Add federation relay support (#7998)

* Add federation relay support

* Add admin UI for managing relays

* Include actor on relay-related activities

* Fix i18n

1 files changed, 74 insertions, 0 deletions

diff --git a/app/models/relay.rb b/app/models/relay.rb
new file mode 100644
index 000000000..76143bb27
--- /dev/null
+++ b/app/models/relay.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: relays
+#
+#  id                 :bigint(8)        not null, primary key
+#  inbox_url          :string           default(""), not null
+#  enabled            :boolean          default(FALSE), not null
+#  follow_activity_id :string
+#  created_at         :datetime         not null
+#  updated_at         :datetime         not null
+#
+
+class Relay < ApplicationRecord
+  PRESET_RELAY = 'https://relay.joinmastodon.org/inbox'
+
+  validates :inbox_url, presence: true, uniqueness: true, url: true, if: :will_save_change_to_inbox_url?
+
+  scope :enabled, -> { where(enabled: true) }
+
+  before_destroy :ensure_disabled
+
+  def enable!
+    activity_id = ActivityPub::TagManager.instance.generate_uri_for(nil)
+    payload     = Oj.dump(follow_activity(activity_id))
+
+    ActivityPub::DeliveryWorker.perform_async(payload, some_local_account.id, inbox_url)
+    update(enabled: true, follow_activity_id: activity_id)
+  end
+
+  def disable!
+    activity_id = ActivityPub::TagManager.instance.generate_uri_for(nil)
+    payload     = Oj.dump(unfollow_activity(activity_id))
+
+    ActivityPub::DeliveryWorker.perform_async(payload, some_local_account.id, inbox_url)
+    update(enabled: false, follow_activity_id: nil)
+  end
+
+  private
+
+  def follow_activity(activity_id)
+    {
+      '@context': ActivityPub::TagManager::CONTEXT,
+      id: activity_id,
+      type: 'Follow',
+      actor: ActivityPub::TagManager.instance.uri_for(some_local_account),
+      object: ActivityPub::TagManager::COLLECTIONS[:public],
+    }
+  end
+
+  def unfollow_activity(activity_id)
+    {
+      '@context': ActivityPub::TagManager::CONTEXT,
+      id: activity_id,
+      type: 'Undo',
+      actor: ActivityPub::TagManager.instance.uri_for(some_local_account),
+      object: {
+        id: follow_activity_id,
+        type: 'Follow',
+        actor: ActivityPub::TagManager.instance.uri_for(some_local_account),
+        object: ActivityPub::TagManager::COLLECTIONS[:public],
+      },
+    }
+  end
+
+  def some_local_account
+    @some_local_account ||= Account.local.find_by(suspended: false)
+  end
+
+  def ensure_disabled
+    return unless enabled?
+    disable!
+  end
+end