Implement GenServer and Application for morse module.

morse/lib/morse_server.ex

@@ -0,0 +1,37 @@
+defmodule MorseServer do
+  use GenServer
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    start_link()
+  end
+
+  def start_link do
+    GenServer.start_link(__MODULE__, :off, name: __MODULE__)
+  end
+
+  def start_morse do
+    GenServer.call(__MODULE__, :start)
+  end
+
+  @impl true
+  def init(state) do
+    {:ok, state}
+  end
+
+  @impl true
+  def handle_call(:start, _from, :on) do
+    {:reply, {:error, :already_started}, :on}
+  end
+
+  def handle_call(:start, _from, :off) do
+    spawn(MorseSignaler, :signal, [self()])
+    {:reply, :ok, :on}
+  end
+
+  @impl true
+  def handle_cast(:done, :on) do
+    {:noreply, :off}
+  end
+end

morse/lib/morse_signaler.ex

@@ -1,4 +1,4 @@
-defmodule Morse do
+defmodule MorseSignaler do
   alias Circuits.GPIO
 
   @moduledoc """
@@ -16,18 +16,17 @@ defmodule Morse do
 
   @doc """
   Signal the provided symbols using GPIO.
-  Also setup the GPIO.
+  Notifies the parent when the signalling is done.
   """
 
-  def signal do
-    signal(Application.fetch_env!(:morse, :morse_message))
-  end
-
-  def signal(symbols) do
-    {:ok, gpio} = GPIO.open(relay_pin(), :output)
-    GPIO.write(gpio, @off)
+  def signal(server_pid) do
+    # {:ok, gpio} = GPIO.open(relay_pin(), :output)
+    # GPIO.write(gpio, @off)
     Process.sleep(@sleep_start)
-    signal_sentence(gpio, String.graphemes(symbols))
+    # signal_sentence(gpio, String.graphemes(secret_code()))
+
+    GenServer.cast(server_pid, :done)
+    :ok
   end
 
   # Signal a whole sentence of symbols with GPIO.
@@ -64,4 +63,8 @@ defmodule Morse do
   defp relay_pin() do
     Application.fetch_env!(:morse, :relay_pin)
   end
+
+  defp secret_code do
+    signal(Application.fetch_env!(:morse, :morse_message))
+  end
 end

morse/mix.exs

@@ -15,7 +15,8 @@ defmodule Morse.MixProject do
   def application do
     [
       extra_applications: [:logger],
-      env: [morse_message: "...---...", relay_pin: 17]
+      env: [morse_message: "...---...", relay_pin: 17],
+      mod: {MorseServer, []}
     ]
   end