using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace gehGassi.Common.Extensions
{
    public static class OrderExtensions
    {

        public static IOrderedQueryable<T> SpecialOrderBy<T>(this IQueryable<T> source, string propertyName, SortDirection sortDirection = SortDirection.Ascending)
        {
            if (sortDirection == SortDirection.Ascending) 
                return source.OrderBy(ToLambda<T>(propertyName));
            return source.OrderByDescending(ToLambda<T>(propertyName));
        }


        public static IOrderedQueryable<T> SpecialThenBy<T>(this IOrderedQueryable<T> source, string propertyName, SortDirection sortDirection = SortDirection.Ascending)
        {
            if (sortDirection == SortDirection.Ascending) 
                return source.ThenBy(ToLambda<T>(propertyName));
            return source.ThenByDescending(ToLambda<T>(propertyName));
        }

        private static Expression<Func<T, object>> ToLambda<T>(string propertyName)
        {
            var parameter = Expression.Parameter(typeof(T));
            var property = Expression.Property(parameter, propertyName);
            var convertedProperty = Expression.Convert(property, typeof(object));

            return Expression.Lambda<Func<T, object>>(convertedProperty, parameter);
        }
    }

    /// <summary>
    /// Sortierrichtung
    /// </summary>
    public enum SortDirection
    {
        /// <summary>
        /// Aufsteigend
        /// </summary>
        Ascending = 1,
        /// <summary>
        /// Absteigend
        /// </summary>
        Descending = 2
    }
}