Extract display into supervision tree.

lib/display.ex

@@ -1,21 +1,80 @@
 defmodule Display do
-  alias IO.ANSI
-  alias Display.ProgressBar
-  alias Display.Intro
-  alias Display.Failure
-  alias Display.Notifications
+  use GenServer
 
-  def invalid_koan(koan, modules) do
+  alias IO.ANSI
+  alias Display.{ProgressBar, Intro, Failure, Notifications}
+
+  def start_link do
+    GenServer.start_link(__MODULE__, %{clear_screen: true}, name: __MODULE__)
+  end
+
+  def disable_clear do
+    GenServer.cast(__MODULE__, :disable_clear)
+  end
+
+  def handle_cast(:disable_clear, state) do
+    {:noreply, %{state | clear_screen: false}}
+  end
+
+  def handle_cast({:invalid, koan, modules}, state) do
     Notifications.invalid_koan(koan, modules)
     |> IO.puts
+
+    {:noreply, state}
+  end
+
+  def handle_cast({:show_failure, failure, module, name}, state) do
+    format(failure, module, name)
+    |> IO.puts
+
+    {:noreply, state}
+  end
+
+  def handle_cast({:show_compile_error, error}, state) do
+    Failure.show_compile_error(error)
+    |> IO.puts
+
+    {:noreply, state}
+  end
+
+  def handle_cast(:congratulate, state) do
+    Notifications.congratulate
+    |> IO.puts
+
+    {:noreply, state}
+  end
+
+  def handle_cast(:clear_screen, state = %{clear_screen: true}) do
+    IO.puts(ANSI.clear)
+    IO.puts(ANSI.home)
+
+    {:noreply, state}
+  end
+  def handle_cast(:clear_screen, state) do
+    {:noreply, state}
+  end
+
+  def invalid_koan(koan, modules) do
+    GenServer.cast(__MODULE__, {:invalid, koan, modules})
   end
 
   def show_failure(failure, module, name) do
-    format(failure, module, name)
-    |> IO.puts
+    GenServer.cast(__MODULE__, {:show_failure, failure, module, name})
   end
 
-  def format(failure, module, name) do
+  def show_compile_error(error) do
+    GenServer.cast(__MODULE__, {:show_compile_error, error})
+  end
+
+  def congratulate do
+    GenServer.cast(__MODULE__, :congratulate)
+  end
+
+  def clear_screen do
+    GenServer.cast(__MODULE__, :clear_screen)
+  end
+
+  defp format(failure, module, name) do
     """
     #{Intro.intro(module, Tracker.visited)}
     Now meditate upon #{format_module(module)}
@@ -26,23 +85,6 @@ defmodule Display do
     """
   end
 
-  def show_compile_error(error) do
-    Failure.show_compile_error(error)
-    |> IO.puts
-  end
-
-  def congratulate do
-    Notifications.congratulate
-    |> IO.puts
-  end
-
-  def clear_screen do
-    if Options.clear_screen? do
-      IO.puts(ANSI.clear)
-      IO.puts(ANSI.home)
-    end
-  end
-
   defp format_module(module) do
     Module.split(module) |> List.last
   end