using UnityEngine;

namespace AibisDream
{
    /// <summary>
    /// 放置验证器实现
    /// 负责验证形状是否可以放置在指定位置
    /// </summary>
    public static class PlacementValidator
    {
        public static SnapResult CheckSnapToGrid(this IBlockPuzzleGrid grid, BlockShape shape)
        {
            // 预制错误结果作为返回值
            SnapResult result = new SnapResult
            {
                canSnap = false,
                snapPosition = shape.transform.position,
                gridX = 0,
                gridY = 0,
                distance = float.MaxValue,
                gridPositions = new Vector2Int[0]
            };

            // 将Shape的世界坐标转换为网格坐标（可以是虚拟坐标）
            bool inGrid = grid.WorldToGrid(shape.transform.position, out int gridX, out int gridY);
            if (!inGrid) return result;

            // 将形状的所有格子转换为网格坐标
            // gridX, gridY 是形状的 (0, 0) 点在网格中的位置
            Vector2Int[] gridCells = ConvertShapeToGridCells(shape, gridX, gridY);
            result.gridX = gridX;
            result.gridY = gridY;
            result.snapPosition = grid.GridToWorld(gridX, gridY);
            result.gridPositions = gridCells;

            // 逐个坐标验证是否可以放置
            var canPlace = grid.CanPlace(gridCells);
            if (!canPlace) return result;
            result.canSnap = true;
            result.distance = Vector3.Distance(shape.transform.position, result.snapPosition);

            return result;
        }

        /// <summary>
        /// 将形状的相对坐标转换为网格坐标
        /// 已知形状的 (0, 0) 点在网格中的位置为 (gridX, gridY)，将形状的其他格子坐标转换为网格坐标
        /// </summary>
        /// <param name="shape">形状</param>
        /// <param name="gridX">网格X坐标（形状左下角位置，即形状的 (0, 0) 点对应的网格坐标）</param>
        /// <param name="gridY">网格Y坐标（形状左下角位置，即形状的 (0, 0) 点对应的网格坐标）</param>
        /// <returns>形状所有格子在网格中的坐标数组</returns>
        public static Vector2Int[] ConvertShapeToGridCells(IBlockShape shape, int gridX, int gridY)
        {
            if (shape == null)
            {
                return new Vector2Int[0];
            }

            Vector2Int[] blockPositions = shape.GetBlockPositions();
            if (blockPositions == null || blockPositions.Length == 0)
            {
                return new Vector2Int[0];
            }

            Vector2Int[] gridCells = new Vector2Int[blockPositions.Length];
            Vector2Int axis = shape.GetAxis();

            for (int i = 0; i < blockPositions.Length; i++)
            {
                // 将形状的相对坐标转换为网格坐标
                // 形状的 (0, 0) 对应网格的 (gridX, gridY)
                // 形状的 (blockPos.x, blockPos.y) 对应网格的 (gridX + blockPos.x, gridY + blockPos.y)
                gridCells[i] = new Vector2Int(
                    gridX + blockPositions[i].x * axis.x,
                    gridY + blockPositions[i].y * axis.y
                );
            }

            return gridCells;
        }

        /// <summary>
        /// 为吸附制作预览
        /// </summary>
        /// <param name="shapeCells">转换后的网格坐标组</param>
        public static void ShowSnapPreview(this IBlockPuzzleGrid grid, Vector2Int[] shapeCells)
        {

        }

        public static void TrySnapToGrid(this IBlockPuzzleGrid grid, BlockShape shape, Vector2Int rootCell)
        {
            // 判断RootCell的位置
            var rootWorldPos = grid.GridToWorld(rootCell.x, rootCell.y);
            // 已经判断是否可吸附，直接吸就好了
            shape.transform.position = rootWorldPos;
            // 设置网格状态
            var shapeCells = ConvertShapeToGridCells(shape, rootCell.x, rootCell.y);
            foreach (var cell in shapeCells)
            {
                grid.SetCellState(cell.x, cell.y, GridCellState.Occupied);
            }
            // 加入网格
            grid.ShapeDict.Add(shape, rootCell);
        }

        /// <summary>
        /// 尝试从网格中移除形状
        /// </summary>
        /// <param name="grid">网格</param>
        /// <param name="shape">形状</param>
        public static void TryRemoveShapeFromGrid(this IBlockPuzzleGrid grid, BlockShape shape)
        {
            if (grid.ShapeDict.TryGetValue(shape, out var rootCell))
            {
                // 设置网格状态
                var shapeCells = ConvertShapeToGridCells(shape, rootCell.x, rootCell.y);
                foreach (var cell in shapeCells)
                {
                    grid.SetCellState(cell.x, cell.y, GridCellState.Empty);
                }
                grid.ShapeDict.Remove(shape);
            }
        }
    }

    /// <summary>
    /// 放置验证结果
    /// </summary>
    public enum PlacementResult
    {
        Success,           // 可以放置
        OutOfBounds,       // 超出边界
        Overlap,           // 与已有块重叠
        InvalidPosition    // 无效位置
    }

    /// <summary>
    /// 吸附检测结果
    /// </summary>
    public struct SnapResult
    {
        public bool canSnap;           // 是否可以吸附
        public Vector3 snapPosition;   // 吸附后的世界坐标位置
        public int gridX;              // 吸附到的网格X坐标（形状左下角位置）
        public int gridY;              // 吸附到的网格Y坐标（形状左下角位置）
        public float distance;         // 到网格单元格的距离
        public Vector2Int[] gridPositions; // 吸附后
        public Vector2Int RootCell => new Vector2Int(gridX, gridY); // 吸附后的根网格坐标
    }
}