using System;
using System.Collections.Generic;
using System.Linq;

namespace ET.Server
{
    [FriendOf(typeof(GachaComponent))]
    public static class GachaComponentSystem
    {
        public static List<RewardEntry> Draw(this GachaComponent self, int poolId, GachaDrawType drawType, BagComponent bag)
        {
            List<GachaPoolWeight> weights = GetPoolWeights(poolId);
            if (weights.Count == 0)
            {
                return new List<RewardEntry>();
            }

            int times = drawType == GachaDrawType.Single ? 1 : 10;
            List<CostEntry> costs = GetDrawCost(poolId, drawType);
            if (!bag.HasItems(costs))
            {
                throw new RpcException(ErrorCode.ERR_GACHA_COST_NOT_ENOUGH, "Gacha cost not enough");
            }

            bool removed = bag.RemoveItems(costs);
            if (!removed)
            {
                throw new RpcException(ErrorCode.ERR_GACHA_COST_NOT_ENOUGH, "Gacha cost remove failed");
            }

            List<RewardEntry> rewards = new(times);
            for (int i = 0; i < times; i++)
            {
                GachaPoolWeight pick = PickByWeight(weights);
                rewards.Add(new RewardEntry { ItemId = pick.ItemId, Count = pick.Count });
                self.UpdateGuarantee(poolId, pick.Rare, 90);
            }

            if (drawType == GachaDrawType.Multi10 && !rewards.Any(r => GetRareByItemId(r.ItemId) >= 4))
            {
                self.ReplaceWithGuaranteed(rewards, weights, 4);
            }

            bag.AddItems(rewards);
            LogExtensions.Audit(
                "Gacha",
                "Draw",
                $"{{\"poolId\":{poolId},\"drawType\":{(int)drawType},\"rewardsCount\":{rewards.Count},\"guaranteeRemain\":{self.GetGuaranteeRemain(poolId)}}}");
            return rewards;
        }

        public static void UpdateGuarantee(this GachaComponent self, int poolId, int rare, int guaranteeCount)
        {
            if (!self.PoolStats.TryGetValue(poolId, out GachaPoolState state))
            {
                state = new GachaPoolState { GuaranteeRemain = guaranteeCount };
                self.PoolStats[poolId] = state;
            }

            state.TotalCount += 1;
            state.LastDrawMs = TimeInfo.Instance.ServerNow();
            if (rare >= 5)
            {
                state.GuaranteeRemain = guaranteeCount;
                return;
            }

            state.GuaranteeRemain = Math.Max(0, state.GuaranteeRemain - 1);
            if (state.GuaranteeRemain == 0)
            {
                state.GuaranteeRemain = guaranteeCount;
            }
        }

        public static void ReplaceWithGuaranteed(this GachaComponent self, List<RewardEntry> rewards, List<GachaPoolWeight> weights, int minRare)
        {
            GachaPoolWeight guaranteed = weights.FirstOrDefault(x => x.Rare >= minRare);
            if (guaranteed == null || rewards.Count == 0)
            {
                return;
            }

            int index = rewards.Count - 1;
            rewards[index] = new RewardEntry { ItemId = guaranteed.ItemId, Count = guaranteed.Count };
        }

        public static int GetGuaranteeRemain(this GachaComponent self, int poolId)
        {
            if (!self.PoolStats.TryGetValue(poolId, out GachaPoolState state))
            {
                return 90;
            }
            return state.GuaranteeRemain;
        }

        private static GachaPoolWeight PickByWeight(List<GachaPoolWeight> weights)
        {
            int total = weights.Sum(x => x.Weight);
            int point = CryptoRandomGenerator.Next(0, Math.Max(total, 1));
            int sum = 0;
            foreach (GachaPoolWeight w in weights)
            {
                sum += w.Weight;
                if (point < sum)
                {
                    return w;
                }
            }

            return weights[weights.Count - 1];
        }

        private static List<CostEntry> GetDrawCost(int poolId, GachaDrawType drawType)
        {
            // TODO: 由 Luban TbGachaPool 驱动。当前使用固定测试配置。
            return drawType == GachaDrawType.Single
                ? new List<CostEntry> { new() { ItemId = poolId == 1 ? 1 : 2, Count = 1 } }
                : new List<CostEntry> { new() { ItemId = poolId == 1 ? 1 : 2, Count = 9 } };
        }

        private static int GetRareByItemId(int itemId)
        {
            if (itemId >= 10000) return 5;
            if (itemId >= 1000) return 4;
            return 3;
        }

        private static List<GachaPoolWeight> GetPoolWeights(int poolId)
        {
            // TODO: 由 Luban TbGachaWeight 读取。当前提供固定测试池。
            if (poolId == 2)
            {
                return new List<GachaPoolWeight>
                {
                    new() { ItemId = 2, Count = 10, Weight = 7000, Rare = 3 },
                    new() { ItemId = 1001, Count = 5, Weight = 2500, Rare = 4 },
                    new() { ItemId = 10001, Count = 1, Weight = 500, Rare = 5 },
                };
            }

            return new List<GachaPoolWeight>
            {
                new() { ItemId = 1, Count = 100, Weight = 7000, Rare = 3 },
                new() { ItemId = 1001, Count = 1, Weight = 2500, Rare = 4 },
                new() { ItemId = 10001, Count = 1, Weight = 500, Rare = 5 },
            };
        }
    }
}