Add the action to get author's ids.

lib/decentralised_book_index/metadata.ex

@@ -38,6 +38,7 @@ defmodule DecentralisedBookIndex.Metadata do
 
       define :list_authors, action: :read
       define :get_author_by_id, args: [:id], action: :by_id
+      define :get_author_ids, args: [:author], action: :get_author_ids
       define :get_author_alternative_names, args: [:author], action: :get_alternative_names
       define :search_author, action: :search, args: [:name]
       define :update_author, action: :update

lib/decentralised_book_index/metadata/author.ex

@@ -82,6 +82,22 @@ defmodule DecentralisedBookIndex.Metadata.Author do
       end
     end
 
+    action :get_author_ids, :vector do
+      argument :author, :struct, allow_nil?: false
+
+      run fn input, _ ->
+        author = input.arguments.author
+
+        {:ok, ids} =
+          DecentralisedBookIndex.Metadata.Author
+          |> Ash.Query.filter(author_alias_registry_id == ^author.author_alias_registry_id)
+          |> Ash.Query.select([:id])
+          |> Ash.read()
+
+        {:ok, Enum.map(ids, & &1.id)}
+      end
+    end
+
     read :search do
       argument :name, :ci_string do
         constraints allow_empty?: true

test/decentralised_book_index/metadata/author_test.exs

@@ -47,4 +47,27 @@ defmodule DecentralisedBookIndex.Metadata.AuthorTest do
       assert alternatives_names = [related_author]
     end
   end
+
+  describe "author's ids" do
+    test "the list has the author's id" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+
+      assert {:ok, ids} = Metadata.get_author_ids(author)
+      assert author.id in ids
+    end
+
+    test "the list has the aliases' ids" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+      {:ok, alias1} =
+        Metadata.add_author_to_related_alias_registry("Author2", "An description2", author.id)
+      {:ok, alias2} =
+        Metadata.add_author_to_related_alias_registry("Author3", "An description3", author.id)
+
+      assert {:ok, ids} = Metadata.get_author_ids(author)
+
+      assert author.id in ids
+      assert alias1.id in ids
+      assert alias2.id in ids
+    end
+  end
 end