Display count of child release groups

lib/music_library/records.ex

@@ -18,6 +18,7 @@ defmodule MusicLibrary.Records do
       :release,
       :genres,
       :musicbrainz_id,
+      :musicbrainz_data,
       :cover_hash
     ]
   end

lib/music_library/records/record.ex

@@ -15,7 +15,7 @@ defmodule MusicLibrary.Records.Record do
     field :cover_data, :binary
     field :cover_hash, :string
     field :musicbrainz_id, Ecto.UUID
-    field :musicbrainz_data, :map
+    field :musicbrainz_data, :map, default: %{}
     field :genres, {:array, :string}
     field :release, :string
     field :purchased_at, :utc_datetime
@@ -53,6 +53,26 @@ defmodule MusicLibrary.Records.Record do
     |> unique_constraint(:musicbrainz_id, name: "records_musicbrainz_id_format_index")
   end
 
+  def child_release_groups(record) do
+    record.musicbrainz_data
+    |> Map.get("relations", [])
+    |> Enum.filter(fn relation ->
+      relation["target-type"] == "release_group" and
+        relation["type"] == "included in" and
+        relation["direction"] == "backward"
+    end)
+  end
+
+  def child_release_groups_count(record) do
+    record.musicbrainz_data
+    |> Map.get("relations", [])
+    |> Enum.count(fn relation ->
+      relation["target-type"] == "release_group" and
+        relation["type"] == "included in" and
+        relation["direction"] == "backward"
+    end)
+  end
+
   @doc false
   def artist_changeset(artist, attrs) do
     artist