Implement FEP 7888: Part 1 - publish conversation context (#35959)

app/controllers/activitypub/contexts_controller.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+class ActivityPub::ContextsController < ActivityPub::BaseController
+  vary_by -> { 'Signature' if authorized_fetch_mode? }
+
+  before_action :require_account_signature!, if: :authorized_fetch_mode?
+  before_action :set_conversation
+  before_action :set_items
+
+  DESCENDANTS_LIMIT = 60
+
+  def show
+    expires_in 3.minutes, public: public_fetch_mode?
+    render_with_cache json: context_presenter, serializer: ActivityPub::ContextSerializer, adapter: ActivityPub::Adapter, content_type: 'application/activity+json'
+  end
+
+  def items
+    expires_in 3.minutes, public: public_fetch_mode?
+    render_with_cache json: items_collection_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter, content_type: 'application/activity+json'
+  end
+
+  private
+
+  def account_required?
+    false
+  end
+
+  def set_conversation
+    @conversation = Conversation.local.find(params[:id])
+  end
+
+  def set_items
+    @items = @conversation.statuses.distributable_visibility.paginate_by_min_id(DESCENDANTS_LIMIT, params[:min_id])
+  end
+
+  def context_presenter
+    first_page = ActivityPub::CollectionPresenter.new(
+      id: items_context_url(@conversation, page_params),
+      type: :unordered,
+      part_of: items_context_url(@conversation),
+      next: next_page,
+      items: @items.map { |status| status.local? ? ActivityPub::TagManager.instance.uri_for(status) : status.uri }
+    )
+
+    ActivityPub::ContextPresenter.from_conversation(@conversation).tap do |presenter|
+      presenter.first = first_page
+    end
+  end
+
+  def items_collection_presenter
+    page = ActivityPub::CollectionPresenter.new(
+      id: items_context_url(@conversation, page_params),
+      type: :unordered,
+      part_of: items_context_url(@conversation),
+      next: next_page,
+      items: @items.map { |status| status.local? ? ActivityPub::TagManager.instance.uri_for(status) : status.uri }
+    )
+
+    return page if page_requested?
+
+    ActivityPub::CollectionPresenter.new(
+      id: items_context_url(@conversation),
+      type: :unordered,
+      first: page
+    )
+  end
+
+  def page_requested?
+    truthy_param?(:page)
+  end
+
+  def next_page
+    return nil if @items.size < DESCENDANTS_LIMIT
+
+    items_context_url(@conversation, page: true, min_id: @items.last.id)
+  end
+
+  def page_params
+    params.permit(:page, :min_id)
+  end
+end