using System;
using System.Linq;
using System.Linq.Expressions;


namespace APT.Infrastructure.Core
{

        /// <summary>
        /// Linq架构里对集合排序实现
        /// </summary>
        /// <typeparam name="T"></typeparam>
        public class Orderable<T> : IOrderable<T>
        {
            private IQueryable<T> _queryable;

            /// <summary>
            /// 排序后的结果集
            /// </summary>
            /// <param name="enumerable"></param>
            public Orderable(IQueryable<T> enumerable)
            {
                _queryable = enumerable;
            }

            /// <summary>
            /// 排序之后的结果集
            /// </summary>
            public IQueryable<T> Queryable
            {
                get { return _queryable; }
            }
            /// <summary>
            /// 递增
            /// </summary>
            /// <typeparam name="TKey"></typeparam>
            /// <param name="keySelector"></param>
            /// <returns></returns>
            public IOrderable<T> Asc<TKey>(Expression<Func<T, TKey>> keySelector)
            {
                _queryable = (_queryable as IOrderedQueryable<T>)
                    .OrderBy(keySelector);
                return this;
            }
            /// <summary>
            /// 然后递增
            /// </summary>
            /// <typeparam name="TKey"></typeparam>
            /// <param name="keySelector"></param>
            /// <returns></returns>
            public IOrderable<T> ThenAsc<TKey>(Expression<Func<T, TKey>> keySelector)
            {
                _queryable = (_queryable as IOrderedQueryable<T>)
                    .ThenBy(keySelector);
                return this;
            }
            /// <summary>
            /// 递减
            /// </summary>
            /// <typeparam name="TKey"></typeparam>
            /// <param name="keySelector"></param>
            /// <returns></returns>
            public IOrderable<T> Desc<TKey>(Expression<Func<T, TKey>> keySelector)
            {
                _queryable = _queryable
                    .OrderByDescending(keySelector);
                return this;
            }
            /// <summary>
            /// 然后递减
            /// </summary>
            /// <typeparam name="TKey"></typeparam>
            /// <param name="keySelector"></param>
            /// <returns></returns>
            public IOrderable<T> ThenDesc<TKey>(Expression<Func<T, TKey>> keySelector)
            {
                _queryable = (_queryable as IOrderedQueryable<T>)
                    .ThenByDescending(keySelector);
                return this;
            }
        }
    
}