using UnityEngine;
using UnityEditor;
using System.Collections.Generic;

public class ReplacePrefabsWithTerrainTrees : EditorWindow
{
    Terrain targetTerrain;

    [MenuItem("Tools/Terrain/Replace Prefabs with Trees")]
    static void ShowWindow()
    {
        GetWindow<ReplacePrefabsWithTerrainTrees>("Replace Prefabs");
    }

    void OnGUI()
    {
        EditorGUILayout.HelpBox("先在 Project 里选中你想替换的 Prefabs，然后点击按钮。", MessageType.Info);

        targetTerrain = (Terrain)EditorGUILayout.ObjectField("目标 Terrain", targetTerrain, typeof(Terrain), true);

        if (GUILayout.Button("替换选中 Prefab 实例为 Terrain 树"))
        {
            if (targetTerrain == null)
                targetTerrain = Terrain.activeTerrain;

            if (targetTerrain == null)
            {
                Debug.LogError("未指定 Terrain，也未检测到活动地形。");
                return;
            }

            ReplacePrefabs();
        }
    }

    void ReplacePrefabs()
    {
        Object[] selectedPrefabs = Selection.GetFiltered(typeof(GameObject), SelectionMode.Assets);
        if (selectedPrefabs.Length == 0)
        {
            Debug.LogWarning("你需要在 Project 面板中选择 Prefab！");
            return;
        }

        TerrainData terrainData = targetTerrain.terrainData;
        Vector3 terrainPos = targetTerrain.transform.position;

        List<TreeInstance> newTrees = new List<TreeInstance>(terrainData.treeInstances);
        int count = 0;

        foreach (GameObject prefab in selectedPrefabs)
        {
            GameObject[] instances = FindObjectsOfType<GameObject>();
            foreach (GameObject obj in instances)
            {
                if (PrefabUtility.GetCorrespondingObjectFromSource(obj) == prefab)
                {
                    Vector3 worldPos = obj.transform.position;

                    // 转换为 Terrain 本地坐标（归一化）
                    Vector3 normalizedPos = (worldPos - terrainPos);
                    normalizedPos.x /= terrainData.size.x;
                    normalizedPos.z /= terrainData.size.z;
                    normalizedPos.y = 0f;

                    // 选择一个随机树种（TreePrototype）
                    int prototypeIndex = Random.Range(0, terrainData.treePrototypes.Length);
                    TreeInstance tree = new TreeInstance
                    {
                        position = new Vector3(normalizedPos.x, 0, normalizedPos.z),
                        prototypeIndex = prototypeIndex,
                        heightScale = 1f,
                        widthScale = 1f,
                        color = Color.white,
                        lightmapColor = Color.white
                    };

                    newTrees.Add(tree);
                    Undo.DestroyObjectImmediate(obj);
                    count++;
                }
            }
        }

        terrainData.treeInstances = newTrees.ToArray();
        Debug.Log($"✅ 替换完成，处理了 {count} 个实例。添加到 Terrain 的 Tree 中。");
    }
}