CliFx/CliFx.Demo/Commands/BookCommand.cs

using System.Threading.Tasks;
using CliFx.Attributes;
using CliFx.Demo.Domain;
using CliFx.Demo.Utils;
using CliFx.Exceptions;
using CliFx.Infrastructure;

namespace CliFx.Demo.Commands;

[Command("book", Description = "Retrieve a book from the library.")]
public class BookCommand : ICommand
{
    private readonly LibraryProvider _libraryProvider;

    [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
    public string Title { get; init; } = "";

    public BookCommand(LibraryProvider libraryProvider)
    {
        _libraryProvider = libraryProvider;
    }

    public ValueTask ExecuteAsync(IConsole console)
    {
        var book = _libraryProvider.TryGetBook(Title);

        if (book is null)
            throw new CommandException("Book not found.", 10);

        console.Output.WriteBook(book);

        return default;
    }
}