implement todo aggregate with create command

Author: ChristianAlexander

lib/todo_backend/app.ex

@@ -1,3 +1,5 @@
 defmodule TodoBackend.App do
   use Commanded.Application, otp_app: :todo_backend
+
+  router(TodoBackend.Router)
 end

lib/todo_backend/router.ex

@@ -0,0 +1,8 @@
+defmodule TodoBackend.Router do
+  use Commanded.Commands.Router
+
+  alias TodoBackend.Todos.Aggregates.Todo
+  alias TodoBackend.Todos.Commands.CreateTodo
+
+  dispatch([CreateTodo], to: Todo, identity: :uuid)
+end

lib/todo_backend/todos/aggregates/todo.ex

@@ -0,0 +1,32 @@
+defmodule TodoBackend.Todos.Aggregates.Todo do
+  defstruct [
+    :uuid,
+    :title,
+    :completed,
+    :order
+  ]
+
+  alias TodoBackend.Todos.Aggregates.Todo
+
+  alias TodoBackend.Todos.Commands.CreateTodo
+
+  alias TodoBackend.Todos.Events.TodoCreated
+
+  def execute(%Todo{uuid: nil}, %CreateTodo{} = create) do
+    %TodoCreated{
+      uuid: create.uuid,
+      title: create.title,
+      completed: create.completed,
+      order: create.order
+    }
+  end
+
+  def apply(%Todo{} = todo, %TodoCreated{} = created) do
+    %Todo{
+      todo
+      | uuid: created.uuid,
+        title: created.title,
+        completed: created.completed,
+        order: created.order
+    }
+  end

lib/todo_backend/todos/commands/create_todo.ex

@@ -0,0 +1,8 @@
+defmodule TodoBackend.Todos.Commands.CreateTodo do
+  defstruct [
+    :uuid,
+    :title,
+    :completed,
+    :order
+  ]
+end

lib/todo_backend/todos/events/todo_created.ex

@@ -0,0 +1,9 @@
+defmodule TodoBackend.Todos.Events.TodoCreated do
+  @derive Jason.Encoder
+  defstruct [
+    :uuid,
+    :title,
+    :completed,
+    :order
+  ]
+end