Undoing: Move undoing likes to the pipeline everywhere.

lib/pleroma/web/activity_pub/side_effects.ex

@@ -5,8 +5,10 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
   liked object, a `Follow` activity will add the user to the follower
   collection, and so on.
   """
+  alias Pleroma.Activity
   alias Pleroma.Notification
   alias Pleroma.Object
+  alias Pleroma.Repo
   alias Pleroma.Web.ActivityPub.Utils
 
   def handle(object, meta \\ [])
@@ -23,8 +25,25 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
     {:ok, object, meta}
   end
 
+  def handle(%{data: %{"type" => "Undo", "object" => undone_object}} = object, meta) do
+    with undone_object <- Activity.get_by_ap_id(undone_object),
+         :ok <- handle_undoing(undone_object) do
+      {:ok, object, meta}
+    end
+  end
+
   # Nothing to do
   def handle(object, meta) do
     {:ok, object, meta}
   end
+
+  def handle_undoing(%{data: %{"type" => "Like"}} = object) do
+    with %Object{} = liked_object <- Object.get_by_ap_id(object.data["object"]),
+         {:ok, _} <- Utils.remove_like_from_object(object, liked_object),
+         {:ok, _} <- Repo.delete(object) do
+      :ok
+    end
+  end
+
+  def handle_undoing(object), do: {:error, ["don't know how to handle", object]}
 end