Add references activitypub support

app/controllers/activitypub/references_controller.rb

@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+class ActivityPub::ReferencesController < ActivityPub::BaseController
+  include SignatureVerification
+  include Authorization
+  include AccountOwnedConcern
+
+  REFERENCES_LIMIT = 5
+
+  before_action :require_signature!, if: :authorized_fetch_mode?
+  before_action :set_status
+
+  def index
+    expires_in 0, public: public_fetch_mode?
+    render json: references_collection_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter, content_type: 'application/activity+json', skip_activities: true
+  end
+
+  private
+
+  def pundit_user
+    signed_request_account
+  end
+
+  def set_status
+    @status = @account.statuses.find(params[:status_id])
+    authorize @status, :show?
+  rescue Mastodon::NotPermittedError
+    not_found
+  end
+
+  def load_statuses
+    cached_references
+  end
+
+  def cached_references
+    cache_collection(Status.where(id: results).reorder(:id), Status)
+  end
+
+  def results
+    @results ||= begin
+      references = @status.reference_objects.order(target_status_id: :asc)
+      references = references.where('target_status_id > ?', page_params[:min_id]) if page_params[:min_id].present?
+      references = references.limit(limit_param(REFERENCES_LIMIT))
+      references.pluck(:target_status_id)
+    end
+  end
+
+  def pagination_min_id
+    results.last
+  end
+
+  def records_continue?
+    results.size == limit_param(REFERENCES_LIMIT)
+  end
+
+  def references_collection_presenter
+    page = ActivityPub::CollectionPresenter.new(
+      id: ActivityPub::TagManager.instance.references_uri_for(@status, page_params),
+      type: :unordered,
+      part_of: ActivityPub::TagManager.instance.references_uri_for(@status),
+      items: load_statuses.map(&:uri),
+      next: next_page
+    )
+
+    return page if page_requested?
+
+    ActivityPub::CollectionPresenter.new(
+      type: :unordered,
+      id: ActivityPub::TagManager.instance.references_uri_for(@status),
+      first: page
+    )
+  end
+
+  def page_requested?
+    truthy_param?(:page)
+  end
+
+  def next_page
+    return unless records_continue?
+
+    ActivityPub::TagManager.instance.references_uri_for(@status, page_params.merge(min_id: pagination_min_id))
+  end
+
+  def page_params
+    params_slice(:min_id, :limit).merge(page: true)
+  end
+end