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

namespace Geekbot.net.Lib.Extensions
{
    public static class DbSetExtensions
    {
        public static EntityEntry<T> AddIfNotExists<T>(this DbSet<T> dbSet, T entity, Expression<Func<T, bool>> predicate = null) where T : class, new()
        {
            var exists = predicate != null ? dbSet.Any(predicate) : dbSet.Any();
            return !exists ? dbSet.Add(entity) : null;
        }
        
        // https://github.com/dotnet/efcore/issues/18124
        public static IAsyncEnumerable<TEntity> AsAsyncEnumerable<TEntity>(this Microsoft.EntityFrameworkCore.DbSet<TEntity> obj) where TEntity : class
        {
            return Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AsAsyncEnumerable(obj);
        }
        public static IQueryable<TEntity> Where<TEntity>(this Microsoft.EntityFrameworkCore.DbSet<TEntity> obj, System.Linq.Expressions.Expression<Func<TEntity, bool>> predicate) where TEntity : class
        {
            return System.Linq.Queryable.Where(obj, predicate);
        }
    }
}