using System.Collections.Generic;
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
    {
        /// <summary>
        /// 检查形状是否可以放置在指定位置
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="shape">要放置的形状</param>
        /// <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>
        /// <returns>放置验证结果</returns>
        public static PlacementResult CanPlace(IBlockPuzzleGrid grid, IBlockShape shape, int gridX, int gridY)
        {
            if (grid == null || shape == null)
            {
                return PlacementResult.InvalidPosition;
            }

            // 获取形状的所有格子位置（相对坐标，基于形状的本地坐标系）
            Vector2Int[] blockPositions = shape.GetBlockPositions();
            if (blockPositions == null || blockPositions.Length == 0)
            {
                return PlacementResult.InvalidPosition;
            }

            // 形状的坐标系统：
            // - GetBlockPositions() 返回的坐标中，(0, 0) 是形状的左下角
            // - pattern[i, j] 中，i 是 x（从左到右），j 是 y（从下到上，j=0 是底部）
            // - 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
                // 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 gridCellX = gridX + blockPos.x;
                int gridCellY = gridY + blockPos.y;

                // 检查是否超出边界
                if (!grid.IsValidPosition(gridCellX, gridCellY))
                {
                    return PlacementResult.OutOfBounds;
                }

                // 检查是否与已有块重叠
                if (!grid.IsCellEmpty(gridCellX, gridCellY))
                {
                    return PlacementResult.Overlap;
                }
            }

            return PlacementResult.Success;
        }

        /// <summary>
        /// 检查形状是否可以放置在指定位置（详细版本）
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="shape">要放置的形状</param>
        /// <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>
        /// <param name="failureReason">失败原因（如果返回false）</param>
        /// <returns>是否可以放置</returns>
        public static bool CanPlaceDetailed(IBlockPuzzleGrid grid, IBlockShape shape, int gridX, int gridY, out PlacementResult failureReason)
        {
            failureReason = CanPlace(grid, shape, gridX, gridY);
            return failureReason == PlacementResult.Success;
        }

        /// <summary>
        /// 获取形状在指定位置的所有占用格子坐标
        /// </summary>
        /// <param name="shape">形状</param>
        /// <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>
        /// <returns>占用格子的网格坐标数组</returns>
        public static (int x, int y)[] GetOccupiedCells(IBlockShape shape, int gridX, int gridY)
        {
            if (shape == null)
            {
                return new (int x, int y)[0];
            }

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

            List<(int x, int y)> occupiedCells = new List<(int x, int y)>();

            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 gridCellX = gridX + blockPos.x;
                int gridCellY = gridY + blockPos.y;
                occupiedCells.Add((gridCellX, gridCellY));
            }

            return occupiedCells.ToArray();
        }
        

        /// <summary>
        /// 将形状的单个相对坐标转换为网格坐标
        /// </summary>
        /// <param name="shapeLocalX">形状内的X坐标（相对坐标，相对于形状左下角）</param>
        /// <param name="shapeLocalY">形状内的Y坐标（相对坐标，相对于形状左下角）</param>
        /// <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>
        /// <returns>对应的网格坐标</returns>
        public static Vector2Int ConvertShapeLocalToGrid(int shapeLocalX, int shapeLocalY, int gridX, int gridY)
        {
            return new Vector2Int(gridX + shapeLocalX, gridY + shapeLocalY);
        }

        /// <summary>
        /// 检查世界坐标是否可以吸附到网格
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="worldPos">世界坐标位置</param>
        /// <param name="snapDistance">吸附距离阈值</param>
        /// <returns>吸附检测结果</returns>
        public static SnapResult CheckSnapToGrid(IBlockPuzzleGrid grid, Vector3 worldPos, float snapDistance)
        {
            SnapResult result = new SnapResult
            {
                canSnap = false,
                snapPosition = worldPos,
                gridX = 0,
                gridY = 0,
                distance = float.MaxValue
            };

            if (grid == null)
            {
                return result;
            }

            // 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 = grid.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 - grid.Origin;
                tempGridX = Mathf.FloorToInt(localPos.x / grid.CellSize);
                tempGridY = Mathf.FloorToInt(localPos.y / grid.CellSize);

                // 检查是否在有效范围内
                if (!grid.IsValidPosition(tempGridX, tempGridY))
                {
                    return result;
                }
            }

            // 获取网格单元格中心的世界坐标
            Vector3 gridCenter = grid.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
                result.gridX = tempGridX;
                result.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 = grid.Origin + new Vector3(
                    tempGridX * grid.CellSize,
                    tempGridY * grid.CellSize,
                    0
                );

                result.snapPosition = gridBottomLeft;
                result.distance = distance;
                result.canSnap = true;
            }

            return result;
        }

        /// <summary>
        /// 检查世界坐标是否可以吸附到网格（简化版本，只返回是否可以吸附和网格坐标）
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="worldPos">世界坐标位置</param>
        /// <param name="snapDistance">吸附距离阈值</param>
        /// <param name="gridX">吸附到的网格X坐标（形状左下角位置）</param>
        /// <param name="gridY">吸附到的网格Y坐标（形状左下角位置）</param>
        /// <returns>是否可以吸附</returns>
        public static bool CheckSnapToGrid(IBlockPuzzleGrid grid, Vector3 worldPos, float snapDistance, out int gridX, out int gridY)
        {
            gridX = 0;
            gridY = 0;

            SnapResult result = CheckSnapToGrid(grid, worldPos, snapDistance);
            if (result.canSnap)
            {
                gridX = result.gridX;
                gridY = result.gridY;
                return true;
            }

            return false;
        }

        /// <summary>
        /// 检查世界坐标是否可以吸附到网格（完整版本，返回吸附位置和网格坐标）
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="worldPos">世界坐标位置</param>
        /// <param name="snapDistance">吸附距离阈值</param>
        /// <param name="snapPos">吸附后的世界坐标位置</param>
        /// <param name="gridX">吸附到的网格X坐标（形状左下角位置）</param>
        /// <param name="gridY">吸附到的网格Y坐标（形状左下角位置）</param>
        /// <returns>是否可以吸附</returns>
        public static bool CheckSnapToGrid(IBlockPuzzleGrid grid, Vector3 worldPos, float snapDistance, out Vector3 snapPos, out int gridX, out int gridY)
        {
            snapPos = worldPos;
            gridX = 0;
            gridY = 0;

            SnapResult result = CheckSnapToGrid(grid, worldPos, snapDistance);
            if (result.canSnap)
            {
                snapPos = result.snapPosition;
                gridX = result.gridX;
                gridY = result.gridY;
                return true;
            }

            return false;
        }

        /// <summary>
        /// 查找最近的网格单元格（即使不在吸附距离内）
        /// </summary>
        /// <param name="grid">网格系统</param>
        /// <param name="worldPos">世界坐标位置</param>
        /// <param name="gridX">最近的网格X坐标</param>
        /// <param name="gridY">最近的网格Y坐标</param>
        /// <returns>是否找到有效的网格单元格</returns>
        public static bool FindNearestGridCell(IBlockPuzzleGrid grid, Vector3 worldPos, out int gridX, out int gridY)
        {
            gridX = 0;
            gridY = 0;

            if (grid == null)
            {
                return false;
            }

            // 先尝试直接转换
            if (grid.WorldToGrid(worldPos, out gridX, out gridY))
            {
                return true;
            }

            // 如果不在网格内，计算最近的网格坐标
            Vector3 localPos = worldPos - grid.Origin;
            gridX = Mathf.FloorToInt(localPos.x / grid.CellSize);
            gridY = Mathf.FloorToInt(localPos.y / grid.CellSize);

            // 限制在有效范围内
            gridX = Mathf.Clamp(gridX, 0, grid.Width - 1);
            gridY = Mathf.Clamp(gridY, 0, grid.Height - 1);

            return grid.IsValidPosition(gridX, gridY);
        }
    }

    /// <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
    }
}