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

namespace BaseGames.World.Map
{
    /// <summary>
    /// 角落小地图 HUD（架构 15_MapShopModule §1.6）。
    /// 以玩家当前房间为中心，仅渲染 ±ViewRadiusCells 格范围内的房间。
    /// 玩家跨格进入新房间时（OnRoomChanged 事件）触发增量重建，无需每帧扫描全局。
    /// <para>
    /// 挂载位置：HUD Canvas 下 Minimap 根节点（需配有 RectMask2D 用于裁剪）。
    /// </para>
    /// 依赖 <see cref="IPlayerPositionProvider"/> 和 <see cref="IMapService"/>，
    /// 均通过 <see cref="ServiceLocator"/> 获取，不持有具体类的 SerializeField 引用。
    /// </summary>
    public class MinimapHUD : MonoBehaviour
    {
        [SerializeField] private MapRoomCellUI _cellPrefab;
        [SerializeField] private RectTransform _cellContainer;  // 带 RectMask2D 的容器，内容在此节点内平移
        [SerializeField] private Image         _playerDot;      // 玩家位置圆点（在 _cellContainer 内）

        [Header("显示范围")]
        [SerializeField, Min(1)] private int   _viewRadiusCells = 3;   // 以玩家房间中心为圆心的可视半径（格）
        [SerializeField]          private float _cellPixels      = 16f; // 每格显示像素数

        [Header("颜色（Inspector 覆盖）")]
        [SerializeField] private Color _colorExplored = Color.white;
        [SerializeField] private Color _colorMapped   = new Color(0.45f, 0.45f, 0.45f, 1f);
        [SerializeField] private Color _colorUnknown  = Color.black;

        [Header("Event Channels")]
        [SerializeField] private StringEventChannelSO _onMapUpdated;  // 房间发现/标注时局部刷新

        private IMapService             _mapSvc;
        private IPlayerPositionProvider _playerProvider;
        private readonly Dictionary<string, MapRoomCellUI> _cells = new();
        private readonly CompositeDisposable _subs = new();

        // 复用 List 避免 RefreshView 每次分配临时 List（GC 友好）
        private readonly List<string> _toRemove = new List<string>(8);

        // 空间索引：格子坐标 → 房间 ID，将 RefreshView step② 的 O(N) 遍历降至 O(viewRadius²)
        private Dictionary<Vector2Int, string> _spatialIndex;
        // 复用 HashSet 避免 RefreshView 每次分配（GC 友好）
        private readonly HashSet<string> _roomsInViewBuffer = new HashSet<string>(32);

        private Vector2Int _currentCenter;
        private string  _lastDotRoomId;
        private Vector2 _lastDotNormPos;

        // ── 生命周期 ──────────────────────────────────────────────────────────

        private void OnEnable()
        {
            _mapSvc         = ServiceLocator.GetOrDefault<IMapService>();
            _playerProvider = ServiceLocator.GetOrDefault<IPlayerPositionProvider>();

            BuildSpatialIndex(_mapSvc?.Database);

            if (_playerProvider != null)
                _playerProvider.OnRoomChanged += OnRoomChanged;

            _onMapUpdated?.Subscribe(OnMapUpdated).AddTo(_subs);

            // 首次显示时立即刷新
            RefreshView();
        }

        private void OnDisable()
        {
            if (_playerProvider != null)
                _playerProvider.OnRoomChanged -= OnRoomChanged;

            _subs.Clear();
            ClearAllCells();
            _lastDotRoomId = null;
            _mapSvc         = null;
            _playerProvider = null;
            _spatialIndex   = null;
        }

        private void ClearAllCells()
        {
            foreach (var cell in _cells.Values)
                if (cell != null) Destroy(cell.gameObject);
            _cells.Clear();
        }

        /// <summary>
        /// 构建格子坐标 → 房间 ID 的哈希映射。
        /// 将 RefreshView step② 从 O(allRooms) 全量遍历降至 O(viewRadius²) 范围格点查询。
        /// 数据库变更时（如热更）应再次调用。
        /// </summary>
        private void BuildSpatialIndex(MapDatabaseSO db)
        {
            _spatialIndex = new Dictionary<Vector2Int, string>();
            if (db?.AllRooms == null) return;
            foreach (var room in db.AllRooms)
            {
                if (room == null) continue;
                for (int x = 0; x < room.GridSize.x; x++)
                for (int y = 0; y < room.GridSize.y; y++)
                    _spatialIndex[new Vector2Int(room.GridPosition.x + x, room.GridPosition.y + y)] = room.RoomId;
            }
        }

        private void LateUpdate()
        {
            UpdatePlayerDot();
        }

        // ── 事件响应 ──────────────────────────────────────────────────────────

        private void OnRoomChanged(string _) => RefreshView();

        private void OnMapUpdated(string roomId)
        {
            if (_cells.TryGetValue(roomId, out var cell))
                cell.SetVisibility(_mapSvc.GetVisibility(roomId));
        }

        // ── 视图重建 ──────────────────────────────────────────────────────────

        /// <summary>
        /// 以玩家当前房间中心为基准，增量更新可视格内的格子：
        /// 回收超出范围的旧格子，实例化刚进入范围的新格子，重定位全部格子到新中心。
        /// </summary>
        private void RefreshView()
        {
            var db = _mapSvc?.Database;
            if (db?.AllRooms == null) return;

            var currentRoomId = _playerProvider?.CurrentRoomId;
            if (string.IsNullOrEmpty(currentRoomId)) return;

            var currentRoom = db.GetRoom(currentRoomId);
            if (currentRoom == null) return;

            _currentCenter = currentRoom.GridPosition + currentRoom.GridSize / 2;

            int minX = _currentCenter.x - _viewRadiusCells;
            int maxX = _currentCenter.x + _viewRadiusCells;
            int minY = _currentCenter.y - _viewRadiusCells;
            int maxY = _currentCenter.y + _viewRadiusCells;

            // ① 回收不在可视范围内的格子（复用 _toRemove 避免每帧 new）
            _toRemove.Clear();
            foreach (var (id, cell) in _cells)
            {
                var r = db.GetRoom(id);
                if (r == null || !RoomInView(r, minX, maxX, minY, maxY))
                {
                    if (cell != null) Destroy(cell.gameObject);
                    _toRemove.Add(id);
                }
            }
            foreach (var id in _toRemove) _cells.Remove(id);

            // ② 用空间索引替代 O(N) 全量遍历，在可视范围格点上查询所属房间
            // 复杂度：O(viewRadius²) 替代 O(allRooms)，大地图下效果显著
            _roomsInViewBuffer.Clear();
            if (_spatialIndex != null)
            {
                for (int x = minX; x <= maxX; x++)
                for (int y = minY; y <= maxY; y++)
                {
                    if (_spatialIndex.TryGetValue(new Vector2Int(x, y), out var rId))
                        _roomsInViewBuffer.Add(rId);
                }
            }

            foreach (var roomId in _roomsInViewBuffer)
            {
                if (_cells.ContainsKey(roomId)) continue;
                var room = db.GetRoom(roomId);
                if (room == null) continue;

                var cell = Instantiate(_cellPrefab, _cellContainer);
                cell.Setup(room, _mapSvc.GetVisibility(room.RoomId), null);
                cell.SetColors(_colorExplored, _colorMapped, _colorUnknown);
                PlaceCell(cell, room);  // 立即设置正确的中心相对坐标，避免 Setup 默认偏移被 step③ 覆盖
                _cells[roomId] = cell;
            }

            // ③ 重定位所有格子（中心发生变化时）
            foreach (var (id, cell) in _cells)
            {
                if (cell == null) continue;
                var r = db.GetRoom(id);
                if (r != null) PlaceCell(cell, r);
            }

            UpdatePlayerDot();
        }

        // ── 格子位置 ──────────────────────────────────────────────────────────

        private void PlaceCell(MapRoomCellUI cell, MapRoomDataSO room)
        {
            cell.RT.sizeDelta = new Vector2(room.GridSize.x * _cellPixels, room.GridSize.y * _cellPixels);
            cell.RT.anchoredPosition = new Vector2(
                (room.GridPosition.x - _currentCenter.x) * _cellPixels,
                (room.GridPosition.y - _currentCenter.y) * _cellPixels);
        }

        private static bool RoomInView(MapRoomDataSO room, int minX, int maxX, int minY, int maxY)
            => room.GridPosition.x + room.GridSize.x > minX &&
               room.GridPosition.x < maxX &&
               room.GridPosition.y + room.GridSize.y > minY &&
               room.GridPosition.y < maxY;

        // ── 玩家圆点 ──────────────────────────────────────────────────────────

        private void UpdatePlayerDot()
        {
            if (_playerDot == null || _playerProvider == null) return;

            var roomId  = _playerProvider.CurrentRoomId;
            var normPos = _playerProvider.NormalizedPositionInRoom;

            // Dirty check: 避免房间和位置均未变化时写 RectTransform
            if (roomId == _lastDotRoomId && normPos == _lastDotNormPos) return;
            _lastDotRoomId  = roomId;
            _lastDotNormPos = normPos;

            if (string.IsNullOrEmpty(roomId) || !_cells.TryGetValue(roomId, out var cell))
            {
                _playerDot.enabled = false;
                return;
            }

            _playerDot.enabled = true;
            _playerDot.rectTransform.anchoredPosition =
                cell.RT.anchoredPosition
                + Vector2.Scale(normPos, cell.RT.sizeDelta);
        }
    }
}