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

namespace ERP.Framework.WebApi
{
    public class BaseRepository<T, TDbContext> where T : BaseEntity where TDbContext : DbContext
    {
        private TDbContext _context;

        public BaseRepository(TDbContext context)
        {
            _context = context;
        }

        public T? FirstOrDefault(Expression<Func<T, bool>> exp = null)
        {
            return Filter(exp).FirstOrDefault();
        }

        public void Add(T entity)
        {
            _context.Set<T>().Add(entity);
            Save();
            _context.Entry(entity).State = EntityState.Detached;
        }

        public void Save()
        {
            try
            {
                var entities = _context.ChangeTracker.Entries()
                    .Where(e => e.State == EntityState.Added
                                || e.State == EntityState.Modified)
                    .Select(e => e.Entity);

                foreach (var entity in entities)
                {
                    var validationContext = new ValidationContext(entity);
                    Validator.ValidateObject(entity, validationContext, validateAllProperties: true);
                }

                _context.SaveChanges();
            }
            catch (ValidationException exc)
            {
                // Todo 抛出异常
                //Console.WriteLine($"{nameof(Save)} validation exception: {exc?.Message}");
                //throw (exc.InnerException as Exception ?? exc);
            }
            catch (Exception ex) //DbUpdateException 
            {
                // Todo 抛出异常
                //throw (ex.InnerException as Exception ?? ex);
            }
        }

        private IQueryable<T> Filter(Expression<Func<T, bool>> exp)
        {
            var dbSet = _context.Set<T>().AsNoTracking().AsQueryable();
            if (exp != null)
                dbSet = dbSet.Where(exp);
            return dbSet;
        }
    }
}