Rename MusicbrainzData -> ReleaseGroup

lib/music_brainz/release_group.ex

@@ -0,0 +1,33 @@
+defmodule MusicBrainz.ReleaseGroup do
+  alias MusicBrainz.ReleaseGroupSearchResult
+
+  def included_release_groups(release_group) do
+    release_group
+    |> get_release_groups()
+    |> Enum.map(fn relation ->
+      ReleaseGroupSearchResult.from_api_response(relation["release_group"])
+    end)
+  end
+
+  def release_ids(release_group) do
+    release_group
+    |> Map.get("releases", [])
+    |> Enum.map(fn release -> release["id"] end)
+  end
+
+  def included_release_group_ids(release_group) do
+    release_group
+    |> included_release_groups()
+    |> Enum.map(fn rg -> rg.id end)
+  end
+
+  defp get_release_groups(release_group) do
+    release_group
+    |> Map.get("relations", [])
+    |> Enum.filter(fn relation ->
+      relation["target-type"] == "release_group" and
+        relation["type"] == "included in" and
+        relation["direction"] == "backward"
+    end)
+  end
+end