using System;
using System.Collections.Generic;

namespace TBL.CSharp.Utilities.Random.Generator
{
    /// <summary>
    /// 已知序列的随机数生成器
    /// <para>用于固定结果的演出教学等特殊用途</para>
    /// </summary>
    public class KnownSeriesGenerator : IRandom<KnownSeriesGenerator.Seed>
    {
        /// <summary>
        /// 已经生成的随机数计数
        /// </summary>
        private long _numberGenerated;

        /// <summary>
        /// 已知序列
        /// </summary>
        private readonly Queue<int> _series;

        /// <summary>
        /// 构造
        /// </summary>
        /// <param name="series">已知序列</param>
        /// <exception cref="ArgumentNullException">已知序列为空</exception>
        public KnownSeriesGenerator(params int[] series)
        {
            if (series == null)
                throw new ArgumentNullException(nameof(series));
            _series = new Queue<int>();
            foreach (var num in series)
                _series.Enqueue(num);
        }

        public int NextRaw()
        {
            var num = _series.Dequeue();
            _series.Enqueue(num);
            ++_numberGenerated;
            return num;
        }

        public Seed DumpSeed() => new Seed(_numberGenerated, _series);

        public void RestoreBySeed(Seed seed)
        {
            _series.Clear();
            foreach (var num in seed.KnownSeries)
                _series.Enqueue(num);
            _numberGenerated = seed.NumberGenerated;
        }

        /// <summary>
        /// 种子
        /// </summary>
        public readonly struct Seed
        {
            /// <summary>
            /// 已经生成的随机数计数
            /// </summary>
            public readonly long NumberGenerated;

            /// <summary>
            /// 已知序列
            /// </summary>
            public readonly int[] KnownSeries;

            /// <summary>
            /// 构造
            /// </summary>
            public Seed(long numberGenerated, Queue<int> knownSeries)
            {
                NumberGenerated = numberGenerated;
                KnownSeries = knownSeries.ToArray();
            }
        }
    }
}