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));
	}
}