using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;

namespace APT.Infrastructure.Core
{
    /// <summary>
    /// Linq 拓展方法类
    /// </summary>
    public static class LinqExtensions
    {
        public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
        {
            Contract.Requires(action != null);
            foreach (var element in source)
                action(element);
        }
        public class DGroupBy<T> : IGrouping<object[], T>
        {
            private List<T> _innerlist = new List<T>();

            private object[] _key;

            public DGroupBy(object[] key) { _key = key; }

            public object[] Key
            {
                get { return _key; }
            }

            public void Add(T value)
            {
                _innerlist.Add(value);
            }

            public IEnumerator<T> GetEnumerator()
            {
                return this._innerlist.GetEnumerator();
            }

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
            {
                return this._innerlist.GetEnumerator();
            }
        }

        public static IEnumerable<IGrouping<object[], T>> DynamicGroupBy<T>(this IEnumerable<T> data, string[] keys)
        {
            List<DGroupBy<T>> list = new List<DGroupBy<T>>();
            foreach (var item in data.Select(x => new {
                k = keys.Select(y => x.GetType().GetProperty(y).GetValue(x, null)).ToArray(),
                v = x
            }))
            {
                DGroupBy<T> existing = list.SingleOrDefault(x => x.Key.Zip(item.k, (a, b) => a.Equals(b)).All(y => y));
                if (existing == null)
                {
                    existing = new DGroupBy<T>(item.k);
                    list.Add(existing);
                }
                existing.Add(item.v);
            }
            return list;
        }
    }
}