Separate responsibilities: start-listening command, API-side JSON converters, bulk track endpoints, mix kinds

backend/Core/Musify.Application/Albums/AddTrackToAlbum.cs

@@ -1,58 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-
-namespace Musify.Application.Albums;
-
-public record AddTrackToAlbumCommand(long UserId, Guid AlbumId, Guid TrackId)
-    : ICommand<ErrorOr<Success>>;
-
-public class AddTrackToAlbumCommandHandler(
-    IDatabase database,
-    ILogger<AddTrackToAlbumCommandHandler> logger)
-    : ICommandHandler<AddTrackToAlbumCommand, ErrorOr<Success>>
-{
-    public async ValueTask<ErrorOr<Success>> Handle(AddTrackToAlbumCommand request, CancellationToken cancellationToken)
-    {
-        var album = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
-        if (album.IsError)
-            return album.Errors;
-
-        var track = await database.Tracks.FindOwnedAsync(request.TrackId, request.UserId, cancellationToken);
-        if (track.IsError)
-            return track.Errors;
-
-        var alreadyAdded = await database.AlbumHasTracks
-            .AsNoTracking()
-            .AnyAsync(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.TrackId == request.TrackId, cancellationToken);
-        if (alreadyAdded)
-            return AlreadyInAlbum;
-
-        // Album track numbers are user-visible, so they start at 1.
-        var nextTrackNumber = (await database.AlbumHasTracks
-            .Where(albumTrack => albumTrack.AlbumId == request.AlbumId)
-            .MaxAsync(albumTrack => (int?)albumTrack.TrackNumber, cancellationToken) ?? 0) + 1;
-
-        await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
-        {
-            AlbumId = request.AlbumId,
-            TrackId = request.TrackId,
-            TrackNumber = nextTrackNumber
-        }, cancellationToken);
-
-        var saved = await database.TrySaveChangesAsync(AlreadyInAlbum, cancellationToken);
-        if (saved.IsError)
-            return saved;
-
-        logger.LogInformation("Added track {TrackId} to album {AlbumId} as number {TrackNumber}",
-            request.TrackId, request.AlbumId, nextTrackNumber);
-
-        return Result.Success;
-    }
-
-    private static Error AlreadyInAlbum => AppErrors.Conflict("Album.TrackAlreadyAdded", "Track is already in the album.");
-}

backend/Core/Musify.Application/Albums/AddTracksToAlbum.cs

@@ -0,0 +1,77 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Albums;
+
+/// <summary>Appends your own tracks to an album in the given order, skipping the ones it already has.</summary>
+public record AddTracksToAlbumCommand(long UserId, Guid AlbumId, IReadOnlyList<Guid> TrackIds)
+    : ICommand<ErrorOr<Success>>;
+
+public class AddTracksToAlbumCommandHandler(
+    IDatabase database,
+    ILogger<AddTracksToAlbumCommandHandler> logger)
+    : ICommandHandler<AddTracksToAlbumCommand, ErrorOr<Success>>
+{
+    public async ValueTask<ErrorOr<Success>> Handle(AddTracksToAlbumCommand request, CancellationToken cancellationToken)
+    {
+        var album = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
+        if (album.IsError)
+            return album.Errors;
+
+        var requestedIds = request.TrackIds.Distinct().ToList();
+
+        var tracks = await database.Tracks
+            .AsNoTracking()
+            .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+            .Select(track => new { track.Id, track.OwnerUserId })
+            .ToListAsync(cancellationToken);
+
+        var missing = requestedIds.FirstOrDefault(id => tracks.All(track => track.Id != id));
+        if (missing != Guid.Empty)
+            return AppErrors.NotFound("Track", missing);
+
+        var foreign = tracks.FirstOrDefault(track => track.OwnerUserId != request.UserId);
+        if (foreign != null)
+            return AppErrors.Forbidden("Track", foreign.Id);
+
+        var alreadyInAlbum = await database.AlbumHasTracks
+            .AsNoTracking()
+            .Where(link => link.AlbumId == request.AlbumId && requestedIds.Contains(link.TrackId))
+            .Select(link => link.TrackId)
+            .ToListAsync(cancellationToken);
+
+        var toAdd = requestedIds.Where(id => !alreadyInAlbum.Contains(id)).ToList();
+        if (toAdd.Count == 0)
+            return Result.Success;
+
+        // Album track numbers are user-visible, so they start at 1.
+        var nextTrackNumber = (await database.AlbumHasTracks
+            .Where(link => link.AlbumId == request.AlbumId)
+            .MaxAsync(link => (int?)link.TrackNumber, cancellationToken) ?? 0) + 1;
+
+        foreach (var trackId in toAdd)
+        {
+            await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
+            {
+                AlbumId = request.AlbumId,
+                TrackId = trackId,
+                TrackNumber = nextTrackNumber++
+            }, cancellationToken);
+        }
+
+        var saved = await database.TrySaveChangesAsync(
+            AppErrors.Conflict("Album.ConcurrentChange", "The album changed while adding tracks. Try again."), cancellationToken);
+        if (saved.IsError)
+            return saved;
+
+        logger.LogInformation("Added {Count} tracks to album {AlbumId}", toAdd.Count, request.AlbumId);
+
+        return Result.Success;
+    }
+}

backend/Core/Musify.Application/Albums/Responses/AlbumApplicationResponse.cs

@@ -1,5 +1,3 @@
-using System.Text.Json.Serialization;
-using Musify.Application.Serialization;
 using Musify.Domain.Entities;
 
 namespace Musify.Application.Albums.Responses;
@@ -9,7 +7,7 @@ public record AlbumApplicationResponse(
     string Title,
     string? Description,
     int? ReleaseYear,
-    [property: JsonConverter(typeof(LongAsStringConverter))] long OwnerUserId,
+    long OwnerUserId,
     int TrackCount,
     string? SmallImageKeyName,
     string? MediumImageKeyName,