Fix credo: extract PagerDuty HMAC verification to reduce nesting

lib/towerops_web/controllers/api/v1/pagerduty_webhook_controller.ex

@@ -52,36 +52,39 @@ defmodule ToweropsWeb.Api.V1.PagerdutyWebhookController do
     webhook_secret = get_in(integration.credentials, ["webhook_secret"])
 
     if is_nil(webhook_secret) or webhook_secret == "" do
-      # No webhook secret configured — accept without verification
-      # (user hasn't set up the V3 webhook extension yet)
       :ok
     else
-      signatures =
-        conn
-        |> Plug.Conn.get_req_header("x-pagerduty-signature")
-        |> Enum.flat_map(&String.split(&1, ","))
-        |> Enum.map(&String.trim/1)
-
-      expected =
-        :hmac
-        |> :crypto.mac(:sha256, webhook_secret, raw_body)
-        |> Base.encode16(case: :lower)
-
-      if Enum.any?(signatures, fn sig ->
-           case sig do
-             "v1=" <> hex -> Plug.Crypto.secure_compare(hex, expected)
-             _ -> false
-           end
-         end) do
-        :ok
-      else
-        Logger.warning("PagerDuty webhook signature mismatch for org #{integration.organization_id}")
-
-        {:error, :invalid_signature}
-      end
+      check_pagerduty_hmac(conn, raw_body, webhook_secret, integration.organization_id)
     end
   end
 
+  defp check_pagerduty_hmac(conn, raw_body, secret, org_id) do
+    signatures =
+      conn
+      |> Plug.Conn.get_req_header("x-pagerduty-signature")
+      |> Enum.flat_map(&String.split(&1, ","))
+      |> Enum.map(&String.trim/1)
+
+    expected =
+      :hmac
+      |> :crypto.mac(:sha256, secret, raw_body)
+      |> Base.encode16(case: :lower)
+
+    if signature_matches?(signatures, expected) do
+      :ok
+    else
+      Logger.warning("PagerDuty webhook signature mismatch for org #{org_id}")
+      {:error, :invalid_signature}
+    end
+  end
+
+  defp signature_matches?(signatures, expected) do
+    Enum.any?(signatures, fn
+      "v1=" <> hex -> Plug.Crypto.secure_compare(hex, expected)
+      _ -> false
+    end)
+  end
+
   defp process_webhook(%{"event" => %{"event_type" => event_type, "data" => data}}, organization_id) do
     case event_type do
       "incident.resolved" ->