Update

lib/nulla_web/controllers/generic/webfinger_controller.ex

@@ -0,0 +1,32 @@
+defmodule NullaWeb.Generic.WebfingerController do
+  use NullaWeb, :controller
+  alias Nulla.Actors
+  alias Nulla.Actors.Actor
+  alias NullaWeb.Generic.WebfingerJSON
+
+  def index(conn, %{"resource" => resource}) do
+    case Regex.run(~r/^acct:(.+)$/, resource) do
+      [_, acct] ->
+        case Actors.get_actor_by(acct: acct) do
+          nil ->
+            conn
+            |> put_resp_content_type("text/plain")
+            |> send_resp(404, "")
+
+          %Actor{} = actor ->
+            json(conn, WebfingerJSON.show(actor))
+        end
+
+      _ ->
+        conn
+        |> put_resp_content_type("text/plain")
+        |> send_resp(400, "")
+    end
+  end
+
+  def index(conn, _params) do
+    conn
+    |> put_resp_content_type("text/plain")
+    |> send_resp(400, "")
+  end
+end