refactor: address review comments for join view

lib/mv_web/live/join_live.ex

@@ -213,9 +213,7 @@ defmodule MvWeb.JoinLive do
       form_data =
         params
         |> Enum.filter(fn {key, _} -> key in allowlist_ids and key not in typed end)
-        |> Map.new()
-        |> Enum.map(fn {k, v} -> {k, String.trim(to_string(v))} end)
-        |> Map.new()
+        |> Map.new(fn {k, v} -> {k, String.trim(to_string(v))} end)
 
       attrs = %{attrs | form_data: form_data}
       {:ok, attrs}
@@ -227,13 +225,37 @@ defmodule MvWeb.JoinLive do
     if is_binary(v), do: String.trim(v), else: nil
   end
 
+  # Prefer X-Forwarded-For / X-Real-IP when behind a reverse proxy; fall back to peer_data.
+  # Uses :inet.ntoa/1 for correct IPv4 and IPv6 string representation.
   defp client_ip_from_socket(socket) do
-    case get_connect_info(socket, :peer_data) do
-      %{address: address} when is_tuple(address) ->
-        address |> Tuple.to_list() |> Enum.join(".")
-
-      _ ->
-        "unknown"
+    with nil <- client_ip_from_headers(socket),
+         %{address: address} when is_tuple(address) <- get_connect_info(socket, :peer_data) do
+      address |> :inet.ntoa() |> to_string()
+    else
+      ip when is_binary(ip) -> ip
+      _ -> "unknown"
     end
   end
+
+  defp client_ip_from_headers(socket) do
+    headers = get_connect_info(socket, :x_headers) || []
+    real_ip = header_value(headers, "x-real-ip")
+    forwarded = header_value(headers, "x-forwarded-for")
+
+    cond do
+      real_ip != nil -> real_ip
+      forwarded != nil -> String.split(forwarded, ~r/,\s*/) |> List.first() |> String.trim()
+      true -> nil
+    end
+  end
+
+  defp header_value(headers, name) do
+    name_lower = String.downcase(name)
+
+    headers
+    |> Enum.find_value(fn
+      {h, v} when is_binary(h) -> if String.downcase(h) == name_lower, do: String.trim(v)
+      _ -> nil
+    end)
+  end
 end