Merge branch 'feature/hellthread-filter-improvements' into 'develop'

Improve hellthread filter

Closes #584

See merge request pleroma/pleroma!766

lib/pleroma/config/deprecation_warnings.ex

@@ -12,6 +12,13 @@ defmodule Pleroma.Config.DeprecationWarnings do
       You are using the old configuration mechanism for the frontend. Please check config.md.
       """)
     end
+
+    if Pleroma.Config.get(:mrf_hellthread, :threshold) do
+      Logger.warn("""
+      !!!DEPRECATION WARNING!!!
+      You are using the old configuration mechanism for the hellthread filter. Please check config.md.
+      """)
+    end
   end
 
   def warn do

lib/pleroma/web/activity_pub/mrf/hellthread_policy.ex

@@ -3,20 +3,46 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.ActivityPub.MRF.HellthreadPolicy do
+  alias Pleroma.User
   @behaviour Pleroma.Web.ActivityPub.MRF
 
-  @impl true
-  def filter(%{"type" => "Create"} = object) do
-    threshold = Pleroma.Config.get([:mrf_hellthread, :threshold])
-    recipients = (object["to"] || []) ++ (object["cc"] || [])
+  defp delist_message(message) do
+    follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
 
-    if length(recipients) > threshold do
-      {:reject, nil}
-    else
-      {:ok, object}
+    message
+    |> Map.put("to", [follower_collection])
+    |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
+  end
+
+  @impl true
+  def filter(%{"type" => "Create"} = message) do
+    delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
+
+    reject_threshold =
+      Pleroma.Config.get(
+        [:mrf_hellthread, :reject_threshold],
+        Pleroma.Config.get([:mrf_hellthread, :threshold])
+      )
+
+    recipients = (message["to"] || []) ++ (message["cc"] || [])
+
+    cond do
+      length(recipients) > reject_threshold and reject_threshold > 0 ->
+        {:reject, nil}
+
+      length(recipients) > delist_threshold and delist_threshold > 0 ->
+        if Enum.member?(message["to"], "https://www.w3.org/ns/activitystreams#Public") or
+             Enum.member?(message["cc"], "https://www.w3.org/ns/activitystreams#Public") do
+          {:ok, delist_message(message)}
+        else
+          {:ok, message}
+        end
+
+      true ->
+        {:ok, message}
     end
   end
 
   @impl true
-  def filter(object), do: {:ok, object}
+  def filter(message), do: {:ok, message}
 end