Musify/backend/Core/Musify.Application/Mixes/GetMixesByUserId.cs

using ErrorOr;
using Mediator;
using Microsoft.EntityFrameworkCore;
using Musify.Application.Contracts;
using Musify.Application.Mixes.Responses;

namespace Musify.Application.Mixes
{
    public record GetMixesByUserIdQuery(long UserId)
        : IQuery<ErrorOr<IReadOnlyList<MixApplicationResponse>>>;

    public class GetMixesByUserIdQueryHandler(IDatabase database)
        : IQueryHandler<GetMixesByUserIdQuery, ErrorOr<IReadOnlyList<MixApplicationResponse>>>
    {
        public async ValueTask<ErrorOr<IReadOnlyList<MixApplicationResponse>>> Handle(GetMixesByUserIdQuery request, CancellationToken cancellationToken)
        {
            var mixes = await database.Mixes
                .AsNoTracking()
                .Where(mix => mix.UserId == request.UserId)
                .Include(mix => mix.Items)
                .OrderBy(mix => mix.Position)
                .ToListAsync(cancellationToken);

            var responses = new List<MixApplicationResponse>(mixes.Count);
            foreach (var mix in mixes)
            {
                var orderedItems = mix.Items.OrderBy(item => item.Position).ToList();
                var coverItems = await MixItemMapper.ToResponsesAsync(
                    database, orderedItems.Take(MixApplicationResponse.CoverItemCount).ToList(), cancellationToken);

                responses.Add(new MixApplicationResponse(mix.Id, mix.Title, mix.Subtitle, orderedItems.Count, coverItems));
            }

            return responses;
        }
    }
}