using System;
using System.Collections.Generic;
using System.Linq;

namespace GFGGame
{
    public static class RandomUtil
    {
        private static readonly Random TempRandom = new Random();

        public static T RandomList<T>(List<T> list)
        {
            var index = TempRandom.Next(list.Count);
            return list[index];
        }

        public static T RandomArr<T>(T[] arr)
        {
            var index = TempRandom.Next(arr.Length);
            return arr[index];
        }

        public static T RandomArr<T>(List<T> arr)
        {
            var index = TempRandom.Next(arr.Count);
            return arr[index];
        }

        //随机一个数 start 包含  end 包含
        public static int RandomInt(int start, int end)
        {
            return TempRandom.Next(start, end + 1);
        }

        public static int RandomNext(int count)
        {
            return TempRandom.Next(count);
        }


        public static T[] RandomN<T>(IEnumerable<T> arr, int n)
        {
            return arr.OrderBy(x => TempRandom.Next()).Take(n).ToArray();
        }

        public static T[] RandomNExtra<T>(T[] arr, T[] arr1, int n)
        {
            var list = arr.Except(arr1).ToList();
            var count = list.Count;
            var needNum = n;
            var result = new List<T>();
            while (needNum > 0 && count > 0)
            {
                var index = TempRandom.Next(count);
                result.Add(list[index]);
                list[index] = list[count - 1];
                count--;
                needNum--;
            }

            if (needNum <= 0) return result.ToArray();
            var extra = arr.Except(result).OrderBy(_ => TempRandom.Next()).Take(needNum);
            result.AddRange(extra);
            return result.ToArray();
        }

        public static int RandomNExtra(int start, int end, List<int> extra)
        {
            var list = new List<int>();
            for (var i = start; i <= end; i++)
            {
                if (extra.Contains(i)) continue;
                list.Add(i);
            }

            var count = list.Count - 1;
            var index = TempRandom.Next(count);
            return list[index];
        }

        public static List<TValue> GetRandomValues<TKey, TValue>(Dictionary<TKey, TValue> dict, int n)
        {
            return dict.Values.OrderBy(x => TempRandom.Next()).Take(n).ToList();
        }
    }
}