Use a Todo list as an example

src/domain/todo-list/TodoList.spec.ts

@@ -0,0 +1,95 @@
+import {GivenWhenThen} from '../../framework/GivenWhenThen'
+import {guid} from '../../framework/Guid'
+import {
+  AddTodoToList,
+  CreateTodoList,
+  MarkTodoAsComplete,
+  RenameTodoList,
+} from './TodoListCommands'
+import {
+  TodoAddedToList,
+  TodoListCreated,
+  TodoListRenamed,
+  TodoMarkedAsComplete,
+} from './TodoListEvents'
+import {
+  DuplicateEntryError,
+  MissingParameterError,
+  NotFoundError,
+} from '../../framework/Errors'
+
+const GWT = GivenWhenThen(`${__dirname}/TodoList`)
+
+test('Create todoList', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    When(new CreateTodoList(todoListId, 'bar'))
+    Then(new TodoListCreated(todoListId, 'bar'))
+  }))
+
+test('Rename todoList', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(new TodoListCreated(todoListId, 'foo'))
+    When(new RenameTodoList(todoListId, 'bar', 1))
+    Then(new TodoListRenamed(todoListId, 'bar'))
+  }))
+
+test('Rename todoList fail', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(new TodoListCreated(todoListId, 'foo'))
+    When(new RenameTodoList(todoListId, '', 1))
+    expect((): void => {
+      Then(new TodoListRenamed(todoListId, 'bar'))
+    }).toThrow(MissingParameterError)
+  }))
+
+test('Add todo to list', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(new TodoListCreated(todoListId, 'foo'))
+    When(new AddTodoToList(todoListId, 'feed the cat', 1))
+    Then(new TodoAddedToList(todoListId, 'feed the cat'))
+  }))
+
+test('Add todo to list fails for duplicate name todos', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(
+      new TodoListCreated(todoListId, 'foo'),
+      new TodoAddedToList(todoListId, 'feed the cat')
+    )
+    When(new AddTodoToList(todoListId, 'feed the cat', 1))
+    expect((): void => {
+      Then(new TodoAddedToList(todoListId, 'feed the cat'))
+    }).toThrow(DuplicateEntryError)
+  }))
+
+test('Mark todo as complete', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(
+      new TodoListCreated(todoListId, 'foo'),
+      new TodoAddedToList(todoListId, 'feed Bob')
+    )
+    When(new MarkTodoAsComplete(todoListId, 'feed Bob', 1))
+    Then(new TodoMarkedAsComplete(todoListId, 'feed Bob'))
+  }))
+
+test('Mark todo as complete fails', () =>
+  GWT((Given, When, Then) => {
+    const todoListId = guid()
+
+    Given(new TodoListCreated(todoListId, 'foo'))
+    When(new MarkTodoAsComplete(todoListId, 'feed Bob', 1))
+    expect((): void => {
+      Then(new TodoMarkedAsComplete(todoListId, 'feed Bob'))
+    }).toThrow(NotFoundError)
+  }))

src/domain/todo-list/TodoList.ts

@@ -0,0 +1,63 @@
+import {AggregateRoot} from '../../framework/AggregateRoot'
+import {
+  TodoAddedToList,
+  TodoListCreated,
+  TodoListRenamed,
+  TodoMarkedAsComplete,
+} from './TodoListEvents'
+import {
+  DuplicateEntryError,
+  MissingParameterError,
+  NotFoundError,
+} from '../../framework/Errors'
+
+class Todo {
+  complete: boolean
+  constructor(public readonly name: string) {}
+}
+
+export class TodoList extends AggregateRoot {
+  private name: string
+  private todos: Todo[] = []
+
+  constructor(guid: string, name: string) {
+    super()
+    this.applyChange(new TodoListCreated(guid, name))
+  }
+  applyTodoListCreated(event: TodoListCreated): void {
+    this._id = event.aggregateId
+    this.name = event.name
+  }
+
+  rename(name: string): void {
+    if (!name) throw new MissingParameterError('Must provide a name')
+    this.applyChange(new TodoListRenamed(this._id, name))
+  }
+  applyTodoListRenamed(event: TodoListRenamed): void {
+    this._id = event.aggregateId
+    this.name = event.name
+  }
+
+  addTodo(todoName: string): void {
+    if (this.todos.find((todo) => todo.name === todoName)) {
+      throw new DuplicateEntryError(`${todoName} already exists`)
+    }
+    this.applyChange(new TodoAddedToList(this._id, todoName))
+  }
+  applyTodoAddedToList(event: TodoAddedToList): void {
+    this.todos.push(new Todo(event.todoName))
+  }
+
+  markTodoAsComplete(todoName: string): void {
+    if (!this.todos.find((todo) => todo.name === todoName)) {
+      throw new NotFoundError(`${todoName} not found`)
+    }
+    this.applyChange(new TodoMarkedAsComplete(this._id, todoName))
+  }
+  applyTodoMarkedAsComplete(event: TodoMarkedAsComplete): void {
+    const matchedTodo = this.todos.find(
+      (todo: Todo) => todo.name === event.todoName
+    )
+    matchedTodo.complete = true
+  }
+}

src/domain/todo-list/TodoListCommandHandlers.ts

@@ -0,0 +1,35 @@
+import {IRepository} from '../../framework/Repository'
+import {TodoList} from './TodoList'
+import {
+  AddTodoToList,
+  CreateTodoList,
+  MarkTodoAsComplete,
+  RenameTodoList,
+} from './TodoListCommands'
+
+export class TodoListCommandHandlers {
+  constructor(private _repository: IRepository<TodoList>) {}
+
+  handleCreateTodoList(command: CreateTodoList): void {
+    const todoList = new TodoList(command.aggregateId, command.name)
+    this._repository.save(todoList, -1)
+  }
+
+  handleRenameTodoList(command: RenameTodoList): void {
+    const todoList = this._repository.getById(command.aggregateId)
+    todoList.rename(command.name)
+    this._repository.save(todoList, command.expectedAggregateVersion)
+  }
+
+  handleAddTodoToList(command: AddTodoToList): void {
+    const todoList = this._repository.getById(command.aggregateId)
+    todoList.addTodo(command.todoName)
+    this._repository.save(todoList, command.expectedAggregateVersion)
+  }
+
+  handleMarkTodoAsComplete(command: MarkTodoAsComplete): void {
+    const todoList = this._repository.getById(command.aggregateId)
+    todoList.markTodoAsComplete(command.todoName)
+    this._repository.save(todoList, command.expectedAggregateVersion)
+  }
+}

src/domain/todo-list/TodoListCommands.ts

@@ -0,0 +1,40 @@
+import {Command} from '../../framework/Command'
+
+export class CreateTodoList extends Command {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly name: string
+  ) {
+    super(-1)
+  }
+}
+
+export class AddTodoToList extends Command {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly todoName: string,
+    public readonly expectedAggregateVersion: number
+  ) {
+    super(expectedAggregateVersion)
+  }
+}
+
+export class MarkTodoAsComplete extends Command {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly todoName: string,
+    public readonly expectedAggregateVersion: number
+  ) {
+    super(expectedAggregateVersion)
+  }
+}
+
+export class RenameTodoList extends Command {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly name: string,
+    public readonly expectedAggregateVersion: number
+  ) {
+    super(expectedAggregateVersion)
+  }
+}

src/domain/todo-list/TodoListEvents.ts

@@ -0,0 +1,37 @@
+import {Event} from '../../framework/Event'
+
+export class TodoListCreated extends Event {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly name: string
+  ) {
+    super(aggregateId)
+  }
+}
+
+export class TodoAddedToList extends Event {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly todoName: string
+  ) {
+    super(aggregateId)
+  }
+}
+
+export class TodoMarkedAsComplete extends Event {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly todoName: string
+  ) {
+    super(aggregateId)
+  }
+}
+
+export class TodoListRenamed extends Event {
+  constructor(
+    public readonly aggregateId: string,
+    public readonly name: string
+  ) {
+    super(aggregateId)
+  }
+}