refactor: collapse nested if/case into pattern-matched helpers

- SharedPacketHandler.handle_packet_update: dispatch on filter-result,
  and use maybe_enrich/2 dispatched on the enrich? boolean instead of
  an inner `if`. lookup_device_info/1 is now a trio of function heads.
- Cluster.Topology.child_spec: build_spec/3 dispatches on
  (cluster_enabled?, topologies) tuples — no more nested `if`.
- Cluster.PacketDistributor.distribute_packet: maybe_broadcast/2
  dispatches on the leader-and-enabled check; the non-leader / disabled
  paths return :ok explicitly instead of relying on an `if` expression's
  implicit nil.

Adds tests for SharedPacketHandler (filter/enrich/match paths,
callsign_filter + callsign_and_weather_filter factories) and extends
Cluster.Topology tests to cover the nil-topology and opts-merge cases.
Coverage 66.41 → 66.81%.

lib/aprsme/cluster/packet_distributor.ex

@@ -16,16 +16,17 @@ defmodule Aprsme.Cluster.PacketDistributor do
 
   def distribute_packet(packet) do
     cluster_enabled = Application.get_env(:aprsme, :cluster_enabled, false)
-
-    if cluster_enabled and LeaderElection.leader_cached?() do
-      Phoenix.PubSub.broadcast(
-        Aprsme.PubSub,
-        @pubsub_topic,
-        {:distributed_packet, packet}
-      )
-    end
+    maybe_broadcast(cluster_enabled and LeaderElection.leader_cached?(), packet)
   end
 
+  # Only the leader broadcasts; non-leader clustered nodes and non-clustered
+  # nodes silently drop the packet.
+  defp maybe_broadcast(true, packet) do
+    Phoenix.PubSub.broadcast(Aprsme.PubSub, @pubsub_topic, {:distributed_packet, packet})
+  end
+
+  defp maybe_broadcast(false, _packet), do: :ok
+
   def subscribe do
     Phoenix.PubSub.subscribe(Aprsme.PubSub, @pubsub_topic)
   end

lib/aprsme/cluster/topology.ex

@@ -5,33 +5,33 @@ defmodule Aprsme.Cluster.Topology do
   require Logger
 
   def child_spec(opts) do
-    if Application.get_env(:aprsme, :cluster_enabled, false) do
-      topologies = Application.get_env(:libcluster, :topologies, [])
+    cluster_enabled = Application.get_env(:aprsme, :cluster_enabled, false)
+    topologies = Application.get_env(:libcluster, :topologies, [])
+    build_spec(cluster_enabled, topologies, opts)
+  end
 
-      # Log the configuration for debugging
-      Logger.info("Cluster.Topology starting with topologies: #{inspect(topologies)}")
+  # Clustering disabled — no-op spec.
+  defp build_spec(false, _topologies, opts), do: noop_spec(opts)
 
-      # Ensure we have valid topologies
-      if topologies == [] or topologies == nil do
-        Logger.warning("No libcluster topologies configured, clustering will not work")
-        # Return a no-op spec
-        %{
-          id: __MODULE__,
-          start: {__MODULE__, :start_link, [opts]},
-          type: :worker
-        }
-      else
-        supervisor_opts = Keyword.merge([name: Aprsme.ClusterSupervisor], opts)
-        {Cluster.Supervisor, [topologies, supervisor_opts]}
-      end
-    else
-      # Return a no-op spec when clustering is disabled
-      %{
-        id: __MODULE__,
-        start: {__MODULE__, :start_link, [opts]},
-        type: :worker
-      }
-    end
+  # Clustering enabled but no topologies configured — no-op + warning.
+  defp build_spec(true, topologies, opts) when topologies in [nil, []] do
+    Logger.warning("No libcluster topologies configured, clustering will not work")
+    noop_spec(opts)
+  end
+
+  # Clustering enabled with topologies — delegate to libcluster's supervisor.
+  defp build_spec(true, topologies, opts) do
+    Logger.info("Cluster.Topology starting with topologies: #{inspect(topologies)}")
+    supervisor_opts = Keyword.merge([name: Aprsme.ClusterSupervisor], opts)
+    {Cluster.Supervisor, [topologies, supervisor_opts]}
+  end
+
+  defp noop_spec(opts) do
+    %{
+      id: __MODULE__,
+      start: {__MODULE__, :start_link, [opts]},
+      type: :worker
+    }
   end
 
   def start_link(_opts), do: :ignore

lib/aprsme_web/live/shared/packet_handler.ex

@@ -21,22 +21,18 @@ defmodule AprsmeWeb.Live.SharedPacketHandler do
     process_fn = Keyword.fetch!(opts, :process_fn)
     enrich_packet? = Keyword.get(opts, :enrich_packet, true)
 
-    if filter_fn.(packet, socket) do
-      enriched_packet =
-        if enrich_packet? do
-          packet
-          |> sanitize_packet()
-          |> enrich_with_device_info()
-        else
-          packet
-        end
-
-      process_fn.(enriched_packet, socket)
-    else
-      {:noreply, socket}
-    end
+    dispatch_packet_update(filter_fn.(packet, socket), packet, socket, process_fn, enrich_packet?)
   end
 
+  defp dispatch_packet_update(false, _packet, socket, _process_fn, _enrich?), do: {:noreply, socket}
+
+  defp dispatch_packet_update(true, packet, socket, process_fn, enrich?) do
+    packet |> maybe_enrich(enrich?) |> process_fn.(socket)
+  end
+
+  defp maybe_enrich(packet, true), do: packet |> sanitize_packet() |> enrich_with_device_info()
+  defp maybe_enrich(packet, false), do: packet
+
   @doc """
   Checks if packet sender matches the given callsign.
   """
@@ -109,13 +105,9 @@ defmodule AprsmeWeb.Live.SharedPacketHandler do
     Map.get(packet, :device_identifier) || Map.get(packet, "device_identifier")
   end
 
-  defp lookup_device_info(device_identifier) do
-    case device_identifier do
-      nil -> nil
-      "" -> nil
-      identifier -> DeviceCache.lookup_device(identifier)
-    end
-  end
+  defp lookup_device_info(nil), do: nil
+  defp lookup_device_info(""), do: nil
+  defp lookup_device_info(identifier), do: DeviceCache.lookup_device(identifier)
 
   defp nil_or_empty?(nil), do: true
   defp nil_or_empty?(""), do: true

test/aprsme/cluster/topology_test.exs

@@ -47,5 +47,25 @@ defmodule Aprsme.Cluster.TopologyTest do
       assert topologies == [gossip: [strategy: Gossip]]
       assert Keyword.get(supervisor_opts, :name) == Aprsme.ClusterSupervisor
     end
+
+    test "returns no-op spec when topologies is nil" do
+      Application.put_env(:aprsme, :cluster_enabled, true)
+      Application.put_env(:libcluster, :topologies, nil)
+
+      spec = Topology.child_spec([])
+
+      assert %{id: Topology, start: {Topology, :start_link, [[]]}, type: :worker} = spec
+    end
+
+    test "merges caller opts onto the default supervisor name" do
+      Application.put_env(:aprsme, :cluster_enabled, true)
+      Application.put_env(:libcluster, :topologies, gossip: [strategy: Gossip])
+
+      spec = Topology.child_spec(shutdown: :brutal_kill)
+
+      assert {Cluster.Supervisor, [_, supervisor_opts]} = spec
+      assert supervisor_opts[:shutdown] == :brutal_kill
+      assert supervisor_opts[:name] == Aprsme.ClusterSupervisor
+    end
   end
 end

test/aprsme_web/live/shared/packet_handler_test.exs

@@ -0,0 +1,148 @@
+defmodule AprsmeWeb.Live.SharedPacketHandlerTest do
+  use ExUnit.Case, async: true
+
+  alias AprsmeWeb.Live.SharedPacketHandler
+
+  defp socket, do: %Phoenix.LiveView.Socket{assigns: %{__changed__: %{}}}
+
+  defp allow_all, do: fn _packet, _socket -> true end
+  defp allow_none, do: fn _packet, _socket -> false end
+
+  defp record_process(ref),
+    do: fn packet, s ->
+      send(ref, {:processed, packet})
+      {:noreply, s}
+    end
+
+  describe "handle_packet_update/3" do
+    test "skips processing when filter returns false" do
+      socket = socket()
+      {result, ^socket} = {nil, socket}
+      _ = result
+
+      assert {:noreply, ^socket} =
+               SharedPacketHandler.handle_packet_update(
+                 %{sender: "K5ABC"},
+                 socket,
+                 filter_fn: allow_none(),
+                 process_fn: record_process(self())
+               )
+
+      refute_received {:processed, _}
+    end
+
+    test "processes and enriches packet when filter returns true" do
+      {:noreply, _} =
+        SharedPacketHandler.handle_packet_update(
+          %{sender: "K5ABC"},
+          socket(),
+          filter_fn: allow_all(),
+          process_fn: record_process(self())
+        )
+
+      assert_received {:processed, packet}
+      # Enrichment added nil device_* keys even for unknown identifier.
+      assert Map.has_key?(packet, :device_model)
+    end
+
+    test "skips enrichment when enrich_packet: false" do
+      {:noreply, _} =
+        SharedPacketHandler.handle_packet_update(
+          %{sender: "K5ABC"},
+          socket(),
+          filter_fn: allow_all(),
+          process_fn: record_process(self()),
+          enrich_packet: false
+        )
+
+      assert_received {:processed, packet}
+      refute Map.has_key?(packet, :device_model)
+    end
+  end
+
+  describe "packet_matches_callsign?/2" do
+    test "matches on atom :sender key" do
+      assert SharedPacketHandler.packet_matches_callsign?(%{sender: "K5ABC"}, "K5ABC")
+    end
+
+    test "matches on string 'sender' key" do
+      assert SharedPacketHandler.packet_matches_callsign?(%{"sender" => "K5ABC"}, "K5ABC")
+    end
+
+    test "string key wins over atom key when both present" do
+      # The implementation prefers the string key via Map.get fallback ordering.
+      assert SharedPacketHandler.packet_matches_callsign?(
+               %{"sender" => "K5ABC", sender: "OTHER"},
+               "K5ABC"
+             )
+    end
+
+    test "comparison is case-insensitive via Callsign.matches?" do
+      assert SharedPacketHandler.packet_matches_callsign?(%{sender: "k5abc"}, "K5ABC")
+    end
+
+    test "returns false when mismatched" do
+      refute SharedPacketHandler.packet_matches_callsign?(%{sender: "K5ABC"}, "W1XYZ")
+    end
+  end
+
+  describe "has_weather_data?/1" do
+    test "returns true when at least one weather field is present" do
+      assert SharedPacketHandler.has_weather_data?(%{temperature: 72.0})
+      assert SharedPacketHandler.has_weather_data?(%{"humidity" => 50})
+    end
+
+    test "returns false when no weather fields are present" do
+      refute SharedPacketHandler.has_weather_data?(%{sender: "K5ABC"})
+      refute SharedPacketHandler.has_weather_data?(%{})
+    end
+  end
+
+  describe "enrich_with_device_info/1" do
+    test "adds nil device_* keys when no device identifier" do
+      result = SharedPacketHandler.enrich_with_device_info(%{sender: "K5ABC"})
+      assert result.device_model == nil
+      assert result.device_vendor == nil
+      assert result.device_contact == nil
+      assert result.device_class == nil
+    end
+
+    test "still adds nil device_* when device_identifier is empty string" do
+      result = SharedPacketHandler.enrich_with_device_info(%{device_identifier: ""})
+      assert result.device_model == nil
+    end
+  end
+
+  describe "enrich_packets_with_device_info/1" do
+    test "enriches each packet in the list" do
+      packets = [
+        %{sender: "A", device_identifier: nil},
+        %{sender: "B", device_identifier: ""},
+        %{sender: "C", device_identifier: "APXYZ"}
+      ]
+
+      enriched = SharedPacketHandler.enrich_packets_with_device_info(packets)
+      assert length(enriched) == 3
+      assert Enum.all?(enriched, &Map.has_key?(&1, :device_model))
+    end
+
+    test "handles empty list" do
+      assert SharedPacketHandler.enrich_packets_with_device_info([]) == []
+    end
+  end
+
+  describe "filter factories" do
+    test "callsign_filter matches packets by sender" do
+      f = SharedPacketHandler.callsign_filter("K5ABC")
+      assert f.(%{sender: "K5ABC"}, :any)
+      refute f.(%{sender: "W1XYZ"}, :any)
+    end
+
+    test "callsign_and_weather_filter requires both" do
+      f = SharedPacketHandler.callsign_and_weather_filter("K5ABC")
+      refute f.(%{sender: "K5ABC"}, :any)
+      refute f.(%{sender: "OTHER", temperature: 72.0}, :any)
+      assert f.(%{sender: "K5ABC", temperature: 72.0}, :any)
+    end
+  end
+end