Add LastFm.Feed.all_artists/0 and LastFm.Feed.all_albums/0

lib/last_fm/feed.ex

@@ -37,6 +37,32 @@ defmodule LastFm.Feed do
     :ets.select_reverse(__MODULE__, m)
   end
 
+  @spec all_artists() :: [LastFm.Artist.t()]
+  def all_artists do
+    m = [
+      {
+        {:"$1", %{artist: :"$2"}},
+        [],
+        [:"$2"]
+      }
+    ]
+
+    :ets.select_reverse(__MODULE__, m) |> Enum.uniq()
+  end
+
+  @spec all_albums() :: [LastFm.Album.t()]
+  def all_albums do
+    m = [
+      {
+        {:"$1", %{album: :"$2"}},
+        [],
+        [:"$2"]
+      }
+    ]
+
+    :ets.select_reverse(__MODULE__, m) |> Enum.uniq()
+  end
+
   @spec subscribe() :: :ok
   def subscribe do
     Phoenix.PubSub.subscribe(LastFm.PubSub, "feed:update")

test/last_fm/feed_test.exs

@@ -46,5 +46,15 @@ defmodule LastFm.FeedTest do
       :ok = Feed.update([@track_two, @track_one])
       assert [@track_two, @track_one] == Feed.all_tracks()
     end
+
+    test "it returns artists in descending order of scrobble" do
+      :ok = Feed.update([@track_two, @track_one])
+      assert [@track_one.artist] == Feed.all_artists()
+    end
+
+    test "it returns albums in descending order of scrobble" do
+      :ok = Feed.update([@track_two, @track_one])
+      assert [@track_one.album] == Feed.all_albums()
+    end
   end
 end