Improve ActivityPub representations (#3844)

* Improve webfinger templates and make tests more flexible

* Clean up AS2 representation of actor

* Refactor outbox

* Create activities representation

* Add representations of followers/following collections, do not redirect /users/:username route if format is empty

* Remove unused translations

* ActivityPub endpoint for single statuses, add ActivityPub::TagManager for better
URL/URI generation

* Add ActivityPub::TagManager#to

* Represent all attachments as Document instead of Image/Video specifically
(Because for remote ones we may not know for sure)

Add mentions and hashtags representation to AP notes

* Add AP-resolvable hashtag URIs

* Use ActiveModelSerializers for ActivityPub

* Clean up unused translations

* Separate route for object and activity

* Adjust cc/to matrices

* Add to/cc to activities, ensure announce activity embeds target status and
not the wrapper status, add "id" to all collections

app/controllers/accounts_controller.rb

@@ -16,7 +16,9 @@ class AccountsController < ApplicationController
         render xml: AtomSerializer.render(AtomSerializer.new.feed(@account, @entries.to_a))
       end
 
-      format.activitystreams2
+      format.json do
+        render json: @account, serializer: ActivityPub::ActorSerializer, adapter: ActivityPub::Adapter
+      end
     end
   end
 

app/controllers/activitypub/outboxes_controller.rb

+# frozen_string_literal: true
+
+class ActivityPub::OutboxesController < Api::BaseController
+  before_action :set_account
+
+  def show
+    @statuses = @account.statuses.permitted_for(@account, current_account).paginate_by_max_id(20, params[:max_id], params[:since_id])
+    @statuses = cache_collection(@statuses, Status)
+
+    render json: outbox_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter
+  end
+
+  private
+
+  def set_account
+    @account = Account.find_local!(params[:account_username])
+  end
+
+  def outbox_presenter
+    ActivityPub::CollectionPresenter.new(
+      id: account_outbox_url(@account),
+      type: :ordered,
+      current: account_outbox_url(@account),
+      size: @account.statuses_count,
+      items: @statuses
+    )
+  end
+end

app/controllers/api/activitypub/activities_controller.rb

-# frozen_string_literal: true
-
-class Api::ActivityPub::ActivitiesController < Api::BaseController
-  include Authorization
-
-  # before_action :set_follow, only: [:show_follow]
-  before_action :set_status, only: [:show_status]
-
-  respond_to :activitystreams2
-
-  # Show a status in AS2 format, as either an Announce (reblog) or a Create (post) activity.
-  def show_status
-    authorize @status, :show?
-
-    if @status.reblog?
-      render :show_status_announce
-    else
-      render :show_status_create
-    end
-  end
-
-  private
-
-  def set_status
-    @status = Status.find(params[:id])
-  end
-end

app/controllers/api/activitypub/notes_controller.rb

-# frozen_string_literal: true
-
-class Api::ActivityPub::NotesController < Api::BaseController
-  include Authorization
-
-  before_action :set_status
-
-  respond_to :activitystreams2
-
-  def show
-    authorize @status, :show?
-  end
-
-  private
-
-  def set_status
-    @status = Status.find(params[:id])
-  end
-end

app/controllers/api/activitypub/outbox_controller.rb

-# frozen_string_literal: true
-
-class Api::ActivityPub::OutboxController < Api::BaseController
-  before_action :set_account
-
-  respond_to :activitystreams2
-
-  def show
-    if params[:max_id] || params[:since_id]
-      show_outbox_page
-    else
-      show_base_outbox
-    end
-  end
-
-  private
-
-  def show_base_outbox
-    @statuses = Status.as_outbox_timeline(@account)
-    @statuses = cache_collection(@statuses)
-
-    set_maps(@statuses)
-
-    set_first_last_page(@statuses)
-
-    render :show
-  end
-
-  def show_outbox_page
-    all_statuses = Status.as_outbox_timeline(@account)
-    @statuses = all_statuses.paginate_by_max_id(limit_param(DEFAULT_STATUSES_LIMIT), params[:max_id], params[:since_id])
-
-    all_statuses = cache_collection(all_statuses)
-    @statuses = cache_collection(@statuses)
-
-    set_maps(@statuses)
-
-    set_first_last_page(all_statuses)
-
-    @next_page_url = api_activitypub_outbox_url(pagination_params(max_id: @statuses.last.id))    unless @statuses.empty?
-    @prev_page_url = api_activitypub_outbox_url(pagination_params(since_id: @statuses.first.id)) unless @statuses.empty?
-
-    @paginated = @next_page_url || @prev_page_url
-    @part_of_url = api_activitypub_outbox_url
-
-    set_pagination_headers(@next_page_url, @prev_page_url)
-
-    render :show_page
-  end
-
-  def cache_collection(raw)
-    super(raw, Status)
-  end
-
-  def set_account
-    @account = Account.find(params[:id])
-  end
-
-  def set_first_last_page(statuses) # rubocop:disable Style/AccessorMethodName
-    return if statuses.empty?
-
-    @first_page_url = api_activitypub_outbox_url(max_id: statuses.first.id + 1)
-    @last_page_url = api_activitypub_outbox_url(since_id: statuses.last.id - 1)
-  end
-
-  def pagination_params(core_params)
-    params.permit(:local, :limit).merge(core_params)
-  end
-end

app/controllers/follower_accounts_controller.rb

@@ -5,5 +5,25 @@ class FollowerAccountsController < ApplicationController
 
   def index
     @follows = Follow.where(target_account: @account).recent.page(params[:page]).per(FOLLOW_PER_PAGE).preload(:account)
+
+    respond_to do |format|
+      format.html
+
+      format.json do
+        render json: collection_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter
+      end
+    end
+  end
+
+  private
+
+  def collection_presenter
+    ActivityPub::CollectionPresenter.new(
+      id: account_followers_url(@account),
+      type: :ordered,
+      current: account_followers_url(@account),
+      size: @account.followers_count,
+      items: @follows.map { |f| ActivityPub::TagManager.instance.uri_for(f.account) }
+    )
   end
 end

app/controllers/following_accounts_controller.rb

@@ -5,5 +5,25 @@ class FollowingAccountsController < ApplicationController
 
   def index
     @follows = Follow.where(account: @account).recent.page(params[:page]).per(FOLLOW_PER_PAGE).preload(:target_account)
+
+    respond_to do |format|
+      format.html
+
+      format.json do
+        render json: collection_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter
+      end
+    end
+  end
+
+  private
+
+  def collection_presenter
+    ActivityPub::CollectionPresenter.new(
+      id: account_following_index_url(@account),
+      type: :ordered,
+      current: account_following_index_url(@account),
+      size: @account.following_count,
+      items: @follows.map { |f| ActivityPub::TagManager.instance.uri_for(f.target_account) }
+    )
   end
 end

app/controllers/statuses_controller.rb

@@ -11,10 +11,22 @@ class StatusesController < ApplicationController
   before_action :check_account_suspension
 
   def show
-    @ancestors   = @status.reply? ? cache_collection(@status.ancestors(current_account), Status) : []
-    @descendants = cache_collection(@status.descendants(current_account), Status)
+    respond_to do |format|
+      format.html do
+        @ancestors   = @status.reply? ? cache_collection(@status.ancestors(current_account), Status) : []
+        @descendants = cache_collection(@status.descendants(current_account), Status)
+
+        render 'stream_entries/show'
+      end
+
+      format.json do
+        render json: @status, serializer: ActivityPub::NoteSerializer, adapter: ActivityPub::Adapter
+      end
+    end
+  end
 
-    render 'stream_entries/show'
+  def activity
+    render json: @status, serializer: ActivityPub::ActivitySerializer, adapter: ActivityPub::Adapter
   end
 
   private

app/controllers/tags_controller.rb

@@ -5,7 +5,27 @@ class TagsController < ApplicationController
 
   def show
     @tag      = Tag.find_by!(name: params[:id].downcase)
-    @statuses = @tag.nil? ? [] : Status.as_tag_timeline(@tag, current_account, params[:local]).paginate_by_max_id(20, params[:max_id])
+    @statuses = Status.as_tag_timeline(@tag, current_account, params[:local]).paginate_by_max_id(20, params[:max_id])
     @statuses = cache_collection(@statuses, Status)
+
+    respond_to do |format|
+      format.html
+
+      format.json do
+        render json: collection_presenter, serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter
+      end
+    end
+  end
+
+  private
+
+  def collection_presenter
+    ActivityPub::CollectionPresenter.new(
+      id: tag_url(@tag),
+      type: :ordered,
+      current: tag_url(@tag),
+      size: @tag.statuses.count,
+      items: @statuses.map { |s| ActivityPub::TagManager.instance.uri_for(s) }
+    )
   end
 end

app/helpers/activitystreams2_builder_helper.rb

-# frozen_string_literal: true
-
-module Activitystreams2BuilderHelper
-  # Gets a usable name for an account, using display name or username.
-  def account_name(account)
-    account.display_name.presence || account.username
-  end
-end

app/lib/activitypub/adapter.rb

+# frozen_string_literal: true
+
+class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
+  def self.default_key_transform
+    :camel_lower
+  end
+
+  def serializable_hash(options = nil)
+    options = serialization_options(options)
+    serialized_hash = { '@context': 'https://www.w3.org/ns/activitystreams' }.merge(ActiveModelSerializers::Adapter::Attributes.new(serializer, instance_options).serializable_hash(options))
+    self.class.transform_key_casing!(serialized_hash, instance_options)
+  end
+end

app/lib/activitypub/tag_manager.rb

+# frozen_string_literal: true
+
+require 'singleton'
+
+class ActivityPub::TagManager
+  include Singleton
+  include RoutingHelper
+
+  COLLECTIONS = {
+    public: 'https://www.w3.org/ns/activitystreams#Public',
+  }.freeze
+
+  def url_for(target)
+    return target.url if target.respond_to?(:local?) && !target.local?
+
+    case target.object_type
+    when :person
+      short_account_url(target)
+    when :note, :comment, :activity
+      short_account_status_url(target.account, target)
+    end
+  end
+
+  def uri_for(target)
+    return target.uri if target.respond_to?(:local?) && !target.local?
+
+    case target.object_type
+    when :person
+      account_url(target)
+    when :note, :comment, :activity
+      account_status_url(target.account, target)
+    end
+  end
+
+  # Primary audience of a status
+  # Public statuses go out to primarily the public collection
+  # Unlisted and private statuses go out primarily to the followers collection
+  # Others go out only to the people they mention
+  def to(status)
+    case status.visibility
+    when 'public'
+      [COLLECTIONS[:public]]
+    when 'unlisted', 'private'
+      [account_followers_url(status.account)]
+    when 'direct'
+      status.mentions.map { |mention| uri_for(mention.account) }
+    end
+  end
+
+  # Secondary audience of a status
+  # Public statuses go out to followers as well
+  # Unlisted statuses go to the public as well
+  # Both of those and private statuses also go to the people mentioned in them
+  # Direct ones don't have a secondary audience
+  def cc(status)
+    cc = []
+
+    case status.visibility
+    when 'public'
+      cc << account_followers_url(status.account)
+    when 'unlisted'
+      cc << COLLECTIONS[:public]
+    end
+
+    cc.concat(status.mentions.map { |mention| uri_for(mention.account) }) unless status.direct_visibility?
+
+    cc
+  end
+end

app/presenters/activitypub/collection_presenter.rb

+# frozen_string_literal: true
+
+class ActivityPub::CollectionPresenter < ActiveModelSerializers::Model
+  attributes :id, :type, :current, :size, :items
+end

app/serializers/activitypub/activity_serializer.rb

+# frozen_string_literal: true
+
+class ActivityPub::ActivitySerializer < ActiveModel::Serializer
+  attributes :id, :type, :actor, :to, :cc
+
+  has_one :proper, key: :object, serializer: ActivityPub::NoteSerializer
+
+  def id
+    [ActivityPub::TagManager.instance.uri_for(object), '/activity'].join
+  end
+
+  def type
+    object.reblog? ? 'Announce' : 'Create'
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(object.account)
+  end
+
+  def to
+    ActivityPub::TagManager.instance.to(object)
+  end
+
+  def cc
+    ActivityPub::TagManager.instance.cc(object)
+  end
+end

app/serializers/activitypub/actor_serializer.rb

+# frozen_string_literal: true
+
+class ActivityPub::ActorSerializer < ActiveModel::Serializer
+  include RoutingHelper
+
+  attributes :id, :type, :following, :followers,
+             :inbox, :outbox, :preferred_username,
+             :name, :summary, :icon, :image
+
+  def id
+    account_url(object)
+  end
+
+  def type
+    'Person'
+  end
+
+  def following
+    account_following_index_url(object)
+  end
+
+  def followers
+    account_followers_url(object)
+  end
+
+  def inbox
+    nil
+  end
+
+  def outbox
+    account_outbox_url(object)
+  end
+
+  def preferred_username
+    object.username
+  end
+
+  def name
+    object.display_name
+  end
+
+  def summary
+    Formatter.instance.simplified_format(object)
+  end
+
+  def icon
+    full_asset_url(object.avatar.url(:original))
+  end
+
+  def image
+    full_asset_url(object.header.url(:original))
+  end
+end

app/serializers/activitypub/collection_serializer.rb

+# frozen_string_literal: true
+
+class ActivityPub::CollectionSerializer < ActiveModel::Serializer
+  def self.serializer_for(model, options)
+    return ActivityPub::ActivitySerializer if model.class.name == 'Status'
+    super
+  end
+
+  attributes :id, :type, :total_items,
+             :current
+
+  has_many :items, key: :ordered_items
+
+  def type
+    case object.type
+    when :ordered
+      'OrderedCollection'
+    else
+      'Collection'
+    end
+  end
+
+  def total_items
+    object.size
+  end
+end

app/serializers/activitypub/note_serializer.rb

+# frozen_string_literal: true
+
+class ActivityPub::NoteSerializer < ActiveModel::Serializer
+  attributes :id, :type, :summary, :content,
+             :in_reply_to, :published, :url,
+             :actor, :to, :cc, :sensitive
+
+  has_many :media_attachments, key: :attachment
+  has_many :virtual_tags, key: :tag
+
+  def id
+    ActivityPub::TagManager.instance.uri_for(object)
+  end
+
+  def type
+    'Note'
+  end
+
+  def summary
+    object.spoiler_text.presence
+  end
+
+  def content
+    Formatter.instance.format(object)
+  end
+
+  def in_reply_to
+    ActivityPub::TagManager.instance.uri_for(object.thread) if object.reply?
+  end
+
+  def published
+    object.created_at.iso8601
+  end
+
+  def url
+    ActivityPub::TagManager.instance.url_for(object)
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(object.account)
+  end
+
+  def to
+    ActivityPub::TagManager.instance.to(object)
+  end
+
+  def cc
+    ActivityPub::TagManager.instance.cc(object)
+  end
+
+  def virtual_tags
+    object.mentions + object.tags
+  end
+
+  class MediaAttachmentSerializer < ActiveModel::Serializer
+    include RoutingHelper
+
+    attributes :type, :media_type, :url
+
+    def type
+      'Document'
+    end
+
+    def media_type
+      object.file_content_type
+    end
+
+    def url
+      object.local? ? full_asset_url(object.file.url(:original, false)) : object.remote_url
+    end
+  end
+
+  class MentionSerializer < ActiveModel::Serializer
+    attributes :type, :href, :name
+
+    def type
+      'Mention'
+    end
+
+    def href
+      ActivityPub::TagManager.instance.uri_for(object.account)
+    end
+
+    def name
+      "@#{object.account.acct}"
+    end
+  end
+
+  class TagSerializer < ActiveModel::Serializer
+    include RoutingHelper
+
+    attributes :type, :href, :name
+
+    def type
+      'Hashtag'
+    end
+
+    def href
+      tag_url(object)
+    end
+
+    def name
+      "##{object.name}"
+    end
+  end
+end

app/views/accounts/show.activitystreams2.rabl

-extends 'activitypub/types/person.activitystreams2.rabl'
-
-object @account
-
-attributes display_name: :name, username: :preferredUsername, note: :summary
-
-node(:icon)   { |account| full_asset_url(account.avatar.url(:original)) }
-node(:image)  { |account| full_asset_url(account.header.url(:original)) }
-node(:outbox) { |account| api_activitypub_outbox_url(account.id) }

app/views/activitypub/base.activitystreams2.rabl

-node(:'@context') { 'https://www.w3.org/ns/activitystreams' }

app/views/activitypub/intransient.activitystreams2.rabl

-extends 'activitypub/base.activitystreams2.rabl'
-
-node(:id) { request.original_url }