Add logger message count to MOTD

lib/nerves_motd.ex

@@ -61,6 +61,8 @@ defmodule NervesMOTD do
         "\n",
         """
         Nerves CLI help: https://hexdocs.pm/nerves/iex-with-nerves.html
+
+        #{logger_text()}
         """
       ]
       |> IO.ANSI.format()
@@ -79,6 +81,17 @@ defmodule NervesMOTD do
     Keyword.get(opts, :logo, @logo)
   end
 
+  @spec logger_text() :: String.t()
+  defp logger_text() do
+    case runtime_mod().count_log_messages() do
+      {:ok, count} ->
+        "You have #{count} unread log messages"
+
+      _ ->
+        ""
+    end
+  end
+
   @spec rows(map(), list()) :: [[cell()]]
   defp rows(apps, opts) do
     [

lib/nerves_motd/runtime.ex

@@ -1,6 +1,7 @@
 defmodule NervesMOTD.Runtime do
   @moduledoc false
   @callback applications() :: %{started: [atom()], loaded: [atom()]}
+  @callback count_log_messages() :: {:ok, non_neg_integer()} | :error
   @callback cpu_temperature() :: {:ok, float()} | :error
   @callback firmware_valid?() :: boolean()
   @callback load_average() :: [String.t()]
@@ -34,6 +35,20 @@ defmodule NervesMOTD.Runtime.Target do
     %{started: started, loaded: loaded}
   end
 
+  if Code.ensure_loaded?(RingLogger) and
+       not is_nil(apply(RingLogger, :__info__, [:functions])[:count_next]) do
+    @impl NervesMOTD.Runtime
+    def count_log_messages() do
+      case apply(RingLogger, :count_next, []) do
+        count when is_integer(count) -> {:ok, count}
+        _ -> :error
+      end
+    end
+  else
+    @impl NervesMOTD.Runtime
+    def count_log_messages(), do: :error
+  end
+
   @impl NervesMOTD.Runtime
   def cpu_temperature() do
     # Read the file /sys/class/thermal/thermal_zone0/temp. The file content is

test/nerves_motd_test.exs

@@ -59,6 +59,13 @@ defmodule NervesMOTDTest do
     refute capture_motd(logo: "") =~ @nerves_logo_regex
   end
 
+  test "Logger text" do
+    NervesMOTD.MockRuntime
+    |> Mox.expect(:applications, 1, default_applications_code())
+
+    assert capture_motd() =~ ~r/You have 123 unread log messages/
+  end
+
   test "Custom rows" do
     NervesMOTD.MockRuntime
     |> Mox.expect(:applications, 1, default_applications_code())

test/support/runtime.ex

@@ -21,6 +21,9 @@ defmodule NervesMOTD.Runtime.Host do
   @impl NervesMOTD.Runtime
   def applications(), do: %{loaded: @apps, started: @apps}
 
+  @impl NervesMOTD.Runtime
+  def count_log_messages(), do: {:ok, 123}
+
   @impl NervesMOTD.Runtime
   def cpu_temperature(), do: {:ok, 41.234}