Add the time in a state to VintageNet.info

lib/vintage_net/info.ex

@@ -105,7 +105,25 @@ defmodule VintageNet.Info do
   defp sanitize_configuration(data), do: data
 
   defp print_if_attribute(ifname, name, print_name) do
-    value = VintageNet.get(["interface", ifname, name])
-    IO.puts("  #{print_name}: #{inspect(value)}")
+    now = :erlang.monotonic_time()
+
+    case VintageNet.PropertyTable.fetch_with_timestamp(VintageNet, ["interface", ifname, name]) do
+      {:ok, value, timestamp} ->
+        IO.puts("  #{print_name}: #{inspect(value)} (#{friendly_time(now - timestamp)})")
+
+      :error ->
+        IO.puts("  #{print_name}: Error retrieving value")
+    end
+  end
+
+  defp friendly_time(delta_ns) do
+    cond do
+      delta_ns < 1000 -> "#{delta_ns} ns"
+      delta_ns < 1_000_000 -> "#{delta_ns / 1000} μs"
+      delta_ns < 1_000_000_000 -> "#{delta_ns / 1_000_000} ms"
+      delta_ns < 60_000_000_000 -> "#{delta_ns / 1_000_000_000} s"
+      delta_ns < 3600_000_000_000 -> "#{delta_ns / 60_000_000_000} m"
+      true -> "#{delta_ns / 3600_000_000_000} h"
+    end
   end
 end