backend/Musify.Api/DataTransferObjects/PlayLists/AddYouTubeTrackRequest.cs

@@ -0,0 +1,8 @@
+namespace Musify.Api.DataTransferObjects.PlayLists;
+
+public record AddYouTubeTrackRequest(
+    string VideoId,
+    string Title,
+    string Artist,
+    int DurationSeconds,
+    string ThumbnailUrl);

backend/Musify.Api/Endpoints/PlayListEndpoints.cs

@@ -93,6 +93,17 @@ public static class PlayListEndpoints
             .Produces(StatusCodes.Status404NotFound)
             .Produces(StatusCodes.Status409Conflict);
 
+        group.MapPost("/{playlistId}/youtube-tracks", AddYouTubeTrackToPlayList)
+            .WithName("AddYouTubeTrackToPlayList")
+            .WithSummary("Add A YouTube Track To A PlayList, Downloading It In The Background If Needed.")
+            .AddEndpointFilter<ValidationFilter<AddYouTubeTrackRequest>>()
+            .RequireAuthorization()
+            .Produces<TrackApplicationResponse>(StatusCodes.Status201Created)
+            .ProducesValidationProblem()
+            .Produces(StatusCodes.Status401Unauthorized)
+            .Produces(StatusCodes.Status404NotFound)
+            .Produces(StatusCodes.Status409Conflict);
+
         group.MapDelete("/{playlistId}/tracks/{trackId}", RemoveTrackFromPlayList)
             .WithName("RemoveTrackFromPlayList")
             .WithSummary("Remove A Track From A PlayList.")
@@ -232,6 +243,27 @@ public static class PlayListEndpoints
         return result.ToHttpResult();
     }
 
+    private static async Task<IResult> AddYouTubeTrackToPlayList(
+        IMediator mediator,
+        CurrentUser currentUser,
+        Guid playlistId,
+        AddYouTubeTrackRequest request,
+        CancellationToken cancellationToken)
+    {
+        var result = await mediator.Send(
+            new AddYouTubeTrackToPlayListCommand(
+                currentUser.RequiredId,
+                playlistId,
+                request.VideoId,
+                request.Title,
+                request.Artist,
+                request.DurationSeconds,
+                request.ThumbnailUrl),
+            cancellationToken);
+
+        return result.ToCreatedResult(track => $"/tracks/{track.Id}");
+    }
+
     private static async Task<IResult> RemoveTrackFromPlayList(
         IMediator mediator,
         CurrentUser currentUser,

backend/Musify.Api/Validators/PlayLists/AddYouTubeTrackRequestValidator.cs

@@ -0,0 +1,29 @@
+using FluentValidation;
+using Musify.Api.DataTransferObjects.PlayLists;
+
+namespace Musify.Api.Validators.PlayLists;
+
+public sealed class AddYouTubeTrackRequestValidator : AbstractValidator<AddYouTubeTrackRequest>
+{
+    public AddYouTubeTrackRequestValidator()
+    {
+        RuleFor(x => x.VideoId)
+            .NotEmpty()
+            .Matches("^[A-Za-z0-9_-]{11}$");
+
+        RuleFor(x => x.Title)
+            .NotEmpty()
+            .MaximumLength(200);
+
+        RuleFor(x => x.Artist)
+            .MaximumLength(400);
+
+        RuleFor(x => x.DurationSeconds)
+            .GreaterThan(0);
+
+        RuleFor(x => x.ThumbnailUrl)
+            .NotEmpty()
+            .Must(url => Uri.TryCreate(url, UriKind.Absolute, out var uri) && uri.Scheme == Uri.UriSchemeHttps)
+            .WithMessage("ThumbnailUrl must be an absolute https URL.");
+    }
+}

backend/Musify.Application/Events/DownloadYouTubeTrackEvent.cs

@@ -0,0 +1,14 @@
+using Musify.Application.Shared;
+
+namespace Musify.Application.Events
+{
+    public record DownloadYouTubeTrackEvent(
+        Guid TrackId,
+        string VideoId,
+        string ThumbnailUrl,
+        string Bucket,
+        string AudioProcessedFolderKey,
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
+}

backend/Musify.Application/PlayLists/AddYouTubeTrackToPlayList.cs

@@ -0,0 +1,170 @@
+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.Shared;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.PlayLists
+{
+    public record AddYouTubeTrackToPlayListCommand(
+        long UserId,
+        Guid PlayListId,
+        string VideoId,
+        string Title,
+        string Artist,
+        int DurationSeconds,
+        string ThumbnailUrl)
+        : ICommand<ErrorOr<TrackApplicationResponse>>;
+
+    public class AddYouTubeTrackToPlayListCommandHandler(
+        IDatabase database,
+        IEventBus eventBus,
+        ApplicationStorageConfiguration storageConfiguration,
+        TrackConfiguration trackConfiguration,
+        ILogger<AddYouTubeTrackToPlayListCommandHandler> logger)
+        : ICommandHandler<AddYouTubeTrackToPlayListCommand, ErrorOr<TrackApplicationResponse>>
+    {
+        public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(AddYouTubeTrackToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var playList = await database.PlayLists.AsNoTracking()
+                .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
+            if (playList is null)
+            {
+                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
+
+            if (playList.UserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
+                return Error.Unauthorized();
+            }
+
+            var trackResult = await GetOrCreateTrackAsync(request, cancellationToken);
+            if (trackResult.IsError)
+                return trackResult.Errors;
+
+            var track = trackResult.Value;
+
+            var alreadyAdded = await database.PlayListHasTracks.AsNoTracking()
+                .AnyAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == track.Id, cancellationToken);
+            if (alreadyAdded)
+            {
+                logger.LogInformation("Track {TrackId} already in playlist {PlayListId}", track.Id, request.PlayListId);
+                return Error.Conflict(description: "Track is already in the playlist.");
+            }
+
+            var nextPosition = await database.PlayListHasTracks
+                .Where(plt => plt.PlayListId == request.PlayListId)
+                .Select(plt => (int?)plt.Position)
+                .MaxAsync(cancellationToken) + 1 ?? 0;
+
+            await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
+            {
+                PlayListId = request.PlayListId,
+                TrackId = track.Id,
+                Position = nextPosition
+            }, cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Added YouTube track {VideoId} ({TrackId}) to playlist {PlayListId} at position {Position}",
+                request.VideoId, track.Id, request.PlayListId, nextPosition);
+
+            var listensCount = await database.ListeningHistories.AsNoTracking()
+                .CountAsync(lh => lh.TrackId == track.Id, cancellationToken);
+
+            return TrackApplicationResponse.FromEntity(track, listensCount);
+        }
+
+        private async Task<ErrorOr<Track>> GetOrCreateTrackAsync(AddYouTubeTrackToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var track = await database.Tracks
+                .SingleOrDefaultAsync(t => t.Source == TrackSource.YouTube && t.ExternalId == request.VideoId, cancellationToken);
+
+            if (track is not null)
+            {
+                if (track.AudioTranscodeProcessingStatus == ProcessingStatus.Failed)
+                {
+                    track.AudioTranscodeProcessingStatus = ProcessingStatus.Pending;
+                    track.PicturesProcessingStatus = ProcessingStatus.Pending;
+                    track.LifeCycleStatus = LifeCycleStatus.Active;
+                    track.RetryCount += 1;
+                    track.LastRetryAt = DateTime.UtcNow;
+                    await PublishDownloadEventAsync(track.Id, request, cancellationToken);
+                    await database.SaveChangesAsync(cancellationToken);
+                    logger.LogInformation("Re-queued failed YouTube track {VideoId} for download", request.VideoId);
+                }
+                return track;
+            }
+
+            var title = Truncate(request.Title, 50);
+            track = new Track
+            {
+                Title = title,
+                NormalizedTitle = title.ToUpperInvariant(),
+                Artist = Truncate(request.Artist, 200),
+                Source = TrackSource.YouTube,
+                ExternalId = request.VideoId,
+                Duration = request.DurationSeconds,
+                OriginalPictureName = string.Empty,
+                OriginalAudioName = string.Empty,
+                SmallPictureName = trackConfiguration.Routes.PresetSmallPicture,
+                MediumPictureName = trackConfiguration.Routes.PresetMediumPicture,
+                LargePictureName = trackConfiguration.Routes.PresetLargePicture,
+                PicturesProcessingStatus = ProcessingStatus.Pending,
+                AudioTranscodeProcessingStatus = ProcessingStatus.Pending
+            };
+
+            await database.Tracks.AddAsync(track, cancellationToken);
+            await PublishDownloadEventAsync(track.Id, request, cancellationToken);
+
+            try
+            {
+                await database.SaveChangesAsync(cancellationToken);
+                logger.LogInformation("Created YouTube track {VideoId} ({TrackId}) and queued its download", request.VideoId, track.Id);
+                return track;
+            }
+            catch (DbUpdateException)
+            {
+                logger.LogInformation("YouTube track {VideoId} was created concurrently", request.VideoId);
+                return Error.Conflict(description: "The track was just created by another request. Retry the operation.");
+            }
+        }
+
+        private async Task PublishDownloadEventAsync(Guid trackId, AddYouTubeTrackToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
+
+            await eventBus.PublishAsync(
+                new DownloadYouTubeTrackEvent(
+                    trackId,
+                    request.VideoId,
+                    request.ThumbnailUrl,
+                    storageConfiguration.Bucket,
+                    audioProcessedFolderKey,
+                    new ImageSize(
+                        trackConfiguration.Routes.SmallPicturesPath,
+                        trackConfiguration.PicturesSizes.SmallPictureWidth,
+                        trackConfiguration.PicturesSizes.SmallPictureHeight),
+                    new ImageSize(
+                        trackConfiguration.Routes.MediumPicturesPath,
+                        trackConfiguration.PicturesSizes.MediumPictureWidth,
+                        trackConfiguration.PicturesSizes.MediumPictureHeight),
+                    new ImageSize(
+                        trackConfiguration.Routes.LargePicturesPath,
+                        trackConfiguration.PicturesSizes.LargePictureWidth,
+                        trackConfiguration.PicturesSizes.LargePictureHeight)),
+                cancellationToken);
+        }
+
+        private static string Truncate(string value, int maxLength) =>
+            value.Length <= maxLength ? value : value[..maxLength];
+    }
+}

backend/Musify.Infrastructure/MassTransit/Activities/Audio/DownloadYouTubeAudioActivity.cs

@@ -0,0 +1,94 @@
+using MassTransit;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+using Musify.Infrastructure.MassTransit.Arguments;
+using Musify.Infrastructure.MassTransit.Logs;
+
+namespace Musify.Infrastructure.MassTransit.Activities.Audio
+{
+    internal class DownloadYouTubeAudioActivity(
+        IDatabase database,
+        IYouTubeDownloaderService youTubeDownloader,
+        ILogger<DownloadYouTubeAudioActivity> logger)
+        : IActivity<DownloadYouTubeAudioArguments, DownloadYouTubeAudioLog>
+    {
+        public const string ExecuteEndpointName = "download-you-tube-audio";
+
+        public async Task<ExecutionResult> Execute(ExecuteContext<DownloadYouTubeAudioArguments> executeContext)
+        {
+            var destinationPath = executeContext.GetVariable<string>(executeContext.Arguments.DestinationFilePathVariable);
+            ArgumentNullException.ThrowIfNull(destinationPath, nameof(destinationPath));
+
+            Track track;
+            try
+            {
+                var getTrack = await database.Tracks.SingleOrDefaultAsync(t => t.Id == executeContext.Arguments.TrackId, executeContext.CancellationToken);
+                track = getTrack ?? throw new InvalidOperationException($"Track with Id {executeContext.Arguments.TrackId} not found");
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to retrieve track with Id {TrackId} from database", executeContext.Arguments.TrackId);
+                throw;
+            }
+
+            try
+            {
+                var downloadResult = await youTubeDownloader.DownloadAudioAsync(
+                    executeContext.Arguments.VideoId,
+                    destinationPath,
+                    executeContext.CancellationToken);
+
+                if (downloadResult.ExitCode != 0)
+                    throw new InvalidOperationException(
+                        $"yt-dlp failed with exit code {downloadResult.ExitCode}: {downloadResult.StandardError}");
+
+                if (!File.Exists(destinationPath))
+                    throw new InvalidOperationException($"yt-dlp did not produce the expected file {destinationPath}.");
+
+                logger.LogInformation("Downloaded YouTube audio for video {VideoId} to {DestinationPath}",
+                    executeContext.Arguments.VideoId, destinationPath);
+
+                return executeContext.Completed(new DownloadYouTubeAudioLog(
+                    executeContext.Arguments.VideoId,
+                    destinationPath));
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to download YouTube audio for video {VideoId}",
+                    executeContext.Arguments.VideoId);
+
+                try
+                {
+                    track.AudioTranscodeProcessingStatus = ProcessingStatus.Failed;
+                    await database.SaveChangesAsync(executeContext.CancellationToken);
+                }
+                catch (Exception dbException)
+                {
+                    logger.LogError(dbException, "Failed to update ProcessingStatus to Failed for track {TrackId}",
+                        executeContext.Arguments.TrackId);
+                }
+
+                throw;
+            }
+        }
+
+        public Task<CompensationResult> Compensate(CompensateContext<DownloadYouTubeAudioLog> compensateContext)
+        {
+            try
+            {
+                if (File.Exists(compensateContext.Log.DestinationFilePath))
+                    File.Delete(compensateContext.Log.DestinationFilePath);
+                return Task.FromResult(compensateContext.Compensated());
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to compensate downloaded YouTube audio {DestinationFilePath}",
+                    compensateContext.Log.DestinationFilePath);
+                return Task.FromResult(compensateContext.Failed(exception));
+            }
+        }
+    }
+}

backend/Musify.Infrastructure/MassTransit/Activities/Files/DownloadFileFromUrlActivity.cs

@@ -0,0 +1,69 @@
+using MassTransit;
+using Microsoft.Extensions.Logging;
+using Musify.Infrastructure.MassTransit.Arguments;
+using Musify.Infrastructure.MassTransit.Logs;
+
+namespace Musify.Infrastructure.MassTransit.Activities.Files
+{
+    internal class DownloadFileFromUrlActivity(
+        IHttpClientFactory httpClientFactory,
+        ILogger<DownloadFileFromUrlActivity> logger)
+        : IActivity<DownloadFileFromUrlArguments, DownloadFileFromUrlLog>
+    {
+        public const string ExecuteEndpointName = "download-file-from-url";
+
+        public async Task<ExecutionResult> Execute(ExecuteContext<DownloadFileFromUrlArguments> executeContext)
+        {
+            var destinationPath = executeContext.GetVariable<string>(executeContext.Arguments.DestinationFilePathVariable);
+            ArgumentNullException.ThrowIfNull(destinationPath, nameof(destinationPath));
+
+            try
+            {
+                var httpClient = httpClientFactory.CreateClient();
+
+                using var response = await httpClient.GetAsync(
+                    executeContext.Arguments.SourceUrl,
+                    HttpCompletionOption.ResponseHeadersRead,
+                    executeContext.CancellationToken);
+                response.EnsureSuccessStatusCode();
+
+                var destinationDirectory = Path.GetDirectoryName(destinationPath);
+                if (!string.IsNullOrWhiteSpace(destinationDirectory))
+                    Directory.CreateDirectory(destinationDirectory);
+
+                await using (var destinationStream = File.Create(destinationPath))
+                {
+                    await response.Content.CopyToAsync(destinationStream, executeContext.CancellationToken);
+                }
+
+                logger.LogInformation("Downloaded {SourceUrl} to {DestinationPath}",
+                    executeContext.Arguments.SourceUrl, destinationPath);
+
+                return executeContext.Completed(new DownloadFileFromUrlLog(
+                    executeContext.Arguments.SourceUrl,
+                    destinationPath));
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to download file from {SourceUrl}", executeContext.Arguments.SourceUrl);
+                throw;
+            }
+        }
+
+        public Task<CompensationResult> Compensate(CompensateContext<DownloadFileFromUrlLog> compensateContext)
+        {
+            try
+            {
+                if (File.Exists(compensateContext.Log.DestinationFilePath))
+                    File.Delete(compensateContext.Log.DestinationFilePath);
+                return Task.FromResult(compensateContext.Compensated());
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to compensate downloaded file {DestinationFilePath}",
+                    compensateContext.Log.DestinationFilePath);
+                return Task.FromResult(compensateContext.Failed(exception));
+            }
+        }
+    }
+}

backend/Musify.Infrastructure/MassTransit/Arguments/DownloadFileFromUrlArguments.cs

@@ -0,0 +1,6 @@
+namespace Musify.Infrastructure.MassTransit.Arguments
+{
+    public record DownloadFileFromUrlArguments(
+        string SourceUrl,
+        string DestinationFilePathVariable);
+}

backend/Musify.Infrastructure/MassTransit/Arguments/DownloadYouTubeAudioArguments.cs

@@ -0,0 +1,7 @@
+namespace Musify.Infrastructure.MassTransit.Arguments
+{
+    public record DownloadYouTubeAudioArguments(
+        Guid TrackId,
+        string VideoId,
+        string DestinationFilePathVariable);
+}

backend/Musify.Infrastructure/MassTransit/Consumers/DownloadYouTubeTrackConsumer.cs

@@ -0,0 +1,26 @@
+using MassTransit;
+using Musify.Application.Events;
+using Musify.Infrastructure.MassTransit.RoutingSlip.Builders;
+
+namespace Musify.Infrastructure.MassTransit.Consumers
+{
+    public class DownloadYouTubeTrackConsumer(
+        IBus bus,
+        YouTubeTrackRoutingSlipBuilder routingSlipBuilder)
+        : IConsumer<DownloadYouTubeTrackEvent>
+    {
+        public async Task Consume(ConsumeContext<DownloadYouTubeTrackEvent> consumeContext)
+        {
+            var audioRoutingSlip = routingSlipBuilder
+                .BuildAudioWorkflow(consumeContext.Message, consumeContext.CorrelationId)
+                .Build();
+
+            var pictureRoutingSlip = routingSlipBuilder
+                .BuildPictureWorkflow(consumeContext.Message, consumeContext.CorrelationId)
+                .Build();
+
+            await bus.Execute(audioRoutingSlip);
+            await bus.Execute(pictureRoutingSlip);
+        }
+    }
+}

backend/Musify.Infrastructure/MassTransit/DependencyInjection/MassTransitDependencyInjection.Registration.cs

@@ -23,6 +23,7 @@ namespace Musify.Infrastructure.MassTransit
             services.AddScoped<DeletePlayListRoutingSlipBuilder>();
             services.AddScoped<CreateTrackRoutingSlipBuilder>();
             services.AddScoped<PlayListPictureSourceRoutingSlipBuilder>();
+            services.AddScoped<YouTubeTrackRoutingSlipBuilder>();
         }
 
         static void RegisterConsumersAndActivities(IBusRegistrationConfigurator options)
@@ -39,6 +40,7 @@ namespace Musify.Infrastructure.MassTransit
             options.AddConsumer<ProcessingSlipFaultConsumer>();
             options.AddConsumer<TrackProcessingFailedConsumer>();
             options.AddConsumer<PlayListProcessingFailedConsumer>();
+            options.AddConsumer<DownloadYouTubeTrackConsumer>();
 
             options.AddExecuteActivity<RemoveFileFromBucketActivity, RemoveFileFromBucketArguments>();
             options.AddExecuteActivity<GenerateAudioWorkflowPathsActivity, GenerateAudioWorkflowPathsArguments>();
@@ -62,6 +64,8 @@ namespace Musify.Infrastructure.MassTransit
             options.AddActivity<UploadFileToBucketActivity, UploadFileToBucketArguments, UploadFileToBucketLog>();
             options.AddActivity<CopyFileInBucketActivity, CopyFileInBucketArguments, CopyFileInBucketLog>();
             options.AddActivity<ConsumeUploadIntentsActivity, ConsumeUploadIntentsArguments, ConsumeUploadIntentsLog>();
+            options.AddActivity<DownloadYouTubeAudioActivity, DownloadYouTubeAudioArguments, DownloadYouTubeAudioLog>();
+            options.AddActivity<DownloadFileFromUrlActivity, DownloadFileFromUrlArguments, DownloadFileFromUrlLog>();
         }
     }
 }

backend/Musify.Infrastructure/MassTransit/Logs/DownloadFileFromUrlLog.cs

@@ -0,0 +1,6 @@
+namespace Musify.Infrastructure.MassTransit.Logs
+{
+    public record DownloadFileFromUrlLog(
+        string SourceUrl,
+        string DestinationFilePath);
+}

backend/Musify.Infrastructure/MassTransit/Logs/DownloadYouTubeAudioLog.cs

@@ -0,0 +1,6 @@
+namespace Musify.Infrastructure.MassTransit.Logs
+{
+    public record DownloadYouTubeAudioLog(
+        string VideoId,
+        string DestinationFilePath);
+}

backend/Musify.Infrastructure/MassTransit/RoutingSlip/ActivityNames.cs

@@ -13,6 +13,8 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip
         internal const string GeneratePictureWorkflowPaths = "GeneratePictureWorkflowPaths";
 
         internal const string DownloadFile = "DownloadFile";
+        internal const string DownloadYouTubeAudio = "DownloadYouTubeAudio";
+        internal const string DownloadThumbnail = "DownloadThumbnail";
 
         internal const string TranscodeAudio = "TranscodeAudio";
 

backend/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/YouTubeTrackRoutingSlipBuilder.cs

@@ -0,0 +1,166 @@
+using MassTransit;
+using MassTransit.Courier.Contracts;
+using Musify.Application.Events;
+using Musify.Application.Shared;
+using Musify.Infrastructure.Configuration;
+using Musify.Infrastructure.MassTransit.Activities.Audio;
+using Musify.Infrastructure.MassTransit.Activities.Files;
+using Musify.Infrastructure.MassTransit.Activities.Pictures;
+using Musify.Infrastructure.MassTransit.Arguments;
+using Musify.Infrastructure.MassTransit.Consumers;
+
+namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
+{
+    public class YouTubeTrackRoutingSlipBuilder(WorkerConfiguration workerConfiguration)
+    {
+        public RoutingSlipBuilder BuildAudioWorkflow(DownloadYouTubeTrackEvent message, Guid? correlationId)
+        {
+            var routingSlipBuilder = new RoutingSlipBuilder(NewId.NextGuid());
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.CorrelationId, correlationId ?? Guid.Empty);
+
+            routingSlipBuilder.AddSubscription(
+                EndpointHelper.BuildConsumerUri(RoutingSlipCleanUpConsumer.QueueName),
+                RoutingSlipEvents.Completed | RoutingSlipEvents.Faulted);
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.GenerateAudioWorkflowPaths,
+                EndpointHelper.BuildExecuteActivityUri(GenerateAudioWorkflowPathsActivity.ExecuteEndpointName),
+                new GenerateAudioWorkflowPathsArguments(
+                    message.TrackId,
+                    workerConfiguration.Routes.TemporaryFilesDirectory,
+                    $"{message.VideoId}.m4a"));
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.DownloadYouTubeAudio,
+                EndpointHelper.BuildExecuteActivityUri(DownloadYouTubeAudioActivity.ExecuteEndpointName),
+                new DownloadYouTubeAudioArguments(
+                    message.TrackId,
+                    message.VideoId,
+                    RoutingSlipVariableNames.Audio.SourceFilePath));
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.TranscodeAudio,
+                EndpointHelper.BuildExecuteActivityUri(TranscodeAudioActivity.ExecuteEndpointName),
+                new TranscodeAudioArguments(
+                    message.TrackId,
+                    RoutingSlipVariableNames.Audio.SourceFilePath,
+                    RoutingSlipVariableNames.Workflow.TemporalDirectory));
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.TransferFiles,
+                EndpointHelper.BuildExecuteActivityUri(TransferFilesToBucketActivity.ExecuteEndpointName),
+                new TransferFilesToBucketArguments(
+                    message.Bucket,
+                    RoutingSlipVariableNames.Audio.TranscodedDirectory,
+                    message.AudioProcessedFolderKey));
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.UpdateTrackAudio,
+                EndpointHelper.BuildExecuteActivityUri(UpdateTrackAudioActivity.ExecuteEndpointName),
+                new UpdateTrackAudioArguments(
+                    message.TrackId,
+                    message.AudioProcessedFolderKey,
+                    RoutingSlipVariableNames.Audio.DurationSeconds));
+
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.SubjectId, message.TrackId);
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.ProcessKind, RoutingSlipVariableNames.ProcessKinds.TrackAudio);
+            routingSlipBuilder.AddSubscription(
+                EndpointHelper.BuildConsumerUri(ProcessingSlipFaultConsumer.QueueName),
+                RoutingSlipEvents.Faulted);
+
+            return routingSlipBuilder;
+        }
+
+        public RoutingSlipBuilder BuildPictureWorkflow(DownloadYouTubeTrackEvent message, Guid? correlationId)
+        {
+            var routingSlipBuilder = new RoutingSlipBuilder(NewId.NextGuid());
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.CorrelationId, correlationId ?? Guid.Empty);
+
+            routingSlipBuilder.AddSubscription(
+                EndpointHelper.BuildConsumerUri(RoutingSlipCleanUpConsumer.QueueName),
+                RoutingSlipEvents.Completed | RoutingSlipEvents.Faulted);
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.GeneratePictureWorkflowPaths,
+                EndpointHelper.BuildExecuteActivityUri(GeneratePictureWorkflowPathsActivity.ExecuteEndpointName),
+                new GeneratePictureWorkflowPathsArguments(
+                    workerConfiguration.Routes.TemporaryFilesDirectory,
+                    $"{message.VideoId}.jpg"));
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.DownloadThumbnail,
+                EndpointHelper.BuildExecuteActivityUri(DownloadFileFromUrlActivity.ExecuteEndpointName),
+                new DownloadFileFromUrlArguments(
+                    message.ThumbnailUrl,
+                    RoutingSlipVariableNames.Picture.OriginalFilePath));
+
+            AddResizeActivity(
+                routingSlipBuilder,
+                ActivityNames.ResizeSmall,
+                ActivityNames.UploadSmall,
+                message.Bucket,
+                RoutingSlipVariableNames.Picture.SmallResizedFilePath,
+                message.Small);
+
+            AddResizeActivity(
+                routingSlipBuilder,
+                ActivityNames.ResizeMedium,
+                ActivityNames.UploadMedium,
+                message.Bucket,
+                RoutingSlipVariableNames.Picture.MediumResizedFilePath,
+                message.Medium);
+
+            AddResizeActivity(
+                routingSlipBuilder,
+                ActivityNames.ResizeLarge,
+                ActivityNames.UploadLarge,
+                message.Bucket,
+                RoutingSlipVariableNames.Picture.LargeResizedFilePath,
+                message.Large);
+
+            routingSlipBuilder.AddActivity(
+                ActivityNames.UpdateTrackPicture,
+                EndpointHelper.BuildExecuteActivityUri(UpdateTrackPictureActivity.ExecuteEndpointName),
+                new UpdateTrackPictureArguments(
+                    message.TrackId,
+                    string.Empty,
+                    RoutingSlipVariableNames.Picture.SmallResizedFilePath,
+                    RoutingSlipVariableNames.Picture.MediumResizedFilePath,
+                    RoutingSlipVariableNames.Picture.LargeResizedFilePath));
+
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.SubjectId, message.TrackId);
+            routingSlipBuilder.AddVariable(RoutingSlipVariableNames.Workflow.ProcessKind, RoutingSlipVariableNames.ProcessKinds.TrackPicture);
+            routingSlipBuilder.AddSubscription(
+                EndpointHelper.BuildConsumerUri(ProcessingSlipFaultConsumer.QueueName),
+                RoutingSlipEvents.Faulted);
+
+            return routingSlipBuilder;
+        }
+
+        static void AddResizeActivity(
+            RoutingSlipBuilder routingSlipBuilder,
+            string resizeActivityName,
+            string uploadActivityName,
+            string bucketName,
+            string destinationFilePathVariableName,
+            ImageSize imageSize)
+        {
+            routingSlipBuilder.AddActivity(
+                resizeActivityName,
+                EndpointHelper.BuildExecuteActivityUri(ResizePictureActivity.ExecuteEndpointName),
+                new ResizePictureLocalArguments(
+                    RoutingSlipVariableNames.Picture.OriginalFilePath,
+                    destinationFilePathVariableName,
+                    imageSize.Width,
+                    imageSize.Height));
+
+            routingSlipBuilder.AddActivity(
+                uploadActivityName,
+                EndpointHelper.BuildExecuteActivityUri(UploadFileToBucketActivity.ExecuteEndpointName),
+                new UploadFileToBucketArguments(
+                    destinationFilePathVariableName,
+                    bucketName,
+                    imageSize.SavePath));
+        }
+    }
+}

backend/Musify.Infrastructure/MassTransit/Sagas/TrackProcessingStateMachine.cs

@@ -9,6 +9,7 @@ namespace Musify.Infrastructure.MassTransit.Sagas
         public State Failed { get; private set; } = null!;
 
         public Event<CreateTrackResourcesEvent> ProcessingStarted { get; private set; } = null!;
+        public Event<DownloadYouTubeTrackEvent> YouTubeDownloadStarted { get; private set; } = null!;
         public Event<TrackPictureProcessed> PictureProcessed { get; private set; } = null!;
         public Event<TrackAudioProcessed> AudioProcessed { get; private set; } = null!;
         public Event<TrackPictureProcessingFailed> PictureFailed { get; private set; } = null!;
@@ -19,6 +20,7 @@ namespace Musify.Infrastructure.MassTransit.Sagas
             InstanceState(state => state.CurrentState);
 
             Event(() => ProcessingStarted, config => config.CorrelateById(context => context.Message.TrackId));
+            Event(() => YouTubeDownloadStarted, config => config.CorrelateById(context => context.Message.TrackId));
             Event(() => PictureProcessed, config => config.CorrelateById(context => context.Message.TrackId));
             Event(() => AudioProcessed, config => config.CorrelateById(context => context.Message.TrackId));
             Event(() => PictureFailed, config => config.CorrelateById(context => context.Message.TrackId));
@@ -34,9 +36,20 @@ namespace Musify.Infrastructure.MassTransit.Sagas
                         context.Saga.PictureKey = context.Message.PictureDestinationKey;
                         context.Saga.AudioKey = context.Message.AudioDestinationKey;
                     } )
+                    .TransitionTo(Processing),
+                When(YouTubeDownloadStarted)
+                    .Then(context =>
+                    {
+                        context.Saga.CreatedAt = DateTime.UtcNow;
+                        context.Saga.UpdatedAt = DateTime.UtcNow;
+                        context.Saga.Bucket = context.Message.Bucket;
+                        context.Saga.PictureKey = string.Empty;
+                        context.Saga.AudioKey = string.Empty;
+                    } )
                     .TransitionTo(Processing));
 
             During(Processing,
+                Ignore(YouTubeDownloadStarted),
                 When(PictureProcessed)
                     .Then(context =>
                     {
@@ -72,7 +85,18 @@ namespace Musify.Infrastructure.MassTransit.Sagas
                 Ignore(PictureProcessed),
                 Ignore(AudioProcessed),
                 Ignore(PictureFailed),
-                Ignore(AudioFailed));
+                Ignore(AudioFailed),
+                When(YouTubeDownloadStarted)
+                    .Then(context =>
+                    {
+                        context.Saga.UpdatedAt = DateTime.UtcNow;
+                        context.Saga.PictureProcessed = false;
+                        context.Saga.AudioProcessed = false;
+                        context.Saga.Bucket = context.Message.Bucket;
+                        context.Saga.PictureKey = string.Empty;
+                        context.Saga.AudioKey = string.Empty;
+                    } )
+                    .TransitionTo(Processing));
 
             SetCompletedWhenFinalized();
         }

backend/Musify.Worker/AppSettings.json

@@ -85,6 +85,12 @@
         },
         "TranscodingTimeout": "00:05:00"
     },
+    "YtDlp": {
+        "ExecutableName": "yt-dlp",
+        "Format": "bestaudio",
+        "AdditionalArguments": "",
+        "DownloadTimeout": "00:05:00"
+    },
     "Workers": {
         "Routes": {
             "TemporaryFilesDirectory": "D:\\tempsFilesDev"

backend/Musify.Worker/Program.cs

@@ -14,6 +14,8 @@ services.AddValidatedOptions<PlayListConfiguration>(configuration, PlayListConfi
 services.AddValidatedOptions<TrackConfiguration>(configuration, TrackConfiguration.SectionName);
 services.AddStorageService(configuration);
 services.AddAudioTranscoder(configuration);
+services.AddYouTubeDownloader(configuration);
+services.AddHttpClient();
 services.AddPictureService(configuration);
 services.AddDatabase(configuration);
 services.AddMassTransitConsumers(configuration);