using System;
using System.Collections.Generic;

namespace DDD
{
    internal static class SpawnScheduleUtils
    {
        public static string NextRoundRobin(IReadOnlyList<string> source, ref int index)
        {
            if (source == null || source.Count == 0) return null;
            
            if (index >= source.Count)
            {
                index = 0;
            }
            
            return source[index++];
        }

        /// <summary>
        /// 비율 분배 시퀀스(N/S)를 생성합니다. 스페셜 우선이 아니라 '노말 우선'입니다.
        /// accumulator += specialQuota; if (accumulator > total) => S, else N.
        /// </summary>
        public static List<CustomerType> BuildProportionalKinds(int normalQuota, int specialQuota)
        {
            int normal = Math.Max(0, normalQuota);
            int special = Math.Max(0, specialQuota);
            int total = normal + special;

            var kinds = new List<CustomerType>(total);
            if (total == 0) return kinds;

            int accumulator = 0;
            for (int i = 0; i < total; i++)
            {
                accumulator += special;
                if (accumulator >= total) // 스페셜 개수 보장
                {
                    kinds.Add(CustomerType.Special);
                    accumulator -= total;
                }
                else
                {
                    kinds.Add(CustomerType.Normal);
                }
            }
            return kinds;
        }
        
        public static void PickUniqueIndices(int total, int pickCount, Random randomGenerator, HashSet<int> output)
        {
            output.Clear();
            pickCount = Math.Min(Math.Max(0, pickCount), total);
            if (pickCount == 0 || total == 0) return;

            // 0..total-1을 부분 Fisher–Yates
            var indices = new int[total];
            for (int i = 0; i < total; i++)
            {
                indices[i] = i;
            }

            for (int i = 0; i < pickCount; i++)
            {
                int j = randomGenerator.Next(i, total);
                (indices[i], indices[j]) = (indices[j], indices[i]);
                output.Add(indices[i]);
            }
        }
    }
}