Libation/Source/DataLayer/EntityExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DataLayer
{
    public static class EntityExtensions
	{
		public static IEnumerable<BookContributor> ByRole(this IEnumerable<BookContributor> contributors, Role role)
			=> contributors
				.Where(a => a.Role == role)
				.OrderBy(a => a.Order);


		extension(Book book)
		{
			public string SeriesSortable() => Formatters.GetSortName(book.SeriesNames(true));
			public string TitleSortable() => Formatters.GetSortName(book.Title + book.Subtitle);

			public string AuthorNames => string.Join(", ", book.Authors.Select(a => a.Name));
			public string NarratorNames => string.Join(", ", book.Narrators.Select(n => n.Name));
			/// <summary>True if IsLiberated or Error. False if NotLiberated</summary>
			public bool AudioExists => book.UserDefinedItem.BookStatus is LiberatedStatus.Liberated or LiberatedStatus.Error;
			/// <summary>True if exists and IsLiberated. Else false</summary>
			public bool PdfExists => book.UserDefinedItem.PdfStatus is LiberatedStatus.Liberated;
			/// <summary> Whether the book has any supplements </summary>
			public bool HasPdf => book.Supplements.Any();

			public string SeriesNames(bool includeIndex = false)
			{
				if (book.SeriesLink is null)
					return "";

				// first: alphabetical by name
				var withNames = book.SeriesLink
					.Where(s => !string.IsNullOrWhiteSpace(s.Series.Name))
					.Select(getSeriesNameString)
					.OrderBy(a => a)
					.ToList();
				// then un-named are alpha by series id
				var nullNames = book.SeriesLink
					.Where(s => string.IsNullOrWhiteSpace(s.Series.Name))
					.Select(s => s.Series.AudibleSeriesId)
					.OrderBy(a => a)
					.ToList();

				var all = withNames.Union(nullNames).ToList();
				return string.Join(", ", all);

				string getSeriesNameString(SeriesBook sb)
					=> includeIndex && !string.IsNullOrWhiteSpace(sb.Order) && sb.Order != "-1"
					? $"{sb.Series.Name} (#{sb.Order})"
					: sb.Series.Name;
			}

			public string[] LowestCategoryNames()
				=> book.CategoriesLink?.Any() is not true ? Array.Empty<string>()
				: book
					.CategoriesLink
					.Select(cl => cl.CategoryLadder.Categories.LastOrDefault()?.Name)
					.Where(c => c is not null)
					.Distinct()
					.ToArray();

			public string[] AllCategoryNames()
				=> book.CategoriesLink?.Any() is not true ? Array.Empty<string>()
				: book
					.CategoriesLink
					.SelectMany(cl => cl.CategoryLadder.Categories)
					.Select(c => c.Name)
					.ToArray();

			public string[] AllCategoryIds()
				=> 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)
		{
			if (libraryBooks is null || !libraryBooks.Any())
				return "";

			max = Math.Max(max, 1);

			var titles = libraryBooks.Select(lb => "- " + lb.Book.TitleWithSubtitle).ToList();
			var titlesAgg = titles.Take(max).Aggregate((a, b) => $"{a}\r\n{b}");
			if (titles.Count == max + 1)
				titlesAgg += $"\r\n\r\nand 1 other";
			else if (titles.Count > max + 1)
				titlesAgg += $"\r\n\r\nand {titles.Count - max } others";
			return titlesAgg;
		}

		public static float FirstScore(this Rating rating)
            => rating.OverallRating > 0 ? rating.OverallRating
            : rating.PerformanceRating > 0 ? rating.PerformanceRating
            : rating.StoryRating;
        public static string ToStarString(this Rating rating)
        {
            var items = new List<string>();

            if (rating.OverallRating > 0)
                items.Add($"Overall:   {getStars(rating.OverallRating)}");
            if (rating.PerformanceRating > 0)
                items.Add($"Perform: {getStars(rating.PerformanceRating)}");
            if (rating.StoryRating > 0)
                items.Add($"Story:      {getStars(rating.StoryRating)}");

            return string.Join("\r\n", items);
        }
        /// <summary>character: ★</summary>
        const char STAR = '\u2605';
        /// <summary>character: ½</summary>
        const char HALF = '\u00BD';
        private static string getStars(float score)
        {
            var fullStars = (int)Math.Floor(score);

            var starString = new string(STAR, fullStars);

            if (score - fullStars >= 0.75f)
                starString += STAR;
            else if (score - fullStars >= 0.25f)
				starString += HALF;

			return starString;
        }
    }
}