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 class PlacementValidator : IPlacementValidator
    {
        /// <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 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) 是形状的左上角（在pattern数组中）
            // - pattern[i, j] 中，i 是 x（从左到右），j 是 y（从上到下，j=0 是顶部）
            // - 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 + shape.Height - 1)
                // 形状的 (i, j) 对应网格的 (gridX + i, gridY + shape.Height - 1 - j)
                int gridCellX = gridX + blockPos.x;
                int gridCellY = gridY + shape.Height - 1 - 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 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 (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）
                int gridCellX = gridX + blockPos.x;
                int gridCellY = gridY + shape.Height - 1 - blockPos.y;
                occupiedCells.Add((gridCellX, gridCellY));
            }

            return occupiedCells.ToArray();
        }
    }
}