Fix 9 design majors: ITrackService interface, IsDescending, ArrayPool base, CliUtils, sort sentinel cleanup, content controller via TrackService, Skip property

DeepDrftWeb.Services/ITrackService.cs

@@ -0,0 +1,15 @@
+using DeepDrftModels.Entities;
+using DeepDrftModels.Models;
+using NetBlocks.Models;
+
+namespace DeepDrftWeb.Services;
+
+public interface ITrackService
+{
+    Task<ResultContainer<TrackEntity?>> GetById(long id);
+    Task<ResultContainer<List<TrackEntity>>> GetAll();
+    Task<ResultContainer<PagedResult<TrackEntity>>> GetPaged(int pageNumber, int pageSize, string? sortColumn, bool sortDescending);
+    Task<ResultContainer<TrackEntity>> Create(TrackEntity newTrack);
+    Task<ResultContainer<TrackEntity>> Update(TrackEntity track);
+    Task<Result> Delete(long id);
+}

DeepDrftWeb.Services/Repositories/TrackRepository.cs

@@ -26,11 +26,18 @@ public class TrackRepository
 
     public async Task<PagedResult<TrackEntity>> GetPage(PagingParameters<TrackEntity> pageParameters)
     {
+        // Two separate queries with no transaction: count and page can be momentarily inconsistent
+        // under concurrent writes. Acceptable — SQLite concurrency is low and the UI is read-only.
+        // If filtering is added, the count query must be updated to apply the same filter.
         var count = await _db.Tracks.CountAsync();
-        
-        var page = await _db.Tracks
-            .OrderBy(pageParameters.OrderBy ?? (t => t.Id))
-            .Skip((pageParameters.Page - 1) * pageParameters.PageSize)
+
+        var orderBy = pageParameters.OrderBy ?? (t => t.Id);
+        var ordered = pageParameters.IsDescending
+            ? _db.Tracks.OrderByDescending(orderBy)
+            : _db.Tracks.OrderBy(orderBy);
+
+        var page = await ordered
+            .Skip(pageParameters.Skip)
             .Take(pageParameters.PageSize)
             .ToListAsync();
         

DeepDrftWeb.Services/TrackService.cs

@@ -6,10 +6,8 @@ using NetBlocks.Models;
 
 namespace DeepDrftWeb.Services;
 
-public class TrackService
+public class TrackService : ITrackService
 {
-    private readonly string _sortLastAscending = Enumerable.Repeat(char.MaxValue, 64).Aggregate(string.Empty, (a, b) => a + b);
-    private readonly string _sortLastDescending = Enumerable.Repeat(char.MinValue.ToString(), 64).Aggregate(string.Empty, (a, b) => a + b);
     private readonly TrackRepository _repository;
 
     public TrackService(TrackRepository repository)
@@ -65,13 +63,13 @@ public class TrackService
                         parameters.OrderBy = entity => entity.Artist;
                         break;
                     case "Album":
-                        parameters.OrderBy = entity => entity.Album ?? _sortLastAscending;
+                        parameters.OrderBy = entity => entity.Album ?? "";
                         break;
                     case "ReleaseDate":
                         parameters.OrderBy = entity => entity.ReleaseDate ?? DateOnly.MaxValue;
                         break;
                     case "Genre":
-                        parameters.OrderBy = entity => entity.Genre ?? _sortLastAscending;
+                        parameters.OrderBy = entity => entity.Genre ?? "";
                         break;
                     
                 }