backend: expose track count and duration on playlist responses

backend/Core/Musify.Application/PlayLists/GetPlayListById.cs

@@ -21,6 +21,8 @@ namespace Musify.Application.PlayLists
                 .Select(p => new
                 {
                     PlayList = p,
+                    TrackCount = p.PlayListTracks.Count,
+                    DurationSeconds = p.PlayListTracks.Sum(plt => (double?)plt.Track.DurationSeconds) ?? 0,
                     CoverTrackIds = p.PlayListTracks
                         .OrderBy(plt => plt.Position)
                         .Take(PlayListApplicationResponse.CoverTrackCount)
@@ -36,7 +38,7 @@ namespace Musify.Application.PlayLists
                 && entry.PlayList.UserId != request.RequestingUserId)
                 return Error.NotFound();
 
-            return PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds);
+            return PlayListApplicationResponse.FromEntity(entry.PlayList, entry.TrackCount, entry.DurationSeconds, entry.CoverTrackIds);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/GetPlayLists.cs

@@ -25,6 +25,8 @@ namespace Musify.Application.PlayLists
                 .Select(p => new
                 {
                     PlayList = p,
+                    TrackCount = p.PlayListTracks.Count,
+                    DurationSeconds = p.PlayListTracks.Sum(plt => (double?)plt.Track.DurationSeconds) ?? 0,
                     CoverTrackIds = p.PlayListTracks
                         .OrderBy(plt => plt.Position)
                         .Take(PlayListApplicationResponse.CoverTrackCount)
@@ -34,7 +36,7 @@ namespace Musify.Application.PlayLists
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
             var pagedPlayLists = new StaticPagedList<PlayListApplicationResponse>(
-                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds)),
+                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.TrackCount, entry.DurationSeconds, entry.CoverTrackIds)),
                 pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
 
             return PaginatedResponse<PlayListApplicationResponse>.FromPagedList(pagedPlayLists);

backend/Core/Musify.Application/PlayLists/GetPlayListsByUserId.cs

@@ -46,6 +46,8 @@ namespace Musify.Application.PlayLists
                 .Select(p => new
                 {
                     PlayList = p,
+                    TrackCount = p.PlayListTracks.Count,
+                    DurationSeconds = p.PlayListTracks.Sum(plt => (double?)plt.Track.DurationSeconds) ?? 0,
                     CoverTrackIds = p.PlayListTracks
                         .OrderBy(plt => plt.Position)
                         .Take(PlayListApplicationResponse.CoverTrackCount)
@@ -55,7 +57,7 @@ namespace Musify.Application.PlayLists
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
             var pagedPlayLists = new StaticPagedList<PlayListApplicationResponse>(
-                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds)),
+                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.TrackCount, entry.DurationSeconds, entry.CoverTrackIds)),
                 pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
 
             return PaginatedResponse<PlayListApplicationResponse>.FromPagedList(pagedPlayLists);

backend/Core/Musify.Application/PlayLists/Responses/PlayListApplicationResponse.cs

@@ -14,6 +14,8 @@ namespace Musify.Application.PlayLists.Responses
         string? LargeImageKeyName,
         [property: JsonConverter(typeof(LongAsStringConverter))] long OwnerUserId,
         PlaylistVisibility Visibility,
+        int TrackCount,
+        double DurationSeconds,
         DateTime CreatedAt,
         DateTime UpdatedAt,
         IReadOnlyList<Guid> CoverTrackIds)
@@ -22,6 +24,8 @@ namespace Musify.Application.PlayLists.Responses
 
         public static PlayListApplicationResponse FromEntity(
             PlayList playList,
+            int trackCount = 0,
+            double durationSeconds = 0,
             IReadOnlyList<Guid>? coverTrackIds = null)
         {
             return new PlayListApplicationResponse(
@@ -33,6 +37,8 @@ namespace Musify.Application.PlayLists.Responses
                 playList.Pictures?.LargeName,
                 playList.UserId,
                 playList.Visibility,
+                trackCount,
+                durationSeconds,
                 playList.CreatedAt,
                 playList.UpdatedAt,
                 coverTrackIds ?? []);

backend/Core/Musify.Application/PlayLists/UpdatePlayList.cs

@@ -112,7 +112,22 @@ namespace Musify.Application.PlayLists
                 .ToListAsync(cancellationToken);
 
             logger.LogInformation("Updated playlist {PlayListId}", playListEntity.Id);
-            return PlayListApplicationResponse.FromEntity(playListEntity, coverTrackIds);
+            var totals = await database.PlayListHasTracks
+                .AsNoTracking()
+                .Where(plt => plt.PlayListId == playListEntity.Id)
+                .GroupBy(plt => plt.PlayListId)
+                .Select(group => new
+                {
+                    TrackCount = group.Count(),
+                    DurationSeconds = group.Sum(plt => plt.Track.DurationSeconds)
+                })
+                .SingleOrDefaultAsync(cancellationToken);
+
+            return PlayListApplicationResponse.FromEntity(
+                playListEntity,
+                totals?.TrackCount ?? 0,
+                totals?.DurationSeconds ?? 0,
+                coverTrackIds);
         }
 
         private async Task<ErrorOr<Success>> PublishUpdatePlayListPictureSourceEventAsync(