Refactor Follows/Followers counter syncronization

- Actually sync counters in the database instead of info cache (which got
overriden after user update was finished anyway)
- Add following count field to user info
- Set hide_followers/hide_follows for remote users based on http status
codes for the first collection page

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -1013,6 +1013,56 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     {:ok, user_data}
   end
 
+  defp maybe_update_follow_information(data) do
+    with {:enabled, true} <-
+           {:enabled, Pleroma.Config.get([:instance, :external_user_synchronization])},
+         {:ok, following_data} <-
+           Fetcher.fetch_and_contain_remote_object_from_id(data.following_address),
+         following_count <- following_data["totalItems"],
+         hide_follows <- collection_private?(following_data),
+         {:ok, followers_data} <-
+           Fetcher.fetch_and_contain_remote_object_from_id(data.follower_address),
+         followers_count <- followers_data["totalItems"],
+         hide_followers <- collection_private?(followers_data) do
+      info = %{
+        "hide_follows" => hide_follows,
+        "follower_count" => followers_count,
+        "following_count" => following_count,
+        "hide_followers" => hide_followers
+      }
+
+      info = Map.merge(data.info, info)
+      Map.put(data, :info, info)
+    else
+      {:enabled, false} ->
+        data
+
+      e ->
+        Logger.error(
+          "Follower/Following counter update for #{data.ap_id} failed.\n" <> inspect(e)
+        )
+
+        data
+    end
+  end
+
+  defp collection_private?(data) do
+    if is_map(data["first"]) and
+         data["first"]["type"] in ["CollectionPage", "OrderedCollectionPage"] do
+      false
+    else
+      with {:ok, _data} <- Fetcher.fetch_and_contain_remote_object_from_id(data["first"]) do
+        false
+      else
+        {:error, {:ok, %{status: code}}} when code in [401, 403] ->
+          true
+
+        _e ->
+          false
+      end
+    end
+  end
+
   def user_data_from_user_object(data) do
     with {:ok, data} <- MRF.filter(data),
          {:ok, data} <- object_to_user_data(data) do
@@ -1024,7 +1074,8 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
 
   def fetch_and_prepare_user_from_ap_id(ap_id) do
     with {:ok, data} <- Fetcher.fetch_and_contain_remote_object_from_id(ap_id),
-         {:ok, data} <- user_data_from_user_object(data) do
+         {:ok, data} <- user_data_from_user_object(data),
+         data <- maybe_update_follow_information(data) do
       {:ok, data}
     else
       e -> Logger.error("Could not decode user at fetch #{ap_id}, #{inspect(e)}")