Restructure Refresh to allow for forced sync refresh

lib/last_fm/refresh.ex

@@ -17,10 +17,9 @@ defmodule LastFm.Refresh do
     GenServer.start_link(__MODULE__, config, name: __MODULE__)
   end
 
-  @spec refresh() :: :refresh
+  @spec refresh() :: :ok
   def refresh do
-    # TODO: Very barebones and naive - can be improved by building a state machine.
-    send(__MODULE__, :refresh)
+    GenServer.call(__MODULE__, :refresh)
   end
 
   @impl true
@@ -36,24 +35,39 @@ defmodule LastFm.Refresh do
   end
 
   @impl true
-  @spec handle_continue(atom(), config) :: {:noreply, config}
+  @spec handle_call(:refresh, GenServer.from(), config) ::
+          {:reply, :ok | {:error, term()}, config, pos_integer()}
+  def handle_call(:refresh, _from, config) do
+    case config.api.get_recent_tracks(config.user, config.api_key) do
+      {:ok, tracks} ->
+        Feed.update(tracks)
+        {:reply, :ok, config, config.refresh_interval}
+
+      error ->
+        # TODO: think about failure scenario - error is logged at the API level
+        {:reply, error, config, config.refresh_interval}
+    end
+  end
+
+  @impl true
+  @spec handle_continue(atom(), config) :: {:noreply, config, pos_integer()}
   def handle_continue(:refresh, config), do: refresh(config)
 
   @impl true
-  @spec handle_info(atom(), config) :: {:noreply, config}
+  @spec handle_info(atom(), config) :: {:noreply, config, pos_integer()}
   def handle_info(:refresh, config), do: refresh(config)
 
+  def handle_info(:timeout, config), do: refresh(config)
+
   defp refresh(config) do
     case config.api.get_recent_tracks(config.user, config.api_key) do
       {:ok, tracks} ->
         Feed.update(tracks)
-        Process.send_after(self(), :refresh, config.refresh_interval)
-        {:noreply, config}
+        {:noreply, config, config.refresh_interval}
 
       {:error, _reason} ->
         # TODO: think about failure scenario - error is logged at the API level
-        Process.send_after(self(), :refresh, config.refresh_interval)
-        {:noreply, config}
+        {:noreply, config, config.refresh_interval}
     end
   end