Musify/backend/Core/Musify.Application/Tracks/CreateTrack.cs

using ErrorOr;
using Mediator;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Musify.Application.Configuration;
using Musify.Application.Contracts;
using Musify.Application.Events;
using Musify.Application.Services;
using Musify.Application.Shared;
using Musify.Application.Tracks.Responses;
using Musify.Domain.Entities;
using Musify.Domain.ValueObjects;

namespace Musify.Application.Tracks
{
    public record CreateTrackCommand(
        long UserId,
        string Title,
        Guid PictureIntentId,
        Guid AudioIntentId,
        IReadOnlyCollection<Genre> Tags,
        bool IsExplicit = false)
        : ICommand<ErrorOr<TrackApplicationResponse>>;

    public class CreateTrackCommandHandler(
        IDatabase database,
        IEventBus eventBus,
        UploadIntentValidator uploadIntentValidator,
        ILogger<CreateTrackCommandHandler> logger,
        TrackConfiguration trackConfiguration)
        : ICommandHandler<CreateTrackCommand, ErrorOr<TrackApplicationResponse>>
    {
        public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(CreateTrackCommand request, CancellationToken cancellationToken)
        {
            var user = await database.Users
                .SingleOrDefaultAsync(u => u.Id == request.UserId, cancellationToken);
            if (user == null)
            {
                logger.LogWarning("User {UserId} not found", request.UserId);
                return Error.NotFound(description: $"User {request.UserId} not found");
            }

            var distinctTags = request.Tags.Distinct().ToList();

            if (request.PictureIntentId == request.AudioIntentId)
                return Error.Validation(description: "Picture and audio must use different upload intents.");

            var pictureValidation = await uploadIntentValidator.ValidateAndLoadAsync(
                request.PictureIntentId, request.UserId, UploadIntentPurpose.TrackPicture, cancellationToken);
            if (pictureValidation.IsError)
                return pictureValidation.Errors;

            var audioValidation = await uploadIntentValidator.ValidateAndLoadAsync(
                request.AudioIntentId, request.UserId, UploadIntentPurpose.TrackAudio, cancellationToken);
            if (audioValidation.IsError)
                return audioValidation.Errors;

            var pictureIntent = pictureValidation.Value;
            var audioIntent = audioValidation.Value;

            var finalPictureKey = trackConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
            var finalAudioKey = trackConfiguration.Routes.BuildOriginalAudioPath(request.UserId, audioIntent.ObjectName);
            var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());

            var trackEntity = new Track
            {
                Title = request.Title.Trim(),
                NormalizedTitle = TextNormalizer.Normalize(request.Title),
                OwnerUserId = user.Id,
                Owner = user,
                IsExplicit = request.IsExplicit,
                Pictures = new TrackPictures
                {
                    OriginalName = pictureIntent.ObjectName,
                    SmallName = trackConfiguration.Routes.PresetSmallPicture,
                    MediumName = trackConfiguration.Routes.PresetMediumPicture,
                    LargeName = trackConfiguration.Routes.PresetLargePicture,
                    ProcessingStatus = ProcessingStatus.Pending
                },
                Audio = new TrackAudio
                {
                    OriginalName = audioIntent.ObjectName,
                    TranscodeStatus = ProcessingStatus.Pending
                }
            };

            trackEntity.Tags = distinctTags
                .Select(tag => new TrackTag { TrackId = trackEntity.Id, Tag = tag })
                .ToList();

            await database.Tracks.AddAsync(trackEntity, cancellationToken);

            var sizes = trackConfiguration.PicturesSizes.ToImageSizes(trackConfiguration.Routes);
            await eventBus.PublishAsync(
                new CreateTrackResourcesEvent(
                    trackEntity.Id,
                    pictureIntent.Id,
                    audioIntent.Id,
                    pictureIntent.Bucket,
                    pictureIntent.Key,
                    finalPictureKey,
                    audioIntent.Key,
                    finalAudioKey,
                    audioProcessedFolderKey,
                    sizes),
                cancellationToken);

            await database.SaveChangesAsync(cancellationToken);

            return TrackApplicationResponse.FromEntity(trackEntity, listensCount: 0);
        }
    }
}