Use Enum to loop over morse symbols.

Reset the progress bar when signalling starts.

morse/lib/morse/server.ex

@@ -20,23 +20,17 @@ defmodule Morse.Server do
 
   @impl true
   def handle_call(:start, _from, {pid, _progress} = state) do
-    cond do
-      pid == nil or not Process.alive?(pid) ->
-        pid = spawn(&Morse.Worker.signal/0)
-        {:reply, :ok, {pid, 0}}
-
-      true ->
-        {:reply, {:error, :already_started}, state}
+    if pid == nil or not Process.alive?(pid) do
+      pid = spawn(&Morse.Worker.signal/0)
+      {:reply, :ok, {pid, 0}}
+    else
+      {:reply, {:error, :already_started}, state}
     end
   end
 
   @impl true
   def handle_cast({:progress, new_progress}, {pid, _progress}) do
-    broadcast_progress(new_progress)
+    GenServer.cast(Ui.SocketAPI, {:broadcast_progress, new_progress})
     {:noreply, {pid, new_progress}}
   end
-
-  defp broadcast_progress(progress) do
-    GenServer.cast(Ui.SocketAPI, {:broadcast_progress, progress})
-  end
 end

morse/lib/morse/worker.ex

@@ -15,56 +15,51 @@ defmodule Morse.Worker do
   @off 1
 
   @doc """
-  Signal the provided symbols using GPIO.
-  Notifies the parent when the signalling is done.
+  Signal the provided morse symbols using the GPIO.
   """
 
-  def signal() do
+  def signal do
+    code = secret_code()
+    code_length = length(code)
+
+    update_progress(0, code_length)
+
     {:ok, gpio} = GPIO.open(relay_pin(), :output)
     GPIO.write(gpio, @off)
     Process.sleep(@sleep_start)
-    update_progress(gpio, String.graphemes(secret_code()))
+
+    code
+    |> Enum.with_index()
+    |> Enum.each(&signal_symbol(gpio, &1, code_length))
+
+    update_progress(100, 100)
   end
 
-  # Update progress for clients, and signals the rest of the sentence.
-  defp update_progress(gpio, symbols) do
-    100 - length(symbols) / String.length(secret_code()) * 100
-    |> Morse.Server.update_progress()
-    if symbols != [] do
-      signal_sentence(gpio, symbols)
-    end
-  end
-
-  # Signal a whole sentence of symbols with GPIO.
-  defp signal_sentence(gpio, []) do
-    GPIO.write(gpio, @off)
-    GPIO.close(gpio)
-    update_progress(gpio, [])
-    :ok
-  end
-
-  defp signal_sentence(gpio, [symbol | rest]) when symbol in [".", "-"] do
+  defp signal_symbol(gpio, {'.', _index}, _length) do
     GPIO.write(gpio, @on)
-
-    case symbol do
-      "." -> Process.sleep(@sleep_short)
-      "-" -> Process.sleep(@sleep_long)
-    end
-
+    Process.sleep(@sleep_short)
     GPIO.write(gpio, @off)
-
     Process.sleep(@sleep_delay)
-    signal_sentence(gpio, rest)
   end
 
-  defp signal_sentence(gpio, [" " | rest]) do
+  defp signal_symbol(gpio, {'-', _index}, _length) do
+    GPIO.write(gpio, @on)
+    Process.sleep(@sleep_long)
+    GPIO.write(gpio, @off)
+    Process.sleep(@sleep_delay)
+  end
+
+  defp signal_symbol(_gpio, {' ', index}, length) do
     Process.sleep(@sleep_pause)
-
-    update_progress(gpio, rest)
+    update_progress(index, length)
   end
 
-  defp signal_sentence(_gpio, [symbol | _rest]) do
-    {:error, "Undefined symbol: " <> symbol}
+  defp signal_symbol(_gpio, {symbol, _index}, _length) do
+    {:error, "Undefined symbol: " <> <<symbol :: utf8>>}
+  end
+
+  defp update_progress(index, length) do
+    Morse.Server.update_progress(index / length * 100)
   end
 
   defp relay_pin() do
@@ -73,5 +68,6 @@ defmodule Morse.Worker do
 
   defp secret_code do
     Application.fetch_env!(:morse, :morse_message)
+    |> String.to_charlist()
   end
 end