feat: add AddTodoListItem command

Author: ar3s3ru

examples/todolist/command/add_todo_list_item.go

@@ -0,0 +1,54 @@
+package command
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/get-eventually/go-eventually/core/command"
+	"github.com/get-eventually/go-eventually/examples/todolist/domain/todolist"
+)
+
+type AddTodoListItem struct {
+	TodoListID  todolist.ID
+	TodoItemID  todolist.ItemID
+	Title       string
+	Description string
+	DueDate     time.Time
+}
+
+// Name implements command.Command
+func (AddTodoListItem) Name() string { return "AddTodoListItem" }
+
+var _ command.Handler[AddTodoListItem] = AddTodoListItemHandler{}
+
+type AddTodoListItemHandler struct {
+	Clock      func() time.Time
+	Repository todolist.Repository
+}
+
+// Handle implements command.Handler
+func (h AddTodoListItemHandler) Handle(ctx context.Context, cmd command.Envelope[AddTodoListItem]) error {
+	todoList, err := h.Repository.Get(ctx, cmd.Message.TodoListID)
+	if err != nil {
+		return fmt.Errorf("command.AddTodoListItem: failed to get TodoList from repository, %w", err)
+	}
+
+	now := h.Clock()
+
+	if err := todoList.AddItem(
+		cmd.Message.TodoItemID,
+		cmd.Message.Title,
+		cmd.Message.Description,
+		cmd.Message.DueDate,
+		now,
+	); err != nil {
+		return fmt.Errorf("command.AddTodoListItem: failed to add item to TodoList, %w", err)
+	}
+
+	if err := h.Repository.Save(ctx, todoList); err != nil {
+		return fmt.Errorf("command.AddTodoListItem: failed to save new TodoList version, %w", err)
+	}
+
+	return nil
+}

examples/todolist/command/add_todo_list_item_test.go

@@ -0,0 +1,70 @@
+package command_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/get-eventually/go-eventually/core/aggregate"
+	"github.com/get-eventually/go-eventually/core/command"
+	"github.com/get-eventually/go-eventually/core/event"
+	"github.com/get-eventually/go-eventually/core/test/scenario"
+	appcommand "github.com/get-eventually/go-eventually/examples/todolist/command"
+	"github.com/get-eventually/go-eventually/examples/todolist/domain/todolist"
+	"github.com/google/uuid"
+)
+
+func TestAddTodoListItem(t *testing.T) {
+	now := time.Now()
+	commandHandlerFactory := func(es event.Store) appcommand.AddTodoListItemHandler {
+		return appcommand.AddTodoListItemHandler{
+			Clock:      func() time.Time { return now },
+			Repository: aggregate.NewEventSourcedRepository(es, todolist.Type),
+		}
+	}
+
+	todoListID := todolist.ID(uuid.New())
+	todoItemID := todolist.ItemID(uuid.New())
+	listTitle := "my list"
+	listOwner := "me"
+
+	t.Run("it fails when the target TodoList does not exist", func(t *testing.T) {
+		scenario.CommandHandler[appcommand.AddTodoListItem, appcommand.AddTodoListItemHandler]().
+			When(command.ToEnvelope(appcommand.AddTodoListItem{
+				TodoListID: todoListID,
+				TodoItemID: todoItemID,
+				Title:      "a todo item that should fail",
+			})).
+			ThenError(aggregate.ErrRootNotFound).
+			AssertOn(t, commandHandlerFactory)
+	})
+
+	t.Run("it works", func(t *testing.T) {
+		scenario.CommandHandler[appcommand.AddTodoListItem, appcommand.AddTodoListItemHandler]().
+			Given(event.Persisted{
+				StreamID: event.StreamID(todoListID.String()),
+				Version:  1,
+				Envelope: event.ToEnvelope(todolist.WasCreated{
+					ID:           todoListID,
+					Title:        listTitle,
+					Owner:        listOwner,
+					CreationTime: now.Add(-2 * time.Minute),
+				}),
+			}).
+			When(command.ToEnvelope(appcommand.AddTodoListItem{
+				TodoListID: todoListID,
+				TodoItemID: todoItemID,
+				Title:      "a todo item that should succeed",
+			})).
+			Then(event.Persisted{
+				StreamID: event.StreamID(todoListID.String()),
+				Version:  2,
+				Envelope: event.ToEnvelope(todolist.ItemWasAdded{
+					ID:           todoItemID,
+					Title:        "a todo item that should succeed",
+					CreationTime: now,
+				}),
+			}).
+			AssertOn(t, commandHandlerFactory)
+	})
+
+}

examples/todolist/domain/todolist/event.go

@@ -12,10 +12,11 @@ type WasCreated struct {
 func (WasCreated) Name() string { return "TodoListWasCreated" }
 
 type ItemWasAdded struct {
-	ID          ItemID
-	Title       string
-	Description string
-	DueDate     time.Time
+	ID           ItemID
+	Title        string
+	Description  string
+	DueDate      time.Time
+	CreationTime time.Time
 }
 
 func (ItemWasAdded) Name() string { return "TodoListItemWasAdded" }

examples/todolist/domain/todolist/item.go

@@ -16,11 +16,12 @@ func (id ItemID) String() string { return uuid.UUID(id).String() }
 type Item struct {
 	aggregate.BaseRoot
 
-	id          ItemID
-	title       string
-	description string
-	completed   bool
-	dueDate     time.Time
+	id           ItemID
+	title        string
+	description  string
+	completed    bool
+	dueDate      time.Time
+	creationTime time.Time
 }
 
 func (item *Item) Apply(event event.Event) error {
@@ -31,6 +32,7 @@ func (item *Item) Apply(event event.Event) error {
 		item.description = evt.Description
 		item.completed = false
 		item.dueDate = evt.DueDate
+		item.creationTime = evt.CreationTime
 
 	case ItemMarkedAsDone:
 		item.completed = true

examples/todolist/domain/todolist/todolist.go

@@ -99,9 +99,12 @@ func (tl *TodoList) Apply(event event.Event) error {
 }
 
 var (
-	ErrEmptyID          = errors.New("todolist.TodoList: empty id provided")
-	ErrEmptyTitle       = errors.New("todolist.TodoList: empty title provided")
-	ErrNoOwnerSpecified = errors.New("todolist.TodoList: no owner specified")
+	ErrEmptyID           = errors.New("todolist.TodoList: empty id provided")
+	ErrEmptyTitle        = errors.New("todolist.TodoList: empty title provided")
+	ErrNoOwnerSpecified  = errors.New("todolist.TodoList: no owner specified")
+	ErrEmptyItemID       = errors.New("todolist.TodoList: empty item id provided")
+	ErrEmptyItemTitle    = errors.New("todolist.TodoList: empty item title provided")
+	ErrItemAlreadyExists = errors.New("todolist.TodoList: item already exists")
 )
 
 func Create(id ID, title, owner string, now time.Time) (*TodoList, error) {
@@ -134,3 +137,43 @@ func Create(id ID, title, owner string, now time.Time) (*TodoList, error) {
 
 	return &todoList, nil
 }
+
+func (todoList *TodoList) itemByID(id ItemID) (*Item, bool) {
+	for _, item := range todoList.items {
+		if item.id == id {
+			return item, true
+		}
+	}
+
+	return nil, false
+}
+
+func (todoList *TodoList) AddItem(id ItemID, title, description string, dueDate, now time.Time) error {
+	wrapErr := func(err error) error {
+		return fmt.Errorf("todolist.AddItem: failed to add new TodoItem to list, %w", err)
+	}
+
+	if uuid.UUID(id) == uuid.Nil {
+		return wrapErr(ErrEmptyItemID)
+	}
+
+	if title == "" {
+		return wrapErr(ErrEmptyTitle)
+	}
+
+	if _, ok := todoList.itemByID(id); ok {
+		return wrapErr(ErrItemAlreadyExists)
+	}
+
+	if err := aggregate.RecordThat[ID](todoList, event.ToEnvelope(ItemWasAdded{
+		ID:           id,
+		Title:        title,
+		Description:  description,
+		DueDate:      dueDate,
+		CreationTime: now,
+	})); err != nil {
+		return fmt.Errorf("todolist.AddItem: failed to apply domain event, %w", err)
+	}
+
+	return nil
+}