Add ActivityExpirationPolicy

lib/pleroma/web/activity_pub/mrf.ex

@@ -8,11 +8,8 @@ defmodule Pleroma.Web.ActivityPub.MRF do
   def filter(policies, %{} = object) do
     policies
     |> Enum.reduce({:ok, object}, fn
-      policy, {:ok, object} ->
-        policy.filter(object)
-
-      _, error ->
-        error
+      policy, {:ok, object} -> policy.filter(object)
+      _, error -> error
     end)
   end
 

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

@@ -0,0 +1,35 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.ActivityExpirationPolicy do
+  @moduledoc "Adds expiration to all local activities"
+  @behaviour Pleroma.Web.ActivityPub.MRF
+
+  @impl true
+  def filter(%{"id" => id} = activity) do
+    activity =
+      if String.starts_with?(id, Pleroma.Web.Endpoint.url()) do
+        maybe_add_expiration(activity)
+      else
+        activity
+      end
+
+    {:ok, activity}
+  end
+
+  @impl true
+  def describe, do: {:ok, %{}}
+
+  defp maybe_add_expiration(activity) do
+    days = Pleroma.Config.get([:mrf_activity_expiration, :days], 365)
+    expires_at = NaiveDateTime.utc_now() |> Timex.shift(days: days)
+
+    with %{"expires_at" => existing_expires_at} <- activity,
+         :lt <- NaiveDateTime.compare(existing_expires_at, expires_at) do
+      activity
+    else
+      _ -> Map.put(activity, "expires_at", expires_at)
+    end
+  end
+end