using UnityEngine;
using UnityEditor;

public class FlattenTerrainLayerToWorldHeight : EditorWindow
{
    Terrain terrain;
    string targetLayerName = "Road";
    float targetWorldHeight = 10f; // 米
    float layerThreshold = 0.5f;

    [MenuItem("Tools/Terrain/Flatten Layer To World Height")]
    public static void ShowWindow()
    {
        GetWindow<FlattenTerrainLayerToWorldHeight>("Flatten Layer Height");
    }

    void OnGUI()
    {
        terrain = (Terrain)EditorGUILayout.ObjectField("目标 Terrain", terrain, typeof(Terrain), true);
        targetLayerName = EditorGUILayout.TextField("目标 Terrain Layer 名", targetLayerName);
        targetWorldHeight = EditorGUILayout.FloatField("世界空间高度 (米)", targetWorldHeight);
        layerThreshold = EditorGUILayout.Slider("图层混合阈值", layerThreshold, 0f, 1f);

        if (GUILayout.Button("拉平图层区域至目标高度"))
        {
            if (terrain == null) terrain = Terrain.activeTerrain;
            if (terrain != null) FlattenLayerArea();
            else Debug.LogError("未找到 Terrain");
        }
    }

    void FlattenLayerArea()
    {
        TerrainData data = terrain.terrainData;
        int heightmapWidth = data.heightmapResolution;
        int heightmapHeight = data.heightmapResolution;
        float[,] heights = data.GetHeights(0, 0, heightmapWidth, heightmapHeight);

        int alphaWidth = data.alphamapWidth;
        int alphaHeight = data.alphamapHeight;
        float[,,] alphaMaps = data.GetAlphamaps(0, 0, alphaWidth, alphaHeight);

        int layerIndex = -1;
        for (int i = 0; i < data.terrainLayers.Length; i++)
        {
            if (data.terrainLayers[i].name == targetLayerName)
            {
                layerIndex = i;
                break;
            }
        }

        if (layerIndex == -1)
        {
            Debug.LogError("找不到指定的 Terrain Layer：" + targetLayerName);
            return;
        }

        float normalizedHeight = targetWorldHeight / data.size.y;
        int changed = 0;

        for (int y = 0; y < heightmapHeight; y++)
        {
            for (int x = 0; x < heightmapWidth; x++)
            {
                int alphaX = Mathf.Clamp(Mathf.RoundToInt((float)x / heightmapWidth * alphaWidth), 0, alphaWidth - 1);
                int alphaY = Mathf.Clamp(Mathf.RoundToInt((float)y / heightmapHeight * alphaHeight), 0, alphaHeight - 1);
                float weight = alphaMaps[alphaY, alphaX, layerIndex];

                if (weight > layerThreshold)
                {
                    heights[y, x] = normalizedHeight;
                    changed++;
                }
            }
        }

        data.SetHeights(0, 0, heights);
        Debug.Log($"✅ 拉平完成！将 {changed} 个点高度设置为 {targetWorldHeight} 米");
    }
}