// using System;
using System.Collections.Generic;

namespace EventCubeMelt.Utils
{
    class UniqueRandom99
    {
        private readonly List<(int r, int c)> _pool = new List<(int, int)>();
        // private readonly Random _rng = new Random();
        private int _idx = 0;

        public UniqueRandom99(int[,] arr)
        {
            int m = arr.GetLength(0);
            int n = arr.GetLength(1);
            for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (arr[i, j] == 99)
                    _pool.Add((i, j));
            Shuffle();          // 初始随机化
        }

        /// <summary>
        /// 返回一个从未返回过的 99 坐标；若数组里本来就没有 99，则一直返回 (-1,-1)
        /// 所有 99 用完后自动洗牌进入下一轮。
        /// </summary>
        public (int r, int c) Next()
        {
            if (_pool.Count == 0) return (-1, -1);

            if (_idx == _pool.Count)      // 本轮用完，重置并洗牌
            {
                // _idx = 0;
                // Shuffle();
                return (-1, -1);
            }

            return _pool[_idx++];
        }

        private void Shuffle()
        {
            for (int i = _pool.Count - 1; i > 0; i--)
            {
                var j = UnityEngine.Random.Range(0, i + 1);
                (_pool[i], _pool[j]) = (_pool[j], _pool[i]);
            }
        }
    }
}