Redesign public hashtag pages (#5237)

app/controllers/tags_controller.rb

@@ -1,17 +1,22 @@
 # frozen_string_literal: true
 
 class TagsController < ApplicationController
-  layout 'public'
+  before_action :set_body_classes
+  before_action :set_instance_presenter
 
   def show
-    @tag      = Tag.find_by!(name: params[:id].downcase)
-    @statuses = Status.as_tag_timeline(@tag, current_account, params[:local]).paginate_by_max_id(20, params[:max_id])
-    @statuses = cache_collection(@statuses, Status)
+    @tag = Tag.find_by!(name: params[:id].downcase)
 
     respond_to do |format|
-      format.html
+      format.html do
+        serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
+        @initial_state_json   = serializable_resource.to_json
+      end
 
       format.json do
+        @statuses = Status.as_tag_timeline(@tag, current_account, params[:local]).paginate_by_max_id(20, params[:max_id])
+        @statuses = cache_collection(@statuses, Status)
+
         render json: collection_presenter,
                serializer: ActivityPub::CollectionSerializer,
                adapter: ActivityPub::Adapter,
@@ -22,6 +27,14 @@ class TagsController < ApplicationController
 
   private
 
+  def set_body_classes
+    @body_classes = 'tag-body'
+  end
+
+  def set_instance_presenter
+    @instance_presenter = InstancePresenter.new
+  end
+
   def collection_presenter
     ActivityPub::CollectionPresenter.new(
       id: tag_url(@tag),
@@ -30,4 +43,11 @@ class TagsController < ApplicationController
       items: @statuses.map { |s| ActivityPub::TagManager.instance.uri_for(s) }
     )
   end
+
+  def initial_state_params
+    {
+      settings: {},
+      token: current_session&.token,
+    }
+  end
 end