public class LibraryContext : DbContext
{
    public DbSet<Book> Books { get; set; } = null!;
    public DbSet<Author> Authors { get; set; } = null!;
    public DbSet<Genre> Genres { get; set; } = null!;
    public DbSet<Reader> Readers { get; set; } = null!;
    public DbSet<Loan> Loans { get; set; } = null!;

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=LibraryDb;Trusted_Connection=true;");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Настройка отношений
        modelBuilder.Entity<Book>HasOne(b => b.Author)
            .WithMany(a => a.Books)
            .HasForeignKey(b => b.AuthorId);

        modelBuilder.Entity<Book>HasOne(b => b.Genre)
            .WithMany(g => g.Books)
            .HasForeignKey(b => b.GenreId);

        modelBuilder.Entity<Loan>HasOne(l => l.Book)
            .WithMany(b => b.Loans)
            .HasForeignKey(l => l.BookId);

        modelBuilder.Entity<Loan>HasOne(l => l.Reader)
            .WithMany(r => r.Loans)
            .HasForeignKey(l => l.ReaderId);
    }
}