Refactor Mobilizon.Federation.ActivityPub.Types.Events tags handling

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/federation/activity_pub/types/events.ex

@@ -268,14 +268,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
           description: description,
           mentions: mentions,
           # Exclude tags with length > 40
-          tags:
+          tags: Enum.filter(tags, &exclude_too_long_tags/1)
-            Enum.filter(tags, fn tag ->
-              case tag do
-                # For some reason transmogrifier gives us this
-                %{title: tag} -> String.length(tag) < 40
-                tag -> String.length(tag) < 40
-              end
-            end)
         })
       else
         args
@@ -287,13 +280,7 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
         args,
         :tags,
         [],
-        &Enum.uniq_by(&1, fn tag ->
+        &Enum.uniq_by(&1, fn tag -> tag |> tag_to_string() |> String.downcase() end)
-          case tag do
-            # For some reason transmogrifier gives us this
-            %{title: tag} -> String.downcase(tag)
-            tag -> String.downcase(tag)
-          end
-        end)
       )
 
     # Check that we can only allow anonymous participation if our instance allows it
@@ -315,4 +302,16 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Events do
     |> Map.update(:tags, [], &ConverterUtils.fetch_tags/1)
     |> Map.update(:contacts, [], &ConverterUtils.fetch_actors/1)
   end
+
+  @spec exclude_too_long_tags(%{title: String.t()} | String.t()) :: boolean()
+  defp exclude_too_long_tags(tag) do
+    tag
+    |> tag_to_string()
+    |> String.length()
+    |> Kernel.<(40)
+  end
+
+  @spec tag_to_string(%{title: String.t()} | String.t()) :: String.t()
+  defp tag_to_string(%{title: tag}), do: tag
+  defp tag_to_string(tag), do: tag
 end