MRF: simple policy: refactor module to use guards and pattern matching

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

@@ -5,59 +5,51 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
   @mrf_policy Application.get_env(:pleroma, :mrf_simple)
 
   @accept Keyword.get(@mrf_policy, :accept)
-  defp check_accept(actor_info, object) do
+  defp check_accept(%{host: actor_host} = actor_info, object)
-    if length(@accept) > 0 and not (actor_info.host in @accept) do
+       when length(@accept) > 0 and not (actor_host in @accept) do
     {:reject, nil}
-    else
-      {:ok, object}
-    end
   end
 
+  defp check_accept(actor_info, object), do: {:ok, object}
+
   @reject Keyword.get(@mrf_policy, :reject)
-  defp check_reject(actor_info, object) do
+  defp check_reject(%{host: actor_host} = actor_info, object) when actor_host in @reject do
-    if actor_info.host in @reject do
     {:reject, nil}
-    else
-      {:ok, object}
-    end
   end
 
+  defp check_reject(actor_info, object), do: {:ok, object}
+
   @media_removal Keyword.get(@mrf_policy, :media_removal)
-  defp check_media_removal(actor_info, %{"type" => activity_type} = object)
+  defp check_media_removal(%{host: actor_host} = actor_info, %{"type" => "Create"} = object)
-       when activity_type == "Create" do
+       when actor_host in @media_removal do
-    if actor_info.host in @media_removal do
     child_object = Map.delete(object["object"], "attachment")
     object = Map.put(object, "object", child_object)
     {:ok, object}
-    else
-      {:ok, object}
-    end
   end
 
   defp check_media_removal(actor_info, object), do: {:ok, object}
 
   @media_nsfw Keyword.get(@mrf_policy, :media_nsfw)
-  defp check_media_nsfw(actor_info, %{"type" => activity_type} = object)
+  defp check_media_nsfw(
-       when activity_type == "Create" do
+         %{host: actor_host} = actor_info,
-    child_object = object["object"]
+         %{
-
+           "type" => "Create",
-    if actor_info.host in @media_nsfw and child_object["attachment"] != nil and
+           "object" => %{"attachment" => child_attachment} = child_object
-         length(child_object["attachment"]) > 0 do
+         } = object
+       )
+       when actor_host in @media_nsfw and length(child_attachment) > 0 do
     tags = (child_object["tag"] || []) ++ ["nsfw"]
     child_object = Map.put(child_object, "tags", tags)
     child_object = Map.put(child_object, "sensitive", true)
     object = Map.put(object, "object", child_object)
     {:ok, object}
-    else
-      {:ok, object}
-    end
   end
 
   defp check_media_nsfw(actor_info, object), do: {:ok, object}
 
   @ftl_removal Keyword.get(@mrf_policy, :federated_timeline_removal)
-  defp check_ftl_removal(actor_info, object) do
+  defp check_ftl_removal(%{host: actor_host} = actor_info, object)
-    if actor_info.host in @ftl_removal do
+       when actor_host in @ftl_removal do
     user = User.get_by_ap_id(object["actor"])
 
     # flip to/cc relationship to make the post unlisted
@@ -79,11 +71,10 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
         object
       end
 
-      {:ok, object}
-    else
     {:ok, object}
   end
-  end
+
+  defp check_ftl_removal(actor_info, object), do: {:ok, object}
 
   @impl true
   def filter(object) do