Add the Publisher resource.

lib/decentralised_book_index/metadata.ex

@@ -88,5 +88,13 @@ defmodule DecentralisedBookIndex.Metadata do
       define :update_book_id, action: :update
       define :destroy_book_id, action: :destroy
     end
+
+    resource DecentralisedBookIndex.Metadata.Publisher do
+      define :create_publisher, action: :create, args: [:name]
+      define :list_publishers, action: :read
+      define :get_publisher_by_id, args: [:id], action: :by_id
+      define :update_publisher, action: :update
+      define :destroy_publisher, action: :destroy
+    end
   end
 end

lib/decentralised_book_index/metadata/book.ex

@@ -17,7 +17,7 @@ defmodule DecentralisedBookIndex.Metadata.Book do
 
     create :create do
       primary? true
-      accept [:title, :description, :book_editions_registry_id]
+      accept [:title, :description, :publisher_id, :book_editions_registry_id]
       argument :bids, {:array, :map}
       argument :author_roles, {:array, :map}
 
@@ -38,7 +38,7 @@ defmodule DecentralisedBookIndex.Metadata.Book do
     end
 
     create :add_book_to_related_editions_registry do
-      accept [:title, :description]
+      accept [:title, :description, :publisher_id]
 
       argument :related_book_id, :uuid do
         allow_nil? false
@@ -121,6 +121,8 @@ defmodule DecentralisedBookIndex.Metadata.Book do
   relationships do
     belongs_to :book_editions_registry, Metadata.BookEditionsRegistry
 
+    belongs_to :publisher, Metadata.Publisher
+
     has_many :author_roles, Metadata.AuthorRole do
       sort order: :asc
       public? true

lib/decentralised_book_index/metadata/publisher.ex

@@ -0,0 +1,44 @@
+defmodule DecentralisedBookIndex.Metadata.Publisher do
+  use Ash.Resource,
+    otp_app: :decentralised_book_index,
+    domain: DecentralisedBookIndex.Metadata,
+    data_layer: AshPostgres.DataLayer
+
+  require Ash.Query
+  alias DecentralisedBookIndex.Metadata
+
+  postgres do
+    table "publishers"
+    repo DecentralisedBookIndex.Repo
+  end
+
+  actions do
+    defaults [:read, :update, :destroy]
+
+    create :create do
+      primary? true
+      accept [:name]
+    end
+
+    read :by_id do
+      argument :id, :uuid, allow_nil?: false
+      get? true
+      filter expr(id == ^arg(:id))
+    end
+  end
+
+  attributes do
+    uuid_primary_key :id
+
+    attribute :name, :string do
+      allow_nil? false
+      public? true
+    end
+
+    timestamps()
+  end
+
+  relationships do
+    has_many :books, Metadata.Book
+  end
+end