPLE an operator can point a rule at, or compose into a saved segment with
// and/or/not — "the members of guild 1042", "the governors", "everyone who has
// linked a game account".
//
// **This is a different mechanism from the `members` audience the guild triggers
// use, and the difference is worth stating because the words are the same.** A
// guild event is about the members of THAT guild, which is a different answer for
// every firing; a segment's parameters are CONSTANTS, so it cannot express it,
// and the access-checked set travels on the envelope as `recipientUserIds`
// instead (Phase 6, decision 2). What is here answers the same question every
// time it is asked, which is exactly what makes it composable and storable.
//
// **Four rules, all of them from §5.1a:**
//
//   1. **Core learns no game vocabulary.** It knows an id, a label, a parameter
//      list and a `resolve` it may call. It has never heard of a guild.
//   2. **The resolver returns user ids and NOTHING else.** It is not handed a
//      template, a channel or an address and cannot enumerate them. A module still
//      cannot send mail, and this must not become the door that lets it — core
//      maps ids to addresses on its own side, after preferences, suppression and
//      the verification gate.
//   3. **Composition narrows, never widens.** The `ceiling` below is the widest
//      this audience can EVER resolve to; a segment takes the narrowest ceiling it
//      contains, and the result is still checked against the trigger's own.
//   4. **An uninstalled module's audience goes dormant**, resolving empty, rather
//      than erroring or silently reaching a different set of people.
//
// All three ceiling at `members`, and none higher. `members` is the lattice value
// for "a module-declared list", and it is the honest one here: these sets are not
// "everyone signed in" narrowed down, they are lists this module happens to know.
//
// Every resolver is bounded by `shardLinks.MAX_AUDIENCE` through the queries it
// calls, and every one of them fails to the EMPTY set rather than throwing — a
// dormant audience is a rule that reaches nobody, which is §5.1a rule 4's
// behaviour and much better than a rule that 500s the engine.

const shardLinks = require('../model/shardLinks/shardLinks.model')
const shardState = require('../model/shardState/shardState.model')
const core = require('../core')

const log = core.logger('shard-audiences')

// One wrapper, so every resolver has the same failure behaviour and none of them
// has to remember it. A resolver that throws would fail the whole enqueue for
// every other audience in the same segment.
const safely = (id, fn) => async (params) => {
  try {
    return await fn(params || {})
  } catch (err) {
    log.warn('audience resolve failed — treating as empty', { audience: id, message: err.message })
    return []
  }
}

const AUDIENCES = [
  {
    // `namespaced()` requires the module's own prefix, so these are declared with
    // it rather than relying on core to add one. Audiences have their own id
    // space — an audience names a set of PEOPLE and a trigger names an EVENT — so
    // `uo.guild.members` here does not collide with any trigger id.
    id: 'uo.guild.members',
    label: 'Members of a guild',
    description: 'Everyone with a linked game account on one guild\'s roster.',
    params: [{ id: 'guildId', type: 'int', required: true }],
    ceiling: 'members',
    resolve: safely('uo.guild.members', async ({ guildId }) => {
      if (guildId == null) return []
      const accounts = await shardState.listGuildMemberAccounts(guildId)
      return shardLinks.userIdsForAccounts(accounts)
    }),
  },
  {
    id: 'uo.governors',
    label: 'Town governors',
    description: 'Everyone with a linked game account currently holding a city governorship.',
    params: [],
    ceiling: 'members',
    resolve: safely('uo.governors', async () => {
      const accounts = await shardState.listGovernorAccounts()
      return shardLinks.userIdsForAccounts(accounts)
    }),
  },
  {
    id: 'uo.linked.accounts',
    label: 'Players with a linked game account',
    // The set an operator reaches for first, and — more usefully — the one a
    // `not` composes against: "everyone who has NOT linked" is the audience for
    // the message that asks them to.
    description: 'Every website user who has linked at least one game account.',
    params: [],
    ceiling: 'members',
    resolve: safely('uo.linked.accounts', () => shardLinks.allLinkedUserIds()),
  },
]

module.exports = { AUDIENCES }