From a85f74ec3f959b81941eb9f1cc6de04e4ff0e049 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Thu, 23 Apr 2026 14:27:43 -0500
Subject: [PATCH] refactor: leadership_change handler pattern-matches instead
 of cond
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Cluster.ConnectionManager.handle_info({:leadership_change, ...}) used
a cond on the (became_leader, node, connection_started) triple. Split
into handle_leadership_change/3 with three clauses:

- became_leader=true, us=true, not already started → start APRS-IS
- became_leader=false, us=true, already started → stop APRS-IS
- everything else → no-op

Makes the three state transitions visible in the function heads and
eliminates one more cond from the codebase.
---
 lib/aprsme/cluster/connection_manager.ex | 33 +++++++++++++-----------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/lib/aprsme/cluster/connection_manager.ex b/lib/aprsme/cluster/connection_manager.ex
index 14ec32e..04103d5 100644
--- a/lib/aprsme/cluster/connection_manager.ex
+++ b/lib/aprsme/cluster/connection_manager.ex
@@ -40,25 +40,28 @@ defmodule Aprsme.Cluster.ConnectionManager do
 
   @impl true
   def handle_info({:leadership_change, node, became_leader}, state) do
-    cond do
-      became_leader and node == node() and not state.connection_started ->
-        Logger.info("This node became the leader, starting APRS-IS connection")
-        start_aprs_connection()
-        {:noreply, %{state | connection_started: true}}
-
-      not became_leader and node == node() and state.connection_started ->
-        Logger.info("This node lost leadership, stopping APRS-IS connection")
-        stop_aprs_connection()
-        {:noreply, %{state | connection_started: false}}
-
-      true ->
-        {:noreply, state}
-    end
+    handle_leadership_change(became_leader, node == node(), state)
   end
 
-  @impl true
   def handle_info(_msg, state), do: {:noreply, state}
 
+  # Became the cluster leader and we weren't already running — start APRS-IS.
+  defp handle_leadership_change(true, true, %{connection_started: false} = state) do
+    Logger.info("This node became the leader, starting APRS-IS connection")
+    start_aprs_connection()
+    {:noreply, %{state | connection_started: true}}
+  end
+
+  # Lost leadership while we were running — stop APRS-IS.
+  defp handle_leadership_change(false, true, %{connection_started: true} = state) do
+    Logger.info("This node lost leadership, stopping APRS-IS connection")
+    stop_aprs_connection()
+    {:noreply, %{state | connection_started: false}}
+  end
+
+  # Any other combination (different node, already in the right state) is a no-op.
+  defp handle_leadership_change(_became_leader, _us?, state), do: {:noreply, state}
+
   @impl true
   def terminate(_reason, _state) do
     Phoenix.PubSub.unsubscribe(Aprsme.PubSub, "cluster:leadership")