implement todo update command

lib/todo_backend/router.ex

@@ -4,7 +4,9 @@ defmodule TodoBackend.Router do
   alias TodoBackend.Todos.Aggregates.Todo
   alias TodoBackend.Todos.Commands.CreateTodo
   alias TodoBackend.Todos.Commands.DeleteTodo
+  alias TodoBackend.Todos.Commands.UpdateTodo
 
   dispatch([CreateTodo], to: Todo, identity: :uuid)
   dispatch([DeleteTodo], to: Todo, identity: :uuid)
+  dispatch([UpdateTodo], to: Todo, identity: :uuid)
 end

lib/todo_backend/todos/aggregates/todo.ex

@@ -10,9 +10,14 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
 
   alias TodoBackend.Todos.Commands.CreateTodo
   alias TodoBackend.Todos.Commands.DeleteTodo
+  alias TodoBackend.Todos.Commands.UpdateTodo
 
   alias TodoBackend.Todos.Events.TodoCreated
   alias TodoBackend.Todos.Events.TodoDeleted
+  alias TodoBackend.Todos.Events.TodoCompleted
+  alias TodoBackend.Todos.Events.TodoUncompleted
+  alias TodoBackend.Todos.Events.TodoTitleUpdated
+  alias TodoBackend.Todos.Events.TodoOrderUpdated
 
   def execute(%Todo{uuid: nil}, %CreateTodo{} = create) do
     %TodoCreated{
@@ -27,6 +32,28 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
     %TodoDeleted{uuid: uuid}
   end
 
+  # TODO: validate
+  def execute(%Todo{} = todo, %UpdateTodo{} = update) do
+    completion_command =
+      if todo.completed != update.completed and not is_nil(update.completed) do
+        if update.completed do
+          %TodoCompleted{uuid: todo.uuid}
+        else
+          %TodoUncompleted{uuid: todo.uuid}
+        end
+      end
+
+    title_command =
+      if todo.title != update.title and not is_nil(update.title),
+        do: %TodoTitleUpdated{uuid: todo.uuid, title: update.title}
+
+    order_command =
+      if todo.order != update.order and not is_nil(update.order),
+        do: %TodoOrderUpdated{uuid: todo.uuid, order: update.order}
+
+    [completion_command, title_command, order_command] |> Enum.filter(&Function.identity/1)
+  end
+
   def apply(%Todo{} = todo, %TodoCreated{} = created) do
     %Todo{
       todo
@@ -37,6 +64,22 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
     }
   end
 
+  def apply(%Todo{} = todo, %TodoCompleted{}) do
+    %Todo{todo | completed: true}
+  end
+
+  def apply(%Todo{} = todo, %TodoUncompleted{}) do
+    %Todo{todo | completed: false}
+  end
+
+  def apply(%Todo{} = todo, %TodoTitleUpdated{title: title}) do
+    %Todo{todo | title: title}
+  end
+
+  def apply(%Todo{} = todo, %TodoOrderUpdated{order: order}) do
+    %Todo{todo | order: order}
+  end
+
   def apply(%Todo{uuid: uuid}, %TodoDeleted{uuid: uuid}) do
     nil
   end

lib/todo_backend/todos/commands/update_todo.ex

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

lib/todo_backend/todos/events/todo_completed.ex

@@ -0,0 +1,6 @@
+defmodule TodoBackend.Todos.Events.TodoCompleted do
+  @derive Jason.Encoder
+  defstruct [
+    :uuid
+  ]
+end

lib/todo_backend/todos/events/todo_order_updated.ex

@@ -0,0 +1,7 @@
+defmodule TodoBackend.Todos.Events.TodoOrderUpdated do
+  @derive Jason.Encoder
+  defstruct [
+    :uuid,
+    :order
+  ]
+end

lib/todo_backend/todos/events/todo_title_updated.ex

@@ -0,0 +1,7 @@
+defmodule TodoBackend.Todos.Events.TodoTitleUpdated do
+  @derive Jason.Encoder
+  defstruct [
+    :uuid,
+    :title
+  ]
+end

lib/todo_backend/todos/events/todo_uncompleted.ex

@@ -0,0 +1,6 @@
+defmodule TodoBackend.Todos.Events.TodoUncompleted do
+  @derive Jason.Encoder
+  defstruct [
+    :uuid
+  ]
+end