using BudgetApp.Enums;
using Microsoft.EntityFrameworkCore;

namespace BudgetApp.Storage
{
    public class BudgetContext : DbContext
    {
        public BudgetContext() { }
        public BudgetContext(DbContextOptions options) : base(options) { }

        public DbSet<Transaction> Transactions { get; set; }
        public DbSet<UpdateStatus> UpdateStatuses { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<UpdateStatus>(entity =>
            {
                entity.Property(x => x.Id).ValueGeneratedNever();
                entity.ToTable("UpdateStatus", tableBuilder =>
                {
                    tableBuilder.HasCheckConstraint("CK_UpdateStatus_SingletonId", "`Id` = 1");
                });
                entity.HasData(new UpdateStatus
                {
                    Id = 1,
                    State = UpdateStatusState.Done,
                    Created = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc),
                    Updated = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc)
                });
            });

            base.OnModelCreating(modelBuilder);
        }

        public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default)
        {
            EnsureUpdateStatusChangesAreValid();
            var entries = ChangeTracker
                .Entries()
                .Where(x => x.Entity is BaseModel && (x.State == EntityState.Added || x.State == EntityState.Modified));
            foreach (var entityEntry in entries)
            {
                ((BaseModel)entityEntry.Entity).Updated = DateTime.Now;
                if (entityEntry.State == EntityState.Added)
                {
                    ((BaseModel)entityEntry.Entity).Created = DateTime.Now;
                }
            }
            return await base.SaveChangesAsync(cancellationToken).ConfigureAwait(false);
        }

        public override int SaveChanges()
        {
            EnsureUpdateStatusChangesAreValid();
            var entries = ChangeTracker
                .Entries()
                .Where(x => x.Entity is BaseModel && (x.State == EntityState.Added || x.State == EntityState.Modified));
            foreach (var entityEntry in entries)
            {
                ((BaseModel)entityEntry.Entity).Updated = DateTime.Now;
                if (entityEntry.State == EntityState.Added)
                {
                    ((BaseModel)entityEntry.Entity).Created = DateTime.Now;
                }
            }
            return base.SaveChanges();
        }

        private void EnsureUpdateStatusChangesAreValid()
        {
            var invalidUpdateStatusChange = ChangeTracker
                .Entries<UpdateStatus>()
                .Any(x => x.State is EntityState.Added or EntityState.Deleted);

            if (invalidUpdateStatusChange)
            {
                throw new InvalidOperationException("UpdateStatus is a singleton row. Add and delete operations are not allowed.");
            }
        }
    }
}