using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using WIDESEAWCS_DTO.PlacedBlockDTO;
using WIDESEAWCS_IBasicInfoService;

namespace WIDESEAWCS_BasicInfoService
{
    public class PlaceBlockService
    {
        public const int SPACING = 5;

        /// <summary>
        /// 容器尺寸
        /// </summary>
        public ContainerSize ContainerSize { get; private set; }

        /// <summary>
        /// 已放置货物
        /// </summary>
        public List<PlacedBlock> PlacedBlocks { get; private set; }

        private readonly PlacedBlock containerFloor;

        public PlaceBlockService(ContainerSize containerSize, List<PlacedBlock>? placedBlocks = null)
        {
            containerSize.Length = containerSize.Length;
            containerSize.Width = containerSize.Width;
            ContainerSize = containerSize;
            if (placedBlocks == null || placedBlocks.Count == 0)
            {
                PlacedBlocks = new List<PlacedBlock>();
            }
            else
            {
                PlacedBlocks = placedBlocks;
            }


            containerFloor = new PlacedBlock(new Point3D(0, 0, 0), ContainerSize.Length, ContainerSize.Width, 0);
        }

        /// <summary>
        /// 主放置方法：尝试放置指定尺寸的货物
        /// </summary>
        /// <param name="length">货物长度（X轴方向）</param>
        /// <param name="width">货物宽度（Y轴方向）</param>
        /// <param name="height">货物高度（Z轴方向）</param>
        /// <returns>
        /// 成功：返回可放置位置的左下前角Point3D坐标
        /// 失败：返回null（尺寸无效或空间不足）
        /// </returns>
        public Point3D? PlaceBlock(int length, int width, int height)
        {
            if (!IsValidBlock(length, width, height))
                return null;

            return FindStackablePosition(length, width, height);
        }

        /// <summary>
        /// 验证货物尺寸有效性
        /// 校验规则：
        /// 1. 各维度尺寸必须大于等于50mm
        /// 2. 各维度尺寸不得超过容器对应维度（扣除间隔后）
        /// 3. 高度必须 <= 容器剩余高度
        /// </summary>
        /// <param name="l"></param>
        /// <param name="w"></param>
        /// <param name="h"></param>
        /// <returns></returns>
        private bool IsValidBlock(int l, int w, int h)
        {
            return l > 0 && w > 0 && h > 0 &&
                   l <= ContainerSize.Length - 2 * SPACING &&
                   w <= ContainerSize.Width - 2 * SPACING &&
                   h < ContainerSize.Height;
        }

        /// <summary>
        /// 在现有货物顶部寻找叠放位置（堆叠模式）
        /// 叠放条件：
        /// - 支撑面积 >= 被支撑面面积的70%
        /// - 新货物完全位于支撑货物上方
        /// - 满足间隔要求
        /// </summary>
        /// <param name="l">长度</param>
        /// <param name="w">宽度</param>
        /// <param name="h">高度</param>
        /// <returns></returns>
        private Point3D? FindStackablePosition(int l, int w, int h)
        {
            // 生成候选支撑层（包含容器底部）
            var candidateLayers = PlacedBlocks
                .Select(b => b.Position.Z + b.Height)
                .Append(0)
                .Distinct()
                .OrderBy(z => z)
                .ToList();

            foreach (var baseZ in candidateLayers)
            {
                if (baseZ + h > ContainerSize.Height) continue;

                // 获取当前层的支撑块（包含虚拟容器底部）
                var supports = GetSupportBlocks(baseZ);

                foreach (var support in supports)
                {
                    // 计算有效叠放区域（修正间隔逻辑）
                    int xStart = support.Position.X;
                    int yStart = support.Position.Y;

                    // 容器底部支撑必须内缩间隔（即使尺寸相同）
                    if (support == containerFloor)
                    {
                        xStart = support.Position.X;
                        yStart = support.Position.Y;
                    }

                    int xEnd = support.Position.X + support.Length - l;
                    int yEnd = support.Position.Y + support.Width - w;

                    // 普通支撑块仅在尺寸不同时加间隔
                    if (support != containerFloor &&
                       (l != support.Length && w != support.Width))
                    {
                        xStart += SPACING;
                        yStart += SPACING;
                        xEnd -= SPACING;
                        yEnd -= SPACING;
                    }

                    // 最终容器边界约束
                    xEnd = Math.Min(xEnd, ContainerSize.Length - l - SPACING);
                    yEnd = Math.Min(yEnd, ContainerSize.Width - w - SPACING);

                    if (xStart > xEnd || yStart > yEnd) continue;

                    // 优化搜索：优先角落位置
                    for (int y = yStart; y <= yEnd; y += 10)
                    {
                        for (int x = xStart; x <= xEnd; x += 10)
                        {
                            var candidate = new Point3D(x, y, baseZ);
                            if (IsPositionValid(candidate, l, w, h))
                            {
                                var placed = new PlacedBlock(candidate, l, w, h);
                                //PlacedBlocks.Add(placed);
                                return candidate;
                            }
                        }
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// 获取支撑当前货物的底层货物列表
        /// 特殊处理：当baseZ=0时返回虚拟容器底部作为支撑
        /// 支撑条件：货物底面与支撑货物顶面接触且Z坐标匹配
        /// </summary>
        /// <param name="baseZ">支撑块高度</param>
        /// <returns></returns>
        private IEnumerable<PlacedBlock> GetSupportBlocks(int baseZ)
        {
            var blocks = PlacedBlocks
                .Where(b => b.Position.Z + b.Height == baseZ)
                .OrderByDescending(b => b.Length * b.Width).ToList();

            // 当baseZ=0时添加容器底部支撑
            if (baseZ == 0 && blocks.Count == 0)
            {
                return new List<PlacedBlock> { containerFloor };
            }

            return blocks;
        }

        /// <summary>
        /// 验证指定位置是否合法
        /// 校验内容：
        /// 1. 边界条件：货物不得超出容器有效空间
        /// 2. 碰撞检测：与已放置货物无空间重叠
        /// 3. 间隔要求：保持最小间隔（SPACING常量）
        /// </summary>
        /// <param name="pos">坐标</param>
        /// <param name="l">长度</param>
        /// <param name="w">宽度</param>
        /// <param name="h">高度</param>
        /// <returns></returns>
        private bool IsPositionValid(Point3D pos, int l, int w, int h)
        {
            // 边界检查（含容器边缘间隔）
            if (pos.X < SPACING ||
                pos.Y < SPACING ||
                pos.X + l > ContainerSize.Length - SPACING ||
                pos.Y + w > ContainerSize.Width - SPACING)
                return false;

            // 三维碰撞检测
            var newBlock = new PlacedBlock(pos, l, w, h);
            return !PlacedBlocks.Any(existing =>
            {
                bool xOverlap = newBlock.Position.X < existing.Position.X + existing.Length + SPACING &&
                              newBlock.Position.X + newBlock.Length + SPACING > existing.Position.X;

                bool yOverlap = newBlock.Position.Y < existing.Position.Y + existing.Width + SPACING &&
                              newBlock.Position.Y + newBlock.Width + SPACING > existing.Position.Y;

                bool zOverlap = newBlock.Position.Z < existing.Position.Z + existing.Height &&
                              newBlock.Position.Z + h > existing.Position.Z;

                return xOverlap && yOverlap && zOverlap;
            });
        }
    }
}