using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace CsTest.ChangeTracking
{
    class TestContext : DbContext
    {
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlite("DataSource=test.db");
            base.OnConfiguring(optionsBuilder);
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Ownership>().HasKey(t => new {t.HumanId, t.PetId});
            modelBuilder.Entity<Ownership>().HasOne(t => t.Human).WithMany(t => t.Ownerships)
                .HasForeignKey(t => t.HumanId);
            modelBuilder.Entity<Ownership>().HasOne(t => t.Pet).WithMany().HasForeignKey(t => t.PetId);
        }

        public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = new CancellationToken())
        {
            Console.WriteLine("TRACE");
            foreach (var entityEntry in ChangeTracker.Entries())
            {
                Console.WriteLine("[{0}] entity ({1})", entityEntry.State, entityEntry.Entity.ToString());
            }
            Console.WriteLine("ENDTRACE");
            return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
        }
    }

    class Pet
    {
        [Key]
        public Guid Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("{0}({1})", GetType().Name, Id);
        }
    }

    class Human
    {
        [Key]
        public Guid Id { get; set; }
        public string Name { get; set; }

        public virtual HashSet<Ownership> Ownerships { get; set; }

        public override string ToString()
        {
            return string.Format("{0}({1})", GetType().Name, Id);
        }

        public void AddPets(params Guid[] ids)
        {
            ids.Select(t => new Ownership()
            {
                PetId = t,
                HumanId = Id
            }).ToList()
            .ForEach(t => Ownerships.Add(t));
        }
    }

    class Ownership
    {
        public Guid PetId { get; set; }
        public Pet Pet { get; set; }

        public Human Human { get; set; }
        public Guid HumanId { get; set; }

        public override string ToString()
        {
            return string.Format("{0}({1}-{2})", GetType().Name, HumanId, PetId);
        }

        public override bool Equals(object b)
        {
            var a = b as Ownership;
            Console.WriteLine(b);
            return b is Ownership o
                   && o.HumanId == HumanId && o.PetId == PetId;
        }

        public override int GetHashCode()
        {
            return HumanId.GetHashCode() + PetId.GetHashCode();
        }
    }

    class Program
    {
        public static void Main(string[] args)
        {
            Guid kristenId;
            Guid samId;

            using (var db = new TestContext())
            {
                db.Database.EnsureCreated();
                var bucky = db.Add(new Pet() {Name = "Buck"}).Entity;
                var sam = db.Add(new Pet() {Name = "Sam"}).Entity;

                db.Add(new Human() {Name = "John"});
                var kristen = db.Add(new Human()
                {
                    Name = "Kristen",
                    Ownerships = new HashSet<Ownership>()
                    {
                        new Ownership()
                        {
                            PetId = bucky.Id
                        }
                    }
                }).Entity;

                db.SaveChangesAsync();

                kristenId = kristen.Id;
                samId = sam.Id;
                Console.WriteLine("======");
            }

            using (var db = new TestContext())
            {
                var allPets = db.Set<Pet>().Select(t => t.Id).ToArray();
                var kristen = db.Set<Human>().Include(t => t.Ownerships).FirstOrDefault(t => t.Id == kristenId);
                kristen?.AddPets(allPets);

                Console.WriteLine("Kristen now have all {0} pets", kristen.Ownerships.Count);
                db.Update(kristen);
                db.SaveChangesAsync();
            }
        }
    }
}