using System;
using System.Collections.Generic;
using static DDD.SpawnScheduleUtils;

namespace DDD
{
    public class RandomSpawnScheduleBuilder : ISpawnScheduleBuilder
    {
        public SpawnSchedule Build(SpawnScheduleBuildArgs args)
        {
            var randomGenerator = new Random(args.Seed);

            int normalQuota  = Math.Max(0, args.NormalQuota);
            int specialQuota = Math.Max(0, args.SpecialQuota);
            if (args.NormalIds  == null || args.NormalIds.Count  == 0) normalQuota  = 0;
            if (args.SpecialIds == null || args.SpecialIds.Count == 0) specialQuota = 0;

            int total = normalQuota + specialQuota;
            if (total == 0) return new SpawnSchedule(Array.Empty<string>());

            // 스페셜 위치만 무작위 고정(정확히 specialQuota개)
            var specialPositions = new HashSet<int>();
            PickUniqueIndices(total, specialQuota, randomGenerator, specialPositions);

            int normalIndex = 0;
            int specialIndex = 0;
            var result = new List<string>(total);

            for (int i = 0; i < total; i++)
            {
                bool isSpecial = specialPositions.Contains(i);
                if (isSpecial)
                {
                    var id = NextRoundRobin(args.SpecialIds, ref specialIndex);
                    if (string.IsNullOrEmpty(id) == false)
                    {
                        result.Add(id);
                    }
                }
                else
                {
                    var id = NextRoundRobin(args.NormalIds, ref normalIndex);
                    if (string.IsNullOrEmpty(id) == false)
                    {
                        result.Add(id);
                    }
                }
            }

            return new SpawnSchedule(result);
        }
    }
}