Reduce nesting depth in regex_cache, connection_monitor, and device_identification

Extract nested logic into helper functions to improve readability:
- regex_cache.ex: Extract compile_and_cache/1 for regex compilation and caching
- connection_monitor.ex: Extract calculate_scheduler_utilization/1 for CPU stat calculation
- device_identification.ex: Extract fetch_devices_from_url/0 for HTTP request handling

Co-Authored-By: Graham <noreply@anthropic.com>

lib/aprsme/connection_monitor.ex

@@ -204,9 +204,7 @@ defmodule Aprsme.ConnectionMonitor do
         # Fallback to scheduler wall time
         :scheduler_wall_time_all
         |> :erlang.statistics()
-        |> Enum.map(fn {_, active, total} ->
-          if total > 0, do: active / total, else: 0.0
-        end)
+        |> Enum.map(&calculate_scheduler_utilization/1)
         |> Enum.sum()
         |> Kernel./(System.schedulers_online())
     end
@@ -214,6 +212,10 @@ defmodule Aprsme.ConnectionMonitor do
     _ -> 0.0
   end
 
+  defp calculate_scheduler_utilization({_, active, total}) do
+    if total > 0, do: active / total, else: 0.0
+  end
+
   defp get_memory_usage do
     # Get memory usage as a percentage
     mem_data = :erlang.memory()

lib/aprsme/device_identification.ex

@@ -136,27 +136,25 @@ defmodule Aprsme.DeviceIdentification do
   end
 
   def fetch_and_upsert_devices do
-    case CircuitBreaker.call(
-           :aprs_foundation_api,
-           fn ->
-             case Req.get(@url) do
-               {:ok, %Req.Response{status: 200, body: body}} ->
-                 upsert_devices(body)
-
-               {:ok, %Req.Response{status: status}} ->
-                 {:error, {:http_error, status}}
-
-               {:error, reason} ->
-                 {:error, reason}
-             end
-           end,
-           15_000
-         ) do
+    case CircuitBreaker.call(:aprs_foundation_api, &fetch_devices_from_url/0, 15_000) do
       {:ok, result} -> result
       {:error, reason} -> {:error, reason}
     end
   end
 
+  defp fetch_devices_from_url do
+    case Req.get(@url) do
+      {:ok, %Req.Response{status: 200, body: body}} ->
+        upsert_devices(body)
+
+      {:ok, %Req.Response{status: status}} ->
+        {:error, {:http_error, status}}
+
+      {:error, reason} ->
+        {:error, reason}
+    end
+  end
+
   def upsert_devices(json) do
     tocalls = Map.get(json, "tocalls", %{})
     mice = Map.get(json, "mice", %{})

lib/aprsme/regex_cache.ex

@@ -31,19 +31,23 @@ defmodule Aprsme.RegexCache do
         {:ok, regex}
 
       [] ->
-        case Regex.compile(pattern_string) do
-          {:ok, regex} ->
-            # Check cache size and clear if needed
-            if :ets.info(@table_name, :size) >= @max_cache_size do
-              clear_oldest_entries()
-            end
+        compile_and_cache(pattern_string)
+    end
+  end
 
-            :ets.insert(@table_name, {pattern_string, regex})
-            {:ok, regex}
-
-          error ->
-            error
+  defp compile_and_cache(pattern_string) do
+    case Regex.compile(pattern_string) do
+      {:ok, regex} ->
+        # Check cache size and clear if needed
+        if :ets.info(@table_name, :size) >= @max_cache_size do
+          clear_oldest_entries()
         end
+
+        :ets.insert(@table_name, {pattern_string, regex})
+        {:ok, regex}
+
+      error ->
+        error
     end
   end