using System;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using MindPowerSdk;

public static class TerrainGenerator
{
    /// <summary>
    /// 利用 MPMap 数据生成 Terrain，采用自定义材质实现贴图混合
    /// </summary>
    /// <param name="map">地图数据</param>
    /// <param name="chunkSize">每块区域的瓦片数（例如 64）</param>
    /// <param name="terrainMaterial">基于自定义Shader（例如 Custom/TerrainUVBlendShader）的材质</param>
    /// <param name="parent">生成的 Terrain 父节点</param>
    /// <param name="entryMapName"></param>
    /// <param name="isSmoothing"></param>
    public static List<Texture> GenTerrain(MPMap  map, int chunkSize, Material terrainMaterial, Transform parent,
                                           string entryMapName, bool isSmoothing = true)
    {
        List<Texture> textureList = new List<Texture>();
        // 计算全局高度范围（归一化用）
        (float globalMin, float globalMax) = ComputeGlobalHeightRange(map);

        int xCnt       = Mathf.CeilToInt((float)map.Width  / chunkSize);
        int yCnt       = Mathf.CeilToInt((float)map.Height / chunkSize);
        var terrainMap = new GameObject(entryMapName);
        terrainMap.transform.parent = parent;
        
        Debug.Log($"开始生成地形: 地图尺寸({map.Width}, {map.Height}), 块大小={chunkSize}, 将生成{xCnt}x{yCnt}={xCnt*yCnt}个地形块");
        
        for (int i = 0; i < yCnt; i++)
        {
            for (int j = 0; j < xCnt; j++)
            {
                int startX = j * chunkSize;
                int startY = i * chunkSize;
                // 修复：正确计算边界，确保最后一块包含所有剩余像素
                int endX = Mathf.Min(startX + chunkSize, map.Width);
                int endY = Mathf.Min(startY + chunkSize, map.Height);
                int resX = endX - startX; // 横向瓦片数
                int resY = endY - startY; // 纵向瓦片数
                
                Debug.Log($"地形块[{i},{j}]: startX={startX}, startY={startY}, endX={endX}, endY={endY}, resX={resX}, resY={resY}");

                // 优化：使用合理的分辨率，避免过高的分辨率导致性能和兼容性问题
                // 根据chunk大小动态计算分辨率，确保每个tile至少有4个像素
                int newRes = Mathf.NextPowerOfTwo(Mathf.Max(resX, resY) * 4) + 1;
                newRes = Mathf.Clamp(newRes, 129, 1025); // 限制在合理范围内

                // 创建 TerrainData，设置高度图和混合图分辨率以及尺寸
                TerrainData terrainData = new TerrainData();
                terrainData.heightmapResolution = newRes;
                terrainData.alphamapResolution  = newRes;
                
                // 设置地形尺寸，确保与实际数据对应
                float terrainWidth = resX;
                float terrainLength = resY;
                float terrainHeight = globalMax - globalMin;
                terrainData.size = new Vector3(terrainWidth, terrainHeight, terrainLength);
                
                // 设置地形的边界处理模式，确保能被正确拆分
                #if UNITY_EDITOR
                // 这些设置有助于地形被第三方工具正确处理
                terrainData.wavingGrassStrength = 0.5f;
                terrainData.wavingGrassAmount = 0.5f;
                terrainData.wavingGrassSpeed = 0.5f;
                terrainData.wavingGrassTint = Color.white;
                #endif

                // 生成高度图（归一化到 [0,1]）
                float[,] heights = GenerateHeightMap(map, startX, startY, resX, resY, newRes, globalMin, globalMax,
                                                     isSmoothing);
                terrainData.SetHeights(0, 0, heights);

                // ---------------------- 贴图设置部分 -------------------------
                // 生成贴图编号和遮罩贴图
                // 注意：贴图采样使用原始的resX, resY (不包含+1边界)
                int texResX = endX - startX;
                int texResY = endY - startY;
                Debug.LogWarning($"生成地形块: startX={startX}, startY={startY}, texResX={texResX}, texResY={texResY}");
                (Texture2D texNo, Texture2D maskNo) = map.GenTxtNoTexture((short)startX, (short)startY, texResX);

                textureList.Add(texNo);
                textureList.Add(maskNo);
                if (terrainMaterial== null)
                {
                    Debug.LogError("地形材质未设置，请提供一个自定义材质或使用内置材质系统。");
                    return null;
                }
                // 创建材质实例，并设置贴图
                Material matInstance = new Material(terrainMaterial);
                matInstance.SetTexture("_TexNo",  texNo);
                matInstance.SetTexture("_MaskNo", maskNo);

                // 计算每个 tile 在 UV 空间内的尺寸
                Vector2 mainTileScale = new Vector2(1.0f / texResX, 1.0f / texResY);
                matInstance.SetVector("_MainTileOffset", new Vector4(mainTileScale.x, mainTileScale.y, 0, 0));

                // 设置 Terrain 尺寸参数
                matInstance.SetVector("_TerrainSize", new Vector4(resX, resY, 0, 0));
                matInstance.SetFloat("_Repeat", resX);
                // ---------------------- 贴图设置结束 -------------------------

                // 生成 Terrain 游戏对象并设置位置
                GameObject terrainGO = Terrain.CreateTerrainGameObject(terrainData);
                terrainGO.name               = $"terrain_{i}_{j}";
                terrainGO.transform.parent   = terrainMap.transform;
                
                // 修复：正确的位置计算，确保地形块能正确拼接
                // 地图坐标系转换到Unity坐标系：
                // X轴保持不变，Y轴是高度，Z轴需要翻转
                // 原地图的Y=0对应Unity的Z=map.Height，Y=map.Height对应Unity的Z=0
                float unityPosX = startX;
                float unityPosY = globalMin;
                float unityPosZ = map.Height - startY - resY;
                
                Vector3 terrainPosition = new Vector3(unityPosX, unityPosY, unityPosZ);
                terrainGO.transform.position = terrainPosition;
                
                Debug.Log($"地形块 {terrainGO.name}: 位置={terrainPosition}, 尺寸={terrainData.size}, 高度图分辨率={newRes}");

                // 设置 Terrain 组件
                Terrain terrainComponent = terrainGO.GetComponent<Terrain>();
                TerrainCollider terrainCollider = terrainGO.GetComponent<TerrainCollider>();
                
                // 设置地形渲染和性能参数
                terrainComponent.heightmapPixelError = 5;
                terrainComponent.basemapDistance = 1000;
                terrainComponent.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.On;
                terrainComponent.reflectionProbeUsage = UnityEngine.Rendering.ReflectionProbeUsage.BlendProbes;
                
                // 确保TerrainCollider正确关联TerrainData
                if (terrainCollider != null)
                {
                    terrainCollider.terrainData = terrainData;
                }
                
                // 优化：为了更好的兼容性，同时支持自定义材质和内置材质系统
                if (terrainMaterial != null)
                {
                    terrainComponent.materialType     = Terrain.MaterialType.Custom;
                    terrainComponent.materialTemplate = matInstance;
                }
                else
                {
                    // 如果没有自定义材质，使用内置材质系统
                    terrainComponent.materialType = Terrain.MaterialType.BuiltInStandard;
                }
                
                // 设置地形的相邻关系，确保无缝拼接
                SetupTerrainNeighbors(terrainMap.transform, i, j, yCnt, xCnt);
            }
        }

        return textureList;
    }

    /// <summary>
    /// 设置地形的相邻关系，确保地形块之间无缝拼接
    /// </summary>
    private static void SetupTerrainNeighbors(Transform terrainParent, int i, int j, int yCnt, int xCnt)
    {
        // 获取当前地形
        Transform currentTerrain = terrainParent.Find($"terrain_{i}_{j}");
        if (currentTerrain == null) return;
        
        Terrain current = currentTerrain.GetComponent<Terrain>();
        if (current == null) return;

        // 设置相邻地形
        Terrain left   = GetTerrainAt(terrainParent, i, j - 1, yCnt, xCnt);
        Terrain right  = GetTerrainAt(terrainParent, i, j + 1, yCnt, xCnt);
        Terrain top    = GetTerrainAt(terrainParent, i + 1, j, yCnt, xCnt);
        Terrain bottom = GetTerrainAt(terrainParent, i - 1, j, yCnt, xCnt);

        current.SetNeighbors(left, top, right, bottom);
    }

    /// <summary>
    /// 获取指定位置的地形组件
    /// </summary>
    private static Terrain GetTerrainAt(Transform terrainParent, int i, int j, int yCnt, int xCnt)
    {
        if (i < 0 || i >= yCnt || j < 0 || j >= xCnt) return null;
        
        Transform terrainTransform = terrainParent.Find($"terrain_{i}_{j}");
        return terrainTransform?.GetComponent<Terrain>();
    }

    private static float[,] GenerateHeightMap(MPMap map,       int   startX, int startY, int resX, int resY, int newRes,
                                              float globalMin, float globalMax, bool isSmoothing)
    {
        // 采集原始高度数据，并归一化到 [0,1]
        // 注意：为了确保地形连续性，我们需要包含边界像素
        int sampleResX = resX + 1;
        int sampleResY = resY + 1;
        float[,] fullHeights = new float[sampleResY, sampleResX];
        
        for (int z = 0; z < sampleResY; z++)
        {
            for (int x = 0; x < sampleResX; x++)
            {
                int    worldX = startX + x;
                int    worldY = startY + z;
                
                // 边界检查，确保不超出地图范围
                worldX = Mathf.Clamp(worldX, 0, map.Width - 1);
                worldY = Mathf.Clamp(worldY, 0, map.Height - 1);
                
                MPTile tile   = map.GetTile(worldX, worldY);
                float  norm   = (globalMax - globalMin) > 0 ? (tile.Height - globalMin) / (globalMax - globalMin) : 0f;
                // 修复：确保高度图方向与贴图采样一致，Y轴需要翻转以匹配Unity的Terrain坐标系
                fullHeights[sampleResY - z - 1, x] = norm;
            }
        }
        
        // 更新采样参数
        resX = sampleResX;
        resY = sampleResY;

        // 利用双三次插值生成新分辨率高度图
        float[,] resampled = new float[newRes, newRes];
        float    scaleX    = (float)(resX - 1) / (newRes - 1);
        float    scaleY    = (float)(resY - 1) / (newRes - 1);
        for (int z = 0; z < newRes; z++)
        {
            float origZ = z * scaleY;
            for (int x = 0; x < newRes; x++)
            {
                float origX = x * scaleX;
                resampled[z, x] = BicubicInterpolate(fullHeights, origX, origZ, resX, resY);
            }
        }

        if (isSmoothing)
        {
            // 后处理：高斯模糊平滑
            float[,] smoothed = ApplyGaussianBlur(resampled, newRes, newRes);
            return smoothed;
        }
        else
        {
            return resampled;
        }
    }

    private static float BicubicInterpolate(float[,] data, float x, float z, int resX, int resY)
    {
        int   xInt = Mathf.FloorToInt(x);
        int   zInt = Mathf.FloorToInt(z);
        float s    = x - xInt;
        float t    = z - zInt;

        float[] arr = new float[4];
        for (int m = -1; m <= 2; m++)
        {
            int   sampleZ = Mathf.Clamp(zInt + m, 0, resY - 1);
            float p0      = data[sampleZ, Mathf.Clamp(xInt - 1, 0, resX - 1)];
            float p1      = data[sampleZ, Mathf.Clamp(xInt,     0, resX - 1)];
            float p2      = data[sampleZ, Mathf.Clamp(xInt              + 1, 0, resX - 1)];
            float p3      = data[sampleZ, Mathf.Clamp(xInt              + 2, 0, resX - 1)];
            arr[m + 1] = CubicInterpolate(p0, p1, p2, p3, s);
        }

        return CubicInterpolate(arr[0], arr[1], arr[2], arr[3], t);
    }

    private static float CubicInterpolate(float p0, float p1, float p2, float p3, float t)
    {
        float a0 = p3 - p2 - p0 + p1;
        float a1 = p0           - p1 - a0;
        float a2 = p2           - p0;
        float a3 = p1;
        return ((a0 * t + a1) * t + a2) * t + a3;
    }

    private static float[,] ApplyGaussianBlur(float[,] data, int width, int height)
    {
        float[,] result       = new float[height, width];
        int      kernelSize   = 3;
        int      kernelRadius = kernelSize / 2;
        float[,] kernel = new float[,]
        {
            { 1f, 2f, 1f },
            { 2f, 4f, 2f },
            { 1f, 2f, 1f }
        };
        float kernelSum = 16f;

        for (int z = 0; z < height; z++)
        {
            for (int x = 0; x < width; x++)
            {
                float sum = 0f;
                for (int kz = -kernelRadius; kz <= kernelRadius; kz++)
                {
                    int sampleZ = Mathf.Clamp(z + kz, 0, height - 1);
                    for (int kx = -kernelRadius; kx <= kernelRadius; kx++)
                    {
                        int   sampleX = Mathf.Clamp(x + kx, 0, width     - 1);
                        float weight  = kernel[kz     + kernelRadius, kx + kernelRadius];
                        sum += data[sampleZ, sampleX] * weight;
                    }
                }

                result[z, x] = sum / kernelSum;
            }
        }

        return result;
    }

    private static (float, float) ComputeGlobalHeightRange(MPMap map)
    {
        float min = float.MaxValue;
        float max = float.MinValue;
        for (int y = 0; y < map.Height; y++)
        {
            for (int x = 0; x < map.Width; x++)
            {
                float h          = map.GetTile(x, y).Height;
                if (h < min) min = h;
                if (h > max) max = h;
            }
        }

        return (min, max);
    }
}