using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

namespace DataLayer;

// only library importing should use tracking. All else should be NoTracking.
// only library importing should directly query Book. All else should use LibraryBook
public static class BookQueries
{
	public static Book? GetBook_Flat_NoTracking(this LibationContext context, string productId)
		=> context
			.Books
			.AsNoTrackingWithIdentityResolution()
			.GetBook(productId);

	/// <summary>Total rows in <see cref="LibationContext.Books"/> (no related entities loaded).</summary>
	public static int GetBookCount(this LibationContext context)
		=> context.Books.AsNoTracking().Count();

	public static Book? GetBook(this IQueryable<Book> books, string productId)
		=> books
			.GetBooks()
			// 'Single' is more accurate but 'First' is faster and less error prone
			.FirstOrDefault(b => b.AudibleProductId == productId);

	/// <summary>This is still IQueryable. YOU MUST CALL ToList() YOURSELF</summary>
	public static IQueryable<Book> GetBooks(this IQueryable<Book> books, Expression<Func<Book, bool>> predicate)
		=> books
			.GetBooks()
			.Where(predicate);

	/// <summary>This is still IQueryable. YOU MUST CALL ToList() YOURSELF</summary>
	public static IQueryable<Book> GetBooks(this IQueryable<Book> books)
		=> books
			// 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.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;

	public static bool IsEpisodeChild(this Book book)
		=> book.ContentType is ContentType.Episode;

	public static bool IsEpisodeParent(this Book book)
		=> book.ContentType is ContentType.Parent;

	public static IEnumerable<LibraryBook> WithoutParents(this IEnumerable<LibraryBook> libraryBooks)
		=> libraryBooks.Where(lb => !lb.Book.IsEpisodeParent());

	public static bool HasLiberated(this Book book)
			=> book.UserDefinedItem.BookStatus is LiberatedStatus.Liberated ||
			book.UserDefinedItem.PdfStatus is not null and LiberatedStatus.Liberated;
}