Only show similar artists from collection

lib/music_library/artists.ex

@@ -2,7 +2,7 @@ defmodule MusicLibrary.Artists do
   import Ecto.Query, warn: false
   alias MusicLibrary.Repo
 
-  alias MusicLibrary.Records.ArtistRecord
+  alias MusicLibrary.Records.{ArtistRecord, Record}
 
   def get_artist!(musicbrainz_id) do
     q =
@@ -17,11 +17,11 @@ defmodule MusicLibrary.Artists do
   def get_similar_artists(artist) do
     case LastFm.get_similar_artists(artist.musicbrainz_id, artist.name) do
       {:ok, artists} ->
-        all_artist_ids = get_all_artist_ids()
+        collected_artist_ids = get_collected_artist_ids()
 
         {:ok,
          Enum.filter(artists, fn a ->
-           MapSet.member?(all_artist_ids, a.musicbrainz_id)
+           MapSet.member?(collected_artist_ids, a.musicbrainz_id)
          end)}
 
       error ->
@@ -34,4 +34,16 @@ defmodule MusicLibrary.Artists do
 
     q |> Repo.all() |> MapSet.new()
   end
+
+  defp get_collected_artist_ids do
+    q =
+      from ar in ArtistRecord,
+        join: r in Record,
+        on: r.id == ar.record_id,
+        where: not is_nil(r.purchased_at),
+        distinct: true,
+        select: ar.musicbrainz_id
+
+    q |> Repo.all() |> MapSet.new()
+  end
 end