Fix credo warnings and start on design suggestions

Warnings fixed (13 issues):
- Replace expensive length/1 checks with empty list comparisons
- Remove redundant n == n comparison in is_finite guards
- Use proper type notation in @spec instead of struct literal

Design suggestions (3/13 files):
- Add aliases for nested modules in historical_loader, page_controller, mobile_channel

Remaining: 10 design suggestions, 42 refactoring opportunities (complex functions)

lib/aprsme/cluster/leader_election.ex

@@ -71,16 +71,16 @@ defmodule Aprsme.Cluster.LeaderElection do
     else
       connected_nodes = Node.list()
 
-      if length(connected_nodes) > 0 do
-        Logger.info("Cluster formed with #{length(connected_nodes)} other nodes: #{inspect(connected_nodes)}")
-        Logger.info("Proceeding with leader election")
-        Process.send_after(self(), :attempt_election, 100)
-        {:noreply, %{state | election_forced: true}}
-      else
+      if connected_nodes == [] do
         Logger.debug("Cluster not yet formed - waiting...")
         # Check again in 2 seconds
         Process.send_after(self(), :check_cluster_and_elect, 2_000)
         {:noreply, state}
+      else
+        Logger.info("Cluster formed with #{length(connected_nodes)} other nodes: #{inspect(connected_nodes)}")
+        Logger.info("Proceeding with leader election")
+        Process.send_after(self(), :attempt_election, 100)
+        {:noreply, %{state | election_forced: true}}
       end
     end
   end
@@ -91,7 +91,7 @@ defmodule Aprsme.Cluster.LeaderElection do
     if not state.election_forced and not state.is_leader do
       connected_nodes = Node.list()
 
-      if length(connected_nodes) == 0 do
+      if connected_nodes == [] do
         Logger.warning(
           "Cluster formation timeout reached after #{@max_cluster_wait}ms with no connected nodes. " <>
             "Proceeding with leader election in single-node mode to ensure APRS-IS connection."

lib/aprsme/packet_consumer.ex

@@ -308,7 +308,7 @@ defmodule Aprsme.PacketConsumer do
         Logger.error("Batch insert failed: #{inspect(error)}")
 
         # Log sample packet to help debug field issues
-        if length(valid_packets) > 0 do
+        if valid_packets != [] do
           sample_packet = List.first(valid_packets)
           Logger.error("Sample packet fields: #{inspect(Map.keys(sample_packet))}")
           Logger.error("Sample packet data: #{inspect(sample_packet)}")

lib/aprsme/packet_producer.ex

@@ -45,7 +45,7 @@ defmodule Aprsme.PacketProducer do
     end
   end
 
-  defp dispatch_events(buffer, demand) when demand > 0 and length(buffer) > 0 do
+  defp dispatch_events(buffer, demand) when demand > 0 and buffer != [] do
     {events, remaining} = Enum.split(buffer, demand)
     {events, remaining, demand - length(events)}
   end

lib/aprsme_web/channels/mobile_channel.ex

@@ -52,6 +52,8 @@ defmodule AprsmeWeb.MobileChannel do
   """
   use AprsmeWeb, :channel
 
+  alias AprsmeWeb.MapLive.MapHelpers
+
   require Logger
 
   @impl true
@@ -277,7 +279,7 @@ defmodule AprsmeWeb.MobileChannel do
 
   defp build_mobile_packet(packet) do
     # Extract coordinates
-    {lat, lon, _data_extended} = AprsmeWeb.MapLive.MapHelpers.get_coordinates(packet)
+    {lat, lon, _data_extended} = MapHelpers.get_coordinates(packet)
 
     # Build minimal packet data for mobile
     %{
@@ -465,7 +467,7 @@ defmodule AprsmeWeb.MobileChannel do
     Logger.info("Loaded #{length(packets)} historical packets for callsign #{callsign}")
 
     # Send historical packets to client
-    if length(packets) > 0 do
+    if packets != [] do
       Enum.each(packets, fn packet ->
         packet_data = build_mobile_packet(packet)
         push(socket, "packet", packet_data)

lib/aprsme_web/controllers/page_controller.ex

@@ -2,6 +2,8 @@ defmodule AprsmeWeb.PageController do
   @moduledoc false
   use AprsmeWeb, :controller
 
+  alias Aprsme.Cluster.LeaderElection
+
   def home(conn, _params) do
     render(conn, :home)
   end
@@ -80,7 +82,7 @@ defmodule AprsmeWeb.PageController do
 
   def status_json(conn, _params) do
     # Get cluster-wide APRS-IS connection status
-    aprs_status = Aprsme.Cluster.LeaderElection.get_cluster_aprs_status()
+    aprs_status = LeaderElection.get_cluster_aprs_status()
 
     # Get application version
     version = :aprsme |> Application.spec(:vsn) |> List.to_string()

lib/aprsme_web/live/map_live/data_builder.ex

@@ -139,7 +139,7 @@ defmodule AprsmeWeb.MapLive.DataBuilder do
 
   defp valid_coordinates?(_, _), do: false
 
-  defp is_finite(n) when is_float(n), do: n != :infinity and n != :neg_infinity and n == n
+  defp is_finite(n) when is_float(n), do: n != :infinity and n != :neg_infinity
   defp is_finite(n) when is_integer(n), do: true
 
   @doc """

lib/aprsme_web/live/map_live/historical_loader.ex

@@ -6,8 +6,10 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
   import Phoenix.Component, only: [assign: 3]
 
   alias Aprsme.Packets
+  alias AprsmeWeb.Live.Shared.CoordinateUtils
   alias AprsmeWeb.Live.Shared.PacketUtils, as: SharedPacketUtils
   alias AprsmeWeb.MapLive.DataBuilder
+  alias AprsmeWeb.MapLive.RfPath
   alias Phoenix.LiveView
   alias Phoenix.LiveView.Socket
 
@@ -219,7 +221,7 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
             # Filter out packets with invalid coordinates before processing
             valid_packets =
               Enum.filter(historical_packets, fn packet ->
-                {lat, lon, _} = AprsmeWeb.Live.Shared.CoordinateUtils.get_coordinates(packet)
+                {lat, lon, _} = CoordinateUtils.get_coordinates(packet)
 
                 is_number(lat) and is_number(lon) and
                   lat >= -90 and lat <= 90 and lon >= -180 and lon <= 180 and
@@ -416,7 +418,7 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
       packets
       |> Enum.flat_map(fn packet ->
         path = Map.get(packet, :path, "")
-        AprsmeWeb.MapLive.RfPath.parse_rf_path(path)
+        RfPath.parse_rf_path(path)
       end)
       |> Enum.uniq()
       |> Enum.reject(&(&1 == ""))
@@ -431,6 +433,6 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
     socket
   end
 
-  defp is_finite(n) when is_float(n), do: n != :infinity and n != :neg_infinity and n == n
+  defp is_finite(n) when is_float(n), do: n != :infinity and n != :neg_infinity
   defp is_finite(n) when is_integer(n), do: true
 end

lib/aprsme_web/live/map_live/index.ex

@@ -428,14 +428,14 @@ defmodule AprsmeWeb.MapLive.Index do
 
     # Send event to draw the RF path lines
     socket =
-      if length(path_station_positions) > 0 do
+      if path_station_positions == [] do
+        socket
+      else
         push_event(socket, "draw_rf_path", %{
           station_lat: lat_float,
           station_lng: lng_float,
           path_stations: path_station_positions
         })
-      else
-        socket
       end
 
     {:noreply, socket}

lib/aprsme_web/user_auth.ex

@@ -28,7 +28,7 @@ defmodule AprsmeWeb.UserAuth do
   disconnected on log out. The line can be safely removed
   if you are not using LiveView.
   """
-  @spec log_in_user(Plug.Conn.t(), %Aprsme.Accounts.User{}, map()) :: Plug.Conn.t()
+  @spec log_in_user(Plug.Conn.t(), Aprsme.Accounts.User.t(), map()) :: Plug.Conn.t()
   def log_in_user(conn, user, params \\ %{}) do
     token = Accounts.generate_user_session_token(user)
     user_return_to = get_session(conn, :user_return_to)

test/aprsme/packets/clustering_test.exs

@@ -24,7 +24,7 @@ defmodule Aprsme.Packets.ClusteringTest do
       result = Clustering.cluster_packets(packets, 7, %{})
       assert {:heat_map, clusters} = result
       assert is_list(clusters)
-      assert length(clusters) > 0
+      assert clusters != []
     end
 
     test "returns clustered data when zoom level is 8 or less" do
@@ -37,7 +37,7 @@ defmodule Aprsme.Packets.ClusteringTest do
       result = Clustering.cluster_packets(packets, 7, %{})
       assert {:heat_map, clusters} = result
       assert is_list(clusters)
-      assert length(clusters) > 0
+      assert clusters != []
 
       # Check cluster structure
       [first_cluster | _] = clusters

test/aprsme/packets_test.exs

@@ -339,7 +339,7 @@ defmodule Aprsme.PacketsTest do
     test "returns stations ordered by distance", %{stations: _stations} do
       results = Packets.get_nearby_stations(39.0, -98.0)
 
-      assert length(results) > 0
+      assert results != []
       # Results should be ordered by distance
       [first | _] = results
       assert first.sender in ["NEAR1", "NEAR2"]