AddToDoItemHandler.cs

using NimblePros.SampleToDo.Core.ProjectAggregate;
using NimblePros.SampleToDo.Core.ProjectAggregate.Specifications;

namespace NimblePros.SampleToDo.UseCases.Projects.Commands.AddToDoItem;

public class AddToDoItemHandler : ICommandHandler<AddToDoItemCommand, Result<ToDoItemId>>
{
  private readonly IRepository<Project> _repository;

  public AddToDoItemHandler(IRepository<Project> repository)
  {
    _repository = repository;
  }

  public async ValueTask<Result<ToDoItemId>> Handle(AddToDoItemCommand request,
    CancellationToken cancellationToken)
  {
    var spec = new ProjectByIdWithItemsSpec(request.ProjectId);
    var entity = await _repository.FirstOrDefaultAsync(spec, cancellationToken);
    if (entity == null)
    {
      return Result.NotFound();
    }

    var newItem = new ToDoItem(title: request.Title!, description: request.Description!);

    if (request.ContributorId.HasValue)
    {
      newItem.AddContributor(request.ContributorId.Value);
    }
    entity.AddItem(newItem);
    await _repository.UpdateAsync(entity);

    return Result.Success(newItem.Id);
  }
}