Add category ladders

Source/ApplicationServices/LibraryExporter.cs

@@ -141,7 +141,7 @@ namespace ApplicationServices
 				PictureId = a.Book.PictureId,
 				IsAbridged = a.Book.IsAbridged,
 				DatePublished = a.Book.DatePublished,
-				CategoriesNames = a.Book.CategoriesNames().Any() ? a.Book.CategoriesNames().Aggregate((a, b) => $"{a}, {b}") : "",
+				CategoriesNames = a.Book.LowestCategoryNames().Any() ? a.Book.LowestCategoryNames().Aggregate((a, b) => $"{a}, {b}") : "",
 				MyRatingOverall = a.Book.UserDefinedItem.Rating.OverallRating,
 				MyRatingPerformance = a.Book.UserDefinedItem.Rating.PerformanceRating,
 				MyRatingStory = a.Book.UserDefinedItem.Rating.StoryRating,

Source/DataLayer/Configurations/BookCategoryConfig.cs

@@ -0,0 +1,26 @@
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore;
+
+namespace DataLayer.Configurations
+{
+	internal class BookCategoryConfig : IEntityTypeConfiguration<BookCategory>
+	{
+		public void Configure(EntityTypeBuilder<BookCategory> entity)
+		{
+			entity.HasKey(bc => new { bc.BookId, bc.CategoryLadderId });
+
+			entity.HasIndex(bc => bc.BookId);
+			entity.HasIndex(bc => bc.CategoryLadderId);
+
+			entity
+				.HasOne(bc => bc.Book)
+				.WithMany(b => b.CategoriesLink)
+				.HasForeignKey(bc => bc.BookId);
+
+			entity
+				.HasOne(bc => bc.CategoryLadder)
+				.WithMany(c => c.BooksLink)
+				.HasForeignKey(bc => bc.CategoryLadderId);
+		}
+	}
+}

Source/DataLayer/Configurations/BookConfig.cs

@@ -72,9 +72,10 @@ namespace DataLayer.Configurations
                 .SetPropertyAccessMode(PropertyAccessMode.Field);
 
             entity
-                .HasOne(b => b.Category)
+                .Metadata
-                .WithMany()
+                .FindNavigation(nameof(Book.CategoriesLink))
-                .HasForeignKey(b => b.CategoryId);
+				// PropertyAccessMode.Field : Categories is a get-only property, not a field, so use its backing field
+				.SetPropertyAccessMode(PropertyAccessMode.Field);
         }
     }
 }

Source/DataLayer/Configurations/CategoryConfig.cs

@@ -10,8 +10,11 @@ namespace DataLayer.Configurations
             entity.HasKey(c => c.CategoryId);
             entity.HasIndex(c => c.AudibleCategoryId);
 
-            // seeds go here. examples in Dinah.EntityFrameworkCore.Tests\DbContextFactoryExample.cs
+            entity.Ignore(c => c.CategoryLadders);
-            entity.HasData(Category.GetEmpty());
+
+            entity
+                .HasMany(e => e._categoryLadders)
+                .WithMany(e => e._categories);
         }
     }
 }

Source/DataLayer/Configurations/CategoryLadderConfig.cs

@@ -0,0 +1,24 @@
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore;
+
+namespace DataLayer.Configurations
+{
+	internal class CategoryLadderConfig : IEntityTypeConfiguration<CategoryLadder>
+	{
+		public void Configure(EntityTypeBuilder<CategoryLadder> entity)
+		{
+			entity.HasKey(cl => cl.CategoryLadderId);
+
+			entity.Ignore(cl => cl.Categories);
+
+			entity
+				.HasMany(cl => cl._categories)
+				.WithMany(c => c._categoryLadders);
+
+			entity
+				.Metadata
+				.FindNavigation(nameof(CategoryLadder.BooksLink))
+				.SetPropertyAccessMode(PropertyAccessMode.Field);
+		}
+	}
+}

Source/DataLayer/EfClasses/Book.cs

@@ -55,10 +55,6 @@ namespace DataLayer
         public DateTime? DatePublished { get; private set; }
         public string Language { get; private set; }
 
-        // non-null. use "empty pattern"
-        internal int CategoryId { get; private set; }
-        public Category Category { get; private set; }
-
         // is owned, not optional 1:1
         public UserDefinedItem UserDefinedItem { get; private set; }
 
@@ -79,7 +75,6 @@ namespace DataLayer
             ContentType contentType,
 			IEnumerable<Contributor> authors,
 			IEnumerable<Contributor> narrators,
-			Category category,
             string localeName)
         {
             // validate
@@ -96,11 +91,10 @@ namespace DataLayer
             // non-ef-ctor init.s
             UserDefinedItem = new UserDefinedItem(this);
             _contributorsLink = new HashSet<BookContributor>();
+            _categoriesLink = new HashSet<BookCategory>();
             _seriesLink = new HashSet<SeriesBook>();
             _supplements = new HashSet<Supplement>();
 
-			Category = category;
-
             // simple assigns
             UpdateTitle(title, subtitle);
 			Description = description?.Trim() ?? "";
@@ -182,9 +176,30 @@ namespace DataLayer
 
 			return entry;
 		}
+		#region categories
+		private HashSet<BookCategory> _categoriesLink;
+		public IEnumerable<BookCategory> CategoriesLink => _categoriesLink?.ToList();
+		public void UpsertCategories(CategoryLadder ladder)
+		{
+			ArgumentValidator.EnsureNotNull(ladder, nameof(ladder));
 
-        #region series
+			var singleBookCategory = _categoriesLink.SingleOrDefault(bc => bc.CategoryLadder.Equals(ladder));
-        private HashSet<SeriesBook> _seriesLink;
+
+			if (singleBookCategory is null)
+				_categoriesLink.Add(new BookCategory(this, ladder));
+            else
+            {
+                for (var i = 0; i < ladder._categories.Count; i++)
+                {
+                    //Update the category name
+					singleBookCategory.CategoryLadder._categories[i].Name = ladder._categories[i].Name;
+				}
+            }
+		}
+		#endregion
+
+		#region series
+		private HashSet<SeriesBook> _seriesLink;
         public IEnumerable<SeriesBook> SeriesLink => _seriesLink?.ToList();
 
         public void UpsertSeries(Series series, string order, DbContext context = null)
@@ -234,15 +249,6 @@ namespace DataLayer
             Language = language?.FirstCharToUpper() ?? Language;
         }
 
-        public void UpdateCategory(Category category, DbContext context = null)
-		{
-			// since category is never null, nullity means it hasn't been loaded
-			if (Category is null)
-				getEntry(context).Reference(s => s.Category).Load();
-
-			Category = category;
-        }
-
         public override string ToString() => $"[{AudibleProductId}] {TitleWithSubtitle}";
 	}
 }

Source/DataLayer/EfClasses/BookCategory.cs

@@ -0,0 +1,20 @@
+using Dinah.Core;
+
+namespace DataLayer
+{
+	public class BookCategory
+	{
+		internal int BookId { get; private set; }
+		internal int CategoryLadderId { get; private set; }
+
+		public Book Book { get; private set; }
+		public CategoryLadder CategoryLadder { get; private set; }
+		private BookCategory() { }
+
+		internal BookCategory(Book book, CategoryLadder categoriesList)
+		{
+			Book = ArgumentValidator.EnsureNotNull(book, nameof(book));
+			CategoryLadder = ArgumentValidator.EnsureNotNull(categoriesList, nameof(categoriesList));
+		}
+	}
+}

Source/DataLayer/EfClasses/Category.cs

@@ -1,8 +1,5 @@
-using System;
+using System.Collections.Generic;
-using System.Collections.Generic;
-using System.Linq;
 using Dinah.Core;
-using Microsoft.EntityFrameworkCore;
 
 namespace DataLayer
 {
@@ -15,20 +12,20 @@ namespace DataLayer
             Id = id;
         }
     }
+
     public class Category
     {
-        // Empty is a special case. use private ctor w/o validation
-        public static Category GetEmpty() => new() { CategoryId = -1, AudibleCategoryId = "", Name = "" };
-
         internal int CategoryId { get; private set; }
         public string AudibleCategoryId { get; private set; }
 
-        public string Name { get; private set; }
+        public string Name { get; internal set; }
-        public Category ParentCategory { get; private set; }
 
-        private Category() { }
+        internal List<CategoryLadder> _categoryLadders = new();
+        public IReadOnlyCollection<CategoryLadder> CategoryLadders => _categoryLadders.AsReadOnly();
+
+		private Category() { }
         /// <summary>special id class b/c it's too easy to get string order mixed up</summary>
-        public Category(AudibleCategoryId audibleSeriesId, string name, Category parentCategory = null)
+        public Category(AudibleCategoryId audibleSeriesId, string name)
         {
             ArgumentValidator.EnsureNotNull(audibleSeriesId, nameof(audibleSeriesId));
             var id = audibleSeriesId.Id;
@@ -37,15 +34,6 @@ namespace DataLayer
 
             AudibleCategoryId = id;
             Name = name;
-
-            UpdateParentCategory(parentCategory);
-        }
-
-        public void UpdateParentCategory(Category parentCategory)
-        {
-            // don't overwrite with null but not an error
-            if (parentCategory is not null)
-                ParentCategory = parentCategory;
         }
 
 		public override string ToString() => $"[{AudibleCategoryId}] {Name}";

Source/DataLayer/EfClasses/CategoryLadder.cs

@@ -0,0 +1,48 @@
+using Dinah.Core;
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+
+namespace DataLayer
+{
+	public class CategoryLadder : IEquatable<CategoryLadder>
+	{
+		internal int CategoryLadderId { get; private set; }
+
+		internal List<Category> _categories;
+		public ReadOnlyCollection<Category> Categories => _categories.AsReadOnly();
+
+		private HashSet<BookCategory> _booksLink;
+		public IEnumerable<BookCategory> BooksLink => _booksLink?.ToList();
+		private CategoryLadder() { _categories = new(); }
+		public CategoryLadder(List<Category> categories)
+		{
+			ArgumentValidator.EnsureNotNull(categories, nameof(categories));
+			ArgumentValidator.EnsureGreaterThan(categories.Count, nameof(categories), 0);
+			_booksLink = new HashSet<BookCategory>();
+			_categories = categories;
+		}
+
+		public override int GetHashCode()
+		{
+			HashCode hashCode = default;
+			foreach (var category in _categories)
+				hashCode.Add(category.AudibleCategoryId);
+			return hashCode.ToHashCode();
+		}
+
+		public bool Equals(CategoryLadder other)
+		{
+			if (other?._categories is null)
+				return false;
+
+			return Equals(other._categories.Select(c => c.AudibleCategoryId));
+		}
+		public bool Equals(IEnumerable<string> categoryIds)
+			=> _categories.Select(c => c.AudibleCategoryId).SequenceEqual(categoryIds);
+		public override bool Equals(object obj) => obj is CategoryLadder other && Equals(other);
+
+		public override string ToString() => string.Join(" > ", _categories.Select(c => c.Name));
+	}
+}

Source/DataLayer/EntityExtensions.cs

@@ -46,14 +46,23 @@ namespace DataLayer
                 ? $"{sb.Series.Name} (#{sb.Order})"
                 : sb.Series.Name;
 		}
-        public static string[] CategoriesNames(this Book book)
+
-            => book.Category is null ? new string[0]
+        public static string[] LowestCategoryNames(this Book book)
-            : book.Category.ParentCategory is null ? new[] { book.Category.Name }
+            => book.CategoriesLink?.Any() is not true ? Array.Empty<string>()
-            : new[] { book.Category.ParentCategory.Name, book.Category.Name };
+			: book
-        public static string[] CategoriesIds(this Book book)
+                .CategoriesLink
-            => book.Category is null ? null
+                .Select(cl => cl.CategoryLadder.Categories.LastOrDefault()?.Name)
-            : book.Category.ParentCategory is null ? new[] { book.Category.AudibleCategoryId }
+                .Where(c => c is not null)
-            : new[] { book.Category.ParentCategory.AudibleCategoryId, book.Category.AudibleCategoryId };
+                .Distinct()
+                .ToArray();
+
+		public static string[] CategoriesIds(this Book book)
+            => book.CategoriesLink?.Any() is not true ? null
+            : book
+                .CategoriesLink
+                .SelectMany(cl => cl.CategoryLadder.Categories)
+                .Select(c => c.AudibleCategoryId)
+                .ToArray();
 
         public static string AggregateTitles(this IEnumerable<LibraryBook> libraryBooks, int max = 5)
 		{

Source/DataLayer/LibationContext.cs

@@ -23,6 +23,7 @@ namespace DataLayer
         public DbSet<Contributor> Contributors { get; private set; }
         public DbSet<Series> Series { get; private set; }
         public DbSet<Category> Categories { get; private set; }
+        public DbSet<CategoryLadder> CategoryLadders { get; private set; }
 
         public static LibationContext Create(string connectionString)
         {
@@ -39,13 +40,15 @@ namespace DataLayer
         {
             base.OnModelCreating(modelBuilder);
 
-            modelBuilder.ApplyConfiguration(new BookConfig());
+			modelBuilder.ApplyConfiguration(new BookConfig());
             modelBuilder.ApplyConfiguration(new ContributorConfig());
             modelBuilder.ApplyConfiguration(new BookContributorConfig());
             modelBuilder.ApplyConfiguration(new LibraryBookConfig());
             modelBuilder.ApplyConfiguration(new SeriesConfig());
             modelBuilder.ApplyConfiguration(new SeriesBookConfig());
             modelBuilder.ApplyConfiguration(new CategoryConfig());
+			modelBuilder.ApplyConfiguration(new CategoryLadderConfig());
+			modelBuilder.ApplyConfiguration(new BookCategoryConfig());
 
 			// views are now supported via "keyless entity types" (instead of "entity types" or the prev "query types"):
 			// https://docs.microsoft.com/en-us/ef/core/modeling/keyless-entity-types

Source/DataLayer/Migrations/20230717220642_AddCategoriesList.Designer.cs

@@ -0,0 +1,479 @@
+// <auto-generated />
+using System;
+using DataLayer;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace DataLayer.Migrations
+{
+    [DbContext(typeof(LibationContext))]
+    [Migration("20230717220642_AddCategoriesList")]
+    partial class AddCategoriesList
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "7.0.5");
+
+            modelBuilder.Entity("CategoryCategoryLadder", b =>
+                {
+                    b.Property<int>("_categoriesCategoryId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("_categoryLaddersCategoryLadderId")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("_categoriesCategoryId", "_categoryLaddersCategoryLadderId");
+
+                    b.HasIndex("_categoryLaddersCategoryLadderId");
+
+                    b.ToTable("CategoryCategoryLadder");
+                });
+
+            modelBuilder.Entity("DataLayer.Book", b =>
+                {
+                    b.Property<int>("BookId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("AudibleProductId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("ContentType")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTime?>("DatePublished")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Description")
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsAbridged")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Language")
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("LengthInMinutes")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Locale")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("PictureId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("PictureLarge")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Subtitle")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Title")
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("_audioFormat")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("BookId");
+
+                    b.HasIndex("AudibleProductId");
+
+                    b.ToTable("Books");
+                });
+
+            modelBuilder.Entity("DataLayer.BookCategory", b =>
+                {
+                    b.Property<int>("BookId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("CategoryLadderId")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("BookId", "CategoryLadderId");
+
+                    b.HasIndex("BookId");
+
+                    b.HasIndex("CategoryLadderId");
+
+                    b.ToTable("BookCategory");
+                });
+
+            modelBuilder.Entity("DataLayer.BookContributor", b =>
+                {
+                    b.Property<int>("BookId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("ContributorId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("Role")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<byte>("Order")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("BookId", "ContributorId", "Role");
+
+                    b.HasIndex("BookId");
+
+                    b.HasIndex("ContributorId");
+
+                    b.ToTable("BookContributor");
+                });
+
+            modelBuilder.Entity("DataLayer.Category", b =>
+                {
+                    b.Property<int>("CategoryId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("AudibleCategoryId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Name")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("CategoryId");
+
+                    b.HasIndex("AudibleCategoryId");
+
+                    b.ToTable("Categories");
+
+                    b.HasData(
+                        new
+                        {
+                            CategoryId = -1,
+                            AudibleCategoryId = "",
+                            Name = ""
+                        });
+                });
+
+            modelBuilder.Entity("DataLayer.CategoryLadder", b =>
+                {
+                    b.Property<int>("CategoryLadderId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("CategoryLadderId");
+
+                    b.ToTable("CategoryLadders");
+
+                    b.HasData(
+                        new
+                        {
+                            CategoryLadderId = -1
+                        });
+                });
+
+            modelBuilder.Entity("DataLayer.Contributor", b =>
+                {
+                    b.Property<int>("ContributorId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("AudibleContributorId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Name")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("ContributorId");
+
+                    b.HasIndex("Name");
+
+                    b.ToTable("Contributors");
+
+                    b.HasData(
+                        new
+                        {
+                            ContributorId = -1,
+                            Name = ""
+                        });
+                });
+
+            modelBuilder.Entity("DataLayer.LibraryBook", b =>
+                {
+                    b.Property<int>("BookId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<bool>("AbsentFromLastScan")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Account")
+                        .HasColumnType("TEXT");
+
+                    b.Property<DateTime>("DateAdded")
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsDeleted")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("BookId");
+
+                    b.ToTable("LibraryBooks");
+                });
+
+            modelBuilder.Entity("DataLayer.Series", b =>
+                {
+                    b.Property<int>("SeriesId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("AudibleSeriesId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Name")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("SeriesId");
+
+                    b.HasIndex("AudibleSeriesId");
+
+                    b.ToTable("Series");
+                });
+
+            modelBuilder.Entity("DataLayer.SeriesBook", b =>
+                {
+                    b.Property<int>("SeriesId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("BookId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Order")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("SeriesId", "BookId");
+
+                    b.HasIndex("BookId");
+
+                    b.HasIndex("SeriesId");
+
+                    b.ToTable("SeriesBook");
+                });
+
+            modelBuilder.Entity("CategoryCategoryLadder", b =>
+                {
+                    b.HasOne("DataLayer.Category", null)
+                        .WithMany()
+                        .HasForeignKey("_categoriesCategoryId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DataLayer.CategoryLadder", null)
+                        .WithMany()
+                        .HasForeignKey("_categoryLaddersCategoryLadderId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("DataLayer.Book", b =>
+                {
+                    b.OwnsOne("DataLayer.Rating", "Rating", b1 =>
+                        {
+                            b1.Property<int>("BookId")
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<float>("OverallRating")
+                                .HasColumnType("REAL");
+
+                            b1.Property<float>("PerformanceRating")
+                                .HasColumnType("REAL");
+
+                            b1.Property<float>("StoryRating")
+                                .HasColumnType("REAL");
+
+                            b1.HasKey("BookId");
+
+                            b1.ToTable("Books");
+
+                            b1.WithOwner()
+                                .HasForeignKey("BookId");
+                        });
+
+                    b.OwnsMany("DataLayer.Supplement", "Supplements", b1 =>
+                        {
+                            b1.Property<int>("SupplementId")
+                                .ValueGeneratedOnAdd()
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<int>("BookId")
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<string>("Url")
+                                .HasColumnType("TEXT");
+
+                            b1.HasKey("SupplementId");
+
+                            b1.HasIndex("BookId");
+
+                            b1.ToTable("Supplement");
+
+                            b1.WithOwner("Book")
+                                .HasForeignKey("BookId");
+
+                            b1.Navigation("Book");
+                        });
+
+                    b.OwnsOne("DataLayer.UserDefinedItem", "UserDefinedItem", b1 =>
+                        {
+                            b1.Property<int>("BookId")
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<int>("BookStatus")
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<DateTime?>("LastDownloaded")
+                                .HasColumnType("TEXT");
+
+                            b1.Property<string>("LastDownloadedVersion")
+                                .HasColumnType("TEXT");
+
+                            b1.Property<int?>("PdfStatus")
+                                .HasColumnType("INTEGER");
+
+                            b1.Property<string>("Tags")
+                                .HasColumnType("TEXT");
+
+                            b1.HasKey("BookId");
+
+                            b1.ToTable("UserDefinedItem", (string)null);
+
+                            b1.WithOwner("Book")
+                                .HasForeignKey("BookId");
+
+                            b1.OwnsOne("DataLayer.Rating", "Rating", b2 =>
+                                {
+                                    b2.Property<int>("UserDefinedItemBookId")
+                                        .HasColumnType("INTEGER");
+
+                                    b2.Property<float>("OverallRating")
+                                        .HasColumnType("REAL");
+
+                                    b2.Property<float>("PerformanceRating")
+                                        .HasColumnType("REAL");
+
+                                    b2.Property<float>("StoryRating")
+                                        .HasColumnType("REAL");
+
+                                    b2.HasKey("UserDefinedItemBookId");
+
+                                    b2.ToTable("UserDefinedItem");
+
+                                    b2.WithOwner()
+                                        .HasForeignKey("UserDefinedItemBookId");
+                                });
+
+                            b1.Navigation("Book");
+
+                            b1.Navigation("Rating");
+                        });
+
+                    b.Navigation("Rating");
+
+                    b.Navigation("Supplements");
+
+                    b.Navigation("UserDefinedItem");
+                });
+
+            modelBuilder.Entity("DataLayer.BookCategory", b =>
+                {
+                    b.HasOne("DataLayer.Book", "Book")
+                        .WithMany("CategoriesLink")
+                        .HasForeignKey("BookId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DataLayer.CategoryLadder", "CategoryLadder")
+                        .WithMany("BooksLink")
+                        .HasForeignKey("CategoryLadderId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Book");
+
+                    b.Navigation("CategoryLadder");
+                });
+
+            modelBuilder.Entity("DataLayer.BookContributor", b =>
+                {
+                    b.HasOne("DataLayer.Book", "Book")
+                        .WithMany("ContributorsLink")
+                        .HasForeignKey("BookId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DataLayer.Contributor", "Contributor")
+                        .WithMany("BooksLink")
+                        .HasForeignKey("ContributorId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Book");
+
+                    b.Navigation("Contributor");
+                });
+
+            modelBuilder.Entity("DataLayer.LibraryBook", b =>
+                {
+                    b.HasOne("DataLayer.Book", "Book")
+                        .WithOne()
+                        .HasForeignKey("DataLayer.LibraryBook", "BookId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Book");
+                });
+
+            modelBuilder.Entity("DataLayer.SeriesBook", b =>
+                {
+                    b.HasOne("DataLayer.Book", "Book")
+                        .WithMany("SeriesLink")
+                        .HasForeignKey("BookId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DataLayer.Series", "Series")
+                        .WithMany("BooksLink")
+                        .HasForeignKey("SeriesId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Book");
+
+                    b.Navigation("Series");
+                });
+
+            modelBuilder.Entity("DataLayer.Book", b =>
+                {
+                    b.Navigation("CategoriesLink");
+
+                    b.Navigation("ContributorsLink");
+
+                    b.Navigation("SeriesLink");
+                });
+
+            modelBuilder.Entity("DataLayer.CategoryLadder", b =>
+                {
+                    b.Navigation("BooksLink");
+                });
+
+            modelBuilder.Entity("DataLayer.Contributor", b =>
+                {
+                    b.Navigation("BooksLink");
+                });
+
+            modelBuilder.Entity("DataLayer.Series", b =>
+                {
+                    b.Navigation("BooksLink");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

Source/DataLayer/Migrations/20230717220642_AddCategoriesList.cs

@@ -0,0 +1,176 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace DataLayer.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddCategoriesList : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Books_Categories_CategoryId",
+                table: "Books");
+
+            migrationBuilder.DropForeignKey(
+                name: "FK_Categories_Categories_ParentCategoryCategoryId",
+                table: "Categories");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Categories_ParentCategoryCategoryId",
+                table: "Categories");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Books_CategoryId",
+                table: "Books");
+
+            migrationBuilder.DropColumn(
+                name: "ParentCategoryCategoryId",
+                table: "Categories");
+
+            migrationBuilder.DropColumn(
+                name: "CategoryId",
+                table: "Books");
+
+            migrationBuilder.CreateTable(
+                name: "CategoryLadders",
+                columns: table => new
+                {
+                    CategoryLadderId = table.Column<int>(type: "INTEGER", nullable: false)
+                        .Annotation("Sqlite:Autoincrement", true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_CategoryLadders", x => x.CategoryLadderId);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "BookCategory",
+                columns: table => new
+                {
+                    BookId = table.Column<int>(type: "INTEGER", nullable: false),
+                    CategoryLadderId = table.Column<int>(type: "INTEGER", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_BookCategory", x => new { x.BookId, x.CategoryLadderId });
+                    table.ForeignKey(
+                        name: "FK_BookCategory_Books_BookId",
+                        column: x => x.BookId,
+                        principalTable: "Books",
+                        principalColumn: "BookId",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_BookCategory_CategoryLadders_CategoryLadderId",
+                        column: x => x.CategoryLadderId,
+                        principalTable: "CategoryLadders",
+                        principalColumn: "CategoryLadderId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "CategoryCategoryLadder",
+                columns: table => new
+                {
+                    _categoriesCategoryId = table.Column<int>(type: "INTEGER", nullable: false),
+                    _categoryLaddersCategoryLadderId = table.Column<int>(type: "INTEGER", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_CategoryCategoryLadder", x => new { x._categoriesCategoryId, x._categoryLaddersCategoryLadderId });
+                    table.ForeignKey(
+                        name: "FK_CategoryCategoryLadder_Categories__categoriesCategoryId",
+                        column: x => x._categoriesCategoryId,
+                        principalTable: "Categories",
+                        principalColumn: "CategoryId",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_CategoryCategoryLadder_CategoryLadders__categoryLaddersCategoryLadderId",
+                        column: x => x._categoryLaddersCategoryLadderId,
+                        principalTable: "CategoryLadders",
+                        principalColumn: "CategoryLadderId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.InsertData(
+                table: "CategoryLadders",
+                column: "CategoryLadderId",
+                value: -1);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_BookCategory_BookId",
+                table: "BookCategory",
+                column: "BookId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_BookCategory_CategoryLadderId",
+                table: "BookCategory",
+                column: "CategoryLadderId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_CategoryCategoryLadder__categoryLaddersCategoryLadderId",
+                table: "CategoryCategoryLadder",
+                column: "_categoryLaddersCategoryLadderId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "BookCategory");
+
+            migrationBuilder.DropTable(
+                name: "CategoryCategoryLadder");
+
+            migrationBuilder.DropTable(
+                name: "CategoryLadders");
+
+            migrationBuilder.AddColumn<int>(
+                name: "ParentCategoryCategoryId",
+                table: "Categories",
+                type: "INTEGER",
+                nullable: true);
+
+            migrationBuilder.AddColumn<int>(
+                name: "CategoryId",
+                table: "Books",
+                type: "INTEGER",
+                nullable: false,
+                defaultValue: 0);
+
+            migrationBuilder.UpdateData(
+                table: "Categories",
+                keyColumn: "CategoryId",
+                keyValue: -1,
+                column: "ParentCategoryCategoryId",
+                value: null);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Categories_ParentCategoryCategoryId",
+                table: "Categories",
+                column: "ParentCategoryCategoryId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Books_CategoryId",
+                table: "Books",
+                column: "CategoryId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Books_Categories_CategoryId",
+                table: "Books",
+                column: "CategoryId",
+                principalTable: "Categories",
+                principalColumn: "CategoryId",
+                onDelete: ReferentialAction.Cascade);
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Categories_Categories_ParentCategoryCategoryId",
+                table: "Categories",
+                column: "ParentCategoryCategoryId",
+                principalTable: "Categories",
+                principalColumn: "CategoryId");
+        }
+    }
+}

Source/DataLayer/Migrations/LibationContextModelSnapshot.cs

@@ -17,6 +17,21 @@ namespace DataLayer.Migrations
 #pragma warning disable 612, 618
             modelBuilder.HasAnnotation("ProductVersion", "7.0.5");
 
+            modelBuilder.Entity("CategoryCategoryLadder", b =>
+                {
+                    b.Property<int>("_categoriesCategoryId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("_categoryLaddersCategoryLadderId")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("_categoriesCategoryId", "_categoryLaddersCategoryLadderId");
+
+                    b.HasIndex("_categoryLaddersCategoryLadderId");
+
+                    b.ToTable("CategoryCategoryLadder");
+                });
+
             modelBuilder.Entity("DataLayer.Book", b =>
                 {
                     b.Property<int>("BookId")
@@ -26,9 +41,6 @@ namespace DataLayer.Migrations
                     b.Property<string>("AudibleProductId")
                         .HasColumnType("TEXT");
 
-                    b.Property<int>("CategoryId")
-                        .HasColumnType("INTEGER");
-
                     b.Property<int>("ContentType")
                         .HasColumnType("INTEGER");
 
@@ -69,11 +81,26 @@ namespace DataLayer.Migrations
 
                     b.HasIndex("AudibleProductId");
 
-                    b.HasIndex("CategoryId");
-
                     b.ToTable("Books");
                 });
 
+            modelBuilder.Entity("DataLayer.BookCategory", b =>
+                {
+                    b.Property<int>("BookId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("CategoryLadderId")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("BookId", "CategoryLadderId");
+
+                    b.HasIndex("BookId");
+
+                    b.HasIndex("CategoryLadderId");
+
+                    b.ToTable("BookCategory");
+                });
+
             modelBuilder.Entity("DataLayer.BookContributor", b =>
                 {
                     b.Property<int>("BookId")
@@ -109,15 +136,10 @@ namespace DataLayer.Migrations
                     b.Property<string>("Name")
                         .HasColumnType("TEXT");
 
-                    b.Property<int?>("ParentCategoryCategoryId")
-                        .HasColumnType("INTEGER");
-
                     b.HasKey("CategoryId");
 
                     b.HasIndex("AudibleCategoryId");
 
-                    b.HasIndex("ParentCategoryCategoryId");
-
                     b.ToTable("Categories");
 
                     b.HasData(
@@ -129,6 +151,23 @@ namespace DataLayer.Migrations
                         });
                 });
 
+            modelBuilder.Entity("DataLayer.CategoryLadder", b =>
+                {
+                    b.Property<int>("CategoryLadderId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("CategoryLadderId");
+
+                    b.ToTable("CategoryLadders");
+
+                    b.HasData(
+                        new
+                        {
+                            CategoryLadderId = -1
+                        });
+                });
+
             modelBuilder.Entity("DataLayer.Contributor", b =>
                 {
                     b.Property<int>("ContributorId")
@@ -216,14 +255,23 @@ namespace DataLayer.Migrations
                     b.ToTable("SeriesBook");
                 });
 
-            modelBuilder.Entity("DataLayer.Book", b =>
+            modelBuilder.Entity("CategoryCategoryLadder", b =>
                 {
-                    b.HasOne("DataLayer.Category", "Category")
+                    b.HasOne("DataLayer.Category", null)
                         .WithMany()
-                        .HasForeignKey("CategoryId")
+                        .HasForeignKey("_categoriesCategoryId")
                         .OnDelete(DeleteBehavior.Cascade)
                         .IsRequired();
 
+                    b.HasOne("DataLayer.CategoryLadder", null)
+                        .WithMany()
+                        .HasForeignKey("_categoryLaddersCategoryLadderId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("DataLayer.Book", b =>
+                {
                     b.OwnsOne("DataLayer.Rating", "Rating", b1 =>
                         {
                             b1.Property<int>("BookId")
@@ -324,8 +372,6 @@ namespace DataLayer.Migrations
                             b1.Navigation("Rating");
                         });
 
-                    b.Navigation("Category");
-
                     b.Navigation("Rating");
 
                     b.Navigation("Supplements");
@@ -333,6 +379,25 @@ namespace DataLayer.Migrations
                     b.Navigation("UserDefinedItem");
                 });
 
+            modelBuilder.Entity("DataLayer.BookCategory", b =>
+                {
+                    b.HasOne("DataLayer.Book", "Book")
+                        .WithMany("CategoriesLink")
+                        .HasForeignKey("BookId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DataLayer.CategoryLadder", "CategoryLadder")
+                        .WithMany("BooksLink")
+                        .HasForeignKey("CategoryLadderId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Book");
+
+                    b.Navigation("CategoryLadder");
+                });
+
             modelBuilder.Entity("DataLayer.BookContributor", b =>
                 {
                     b.HasOne("DataLayer.Book", "Book")
@@ -352,15 +417,6 @@ namespace DataLayer.Migrations
                     b.Navigation("Contributor");
                 });
 
-            modelBuilder.Entity("DataLayer.Category", b =>
-                {
-                    b.HasOne("DataLayer.Category", "ParentCategory")
-                        .WithMany()
-                        .HasForeignKey("ParentCategoryCategoryId");
-
-                    b.Navigation("ParentCategory");
-                });
-
             modelBuilder.Entity("DataLayer.LibraryBook", b =>
                 {
                     b.HasOne("DataLayer.Book", "Book")
@@ -393,11 +449,18 @@ namespace DataLayer.Migrations
 
             modelBuilder.Entity("DataLayer.Book", b =>
                 {
+                    b.Navigation("CategoriesLink");
+
                     b.Navigation("ContributorsLink");
 
                     b.Navigation("SeriesLink");
                 });
 
+            modelBuilder.Entity("DataLayer.CategoryLadder", b =>
+                {
+                    b.Navigation("BooksLink");
+                });
+
             modelBuilder.Entity("DataLayer.Contributor", b =>
                 {
                     b.Navigation("BooksLink");

Source/DataLayer/QueryObjects/BookQueries.cs

@@ -34,7 +34,7 @@ namespace DataLayer
                 // owned items are always loaded. eg: book.UserDefinedItem, book.Supplements
                 .Include(b => b.SeriesLink).ThenInclude(sb => sb.Series)
                 .Include(b => b.ContributorsLink).ThenInclude(c => c.Contributor)
-                .Include(b => b.Category).ThenInclude(c => c.ParentCategory);
+                .Include(b => b.CategoriesLink).ThenInclude(c => c.CategoryLadder).ThenInclude(c => c._categories);
 
         public static bool IsProduct(this Book book)
             => book.ContentType is not ContentType.Episode and not ContentType.Parent;

Source/DataLayer/QueryObjects/LibraryBookQueries.cs

@@ -55,7 +55,7 @@ namespace DataLayer
                 // owned items are always loaded. eg: book.UserDefinedItem, book.Supplements
                 .Include(le => le.Book).ThenInclude(b => b.SeriesLink).ThenInclude(sb => sb.Series)
                 .Include(le => le.Book).ThenInclude(b => b.ContributorsLink).ThenInclude(c => c.Contributor)
-                .Include(le => le.Book).ThenInclude(b => b.Category).ThenInclude(c => c.ParentCategory);
+                .Include(le => le.Book).ThenInclude(b => b.CategoriesLink).ThenInclude(c => c.CategoryLadder).ThenInclude(c => c._categories);
 
         public static IEnumerable<LibraryBook> ParentedEpisodes(this IEnumerable<LibraryBook> libraryBooks)
             => libraryBooks.Where(lb => lb.Book.IsEpisodeParent()).SelectMany(libraryBooks.FindChildren);

Source/DtoImporterService/BookImporter.cs

@@ -99,20 +99,6 @@ namespace DtoImporterService
                     .Select(n => contributorImporter.Cache[n.Name])
 					.ToList();
 
-			// categories are laid out for a breadcrumb. category is 1st, subcategory is 2nd
-			// absence of categories is also possible
-
-			// CATEGORY HACK: only use the 1st 2 categories
-			// after we support full arbitrary-depth category trees and multiple categories per book, the real impl will be something like this
-			//   var lastCategory = item.Categories.LastOrDefault()?.CategoryId ?? "";
-			var lastCategory
-				= item.Categories.Length == 0 ? ""
-				: item.Categories.Length == 1 ? item.Categories[0].CategoryId
-				// 2+
-				: item.Categories[1].CategoryId;
-
-			var category = categoryImporter.Cache[lastCategory];
-
 			Book book;
 			try
 			{
@@ -125,7 +111,6 @@ namespace DtoImporterService
 					contentType,
 					authors,
 					narrators,
-					category,
 					importItem.LocaleName)
 					).Entity;
 				Cache.Add(book.AudibleProductId, book);
@@ -140,7 +125,6 @@ namespace DtoImporterService
 					contentType,
 					QtyAuthors = authors?.Count,
 					QtyNarrators = narrators?.Count,
-					Category = category?.Name,
 					importItem.LocaleName
 				});
 				throw;
@@ -201,6 +185,17 @@ namespace DtoImporterService
 					book.UpsertSeries(series, seriesEntry.Sequence);
 				}
 			}
+
+			if (item.CategoryLadders is not null)
+			{
+				foreach (var ladder in item.CategoryLadders.Select(cl => cl.Ladder).Where(l => l?.Length > 0))
+				{
+					var categoryIds = ladder.Select(l => l.CategoryId).ToList();
+					var cata = categoryImporter.LadderCache.Single(c => c.Equals(categoryIds));
+
+					book.UpsertCategories(cata);
+				}
+			}
 		}
 
 		private static DataLayer.ContentType GetContentType(Item item)

Source/DtoImporterService/CategoryImporter.cs

@@ -12,7 +12,8 @@ namespace DtoImporterService
 	{
 		protected override IValidator Validator => new CategoryValidator();
 
-		public Dictionary<string, Category> Cache { get; private set; } = new();
+		private Dictionary<string, Category> Cache { get; set; } = new();
+		public HashSet<DataLayer.CategoryLadder> LadderCache { get; private set; } = new();
 
 		public CategoryImporter(LibationContext context) : base(context) { }
 
@@ -30,44 +31,39 @@ namespace DtoImporterService
 			loadLocal_categories(categoryIds);
 
 			// upsert
-			var categoryPairs = importItems
+			var categoryLadders = importItems
-				.Select(i => i.DtoItem)
+				.SelectMany(i => i.DtoItem.CategoryLadders)
-				.GetCategoryPairsDistinct()
+				.Select(cl => cl.Ladder)
+				.Where(l => l?.Length > 0)
 				.ToList();
-			var qtyNew = upsertCategories(categoryPairs);
+
+			var qtyNew = upsertCategories(categoryLadders);
 			return qtyNew;
 		}
 
 		private void loadLocal_categories(List<string> categoryIds)
 		{
-			// must include default/empty/missing
-			categoryIds.Add(Category.GetEmpty().AudibleCategoryId);
-
 			// load existing => local
 			Cache = DbContext.Categories
 				.Where(c => categoryIds.Contains(c.AudibleCategoryId))
 				.ToDictionarySafe(c => c.AudibleCategoryId);
+
+			LadderCache = DbContext.CategoryLadders.ToHashSet();
 		}
 
 		// only use after loading contributors => local
-		private int upsertCategories(List<Ladder[]> categoryPairs)
+		private int upsertCategories(List<Ladder[]> ladders)
 		{
 			var qtyNew = 0;
 
-			foreach (var pair in categoryPairs)
+			foreach (var ladder in ladders)
 			{
-				for (var i = 0; i < pair.Length; i++)
+				var categories = new List<Category>(ladder.Length);
+
+				for (var i = 0; i < ladder.Length; i++)
 				{
-					// CATEGORY HACK: not yet supported: depth beyond 0 and 1
+					var id = ladder[i].CategoryId;
-					if (i > 1)
+					var name = ladder[i].CategoryName;
-						break;
-
-					var id = pair[i].CategoryId;
-					var name = pair[i].CategoryName;
-
-					Category parentCategory = null;
-					if (i == 1)
-						Cache.TryGetValue(pair[0].CategoryId, out parentCategory);
 
 					if (!Cache.TryGetValue(id, out var category))
 					{
@@ -75,13 +71,37 @@ namespace DtoImporterService
 						qtyNew++;
 					}
 
-					category.UpdateParentCategory(parentCategory);
+					categories.Add(category);
+				}
+
+				var categoryLadder = new DataLayer.CategoryLadder(categories);
+				if (!LadderCache.Contains(categoryLadder))
+				{
+					addCategoryLadder(categoryLadder);
+					qtyNew++;
 				}
 			}
 
 			return qtyNew;
 		}
 
+		private DataLayer.CategoryLadder addCategoryLadder(DataLayer.CategoryLadder categoryList)
+		{
+			try
+			{
+				var entityEntry = DbContext.CategoryLadders.Add(categoryList);
+				var entity = entityEntry.Entity;
+
+				LadderCache.Add(entity);
+				return entity;
+			}
+			catch (Exception ex)
+			{
+				Serilog.Log.Logger.Error(ex, "Error adding category ladder. {@DebugInfo}", categoryList);
+				throw;
+			}
+		}
+
 		private Category addCategory(string id, string name)
 		{
 			try

Source/FileLiberator/DownloadDecryptBook.cs

@@ -140,7 +140,7 @@ namespace FileLiberator
                     new AaxcDownloadSingleConverter(outFileName, cacheDir, dlOptions);
 
                 if (config.AllowLibationFixup)
-                    converter.RetrievedMetadata += (_, tags) => tags.Generes = string.Join(", ", libraryBook.Book.CategoriesNames());
+                    converter.RetrievedMetadata += (_, tags) => tags.Generes = string.Join(", ", libraryBook.Book.LowestCategoryNames());
 
                 abDownloader = converter;
             }

Source/LibationAvalonia/Dialogs/BookDetailsDialog.axaml.cs

@@ -115,7 +115,7 @@ Author(s): {Book.AuthorNames()}
 Narrator(s): {Book.NarratorNames()}
 Length: {(Book.LengthInMinutes == 0 ? "" : $"{Book.LengthInMinutes / 60} hr {Book.LengthInMinutes % 60} min")}
 Audio Bitrate: {Book.AudioFormat}
-Category: {string.Join(" > ", Book.CategoriesNames())}
+Category: {string.Join(", ", Book.LowestCategoryNames())}
 Purchase Date: {libraryBook.DateAdded:d}
 Language: {Book.Language}
 Audible ID: {Book.AudibleProductId}

Source/LibationSearchEngine/SearchEngine.cs

@@ -41,7 +41,7 @@ namespace LibationSearchEngine
             { FieldType.String, lb => lb.Book.Publisher, nameof(Book.Publisher) },
             { FieldType.String, lb => lb.Book.SeriesNames(), "SeriesNames", "Narrator", "Series" },
             { FieldType.String, lb => string.Join(", ", lb.Book.SeriesLink.Select(s => s.Series.AudibleSeriesId)), "SeriesId" },
-            { FieldType.String, lb => lb.Book.CategoriesIds() is null ? null : string.Join(", ", lb.Book.CategoriesIds()), nameof(Book.Category), "Categories", "CategoriesId", "CategoryId", "CategoriesNames" },
+            { FieldType.String, lb => lb.Book.CategoriesIds() is null ? null : string.Join(", ", lb.Book.CategoriesIds()), "Category", "Categories", "CategoriesId", "CategoryId", "CategoriesNames" },
             { FieldType.String, lb => lb.Book.UserDefinedItem.Tags, TAGS.FirstCharToUpper() },
             { FieldType.String, lb => lb.Book.Locale, "Locale", "Region" },
             { FieldType.String, lb => lb.Account, "Account", "Email" },

Source/LibationUiBase/GridView/GridEntry[TStatus].cs

@@ -116,7 +116,7 @@ namespace LibationUiBase.GridView
 			ProductRating = Book.Rating ?? new Rating(0, 0, 0);
 			Authors = Book.AuthorNames();
 			Narrators = Book.NarratorNames();
-			Category = string.Join(" > ", Book.CategoriesNames());
+			Category = string.Join(", ", Book.LowestCategoryNames());
 			Misc = GetMiscDisplay(libraryBook);
 			LastDownload = new(Book.UserDefinedItem);
 			LongDescription = GetDescriptionDisplay(Book);

Source/LibationWinForms/Dialogs/BookDetailsDialog.cs

@@ -50,7 +50,7 @@ Author(s): {Book.AuthorNames()}
 Narrator(s): {Book.NarratorNames()}
 Length: {(Book.LengthInMinutes == 0 ? "" : $"{Book.LengthInMinutes / 60} hr {Book.LengthInMinutes % 60} min")}
 Audio Bitrate: {Book.AudioFormat}
-Category: {string.Join(" > ", Book.CategoriesNames())}
+Category: {string.Join(", ", Book.LowestCategoryNames())}
 Purchase Date: {_libraryBook.DateAdded:d}
 Language: {Book.Language}
 Audible ID: {Book.AudibleProductId}