public async Task <Book> AddByISBNAsync(string isbn)
{
//check if an author exists for this ISBN
var authorName = await ISBNService.GetAuthorNameByISBNAsync(isbn);
var author = await AuthorRepository.CreateOrGetByNameAsync(authorName);
var book = await ISBNService.GetByISBNAsync(isbn);
book.SetAuthor(author);
//TODO: this should be represented in a unit of work
await author.AddBookIfNotAlreadyPresentAsync(book);
//commit all the changes
await AuthorRepository.UpdateAuthorAsync(author);
await BookStorage.WriteBookAsync(book);
return(book);
}
