Musify/backend/Core/Musify.Application/Genres/GetAvailableGenres.cs

using Mediator;
using Musify.Application.Genres.Responses;
using Musify.Domain.ValueObjects;

namespace Musify.Application.Genres
{
    public record GetAvailableGenresQuery : IQuery<IReadOnlyList<AvailableGenreResponse>>;

    public class GetAvailableGenresQueryHandler
        : IQueryHandler<GetAvailableGenresQuery, IReadOnlyList<AvailableGenreResponse>>
    {
        public ValueTask<IReadOnlyList<AvailableGenreResponse>> Handle(GetAvailableGenresQuery request, CancellationToken cancellationToken)
        {
            var all = Enum.GetValues<Genre>();

            IReadOnlyList<AvailableGenreResponse> result = all
                .Select(genre => new AvailableGenreResponse(
                    genre,
                    all.Where(other => !GenreCompatibility.AreCompatible(genre, other)).ToList()))
                .ToList();

            return ValueTask.FromResult(result);
        }
    }
}