Update AuthorRole to set author_id.

lib/decentralised_book_index/metadata.ex

@@ -61,7 +61,13 @@ defmodule DecentralisedBookIndex.Metadata do
       define :destroy_book_editions_registry, action: :destroy
     end
 
-    resource DecentralisedBookIndex.Metadata.AuthorRole
+    resource DecentralisedBookIndex.Metadata.AuthorRole do
+      define :create_author_role, action: :create, args: [:author_id, :order, :role]
+      define :list_author_roles, action: :read
+      define :get_author_role_by_id, args: [:id], action: :by_id
+      define :update_author_role, action: :update
+      define :destroy_author_role, action: :destroy
+    end
   end
 
   json_api do

lib/decentralised_book_index/metadata/author_role.ex

@@ -18,6 +18,24 @@ defmodule DecentralisedBookIndex.Metadata.AuthorRole do
       primary? true
       accept [:order, :role]
       argument :author_id, :uuid
+
+      change fn changeset, _ ->
+        author_id = changeset.arguments.author_id
+
+        if author_id != nil do
+          {:ok, author} = DecentralisedBookIndex.Metadata.get_author_by_id(author_id)
+
+          Ash.Changeset.force_change_attribute(changeset, :author_id, author.id)
+        else
+          changeset
+        end
+      end
+    end
+
+    read :by_id do
+      argument :id, :uuid, allow_nil?: false
+      get? true
+      filter expr(id == ^arg(:id))
     end
   end
 

test/decentralised_book_index/metadata/author_roles_test.exs

@@ -0,0 +1,27 @@
+defmodule DecentralisedBookIndex.Metadata.AuthorRolesTest do
+  use DecentralisedBookIndex.DataCase, async: true
+
+  alias DecentralisedBookIndex.Metadata
+
+  describe "create action" do
+    test "an author's role must belongs to an author" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+
+      assert {:ok, author_role} = Metadata.create_author_role(author.id, 1, "role")
+
+      {:ok, author_role} =
+        author_role
+        |> Ash.load(:author)
+
+      assert author.id == author_role.author_id
+    end
+
+    test "an author's role can be blank" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+
+      {:ok, author_role} = Metadata.create_author_role(author.id, 1, "")
+
+      refute author_role.role
+    end
+  end
+end