feat(backend): add the album use cases

Create, update, delete and list albums, plus adding and removing their tracks, mirroring the playlist handlers. Only tracks the user uploaded can go into an album, and removing one renumbers the rest so the tracklist stays 1..n.
2026-07-20 20:10:45 +02:00
parent 8e561f5b2a
commit 712f130e1d
10 changed files with 518 additions and 0 deletions
@@ -0,0 +1,82 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+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.UserAlbums
+                .AsNoTracking()
+                .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
+            if (album is null)
+            {
+                logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
+                return Error.NotFound();
+            }
+
+            if (album.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of album {AlbumId}", request.UserId, request.AlbumId);
+                return Error.Unauthorized();
+            }
+
+            var track = await database.LocalTracks
+                .AsNoTracking()
+                .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (track is null)
+            {
+                logger.LogInformation("Local track {TrackId} not found", request.TrackId);
+                return Error.NotFound(description: "Only tracks you uploaded can be added to an album.");
+            }
+
+            if (track.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} does not own track {TrackId}", request.UserId, request.TrackId);
+                return Error.Unauthorized();
+            }
+
+            var alreadyAdded = await database.AlbumHasTracks
+                .AsNoTracking()
+                .AnyAsync(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.TrackId == request.TrackId, cancellationToken);
+            if (alreadyAdded)
+            {
+                logger.LogInformation("Track {TrackId} already in album {AlbumId}", request.TrackId, request.AlbumId);
+                return Error.Conflict(description: "Track is already in the album.");
+            }
+
+            var albumTracksQuery = database.AlbumHasTracks
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId);
+
+            var hasTracks = await albumTracksQuery.AnyAsync(cancellationToken);
+            var nextTrackNumber = hasTracks
+                ? await albumTracksQuery.MaxAsync(albumTrack => albumTrack.TrackNumber, cancellationToken) + 1
+                : 1;
+
+            await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
+            {
+                AlbumId = request.AlbumId,
+                TrackId = request.TrackId,
+                TrackNumber = nextTrackNumber
+            }, cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Added track {TrackId} to album {AlbumId} as number {TrackNumber}",
+                request.TrackId, request.AlbumId, nextTrackNumber);
+
+            return new Success();
+        }
+    }
+}