Federate updates to collections (#37790)

app/controllers/api/v1_alpha/collections_controller.rb

@@ -51,7 +51,7 @@ class Api::V1Alpha::CollectionsController < Api::BaseController
   def update
     authorize @collection, :update?
 
-    @collection.update!(collection_update_params) # TODO: Create a service for this to federate changes
+    UpdateCollectionService.new.call(@collection, collection_update_params)
 
     render json: @collection, serializer: REST::CollectionSerializer, adapter: :json
   end

app/serializers/activitypub/update_featured_collection_serializer.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class ActivityPub::UpdateFeaturedCollectionSerializer < ActivityPub::Serializer
+  attributes :id, :type, :actor, :to
+
+  has_one :object, serializer: ActivityPub::FeaturedCollectionSerializer
+
+  def id
+    [ActivityPub::TagManager.instance.uri_for(object), '#updates/', object.updated_at.to_i].join
+  end
+
+  def type
+    'Update'
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(object.account)
+  end
+
+  def to
+    [ActivityPub::TagManager::COLLECTIONS[:public]]
+  end
+end

app/services/update_collection_service.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class UpdateCollectionService
+  UPDATEABLE_PARAMS = %w(name description language sensitive discoverable tag_id).freeze
+
+  def call(collection, params)
+    @collection = collection
+    @collection.update!(params)
+
+    distribute_update_activity if Mastodon::Feature.collections_federation_enabled?
+  end
+
+  private
+
+  def distribute_update_activity
+    return unless relevant_attributes_changed?
+
+    ActivityPub::AccountRawDistributionWorker.perform_async(activity_json, @collection.account.id)
+  end
+
+  def activity_json
+    ActiveModelSerializers::SerializableResource.new(@collection, serializer: ActivityPub::UpdateFeaturedCollectionSerializer, adapter: ActivityPub::Adapter).to_json
+  end
+
+  def relevant_attributes_changed?
+    (@collection.saved_changes.keys & UPDATEABLE_PARAMS).any?
+  end
+end

spec/serializers/activitypub/update_featured_collection_serializer_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe ActivityPub::UpdateFeaturedCollectionSerializer do
+  subject { serialized_record_json(collection, described_class, adapter: ActivityPub::Adapter) }
+
+  let(:tag_manager) { ActivityPub::TagManager.instance }
+  let(:collection) { Fabricate(:collection) }
+
+  it 'serializes to the expected json' do
+    expect(subject).to include({
+      'id' => "#{tag_manager.uri_for(collection)}#updates/#{collection.updated_at.to_i}",
+      'type' => 'Update',
+      'actor' => tag_manager.uri_for(collection.account),
+      'to' => ['https://www.w3.org/ns/activitystreams#Public'],
+      'object' => a_hash_including({
+        'id' => tag_manager.uri_for(collection),
+        'type' => 'FeaturedCollection',
+      }),
+    })
+
+    expect(subject).to_not have_key('published')
+    expect(subject).to_not have_key('cc')
+    expect(subject).to_not have_key('target')
+  end
+end

spec/services/update_collection_service_spec.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe UpdateCollectionService do
+  subject { described_class.new }
+
+  let(:collection) { Fabricate(:collection) }
+
+  describe '#call' do
+    context 'when given valid parameters' do
+      it 'updates the collection' do
+        subject.call(collection, { name: 'Newly updated name' })
+
+        expect(collection.name).to eq 'Newly updated name'
+      end
+
+      context 'when something actually changed' do
+        it 'federates an `Update` activity', feature: :collections_federation do
+          subject.call(collection, { name: 'updated' })
+
+          expect(ActivityPub::AccountRawDistributionWorker).to have_enqueued_sidekiq_job
+        end
+      end
+
+      context 'when nothing changed' do
+        it 'does not federate an activity', feature: :collections_federation do
+          subject.call(collection, { name: collection.name })
+
+          expect(ActivityPub::AccountRawDistributionWorker).to_not have_enqueued_sidekiq_job
+        end
+      end
+    end
+
+    context 'when given invalid parameters' do
+      it 'raises an exception' do
+        expect do
+          subject.call(collection, { name: '' })
+        end.to raise_error(ActiveRecord::RecordInvalid)
+      end
+    end
+  end
+end