using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using BaseGames.Core;
using BaseGames.Core.Events;
using BaseGames.Core.Save;

namespace BaseGames.World.Shop
{
    /// <summary>
    /// 商店流程控制器（架构 15_MapShopModule §2.3）。
    /// 管理库存可见性、购买逻辑、补货策略，并通过 ISaveable 持久化购买记录。
    /// </summary>
    public class ShopController : MonoBehaviour, ISaveable
    {
        [SerializeField] private ShopInventorySO _inventory;
        [SerializeField] private ShopPanel       _shopPanel;     // UI 面板（P4 UI 模块实现）

        [Header("Event Channels（广播）")]
        [SerializeField] private StringEventChannelSO       _onShopOpen;           // EVT_ShopOpened（shopId）
        [SerializeField] private VoidEventChannelSO         _onShopClosed;         // EVT_ShopClosed
        [SerializeField] private ShopPurchaseEventChannelSO _onItemPurchased;      // EVT_ItemPurchased

        [Header("Event Channels（订阅补货触发）")]
        [SerializeField] private StringEventChannelSO       _onBossDefeated;       // EVT_BossDefeated
        [SerializeField] private VoidEventChannelSO         _onSavePointActivated; // EVT_SavePointActivated

        // key = itemId，value = 已购次数
        private Dictionary<string, int> _purchaseCounts  = new();
        private HashSet<string>         _soldUniqueItems  = new();
        private List<ShopItemSO>        _availableItemsCache;
        private bool                    _isDirty = true;
        private readonly CompositeDisposable _subs = new();

        private void OnEnable()
        {
            if (_inventory == null) return;
            if (_inventory.RestockPolicy == RestockPolicy.OnBossDefeat)
                _onBossDefeated?.Subscribe(OnBossDefeated).AddTo(_subs);
            if (_inventory.RestockPolicy == RestockPolicy.OnSavePoint)
                _onSavePointActivated?.Subscribe(OnSavePointActivated).AddTo(_subs);
            ServiceLocator.GetOrDefault<ISaveableRegistry>()?.Register(this);
        }

        private void OnDisable()
        {
            _subs.Clear();
            ServiceLocator.GetOrDefault<ISaveableRegistry>()?.Unregister(this);
        }

        private void OnBossDefeated(string _)    => Restock();
        private void OnSavePointActivated()      => Restock();

        // ── 公共 API ──────────────────────────────────────────────────────────

        public void Open()
        {
            _shopPanel?.Show(GetAvailableItems(), this);
            _onShopOpen?.Raise(_inventory.ShopId);
        }

        public void Close()
        {
            _shopPanel?.Hide();
            _onShopClosed?.Raise();
        }

        /// <summary>返回当前可购买的商品列表（过滤已售唯一品及超限商品）。结果在库存变更时才重建。</summary>
        public List<ShopItemSO> GetAvailableItems()
        {
            if (!_isDirty) return _availableItemsCache;
            if (_inventory?.DefaultInventory == null)
            {
                _availableItemsCache = new List<ShopItemSO>();
                _isDirty = false;
                return _availableItemsCache;
            }
            _availableItemsCache = _inventory.DefaultInventory
                .Where(item => item != null
                    && !_soldUniqueItems.Contains(item.ItemId)
                    && (item.MaxPurchaseCount < 0 || GetPurchaseCount(item.ItemId) < item.MaxPurchaseCount))
                .Take(_inventory.MaxDisplaySlots)
                .ToList();
            _isDirty = false;
            return _availableItemsCache;
        }

        /// <summary>
        /// 按 RestockPolicy 补货：重置非唯一商品的购买次数（已售唯一品不恢复）。
        /// </summary>
        public void Restock()
        {
            if (_inventory?.DefaultInventory == null) return;
            var nonUniqueIds = _inventory.DefaultInventory
                .Where(i => i != null && !i.IsUnique)
                .Select(i => i.ItemId);
            foreach (var id in nonUniqueIds)
                _purchaseCounts.Remove(id);
            _isDirty = true;
        }

        /// <summary>
        /// 尝试购买商品。由 ShopPanel 的购买按钮调用。
        /// </summary>
        /// <returns>购买成功返回 true；资金不足或商品不可购返回 false。</returns>
        public bool TryPurchase(ShopItemSO item, int playerGeo)
        {
            if (item == null) return false;
            int effectivePrice = GetEffectivePrice(item);
            if (playerGeo < effectivePrice) return false;
            if (_soldUniqueItems.Contains(item.ItemId)) return false;
            if (item.MaxPurchaseCount >= 0 && GetPurchaseCount(item.ItemId) >= item.MaxPurchaseCount)
                return false;

            // 通过事件频道扣 Geo（PlayerStats 监听 EVT_ItemPurchased）
            _onItemPurchased?.Raise(new ShopPurchaseEvent
            {
                ItemId = item.ItemId,
                Price  = effectivePrice,
            });

            // 更新库存状态
            _purchaseCounts[item.ItemId] = GetPurchaseCount(item.ItemId) + 1;
            if (item.IsUnique) _soldUniqueItems.Add(item.ItemId);
            _isDirty = true;

            return true;
        }

        /// <summary>
        /// 返回应用难度乘数后的实际价格。UI 层可通过此方法显示正确标价。
        /// </summary>
        public int GetEffectivePrice(ShopItemSO item)
        {
            var scaler = ServiceLocator.GetOrDefault<IDifficultyService>()?.CurrentScaler;
            if (scaler == null) return item.BasePrice;
            return Mathf.Max(1, Mathf.RoundToInt(item.BasePrice * scaler.ShopPriceMultiplier));
        }

        private int GetPurchaseCount(string id)
            => _purchaseCounts.TryGetValue(id, out var c) ? c : 0;

        // ── ISaveable ─────────────────────────────────────────────────────────

        public void OnSave(SaveData data)
        {
            if (_inventory == null) return;
            if (!data.Shops.ShopRecords.ContainsKey(_inventory.ShopId))
                data.Shops.ShopRecords[_inventory.ShopId] = new ShopRecord();

            var record = data.Shops.ShopRecords[_inventory.ShopId];
            record.SoldUniqueItems = _soldUniqueItems.ToList();
            record.PurchaseCounts  = new Dictionary<string, int>(_purchaseCounts);
        }

        public void OnLoad(SaveData data)
        {
            if (_inventory == null) return;
            if (data.Shops.ShopRecords.TryGetValue(_inventory.ShopId, out var record))
            {
                _soldUniqueItems = new HashSet<string>(record.SoldUniqueItems ?? new List<string>());
                _purchaseCounts  = record.PurchaseCounts ?? new Dictionary<string, int>();
                _isDirty = true;
            }
        }
    }

    // ─── ShopPanel ──────────────────────────────────────────────────────────

    /// <summary>
    /// 商店 UI 面板基类。
    /// ShopController 通过此接口调用面板显示/隐藏，已解耦具体 UI 实现。
    /// </summary>
    public class ShopPanel : MonoBehaviour
    {
        public virtual void Show(List<ShopItemSO> items, ShopController controller) { }
        public virtual void Hide() { }
    }
}