using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

            var box = new PrizeBox<string>();

            var prize1 =  box.Add( "1獎",20);

            box.Add("2獎", 30);

            box.Add("3獎", 50);

​

            //抽100次

            foreach (var result in Enumerable.Range(0, 100).Select(x => box.DrawOne()).GroupBy(x => x).Select(x => new

            {

                Count = x.Count(),

                Prize = x.Key

            }).OrderBy(x=>x.Prize))

            {

                Console.WriteLine(result.Prize + " 出現 " + result.Count + " 次");

            }

            //更改機率

            Console.WriteLine("更改機率");

            prize1.Weight = 120;

            box.Reset();

            //抽100次

            foreach (var result in Enumerable.Range(0, 100).Select(x => box.DrawOne()).GroupBy(x => x).Select(x => new

            {

                Count = x.Count(),

                Prize = x.Key

            }).OrderBy(x=>x.Prize))

            {

                Console.WriteLine(result.Prize + " 出現 " + result.Count + " 次");

            }

         //直接限制次數

            Console.WriteLine("直接限制次數");

            prize1.MaxTimes=3;

            box.Reset();

            //抽100次

            foreach (var result in Enumerable.Range(0, 100).Select(x => box.DrawOne()).GroupBy(x => x).Select(x => new

            {

                Count = x.Count(),

                Prize = x.Key

            }).OrderBy(x=>x.Prize))

            {

                Console.WriteLine(result.Prize + " 出現 " + result.Count + " 次");

            }

            //關閉獎項

            prize1.CanDraw=false;

            Console.WriteLine("關閉獎項");

            box.Reset();

         //抽100次

            foreach (var result in Enumerable.Range(0, 100).Select(x => box.DrawOne()).GroupBy(x => x).Select(x => new

            {

                Count = x.Count(),

                Prize = x.Key

            }).OrderBy(x=>x.Prize))

            {

                Console.WriteLine(result.Prize + " 出現 " + result.Count + " 次");

            }

    }

     public interface IPrizeBox

    {

        bool BoxCalculated { get; set; }

    }

    public interface IPrize<T>

    {

        T Item { get; set; }

        int Weight { get; set; }

        int? MaxTimes { get; set; }

        int DrawedTimes { get; set; }

        bool CanDraw { get; set; }

    }

​

    public class PrizeBox<T> : IEnumerable<IPrize<T>>, IPrizeBox

    {

        internal class Prize : IPrize<T>

        {

            public T Item { get; set; }

            protected int weight;

            public int Weight

            {

                get { return weight; }

                set

                {

                    weight = value;

                    if (Box != null)

                    {

                        Box.BoxCalculated = false;

                    }

                }

            }

            public int? MaxTimes

            {

                get { return maxTimes; }

                set

                {

                    maxTimes = value;

                    if (Box != null)

                    {

                        Box.BoxCalculated = false;

                    }

                }

            }

            protected int? maxTimes;

            public int DrawedTimes { get; set; }

            protected bool canDraw;

            public bool CanDraw

            {

                get { return canDraw; }

                set

                {

                    canDraw = value;

                    if (Box != null)

                    {

                        Box.BoxCalculated = false;

                    }

                }

            }

            public IPrizeBox Box { get; set; }

            public Prize()

            {

                CanDraw = true;

            }

            public Prize(T item, int weight, int? maxTimes) : this()

            {

                Item = item;

                Weight = weight;

                MaxTimes = maxTimes;

            }

        }

        static Random random = new Random();

        internal List<IPrize<T>> prizeList = new List<IPrize<T>>();

        internal IPrize<T>[] pool;

        protected int max = 0;

        public bool BoxCalculated { get; set; }

        public int Count { get { return prizeList.Count; } }

​

        public bool IsReadOnly { get { return false; } }

        public void Reset()

        {

            foreach (var prize in prizeList)

            {

                prize.DrawedTimes = 0;

            }

        }

​

        public T DrawOne()

        {

            if (!BoxCalculated)

            {

                pool = prizeList.Where(x => x.CanDraw && x.Weight > 0 && (!x.MaxTimes.HasValue || x.DrawedTimes < x.MaxTimes.Value)).ToArray();

                max = pool.Sum(x => x.Weight);

                BoxCalculated = true;

            }

            if (pool.Length > 0)

            {

                var getLuckNumber = random.Next(1, max);

                foreach (var prize in pool)

                {

                    getLuckNumber -= prize.Weight;

                    if (getLuckNumber <= 0)

                    {

                        prize.DrawedTimes++;

                        if (prize.MaxTimes.HasValue && prize.DrawedTimes >= prize.MaxTimes.Value)

                        {

                            BoxCalculated = false;

                        }

                        return prize.Item;

                    }

                }

            }

            else

            {

                return default(T);

            }

            throw new Exception("something wrong");

        }

​

        public IPrize<T> Add(T item, int weight, int? maxTimes = null)

        {

            var old = FindPrize(item);

            if (old != null)

            {

                throw new Exception("項目重複");

            }

            BoxCalculated = false;

            var prize = new Prize(item, weight, maxTimes);

            prize.Box = this;

            prizeList.Add(prize);

            return prize;

        }

​

        public void Clear()

        {

            BoxCalculated = false;

            prizeList.Clear();

        }

        public IPrize<T> FindPrize(T item)

        {

            return prizeList.FirstOrDefault(x => x.Item.Equals(item));

        }

        public bool Remove(T item)

        {

            var find = FindPrize(item);

            if (find != null)

            {

                BoxCalculated = false;

                prizeList.Remove(find);

                return true;

            }

            return false;

        }

​

        public IEnumerator<IPrize<T>> GetEnumerator()

        {

            return prizeList.GetEnumerator();

        }

​

        IEnumerator IEnumerable.GetEnumerator()

        {

            return prizeList.GetEnumerator();

        }

    }

    }