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

namespace BaseGames.Inventory
{
    /// <summary>
    /// 运行时背包管理器。
    /// 挂在 Persistent 场景 [Services] 下，事件驱动记录玩家持有的道具，
    /// 实现 <see cref="ISaveable"/> 持久化。设计对照 <see cref="BaseGames.World.Map.MapManager"/>
    /// 与 <see cref="BaseGames.Equipment.EquipmentManager"/> 的服务注册 / 存档模式。
    /// </summary>
    [DefaultExecutionOrder(-700)]
    public class InventoryManager : MonoBehaviour, ISaveable, IInventoryService
    {
        [SerializeField] private ItemDatabaseSO _database;

        [Header("Event Channels - Listen")]
        [Tooltip("道具拾取（itemId）。Collectible 拾取 Item 类型时广播 EVT_ItemPickup。")]
        [SerializeField] private StringEventChannelSO _onItemPickup;

        [Header("Event Channels - Raise")]
        [Tooltip("道具首次获得时广播（itemId），供 HUD Toast / 地图碎片揭示等订阅。")]
        [SerializeField] private StringEventChannelSO _onItemAcquired;
        [Tooltip("背包内容变化时广播（无负载），供 UI 轻量刷新。")]
        [SerializeField] private VoidEventChannelSO   _onInventoryChanged;
        [Tooltip("地图碎片道具获得时广播揭示区域（regionId）。对应 EVT_RevealRegion。")]
        [SerializeField] private StringEventChannelSO _onRevealRegion;

        private readonly Dictionary<string, int> _counts   = new();
        private readonly HashSet<string>         _newItems = new();
        private readonly List<InventoryEntry>    _view     = new();
        private bool _viewDirty = true;
        private bool _isDuplicate;
        private readonly CompositeDisposable _subs = new();

        public event Action OnInventoryChanged;

        // ── 生命周期 ──────────────────────────────────────────────────────────
        private void Awake()
        {
            if (ServiceLocator.GetOrDefault<IInventoryService>() != null) { _isDuplicate = true; Destroy(gameObject); return; }
            ServiceLocator.Register<IInventoryService>(this);
            Debug.Assert(_database != null, "[InventoryManager] _database 未赋值，请在 Inspector 中指定 ItemDatabaseSO。", this);
        }

        private void OnEnable()
        {
            if (_isDuplicate) return;
            _onItemPickup?.Subscribe(OnItemPickup).AddTo(_subs);
            ServiceLocator.GetOrDefault<ISaveableRegistry>()?.Register(this);
        }

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

        private void OnDestroy()
        {
            if (_isDuplicate) return;
            ServiceLocator.Unregister<IInventoryService>(this);
        }

        // ── 事件驱动拾取 ──────────────────────────────────────────────────────
        private void OnItemPickup(string itemId) => AddItem(itemId, 1);

        // ── IInventoryService ─────────────────────────────────────────────────
        public IReadOnlyList<InventoryEntry> Items
        {
            get { RebuildViewIfDirty(); return _view; }
        }

        public int DistinctCount => _counts.Count;

        public int GetCount(string itemId)
            => !string.IsNullOrEmpty(itemId) && _counts.TryGetValue(itemId, out var c) ? c : 0;

        public bool Has(string itemId) => GetCount(itemId) > 0;

        public int AddItem(string itemId, int amount = 1)
        {
            if (string.IsNullOrEmpty(itemId) || amount <= 0) return 0;
            var item = _database != null ? _database.Find(itemId) : null;
            if (item == null) { Debug.LogWarning($"[InventoryManager] 找不到道具: {itemId}", this); return 0; }

            bool firstTime = !_counts.ContainsKey(itemId);
            int  current   = firstTime ? 0 : _counts[itemId];
            int  target;

            if (!item.stackable)
            {
                if (current >= 1) return 0;   // 非叠加道具已持有，忽略
                target = 1;
            }
            else
            {
                target = current + amount;
                if (item.maxStack > 0) target = Mathf.Min(target, item.maxStack);
            }

            int added = target - current;
            if (added <= 0) return 0;

            _counts[itemId] = target;
            _newItems.Add(itemId);
            _viewDirty = true;

            if (firstTime)
            {
                _onItemAcquired?.Raise(itemId);
                // 地图碎片：揭示对应区域
                if (item.category == ItemCategory.MapShard && !string.IsNullOrEmpty(item.revealRegionId))
                    _onRevealRegion?.Raise(item.revealRegionId);
            }

            RaiseChanged();
            return added;
        }

        public int RemoveItem(string itemId, int amount = 1)
        {
            if (string.IsNullOrEmpty(itemId) || amount <= 0) return 0;
            if (!_counts.TryGetValue(itemId, out var current) || current <= 0) return 0;

            int removed = Mathf.Min(current, amount);
            int target  = current - removed;
            if (target <= 0)
            {
                _counts.Remove(itemId);
                _newItems.Remove(itemId);
            }
            else
            {
                _counts[itemId] = target;
            }

            _viewDirty = true;
            RaiseChanged();
            return removed;
        }

        public void MarkSeen(string itemId)
        {
            if (string.IsNullOrEmpty(itemId)) return;
            if (_newItems.Remove(itemId))
            {
                _viewDirty = true;
                RaiseChanged();
            }
        }

        // ── 内部 ──────────────────────────────────────────────────────────────
        private void RaiseChanged()
        {
            _onInventoryChanged?.Raise();
            OnInventoryChanged?.Invoke();
        }

        private void RebuildViewIfDirty()
        {
            if (!_viewDirty) return;
            _view.Clear();
            foreach (var kv in _counts)
            {
                var item = _database != null ? _database.Find(kv.Key) : null;
                if (item == null) continue;
                _view.Add(new InventoryEntry(item, kv.Value, _newItems.Contains(kv.Key)));
            }
            // 按分类枚举顺序、再按本地化名/ID 稳定排序，供 UI 分组展示
            _view.Sort((a, b) =>
            {
                int c = a.Item.category.CompareTo(b.Item.category);
                return c != 0 ? c : string.CompareOrdinal(a.Item.itemId, b.Item.itemId);
            });
            _viewDirty = false;
        }

        // ── ISaveable ─────────────────────────────────────────────────────────
        public void OnSave(SaveData data)
        {
            data.Inventory.ItemCounts.Clear();
            foreach (var kv in _counts) data.Inventory.ItemCounts[kv.Key] = kv.Value;
            data.Inventory.NewItemIds.Clear();
            data.Inventory.NewItemIds.AddRange(_newItems);
        }

        public void OnLoad(SaveData data)
        {
            _counts.Clear();
            _newItems.Clear();
            if (data.Inventory?.ItemCounts != null)
                foreach (var kv in data.Inventory.ItemCounts)
                    if (!string.IsNullOrEmpty(kv.Key) && kv.Value > 0)
                        _counts[kv.Key] = kv.Value;
            if (data.Inventory?.NewItemIds != null)
                foreach (var id in data.Inventory.NewItemIds)
                    if (_counts.ContainsKey(id)) _newItems.Add(id);

            _viewDirty = true;
            RaiseChanged();
        }
    }
}