festipod/backend/services/attendees.service.js

const urlJoin = require('url-join');
const { PodCollectionsHandlerMixin } = require('@activitypods/app');
const CONFIG = require('../config/config');
const { hasPublicIntent } = require('./public-intent');

// Attaches an `apods:attendees` collection (and a WAC group of the same members) to every
// `as:Event` created in a user's pod that this backend learns of through the outbox watcher —
// plain events as well as meeting points (observed 2026-10-12). A join adds the actor to it.
//
// Who may read the collection: the pod creates it world-readable (`acl:Read` for
// `foaf:Agent`) — a platform default, observed 2026-10-12, not a choice made here. Whether
// attendee lists SHOULD be world-readable is an open product question: the functional-domain
// doctrine places participation in the protected scope. This service does not settle it. On a
// resource carrying Festipod's public intent it also applies `public-read.grant` to the
// collection, which finds it already world-readable and adds nothing; on any other resource the
// backend grants nothing on the collection.
module.exports = {
  name: 'attendees',
  mixins: [PodCollectionsHandlerMixin],
  settings: {
    shapeTreeUri: urlJoin(CONFIG.SHAPE_REPOSITORY_URL, 'shapetrees/as/Event'),
    attachPredicate: 'http://activitypods.org/ns/core#attendees',
    collectionOptions: {
      ordered: false,
      summary: 'Meeting point attendees'
    },
    createWacGroup: true
  },
  dependencies: ['public-read'],
  actions: {
    // Replaces the mixin's action of the same name (`PodCollectionsHandlerMixin`,
    // @activitypods/app 2.3.2) with one difference. `pod-collections.createAndAttach` returns
    // undefined when it attaches nothing — the resource already carries an `apods:attendees`
    // value (written by its creator or by another app), or the pod refused to create the
    // collection — and the mixin then derives a WAC group slug from that undefined URI:
    // `new URL(undefined)` throws. The webhook call that runs the watcher is not awaited by the
    // platform, so that throw ended the whole backend process (observed 2026-10-12, an event
    // POSTed with `apods:attendees` already set). Here, nothing attached means no group to create.
    createAndAttach: {
      async handler(ctx) {
        const { resourceUri, actorUri } = ctx.params;
        const { attachPredicate, collectionOptions, createWacGroup } = this.settings;

        const collectionUri = await ctx.call('pod-collections.createAndAttach', {
          resourceUri,
          attachPredicate,
          collectionOptions,
          actorUri
        });
        if (!collectionUri) {
          this.logger.info(`No attendees collection attached to ${resourceUri} (already carries one, or creation refused)`);
          return undefined;
        }

        if (createWacGroup) {
          await ctx.call('pod-wac-groups.create', {
            groupSlug: this.getGroupSlugFromCollectionUri(collectionUri),
            actorUri
          });
        }
        return collectionUri;
      }
    }
  },
  methods: {
    // Replaces the mixin's `onCreate`. The watcher runs the handlers of one `Create` in sequence
    // and does not catch, in an order that is not fixed (attendees ran before public-read and
    // catalog in the runs observed 2026-10-12): a throw here would skip whichever handlers come
    // after it, and — the webhook call being un-awaited — end the process. So a failure is
    // logged, never thrown.
    async onCreate(ctx, resource, actorUri) {
      const resourceUri = resource.id || resource['@id'];
      try {
        const collectionUri = await this.actions.createAndAttach({ resourceUri, actorUri }, { parentCtx: ctx });
        if (collectionUri && hasPublicIntent(resource)) {
          await ctx.call('public-read.grant', { resourceUri: collectionUri, actorUri });
        }
      } catch (e) {
        this.logger.error(`Could not set up the attendees collection of ${resourceUri}: ${e.message}`);
      }
    }
  }
};