using System;
using AibisDream.Framework;
using UnityEngine;
using UnityEngine.EventSystems;

namespace AibisDream
{
    /// <summary>
    /// 形状拖拽组件
    /// 实现IBlockShapeDragger接口，处理形状的拖拽、吸附和放置逻辑
    /// </summary>
    [RequireComponent(typeof(BlockShape))]
    [RequireComponent(typeof(EventTriggerEx))]
    public class BlockShapeDragger : MonoBehaviour, IBlockShapeDragger
    {
        [Header("拖拽设置")]
        [SerializeField] private bool isDraggable = true;
        [SerializeField] private float snapDistance = 0.5f;
        [SerializeField] private BlockPuzzleGrid targetGridComponent; // Unity组件引用

        [Header("视觉反馈")]
        [SerializeField] private Color snapColor = new Color(0f, 1f, 0f, 0.7f);
        [SerializeField] private Color invalidColor = new Color(1f, 0f, 0f, 0.7f);
        [SerializeField] private Color normalColor = Color.white;
        [SerializeField] private float dragScale = 1.1f;

        // 拖拽状态
        private DragState _currentState = DragState.Idle;
        private bool _isDragging = false;
        private Vector3 _dragOffset;
        private Vector3 _originalPosition;
        private Vector3 _originalScale;
        private int _originalSortingOrder;
        private bool _isSnapping = false;
        private int _snapGridX;
        private int _snapGridY;

        // 组件引用
        private BlockShape _blockShape;
        private SpriteRenderer _spriteRenderer;
        private EventTriggerEx _eventTrigger;

        // 事件
        public event Action<IBlockShape> OnDragStart;
        public event Action<IBlockShape, Vector3> OnDragUpdate;
        public event Action<IBlockShape, bool> OnDragEnd;
        public event Action<IBlockShape, Vector3, int, int> OnSnap;
        public event Action<IBlockShape> OnUnsnap;

        // 接口实现
        public DragState CurrentState => _currentState;
        public bool IsDraggable { get => isDraggable; set => isDraggable = value; }
        public IBlockPuzzleGrid TargetGrid 
        { 
            get => targetGridComponent; 
            set => targetGridComponent = value as BlockPuzzleGrid; 
        }
        public float SnapDistance { get => snapDistance; set => snapDistance = value; }

        // 内部使用的网格引用
        private IBlockPuzzleGrid targetGrid => targetGridComponent;

        private void Awake()
        {
            _blockShape = GetComponent<BlockShape>();
            _spriteRenderer = GetComponent<SpriteRenderer>();
            _eventTrigger = GetComponent<EventTriggerEx>();
            
            RegisterEvent();
        }

        private void RegisterEvent()
        {
            _eventTrigger.Register(EventTriggerType.PointerClick, OnPointerClick);
        }

        private void OnPointerClick(BaseEventData eventData)
        {
            if (eventData is not PointerEventData { button: PointerEventData.InputButton.Left })
            {
                return;
            }

            PointerEventData pointerEventData = eventData as PointerEventData;
            
            Vector3 mouseWorldPos = GetMouseWorldPosition(pointerEventData.position);
            // 如果当前物体不在拖拽中则进入拖拽逻辑
            if (!_isDragging)
            {
                StartDrag(mouseWorldPos);
            }
            // 如果当前物体在拖拽中则取消拖拽
            else
            {
                CancelDrag();
            }
        }

        public void StartDrag(Vector3 mouseWorldPos)
        {
            if (!isDraggable || _isDragging) return;

            _isDragging = true;
            _currentState = DragState.Dragging;
            _originalPosition = transform.position;
            _originalScale = transform.localScale;

            // 计算拖拽偏移量
            _dragOffset = transform.position - mouseWorldPos;

            // 提升层级和缩放
            if (_spriteRenderer != null)
            {
                _originalSortingOrder = _spriteRenderer.sortingOrder;
                _spriteRenderer.sortingOrder = 100;
            }

            transform.localScale = _originalScale * dragScale;

            OnDragStart?.Invoke(_blockShape);
        }

        public void UpdateDrag()
        {
            if (!_isDragging) return;

            Vector3 mouseWorldPos = GetMouseWorldPosition(Input.mousePosition);
            Vector3 targetPosition = mouseWorldPos + _dragOffset;

            if (targetGrid != null)
            {
                // 检查吸附可能
                var snapResult = targetGrid.CheckSnapToGrid(_blockShape);
                if (snapResult.canSnap)
                {
                    // 可以吸附，保存吸附内容
                }
                else
                {
                    // 没有吸附，自由拖拽
                    transform.position = targetPosition;
                    _currentState = DragState.Dragging;
                }
            }
            else
            {
                // 没有网格，自由拖拽
                transform.position = targetPosition;
                _currentState = DragState.Dragging;
            }

            OnDragUpdate?.Invoke(_blockShape, transform.position);
        }

        public void EndDrag()
        {
            if (!_isDragging) return;

            bool placed = false;

            if (_isSnapping && targetGrid != null)
            {
                // 尝试放置到网格
                if (CanPlaceAt(_snapGridX, _snapGridY))
                {
                    if (TryPlaceOnGrid(_snapGridX, _snapGridY))
                    {
                        placed = true;
                        _currentState = DragState.Placed;
                        OnShapePlaced();
                    }
                }
            }

            if (!placed)
            {
                // 返回原位置
                transform.position = _originalPosition;
                _currentState = DragState.Idle;
            }

            // 恢复原始状态
            transform.localScale = _originalScale;
            if (_spriteRenderer != null)
            {
                _spriteRenderer.sortingOrder = _originalSortingOrder;
            }

            ShowSnapPreview(false, false);

            _isDragging = false;
            _isSnapping = false;

            OnDragEnd?.Invoke(_blockShape, placed);
        }

        public void CancelDrag()
        {
            if (!_isDragging) return;

            transform.position = _originalPosition;
            transform.localScale = _originalScale;
            if (_spriteRenderer != null)
            {
                _spriteRenderer.sortingOrder = _originalSortingOrder;
            }

            ShowSnapPreview(false, false);

            _isDragging = false;
            _isSnapping = false;
            _currentState = DragState.Idle;

            OnDragEnd?.Invoke(_blockShape, false);
        }

        public bool CanPlaceAt(int gridX, int gridY)
        {
            if (targetGrid == null || _blockShape == null) return false;

            Vector2Int[] blockPositions = _blockShape.GetBlockPositions();
            if (blockPositions == null || blockPositions.Length == 0) return false;

            // 形状的坐标系统：
            // - GetBlockPositions() 返回的坐标中，(0, 0) 是形状的左下角
            // - gridX, gridY 是形状左下角在网格中的位置
            // - 需要将形状的相对坐标转换为网格坐标
            foreach (var blockPos in blockPositions)
            {
                // 将形状的相对坐标转换为网格坐标（左下角为基准）
                // 形状的 (0, 0) 对应网格的 (gridX, gridY)
                // 形状的 (i, j) 对应网格的 (gridX + i, gridY + j)
                int checkX = gridX + blockPos.x;
                int checkY = gridY + blockPos.y;

                if (!targetGrid.IsValidPosition(checkX, checkY) ||
                    !targetGrid.IsCellEmpty(checkX, checkY))
                {
                    return false;
                }
            }

            return true;
        }

        public bool GetSnapGridPosition(out int gridX, out int gridY)
        {
            if (_isSnapping)
            {
                gridX = _snapGridX;
                gridY = _snapGridY;
                return true;
            }

            gridX = 0;
            gridY = 0;
            return false;
        }

        /// <summary>
        /// 检查是否可以吸附到网格
        /// </summary>
        private bool CheckSnapToGrid(Vector3 worldPos, out Vector3 snapPos, out int gridX, out int gridY)
        {
            snapPos = worldPos;
            gridX = 0;
            gridY = 0;

            if (targetGrid == null) return false;

            // 将世界坐标转换为网格坐标
            // 注意：WorldToGrid 需要世界坐标在网格范围内才能返回true
            // 但我们需要检查所有附近的网格单元格，不仅仅是当前所在的单元格
            // 所以先尝试直接转换，如果失败则查找最近的网格单元格
            
            int tempGridX, tempGridY;
            bool inGrid = targetGrid.WorldToGrid(worldPos, out tempGridX, out tempGridY);
            
            if (!inGrid)
            {
                // 如果不在网格内，尝试查找最近的网格单元格
                // 计算最近的网格坐标
                Vector3 localPos = worldPos - targetGrid.Origin;
                tempGridX = Mathf.FloorToInt(localPos.x / targetGrid.CellSize);
                tempGridY = Mathf.FloorToInt(localPos.y / targetGrid.CellSize);
                
                // 检查是否在有效范围内
                if (!targetGrid.IsValidPosition(tempGridX, tempGridY))
                {
                    return false;
                }
            }

            // 获取网格单元格中心的世界坐标
            Vector3 gridCenter = targetGrid.GridToWorld(tempGridX, tempGridY);

            // 计算距离
            float distance = Vector3.Distance(worldPos, gridCenter);

            if (distance <= snapDistance)
            {
                // 计算形状应该放置的网格位置
                // 形状左下角对齐到网格单元格左下角
                gridX = tempGridX;
                gridY = tempGridY;
                
                // 计算形状左下角的世界坐标
                // 网格单元格左下角的世界坐标 = Origin + (gridX * CellSize, gridY * CellSize)
                Vector3 gridBottomLeft = targetGrid.Origin + new Vector3(
                    gridX * targetGrid.CellSize,
                    gridY * targetGrid.CellSize,
                    0
                );
                
                // 计算形状中心相对于形状左下角的偏移
                // 形状的 pattern 中，(0, 0) 是左下角
                // 在形状的本地坐标系中（假设形状中心在 (0, 0)），形状左下角的位置是：
                // localX = -width * cellSize / 2
                // localY = -height * cellSize / 2
                // 形状中心相对于形状左下角的偏移 = (0, 0) - (localX, localY) = (width * cellSize / 2, height * cellSize / 2)
                
                // 形状左下角对齐到网格单元格左下角
                // 形状中心的世界坐标 = 网格单元格左下角的世界坐标 + 形状中心相对于形状左下角的偏移
                // 使用网格的 CellSize，因为形状的 cellSize 应该与网格的 CellSize 相同
                float shapeCenterOffsetX = _blockShape.Width * targetGrid.CellSize / 2f;
                float shapeCenterOffsetY = _blockShape.Height * targetGrid.CellSize / 2f;
                snapPos = gridBottomLeft + new Vector3(shapeCenterOffsetX, shapeCenterOffsetY, 0);
                
                return true;
            }

            return false;
        }

        /// <summary>
        /// 尝试放置到网格
        /// </summary>
        /// <param name="gridX">网格X坐标（形状左下角位置）</param>
        /// <param name="gridY">网格Y坐标（形状左下角位置）</param>
        private bool TryPlaceOnGrid(int gridX, int gridY)
        {
            if (!CanPlaceAt(gridX, gridY)) return false;

            Vector2Int[] blockPositions = _blockShape.GetBlockPositions();
            if (blockPositions == null) return false;

            // 形状的坐标系统：
            // - GetBlockPositions() 返回的坐标中，(0, 0) 是形状的左下角
            // - gridX, gridY 是形状左下角在网格中的位置
            // - 需要将形状的相对坐标转换为网格坐标
            foreach (var blockPos in blockPositions)
            {
                // 将形状的相对坐标转换为网格坐标（左下角为基准）
                // 形状的 (0, 0) 对应网格的 (gridX, gridY)
                // 形状的 (i, j) 对应网格的 (gridX + i, gridY + j)
                int x = gridX + blockPos.x;
                int y = gridY + blockPos.y;
                targetGrid.SetCellState(x, y, GridCellState.Occupied);
            }

            return true;
        }

        /// <summary>
        /// 显示吸附预览效果
        /// </summary>
        private void ShowSnapPreview(bool show, bool isValid)
        {
            Color previewColor = show ? (isValid ? snapColor : invalidColor) : normalColor;

            // 更新主SpriteRenderer
            if (_spriteRenderer != null)
            {
                _spriteRenderer.color = previewColor;
            }
        }

        /// <summary>
        /// 形状放置完成
        /// </summary>
        private void OnShapePlaced()
        {
            // 可以在这里添加放置后的逻辑
            // 例如：禁用拖拽、播放动画等
            isDraggable = false;
        }

        /// <summary>
        /// 获取鼠标世界坐标
        /// </summary>
        private Vector3 GetMouseWorldPosition(Vector3 mousePos)
        {
            var pos = Camera.main.ScreenToWorldPoint(mousePos);
            return new Vector3(pos.x, pos.y, 0);
        }

        private void OnDisable()
        {
            if (_isDragging)
            {
                CancelDrag();
            }
        }
    }
}