using System;
using System.Collections.Generic;
using System.Text;

namespace ET
{
    public static class MathHelper
    {
        public static int RoundToInt(float d)
        {
            return (int)MathF.Round(d, MidpointRounding.AwayFromZero);
        }
        public static long RoundToLong(float d)
        {
            return (long)MathF.Round(d, MidpointRounding.AwayFromZero);
        }
        public static bool IsHit(float p)
        {
            return p > RandomHelper.RandomFloat();
        }
        public static int GetProbabilityIndex(float[] probabilities)
        {
            int count = probabilities.Length;
            float a = RandomHelper.RandomFloat();
            int index = -1;
            float add = 0;
            foreach (float item in probabilities)
            {
                ++index;
                if(index+1 == count)
                {
                    return index;
                }
                if (add < a &&
                    a <= add+probabilities[index])
                {
                    return index;
                }
                add += item;
            }
            return 0;
        }
        public static int GetProbabilityIndexByWeight(List<int> weights)
        {
            int totalWeight = 0;
            foreach (int item in weights)
            {
                totalWeight += item;
            }
            int count = weights.Count;
            int a = RandomHelper.RandomNumber(0,totalWeight+1);
            int index = -1;
            float add = 0;
            foreach (int item in weights)
            {
                ++index;
                if (index + 1 == count)
                {
                    return index;
                }
                if (add < a &&
                    a <= add + weights[index])
                {
                    return index;
                }
                add += item;
            }
            return 0;
        }
    }
}