lib/todo_backend/router.ex

@@ -2,11 +2,11 @@ defmodule TodoBackend.Router do
   use Commanded.Commands.Router
 
   alias TodoBackend.Todos.Aggregates.Todo
-  alias TodoBackend.Todos.Commands.CreateTodo
-  alias TodoBackend.Todos.Commands.DeleteTodo
-  alias TodoBackend.Todos.Commands.UpdateTodo
+  alias TodoBackend.Todos.Commands.{CreateTodo, DeleteTodo, UpdateTodo, RestoreTodo}
 
-  dispatch([CreateTodo], to: Todo, identity: :uuid)
-  dispatch([DeleteTodo], to: Todo, identity: :uuid)
-  dispatch([UpdateTodo], to: Todo, identity: :uuid)
+  dispatch([CreateTodo, DeleteTodo, UpdateTodo, RestoreTodo],
+    to: Todo,
+    identity: :uuid,
+    lifespan: Todo
+  )
 end

lib/todo_backend/todos.ex

@@ -6,10 +6,7 @@ defmodule TodoBackend.Todos do
   import Ecto.Query, warn: false
   alias TodoBackend.App
   alias TodoBackend.Repo
-  alias TodoBackend.Todos.Commands.CreateTodo
-  alias TodoBackend.Todos.Commands.DeleteTodo
-  alias TodoBackend.Todos.Commands.UpdateTodo
-
+  alias TodoBackend.Todos.Commands.{CreateTodo, DeleteTodo, UpdateTodo, RestoreTodo}
   alias TodoBackend.Todos.Projections.Todo
 
   @doc """
@@ -22,7 +19,10 @@ defmodule TodoBackend.Todos do
 
   """
   def list_todos do
-    Repo.all(Todo)
+    from(t in Todo,
+      where: is_nil(t.deleted_at)
+    )
+    |> Repo.all()
   end
 
   @doc """
@@ -39,7 +39,12 @@ defmodule TodoBackend.Todos do
       ** (Ecto.NoResultsError)
 
   """
-  def get_todo!(uuid), do: Repo.get_by!(Todo, uuid: uuid)
+  def get_todo!(uuid) do
+    from(t in Todo,
+      where: is_nil(t.deleted_at)
+    )
+    |> Repo.get_by!(uuid: uuid)
+  end
 
   @doc """
   Creates a todo.
@@ -81,6 +86,7 @@ defmodule TodoBackend.Todos do
 
   """
   def update_todo(%Todo{uuid: uuid}, attrs) do
+    # TODO: ensure todo is active
     command =
       attrs
       |> UpdateTodo.new()
@@ -106,6 +112,7 @@ defmodule TodoBackend.Todos do
 
   """
   def delete_todo(%Todo{uuid: uuid}) do
+    # TODO: ensure todo exists
     command = DeleteTodo.new(%{uuid: uuid})
 
     with :ok <- App.dispatch(command) do
@@ -115,6 +122,16 @@ defmodule TodoBackend.Todos do
     end
   end
 
+  def restore_todo(id) do
+    command = %RestoreTodo{uuid: id}
+
+    with :ok <- App.dispatch(command, consistency: :strong) do
+      {:ok, get_todo!(id)}
+    else
+      reply -> reply
+    end
+  end
+
   @doc """
   Deletes all todos.
 
@@ -125,6 +142,16 @@ defmodule TodoBackend.Todos do
 
   """
   def delete_all_todos() do
-    Repo.delete_all(Todo)
+    stream = Repo.stream(Todo)
+    correlation_id = Ecto.UUID.generate()
+
+    Repo.transaction(fn ->
+      Enum.each(stream, fn todo ->
+        App.dispatch(
+          DeleteTodo.new(%{uuid: todo.uuid}),
+          correlation_id: correlation_id
+        )
+      end)
+    end)
   end
 end

lib/todo_backend/todos/aggregates/todo.ex

@@ -3,21 +3,25 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
     :uuid,
     :title,
     :completed,
-    :order
+    :order,
+    deleted_at: nil
   ]
 
+  @behaviour Commanded.Aggregates.AggregateLifespan
+
   alias TodoBackend.Todos.Aggregates.Todo
 
-  alias TodoBackend.Todos.Commands.CreateTodo
-  alias TodoBackend.Todos.Commands.DeleteTodo
-  alias TodoBackend.Todos.Commands.UpdateTodo
+  alias TodoBackend.Todos.Commands.{CreateTodo, DeleteTodo, UpdateTodo, RestoreTodo}
 
-  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
+  alias TodoBackend.Todos.Events.{
+    TodoCreated,
+    TodoDeleted,
+    TodoRestored,
+    TodoCompleted,
+    TodoUncompleted,
+    TodoTitleUpdated,
+    TodoOrderUpdated
+  }
 
   def execute(%Todo{uuid: nil}, %CreateTodo{} = create) do
     %TodoCreated{
@@ -28,8 +32,20 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
     }
   end
 
-  def execute(%Todo{uuid: uuid}, %DeleteTodo{uuid: uuid}) do
-    %TodoDeleted{uuid: uuid}
+  def execute(%Todo{uuid: uuid, deleted_at: nil}, %DeleteTodo{uuid: uuid}) do
+    %TodoDeleted{uuid: uuid, datetime: DateTime.utc_now()}
+  end
+
+  def execute(%Todo{}, %DeleteTodo{}) do
+    {:error, "Can not delete todo that is already deleted"}
+  end
+
+  def execute(%Todo{deleted_at: nil}, %RestoreTodo{}) do
+    {:error, "Can only restore deleted todos"}
+  end
+
+  def execute(%Todo{uuid: uuid}, %RestoreTodo{uuid: uuid}) do
+    %TodoRestored{uuid: uuid}
   end
 
   # TODO: validate
@@ -80,7 +96,21 @@ defmodule TodoBackend.Todos.Aggregates.Todo do
     %Todo{todo | order: order}
   end
 
-  def apply(%Todo{uuid: uuid}, %TodoDeleted{uuid: uuid}) do
-    nil
+  def apply(%Todo{uuid: uuid, deleted_at: nil} = todo, %TodoDeleted{
+        uuid: uuid,
+        datetime: effective_datetime
+      }) do
+    %Todo{todo | deleted_at: effective_datetime}
+  end
+
+  def apply(%Todo{uuid: uuid} = todo, %TodoRestored{uuid: uuid}) do
+    %Todo{todo | deleted_at: nil}
   end
+
+  def after_command(_command), do: :timer.minutes(1)
+
+  def after_event(%TodoDeleted{}), do: :stop
+  def after_event(_event), do: :timer.minutes(1)
+
+  def after_error(_error), do: :timer.minutes(1)
 end

lib/todo_backend/todos/commands/restore_todo.ex

@@ -0,0 +1,5 @@
+defmodule TodoBackend.Todos.Commands.RestoreTodo do
+  defstruct [
+    :uuid
+  ]
+end

lib/todo_backend/todos/events/todo_deleted.ex

@@ -1,6 +1,26 @@
 defmodule TodoBackend.Todos.Events.TodoDeleted do
   @derive Jason.Encoder
   defstruct [
-    :uuid
+    :uuid,
+    :datetime
   ]
+
+  alias TodoBackend.Todos.Events.TodoDeleted
+
+  defimpl Commanded.Serialization.JsonDecoder, for: TodoDeleted do
+    @doc """
+    Parse the datetime included in the aggregate state
+    """
+    def decode(%TodoDeleted{} = state) do
+      %TodoDeleted{datetime: datetime} = state
+
+      if datetime == nil do
+        %TodoDeleted{state | datetime: DateTime.utc_now()}
+      else
+        {:ok, dt, _} = DateTime.from_iso8601(datetime)
+
+        %TodoDeleted{state | datetime: dt}
+      end
+    end
+  end
 end

lib/todo_backend/todos/events/todo_restored.ex

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

lib/todo_backend/todos/projections/todo.ex

@@ -9,6 +9,7 @@ defmodule TodoBackend.Todos.Projections.Todo do
     field :completed, :boolean, default: false
     field :title, :string
     field :order, :integer, default: 0
+    field :deleted_at, :naive_datetime_usec, default: nil
 
     timestamps()
   end
@@ -17,4 +18,9 @@ defmodule TodoBackend.Todos.Projections.Todo do
     todo
     |> cast(attrs, [:title, :completed, :order])
   end
+
+  def delete_changeset(todo, attrs \\ %{}) do
+    todo
+    |> cast(attrs, [:deleted_at])
+  end
 end

lib/todo_backend/todos/projectors/todo.ex

@@ -6,12 +6,15 @@ defmodule TodoBackend.Todos.Projectors.Todo do
 
   alias TodoBackend.Repo
 
-  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
+  alias TodoBackend.Todos.Events.{
+    TodoCreated,
+    TodoDeleted,
+    TodoRestored,
+    TodoCompleted,
+    TodoUncompleted,
+    TodoTitleUpdated,
+    TodoOrderUpdated
+  }
 
   alias TodoBackend.Todos.Projections.Todo
 
@@ -24,8 +27,28 @@ defmodule TodoBackend.Todos.Projectors.Todo do
     })
   end)
 
-  project(%TodoDeleted{uuid: uuid}, _, fn multi ->
-    Ecto.Multi.delete(multi, :todo, fn _ -> %Todo{uuid: uuid} end)
+  project(%TodoDeleted{uuid: uuid, datetime: effective_datetime}, _, fn multi ->
+    case Repo.get(Todo, uuid) do
+      nil ->
+        multi
+
+      todo ->
+        Ecto.Multi.update(
+          multi,
+          :todo,
+          Todo.delete_changeset(todo, %{deleted_at: effective_datetime})
+        )
+    end
+  end)
+
+  project(%TodoRestored{uuid: uuid}, _, fn multi ->
+    case Repo.get(Todo, uuid) do
+      nil ->
+        multi
+
+      todo ->
+        Ecto.Multi.update(multi, :todo, Todo.delete_changeset(todo, %{deleted_at: nil}))
+    end
   end)
 
   project(%TodoCompleted{uuid: uuid}, _, fn multi ->

lib/todo_backend_web/controllers/todo_controller.ex

@@ -25,6 +25,12 @@ defmodule TodoBackendWeb.TodoController do
     render(conn, "show.json", todo: todo)
   end
 
+  def restore(conn, %{"id" => id}) do
+    with {:ok, %Todo{} = todo} <- Todos.restore_todo(id) do
+      render(conn, "show.json", todo: todo)
+    end
+  end
+
   def update(conn, %{"id" => id}) do
     todo = Todos.get_todo!(id)
 

lib/todo_backend_web/router.ex

@@ -10,5 +10,6 @@ defmodule TodoBackendWeb.Router do
 
     resources "/todos", TodoController
     delete "/todos", TodoController, :delete_all
+    put "/todos/:id/restore", TodoController, :restore
   end
 end

priv/repo/migrations/20220508052654_add_deleted_at_to_todo.exs

@@ -0,0 +1,11 @@
+defmodule TodoBackend.Repo.Migrations.AddDeletedAtToTodo do
+  use Ecto.Migration
+
+  def change do
+    alter table(:todos) do
+      add :deleted_at, :naive_datetime_usec
+    end
+
+    create index(:todos, [:deleted_at])
+  end
+end