CQRS & Event Handlers

export class AuthRegisterCommand implements ICommand {
  constructor(public readonly input: IUserRegistrationInput) {}
}

@CommandHandler(AuthRegisterCommand)
export class AuthRegisterHandler implements ICommandHandler<AuthRegisterCommand> {
  constructor(private readonly authService: AuthService) {}

  async execute(command: AuthRegisterCommand): Promise<IUser> {
    return this.authService.register(command.input);
  }
}

@Controller("/auth")
export class AuthController {
  constructor(private readonly commandBus: CommandBus) {}

  @Post("register")
  async register(@Body() input: RegisterUserDTO) {
    return this.commandBus.execute(new AuthRegisterCommand(input));
  }
}

// Query
export class GetEmployeeQuery implements IQuery {
  constructor(public readonly id: string) {}
}

// Handler
@QueryHandler(GetEmployeeQuery)
export class GetEmployeeHandler implements IQueryHandler<GetEmployeeQuery> {
  async execute(query: GetEmployeeQuery): Promise<IEmployee> {
    return this.employeeService.findOneByIdString(query.id);
  }
}

// Event
export class EmployeeCreatedEvent {
  constructor(public readonly employee: IEmployee) {}
}

// Event Handler
@EventsHandler(EmployeeCreatedEvent)
export class EmployeeCreatedHandler implements IEventHandler<EmployeeCreatedEvent> {
  handle(event: EmployeeCreatedEvent) {
    // Send welcome email, update analytics, etc.
  }
}