Small enhancement in code clarity

lib/lambda_ethereum_consensus/p2p/peerbook.ex

@@ -111,24 +111,26 @@ defmodule LambdaEthereumConsensus.P2P.Peerbook do
   defp prune() do
     peerbook = fetch_peerbook!()
     len = map_size(peerbook)
+    prune_size = if len > 0, do: calculate_prune_size(peerbook, len), else: 0
 
-    if len != 0 do
-      prune_size =
-        (len * @prune_percentage)
-        |> round()
-        |> min(@max_prune_size)
-        |> min(len - @target_peers)
-        |> max(0)
-
-      if prune_size > 0 do
-        peerbook
-        |> Enum.sort_by(fn {_peer_id, score} -> -score end)
-        |> Enum.take(prune_size)
-        |> Enum.each(fn peer_id -> Task.start(__MODULE__, :challenge_peer, [peer_id]) end)
-      end
+    if prune_size > 0 do
+      Logger.debug("[Peerbook] Pruning #{prune_size} peers by challenge")
+
+      peerbook
+      |> Enum.sort_by(fn {_peer_id, score} -> -score end)
+      |> Enum.take(prune_size)
+      |> Enum.each(fn peer_id -> Task.start(__MODULE__, :challenge_peer, [peer_id]) end)
     end
   end
 
+  defp calculate_prune_size(peerbook, len) do
+    (len * @prune_percentage)
+    |> round()
+    |> min(@max_prune_size)
+    |> min(len - @target_peers)
+    |> max(0)
+  end
+
   defp store_peerbook(peerbook), do: put("", peerbook)
 
   defp fetch_peerbook(), do: get("")