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

namespace IRaCIS.Core.Infrastructure.Extention
{
    public static class RandomExtensions
    {
        private static Random _random = new Random();

        public static List<T> GetRandomCountList<T>(this List<T> list, int count)
        {
            if (count > list.Count)
            {
                throw new ArgumentException("Sample size cannot be greater than list size.");
            }

            // 使用 Fisher-Yates 洗牌算法来随机选择元素
            List<T> result = list.ToList(); // 复制原始列表，以避免修改原始列表
            int n = result.Count;

            while (n > 1)
            {
                n--;
                int k = _random.Next(n + 1);
                T value = result[k];
                result[k] = result[n];
                result[n] = value;
            }

            // 返回所需数量的元素
            return result.Take(count).ToList();
        }
    }
}