Add server banner to web app, add `GET /api/v2/instance` to REST API (#19294)

Cherry-picked d2528b26b6da34f34b5d7a392e263428d3c09d69

Conflicts:
- `app/serializers/initial_state_serializer.rb`:
  Upstream changed stuff, we had extra attributes.
  Applied upstream changes while keeping our extra attributes.
- `app/serializers/rest/instance_serializer.rb`:
  Upstream actually moved that to `app/serializers/rest/v1/instance_serializer.rb`,
  so updated that file by keeping our extra attributes, and took upstream's
  version of `app/serializers/rest/instance_serializer.rb`.
- `spec/views/about/show.html.haml_spec.rb`:
  Took upstream's version.

4 files changed, 146 insertions, 86 deletions

diff --git a/app/serializers/initial_state_serializer.rb b/app/serializers/initial_state_serializer.rb
index 45a5cda6f..aa36f82a1 100644
--- a/app/serializers/initial_state_serializer.rb
+++ b/app/serializers/initial_state_serializer.rb
@@ -6,7 +6,7 @@ class InitialStateSerializer < ActiveModel::Serializer
   attributes :meta, :compose, :accounts,
              :media_attachments, :settings,
              :max_toot_chars, :poll_limits,
-             :languages, :server
+             :languages
 
   has_one :push_subscription, serializer: REST::WebPushSubscriptionSerializer
   has_one :role, serializer: REST::RoleSerializer
@@ -24,18 +24,19 @@ class InitialStateSerializer < ActiveModel::Serializer
     }
   end
 
+  # rubocop:disable Metrics/AbcSize
   def meta
     store = {
       streaming_api_base_url: Rails.configuration.x.streaming_api_base_url,
       access_token: object.token,
       locale: I18n.locale,
-      domain: Rails.configuration.x.local_domain,
-      title: instance_presenter.site_title,
+      domain: instance_presenter.domain,
+      title: instance_presenter.title,
       admin: object.admin&.id&.to_s,
       search_enabled: Chewy.enabled?,
       repository: Mastodon::Version.repository,
-      source_url: Mastodon::Version.source_url,
-      version: Mastodon::Version.to_s,
+      source_url: instance_presenter.source_url,
+      version: instance_presenter.version,
       limited_federation_mode: Rails.configuration.x.whitelist_mode,
       mascot: instance_presenter.mascot&.file&.url,
       profile_directory: Setting.profile_directory,
@@ -71,6 +72,7 @@ class InitialStateSerializer < ActiveModel::Serializer
 
     store
   end
+  # rubocop:enable Metrics/AbcSize
 
   def compose
     store = {}
@@ -102,13 +104,6 @@ class InitialStateSerializer < ActiveModel::Serializer
     LanguagesHelper::SUPPORTED_LOCALES.map { |(key, value)| [key, value[0], value[1]] }
   end
 
-  def server
-    {
-      hero: instance_presenter.hero&.file&.url || instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'),
-      description: instance_presenter.site_short_description.presence || I18n.t('about.about_mastodon_html'),
-    }
-  end
-
   private
 
   def instance_presenter
diff --git a/app/serializers/manifest_serializer.rb b/app/serializers/manifest_serializer.rb
index 9827323a8..6b5296480 100644
--- a/app/serializers/manifest_serializer.rb
+++ b/app/serializers/manifest_serializer.rb
@@ -22,11 +22,11 @@ class ManifestSerializer < ActiveModel::Serializer
              :share_target, :shortcuts
 
   def name
-    object.site_title
+    object.title
   end
 
   def short_name
-    object.site_title
+    object.title
   end
 
   def icons
diff --git a/app/serializers/rest/instance_serializer.rb b/app/serializers/rest/instance_serializer.rb
index 575c6214e..f4ea49427 100644
--- a/app/serializers/rest/instance_serializer.rb
+++ b/app/serializers/rest/instance_serializer.rb
@@ -1,74 +1,39 @@
 # frozen_string_literal: true
 
 class REST::InstanceSerializer < ActiveModel::Serializer
-  include RoutingHelper
-
-  attributes :uri, :title, :short_description, :description, :email,
-             :version, :urls, :stats, :thumbnail, :max_toot_chars, :poll_limits,
-             :languages, :registrations, :approval_required, :invites_enabled,
-             :configuration
-
-  has_one :contact_account, serializer: REST::AccountSerializer
-
-  has_many :rules, serializer: REST::RuleSerializer
-
-  delegate :contact_account, :rules, to: :instance_presenter
-
-  def uri
-    Rails.configuration.x.local_domain
-  end
-
-  def title
-    Setting.site_title
-  end
+  class ContactSerializer < ActiveModel::Serializer
+    attributes :email
 
-  def short_description
-    Setting.site_short_description
+    has_one :account, serializer: REST::AccountSerializer
   end
 
-  def description
-    Setting.site_description
-  end
+  include RoutingHelper
 
-  def email
-    Setting.site_contact_email
-  end
+  attributes :domain, :title, :version, :source_url, :description,
+             :usage, :thumbnail, :languages, :configuration,
+             :registrations
 
-  def version
-    Mastodon::Version.to_s
-  end
+  has_one :contact, serializer: ContactSerializer
+  has_many :rules, serializer: REST::RuleSerializer
 
   def thumbnail
-    instance_presenter.thumbnail ? full_asset_url(instance_presenter.thumbnail.file.url) : full_pack_url('media/images/preview.png')
+    object.thumbnail ? full_asset_url(object.thumbnail.file.url) : full_pack_url('media/images/preview.png')
   end
 
-  def max_toot_chars
-    StatusLengthValidator::MAX_CHARS
-  end
-
-  def poll_limits
+  def usage
     {
-      max_options: PollValidator::MAX_OPTIONS,
-      max_option_chars: PollValidator::MAX_OPTION_CHARS,
-      min_expiration: PollValidator::MIN_EXPIRATION,
-      max_expiration: PollValidator::MAX_EXPIRATION,
-    }
-  end
-
-  def stats
-    {
-      user_count: instance_presenter.user_count,
-      status_count: instance_presenter.status_count,
-      domain_count: instance_presenter.domain_count,
+      users: {
+        active_month: object.active_user_count(4),
+      },
     }
   end
 
-  def urls
-    { streaming_api: Rails.configuration.x.streaming_api_base_url }
-  end
-
   def configuration
     {
+      urls: {
+        streaming: Rails.configuration.x.streaming_api_base_url,
+      },
+
       statuses: {
         max_characters: StatusLengthValidator::MAX_CHARS,
         max_media_attachments: 4,
@@ -93,25 +58,10 @@ class REST::InstanceSerializer < ActiveModel::Serializer
     }
   end
 
-  def languages
-    [I18n.default_locale]
-  end
-
   def registrations
-    Setting.registrations_mode != 'none' && !Rails.configuration.x.single_user_mode
-  end
-
-  def approval_required
-    Setting.registrations_mode == 'approved'
-  end
-
-  def invites_enabled
-    UserRole.everyone.can?(:invite_users)
-  end
-
-  private
-
-  def instance_presenter
-    @instance_presenter ||= InstancePresenter.new
+    {
+      enabled: Setting.registrations_mode != 'none' && !Rails.configuration.x.single_user_mode,
+      approval_required: Setting.registrations_mode == 'approved',
+    }
   end
 end
diff --git a/app/serializers/rest/v1/instance_serializer.rb b/app/serializers/rest/v1/instance_serializer.rb
new file mode 100644
index 000000000..fefbed8ee
--- /dev/null
+++ b/app/serializers/rest/v1/instance_serializer.rb
@@ -0,0 +1,115 @@
+# frozen_string_literal: true
+
+class REST::V1::InstanceSerializer < ActiveModel::Serializer
+  include RoutingHelper
+
+  attributes :uri, :title, :short_description, :description, :email,
+             :version, :urls, :stats, :thumbnail, :max_toot_chars, :poll_limits,
+             :languages, :registrations, :approval_required, :invites_enabled,
+             :configuration
+
+  has_one :contact_account, serializer: REST::AccountSerializer
+
+  has_many :rules, serializer: REST::RuleSerializer
+
+  def uri
+    object.domain
+  end
+
+  def short_description
+    object.description
+  end
+
+  def description
+    Setting.site_description # Legacy
+  end
+
+  def email
+    object.contact.email
+  end
+
+  def contact_account
+    object.contact.account
+  end
+
+  def thumbnail
+    instance_presenter.thumbnail ? full_asset_url(instance_presenter.thumbnail.file.url) : full_pack_url('media/images/preview.png')
+  end
+
+  def max_toot_chars
+    StatusLengthValidator::MAX_CHARS
+  end
+
+  def poll_limits
+    {
+      max_options: PollValidator::MAX_OPTIONS,
+      max_option_chars: PollValidator::MAX_OPTION_CHARS,
+      min_expiration: PollValidator::MIN_EXPIRATION,
+      max_expiration: PollValidator::MAX_EXPIRATION,
+    }
+  end
+
+  def stats
+    {
+      user_count: instance_presenter.user_count,
+      status_count: instance_presenter.status_count,
+      domain_count: instance_presenter.domain_count,
+    }
+  end
+
+  def urls
+    { streaming_api: Rails.configuration.x.streaming_api_base_url }
+  end
+
+  def usage
+    {
+      users: {
+        active_month: instance_presenter.active_user_count(4),
+      },
+    }
+  end
+
+  def configuration
+    {
+      statuses: {
+        max_characters: StatusLengthValidator::MAX_CHARS,
+        max_media_attachments: 4,
+        characters_reserved_per_url: StatusLengthValidator::URL_PLACEHOLDER_CHARS,
+      },
+
+      media_attachments: {
+        supported_mime_types: MediaAttachment::IMAGE_MIME_TYPES + MediaAttachment::VIDEO_MIME_TYPES + MediaAttachment::AUDIO_MIME_TYPES,
+        image_size_limit: MediaAttachment::IMAGE_LIMIT,
+        image_matrix_limit: Attachmentable::MAX_MATRIX_LIMIT,
+        video_size_limit: MediaAttachment::VIDEO_LIMIT,
+        video_frame_rate_limit: MediaAttachment::MAX_VIDEO_FRAME_RATE,
+        video_matrix_limit: MediaAttachment::MAX_VIDEO_MATRIX_LIMIT,
+      },
+
+      polls: {
+        max_options: PollValidator::MAX_OPTIONS,
+        max_characters_per_option: PollValidator::MAX_OPTION_CHARS,
+        min_expiration: PollValidator::MIN_EXPIRATION,
+        max_expiration: PollValidator::MAX_EXPIRATION,
+      },
+    }
+  end
+
+  def registrations
+    Setting.registrations_mode != 'none' && !Rails.configuration.x.single_user_mode
+  end
+
+  def approval_required
+    Setting.registrations_mode == 'approved'
+  end
+
+  def invites_enabled
+    UserRole.everyone.can?(:invite_users)
+  end
+
+  private
+
+  def instance_presenter
+    @instance_presenter ||= InstancePresenter.new
+  end
+end