import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.mojang.blaze3d.pipeline.MainTarget;
import com.mojang.blaze3d.platform.DisplayData;
import com.mojang.blaze3d.systems.RenderSystem;
import com.mojang.authlib.GameProfile;
import com.mojang.authlib.properties.PropertyMap;
import net.minecraft.SharedConstants;
import net.minecraft.client.Minecraft;
import net.minecraft.client.User;
import net.minecraft.client.main.GameConfig;
import net.minecraft.client.multiplayer.ClientLevel;
import net.minecraft.client.multiplayer.ClientPacketListener;
import net.minecraft.client.telemetry.TelemetryEventSender;
import net.minecraft.client.telemetry.WorldSessionTelemetryManager;
import net.minecraft.core.BlockPos;
import net.minecraft.core.Holder;
import net.minecraft.core.RegistryAccess;
import net.minecraft.core.registries.BuiltInRegistries;
import net.minecraft.core.registries.Registries;
import net.minecraft.network.Connection;
import net.minecraft.network.FriendlyByteBuf;
import net.minecraft.network.protocol.PacketFlow;
import net.minecraft.resources.RegistryDataLoader;
import net.minecraft.resources.ResourceKey;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.server.Bootstrap;
import net.minecraft.server.packs.resources.ResourceManager;
import net.minecraft.util.profiling.InactiveProfiler;
import net.minecraft.world.Difficulty;
import net.minecraft.world.level.ChunkPos;
import net.minecraft.world.level.Level;
import net.minecraft.world.level.LightLayer;
import net.minecraft.world.level.block.Block;
import net.minecraft.world.level.block.state.BlockBehaviour;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.core.Registry;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.chunk.DataLayer;
import net.minecraft.world.level.chunk.LevelChunk;
import net.minecraft.world.level.chunk.LevelChunkSection;
import net.minecraft.world.level.dimension.DimensionType;
import org.lwjgl.opengl.GL11;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Proxy;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.Base64;
import java.util.Optional;
import java.util.OptionalInt;
import java.util.UUID;

/**
 * mcfold 渲染服务：常驻进程，NDJSON(行分隔 JSON) 协议，由 Python 侧驱动。
 *
 * 设计约束（用户 2026-09-25）：
 *   - 不起完整客户端：不跑主循环、不连服、不登录、不作玩家
 *   - 我们的世界数据喂给官方渲染器出图
 *
 * 协议（stdin/stdout 各一行一个 JSON）：
 *   → {"id":1,"cmd":"chunk","cx":0,"cz":0,"data":"<b64>","heightmaps":null}
 *   → {"id":2,"cmd":"camera","x":8,"y":70,"z":8,"yaw":0,"pitch":0}
 *   → {"id":3,"cmd":"render","frames":60,"out":"/tmp/a.png"}
 *   ← {"id":3,"ok":true,"width":854,"height":480,"chunksRendered":29,
 *      "distinctColors":1450,"image":"<b64 png>"}
 *
 * 启动就绪时主动发 {"event":"ready"}。
 *
 * ★ 关键实现点（全部实测得来，详见 scaffold/README.md）：
 *   1. tryDetectVersion 必须先于 Bootstrap.bootStrap
 *   2. FolderData 顺序 (gameDir, resourcePackDir, assets, assetIndex)，assetIndex 用落盘名
 *   3. 资源必须手工同步重载（各 listener 的 public reload()），不能 join Minecraft 的
 *   4. LoadingOverlay + ReceivingLevelScreen 都要清，否则渲出加载屏
 *   5. 每帧 mc.tick() 才能推进区块网格重建队列
 *   6. 读像素必须绑 FBO
 *   7. chunk 数据走官方 replaceWithPacketData（与网络包同路径）
 */
public class McfoldRenderServer {

    static final Gson GSON = new Gson();
    static final PrintStream OUT = new PrintStream(
            new java.io.FileOutputStream(java.io.FileDescriptor.out), true, StandardCharsets.UTF_8);

    static Minecraft mc;
    static ClientLevel level;
    static int width = 854, height = 480;

    public static void main(String[] args) throws Exception {
        // stdout 只放协议 JSON，MC 的 INFO/WARN 全部赶到 stderr
        System.setOut(new PrintStream(new java.io.FileOutputStream(java.io.FileDescriptor.err), true));

        // ★ 不硬编码实例目录（版本隔离策略）：
        //   实例目录 = mods/config/options 的独占边界，必须由调用方按档案指定。
        //   缺省只给一个不含 mods 的临时目录，避免污染任何真实实例。
        String gameDir  = arg(args, "--gameDir", System.getProperty("java.io.tmpdir")
                + "/mcfold-noinstance");
        String assets   = arg(args, "--assets",  "/home/newqqagent/mcview/store/vanilla-1.20.1/assets");
        String assetIdx = arg(args, "--assetIndex", "1.20.1");
        width  = Integer.parseInt(arg(args, "--width",  "854"));
        height = Integer.parseInt(arg(args, "--height", "480"));

        try {
            boot(gameDir, assets, assetIdx);
        } catch (Throwable t) {
            emitError(null, "启动失败: " + t);
            t.printStackTrace(System.err);
            System.exit(1);
        }
        event("ready", null);

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in, StandardCharsets.UTF_8));
        String line;
        while ((line = in.readLine()) != null) {
            line = line.trim();
            if (line.isEmpty()) continue;
            JsonObject req;
            try {
                req = JsonParser.parseString(line).getAsJsonObject();
            } catch (Exception e) {
                emitError(null, "非法 JSON: " + e.getMessage());
                continue;
            }
            Integer id = req.has("id") ? req.get("id").getAsInt() : null;
            try {
                handle(id, req);
            } catch (Throwable t) {
                emitError(id, t.toString());
                t.printStackTrace(System.err);
            }
        }
        System.exit(0);
    }

    // ---------------- 协议处理 ----------------

    static void handle(Integer id, JsonObject req) throws Exception {
        String cmd = req.get("cmd").getAsString();
        switch (cmd) {
            case "shutdown": {
                JsonObject r = new JsonObject(); r.addProperty("ok", true);
                emit(id, r);
                System.exit(0);
            }
            case "chunk": {
                int cx = req.get("cx").getAsInt(), cz = req.get("cz").getAsInt();
                byte[] data = decode(req.get("data").getAsString());
                var resp = applyChunk(cx, cz, data);
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.add("result", resp);
                emit(id, r);
                break;
            }
            case "chunks": {
                JsonArray items = req.getAsJsonArray("items");
                int ok = 0, failed = 0;
                String firstErr = null;
                for (JsonElement el : items) {
                    JsonObject it = el.getAsJsonObject();
                    try {
                        applyChunk(it.get("cx").getAsInt(), it.get("cz").getAsInt(),
                                   decode(it.get("data").getAsString()));
                        ok++;
                    } catch (Throwable t) {
                        failed++;
                        if (firstErr == null) {
                            firstErr = it.get("cx") + "," + it.get("cz") + ": " + t;
                        }
                    }
                }
                levelRendererAllChanged();
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("injected", ok);
                r.addProperty("failed", failed);
                if (firstErr != null) r.addProperty("firstError", firstErr);
                var cache2 = (net.minecraft.client.multiplayer.ClientChunkCache) level.getChunkSource();
                r.addProperty("loadedChunks", cache2.getLoadedChunksCount());
                emit(id, r);
                break;
            }
            case "setblocks": {
                // ★ 世代无关：Python 只做路由，方块写入、调色板组装、入 cache
                //   全部由 Java 用官方 API 完成 —— 版本差异不落回 Python。
                //   载荷：sections[].rle = [[stateId,count],...]，按 (y,z,x) 线性序覆盖该 section 4096 格。
                //   优势：协议位打包（历代改过）不再由 Python 复制；入 cache 走官方
                //        ClientboundLevelChunkPacketData(LevelChunk) → getReadBuffer()，
                //        签名两代一致，**无需反射**。
                int cx = req.get("cx").getAsInt(), cz = req.get("cz").getAsInt();
                LevelChunk chunk = new LevelChunk(level, new ChunkPos(cx, cz));
                LevelChunkSection[] sections = chunk.getSections();
                int placed = 0;
                long cells = 0;
                for (JsonElement se : req.getAsJsonArray("sections")) {
                    JsonObject so = se.getAsJsonObject();
                    int si = so.get("index").getAsInt();
                    if (si < 0 || si >= sections.length) continue;
                    LevelChunkSection sec = sections[si];
                    int x = 0, y = 0, z = 0;
                    for (JsonElement re : so.getAsJsonArray("rle")) {
                        JsonArray pair = re.getAsJsonArray();
                        int stateId = pair.get(0).getAsInt();
                        int count = pair.get(1).getAsInt();
                        BlockState st = stateId == 0 ? null : Block.stateById(stateId);
                        for (int i = 0; i < count; i++) {
                            if (st != null) { sec.setBlockState(x, y, z, st); placed++; }
                            cells++;
                            if (++x == 16) { x = 0; if (++z == 16) { z = 0; y++; } }
                        }
                    }
                }
                // 光照（无光照数据则全亮，否则地形全黑）
                var light = level.getChunkSource().getLightEngine();
                for (int sy = level.getMinSection(); sy < level.getMaxSection(); sy++) {
                    DataLayer sky = new DataLayer();
                    for (int lx = 0; lx < 16; lx++)
                        for (int ly = 0; ly < 16; ly++)
                            for (int lz = 0; lz < 16; lz++) sky.set(lx, ly, lz, 15);
                    light.queueSectionData(LightLayer.SKY, net.minecraft.core.SectionPos.of(cx, sy, cz), sky);
                    light.queueSectionData(LightLayer.BLOCK, net.minecraft.core.SectionPos.of(cx, sy, cz), sky);
                }
                // ★ 官方序列化 → 官方入口入 cache（两代签名一致）
                var pkt = new net.minecraft.network.protocol.game.ClientboundLevelChunkPacketData(chunk);
                level.getChunkSource().replaceWithPacketData(cx, cz,
                        pkt.getReadBuffer(), pkt.getHeightmaps(),
                        new java.util.function.Consumer<
                            net.minecraft.network.protocol.game.ClientboundLevelChunkPacketData.BlockEntityTagOutput>() {
                            @Override public void accept(
                                net.minecraft.network.protocol.game.ClientboundLevelChunkPacketData.BlockEntityTagOutput t) { }
                        });
                light.setLightEnabled(new ChunkPos(cx, cz), true);
                light.runLightUpdates();
                // ★ 必须触发网格重建 —— 否则渲染器不知道该 section 有数据（实测）
                mc.levelRenderer.allChanged();
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("placed", placed);
                r.addProperty("cells", cells);
                r.addProperty("sections", sections.length);
                r.addProperty("loadedChunks", level.getChunkSource().getLoadedChunksCount());
                emit(id, r);
                break;
            }
            case "mods": {
                // ★ mod 支持全在 Java 侧完成（用户 2026-09-25 定向）：
                //   Java 自己扫 mods 目录、自己读 jar、自己注册方块、自己加载资源包。
                //   Python 只传目录路径。
                String dir = req.has("dir") ? req.get("dir").getAsString() : null;
                if (dir == null) {
                    JsonObject r = new JsonObject();
                    r.addProperty("ok", true);
                    r.addProperty("mods", 0);
                    r.addProperty("note", "未提供 dir");
                    emit(id, r);
                    break;
                }
                JsonObject res = loadMods(dir);
                emit(id, res);
                break;
            }
            case "modelcheck": {
                // ★ 程序化判据：mod 方块的 baked model 是否就是 missing model
                //   （画面里看到紫黑棋盘格是「缺贴图」的视觉表现，这里给出可断言的答案）
                JsonArray specs = req.getAsJsonArray("blocks");
                var shaper = mc.getBlockRenderer().getBlockModelShaper();
                Object missing = null;
                try {
                    var mmF = Minecraft.class.getDeclaredField("modelManager");
                    mmF.setAccessible(true);
                    Object mm = mmF.get(mc);
                    missing = mm.getClass().getMethod("getMissingModel").invoke(mm);
                } catch (Throwable t) { }
                var lookup = BuiltInRegistries.BLOCK.asLookup();
                JsonArray rows = new JsonArray();
                for (JsonElement el : specs) {
                    String spec = el.getAsString();
                    JsonObject ro = new JsonObject();
                    ro.addProperty("spec", spec);
                    try {
                        var pr = net.minecraft.commands.arguments.blocks.BlockStateParser
                                .parseForBlock(lookup, spec, false);
                        var st = pr.blockState();
                        Object baked = shaper.getBlockModel(st);
                        ro.addProperty("isMissing", baked == missing);
                        ro.addProperty("modelClass", baked.getClass().getSimpleName());
                        try {
                            Object icon = baked.getClass().getMethod("getParticleIcon",
                                    com.mojang.serialization.Codec.class).invoke(baked,
                                    net.minecraft.client.renderer.texture.TextureAtlasSprite.class == null ? null : null);
                        } catch (Throwable ignore) { }
                    } catch (Throwable t) {
                        ro.addProperty("error", String.valueOf(t));
                    }
                    rows.add(ro);
                }
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.add("results", rows);
                emit(id, r);
                break;
            }
            case "atlascheck": {
                // ★ 判据：mod 贴图是否真进了 blocks atlas
                //   正确 API 是 Minecraft.getTextureAtlas(...) → Function<RL,Sprite>
                //   （早先用 ModelManager.getAtlasSet 是错的，导致全 NPE 假绿）
                JsonArray arr = req.getAsJsonArray("textures");
                var fn = mc.getTextureAtlas(
                        net.minecraft.client.renderer.texture.TextureAtlas.LOCATION_BLOCKS);
                JsonArray rows = new JsonArray();
                for (JsonElement el : arr) {
                    String tex = el.getAsString();
                    JsonObject ro = new JsonObject();
                    ro.addProperty("texture", tex);
                    ro.addProperty("isMissing", true);
                    ro.addProperty("sprite", "");
                    try {
                        var sprite = fn.apply(ResourceLocation.parse(tex));
                        String reg = sprite.contents().name().toString();
                        ro.addProperty("sprite", reg);
                        ro.addProperty("isMissing", reg.contains("missingno"));
                    } catch (Throwable t) {
                        ro.addProperty("sprite", "ERROR: " + t);
                    }
                    rows.add(ro);
                }
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.add("results", rows);
                emit(id, r);
                break;
            }
            case "blockinfo": {
                // ★ 方块信息查询（Java 侧，因为只有它有 level + 注册表 + 模型状态）。
                //   Python 只路由，不做任何格式/语义判断。
                //   入参：{"cmd":"blockinfo","x":..,"y":..,"z":..}
                int bx = req.get("x").getAsInt();
                int by = req.get("y").getAsInt();
                int bz = req.get("z").getAsInt();
                BlockPos pos = new BlockPos(bx, by, bz);
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("x", bx); r.addProperty("y", by); r.addProperty("z", bz);

                int pcx = bx >> 4, pcz = bz >> 4;
                // ★ 判据必须是「真拿到了 LevelChunk」：
                //   ClientLevel.hasChunk() 实测**恒返回 true**（反编译见 306 行），
                //   基类 ChunkSource.hasChunk() 走 getChunk(...,false)，
                //   而 ClientChunkCache 覆写后在该参数下返回 emptyChunk（void_air 占位）
                //   ⇒ 都不可用于「未加载 vs 空气」的区分。
                //   可靠做法：getChunk(..., requireChunk=**false**) —— 反编译实测
                //     return requireChunk ? emptyChunk : null;
                //   即 requireChunk=false 时**未加载才给 null**（传 true 反而给占位）。
                var realChunk = level.getChunkSource()
                        // ★ 世代差异：1.21 把 ChunkStatus 移到 world.level.chunk.status
                        .getChunk(pcx, pcz,
                                net.minecraft.world.level.chunk.status.ChunkStatus.FULL, false);
                boolean loaded = realChunk != null;
                r.addProperty("chunkLoaded", loaded);
                r.addProperty("inBuildHeight", level.isInWorldBounds(pos));

                if (!loaded) {
                    // ★ 未加载 ≠ 空气（设计文档附录 D 强调的语义区分）
                    r.addProperty("known", false);
                    r.addProperty("reason", "chunk_not_loaded");
                    emit(id, r);
                    break;
                }

                BlockState st = level.getBlockState(pos);
                Block blk = st.getBlock();
                ResourceLocation key = BuiltInRegistries.BLOCK.getKey(blk);

                r.addProperty("known", true);
                r.addProperty("block", key == null ? "unknown" : key.toString());
                r.addProperty("stateId", Block.getId(st));
                r.addProperty("state", st.toString());
                r.addProperty("isAir", st.isAir());
                r.addProperty("isSolid", st.isSolid());

                // 方块属性（朝向/开关等）—— 渲染与指令都需要
                JsonObject props = new JsonObject();
                try {
                    for (var e : st.getValues().entrySet()) {
                        props.addProperty(e.getKey().getName(), String.valueOf(e.getValue()));
                    }
                } catch (Throwable ignore) { }
                r.add("properties", props);

                // 光照与硬度（agent 判断「这能不能挖/亮不亮」用）
                try {
                    r.addProperty("lightEmission", st.getLightEmission());
                    r.addProperty("destroySpeed", st.getDestroySpeed(level, pos));
                    r.addProperty("canOcclude", st.canOcclude());
                    r.addProperty("hasBlockEntity", st.hasBlockEntity());
                } catch (Throwable ignore) { }

                // 贴图是否真的在 atlas 里（缺贴图的**程序化判据**，不靠看图）
                //   BlockModelShaper.getParticleIcon(BlockState) 是静态的；
                //   它返回的 sprite 名字若含 missingno 就是缺贴图。
                try {
                    var shaper = mc.getBlockRenderer().getBlockModelShaper();
                    // 实例方法（1.20.1 与 1.21.1 签名一致）
                    var icon = shaper.getParticleIcon(st);
                    String reg = icon.contents().name().toString();
                    r.addProperty("particleTexture", reg);
                    r.addProperty("isMissingTexture", reg.contains("missingno"));
                } catch (Throwable t) {
                    r.addProperty("particleTexture", "unavailable: " + t.getClass().getSimpleName());
                }

                // 是否来自 mod（零加载器注册的方块 namespace 不在 minecraft）
                r.addProperty("fromMod", key != null && !key.getNamespace().equals("minecraft"));

                emit(id, r);
                break;
            }
            case "camera": {
                double x = req.get("x").getAsDouble(), y = req.get("y").getAsDouble(), z = req.get("z").getAsDouble();
                float yaw = req.has("yaw") ? req.get("yaw").getAsFloat() : 0f;
                float pitch = req.has("pitch") ? req.get("pitch").getAsFloat() : 0f;
                // ★ 必须 setPosRaw + 手动更新 chunk 追踪，否则实体仍属旧区块
                mc.player.setPosRaw(x, y, z);
                mc.player.xo = x; mc.player.yo = y; mc.player.zo = z;
                mc.player.setYRot(yaw);
                mc.player.setXRot(pitch);
                mc.player.yRotO = yaw;
                mc.player.xRotO = pitch;
                mc.setCameraEntity(mc.player);
                // 视野中心跟着相机走，否则目标区域区块被 ClientChunkCache 丢弃
                level.getChunkSource().updateViewCenter((int)Math.floor(x) >> 4, (int)Math.floor(z) >> 4);
                mc.levelRenderer.allChanged();
                tickFrames(5);
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                JsonArray c = new JsonArray(); c.add(x); c.add(y); c.add(z);
                r.add("camera", c);
                emit(id, r);
                break;
            }
            case "view": {
                if (req.has("cameraType")) {
                    mc.options.setCameraType(net.minecraft.client.CameraType.valueOf(req.get("cameraType").getAsString()));
                }
                if (req.has("renderDistance")) {
                    int rd = req.get("renderDistance").getAsInt();
                    // ★ 两处都要设：renderDistance 是本地设置；
                    //   serverRenderDistance 模拟服务端下发的视距上限
                    //   （getEffectiveRenderDistance = min(两者)）
                    mc.options.renderDistance().set(rd);
                    mc.options.setServerRenderDistance(rd);
                    // ★ 必须同步 ClientChunkCache 的 storage 半径，
                    //   否则区块被 inRange 丢弃（官方靠服务端包触发 updateViewRadius）
                    level.getChunkSource().updateViewRadius(rd);
                    mc.levelRenderer.allChanged();
                }
                if (req.has("fov")) {
                    mc.options.fov().set(req.get("fov").getAsInt());
                }
                // ── 原版画质选项（光影的基础层）──
                if (req.has("graphicsMode")) {
                    mc.options.graphicsMode().set(net.minecraft.client.GraphicsStatus
                            .valueOf(req.get("graphicsMode").getAsString()));
                    mc.levelRenderer.allChanged();   // FANCY 会启用更多渲染层
                }
                if (req.has("ambientOcclusion")) {
                    mc.options.ambientOcclusion().set(req.get("ambientOcclusion").getAsBoolean());
                    mc.levelRenderer.allChanged();
                }
                if (req.has("mipmapLevels")) {
                    mc.options.mipmapLevels().set(req.get("mipmapLevels").getAsInt());
                }
                if (req.has("gamma")) {
                    mc.options.gamma().set(req.get("gamma").getAsDouble());
                }
                if (req.has("entityShadows")) {
                    mc.options.entityShadows().set(req.get("entityShadows").getAsBoolean());
                }
                if (req.has("clouds")) {
                    mc.options.cloudStatus().set(net.minecraft.client.CloudStatus
                            .valueOf(req.get("clouds").getAsString()));
                }
                if (req.has("particles")) {
                    mc.options.particles().set(net.minecraft.client.ParticleStatus
                            .valueOf(req.get("particles").getAsString()));
                }
                // ── 原版后处理链（PostChain 基础设施）──
                if (req.has("postEffect")) {
                    String eff = req.get("postEffect").getAsString();
                    if (eff.isEmpty() || eff.equals("none")) {
                        mc.gameRenderer.shutdownEffect();
                    } else {
                        // loadEffect 是包私有 → 走同包 bridge
                        net.minecraft.client.renderer.McfoldBridge.loadEffect(
                                mc.gameRenderer, ResourceLocation.parse(eff));
                    }
                }
                // 回包带上真实生效值，便于验证
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                JsonObject cur = new JsonObject();
                try {
                    java.lang.reflect.Field pf = net.minecraft.client.renderer.GameRenderer.class
                            .getDeclaredField("postEffect");
                    pf.setAccessible(true);
                    cur.addProperty("postEffect", pf.get(mc.gameRenderer) != null ? "active" : "none");
                } catch (Throwable ignore) {
                    cur.addProperty("postEffect", "unknown");
                }
                cur.addProperty("graphicsMode", mc.options.graphicsMode().get().name());
                cur.addProperty("ambientOcclusion", mc.options.ambientOcclusion().get());
                cur.addProperty("mipmapLevels", mc.options.mipmapLevels().get());
                cur.addProperty("gamma", mc.options.gamma().get());
                cur.addProperty("entityShadows", mc.options.entityShadows().get());
                cur.addProperty("clouds", mc.options.cloudStatus().get().name());
                cur.addProperty("renderDistance", mc.options.getEffectiveRenderDistance());
                r.add("current", cur);
                emit(id, r);
                break;
            }
            case "capacity": {
                // ★ 世界尺寸由运行时提供 —— Python 不硬编码版本相关常量。
                //   这些方法都在 LevelHeightAccessor 上（Level 实现），两代 API 一致。
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("sectionsCount", level.getSectionsCount());
                r.addProperty("minSection", level.getMinSection());
                r.addProperty("maxSection", level.getMaxSection());
                r.addProperty("minBuildHeight", level.getMinBuildHeight());
                r.addProperty("maxBuildHeight", level.getMaxBuildHeight());
                r.addProperty("height", level.getHeight());
                // 生物群系默认 id（不硬编码 1）
                try {
                    var bio = mc.level.registryAccess().registryOrThrow(Registries.BIOME);
                    var key = bio.getKey(bio.byId(1));
                    r.addProperty("defaultBiome", key != null ? key.toString() : "minecraft:plains");
                } catch (Throwable t) {
                    r.addProperty("defaultBiome", "minecraft:plains");
                }
                emit(id, r);
                break;
            }
            case "registry": {
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("blockCount", BuiltInRegistries.BLOCK.size());
                r.addProperty("stateCount", Block.BLOCK_STATE_REGISTRY.size());
                emit(id, r);
                break;
            }
            case "lookup": {
                int sid = req.get("stateId").getAsInt();
                BlockState st = Block.stateById(sid);
                ResourceLocation key = BuiltInRegistries.BLOCK.getKey(st.getBlock());
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("stateId", sid);
                r.addProperty("block", key.toString());
                r.addProperty("state", st.toString());
                r.addProperty("inRange", sid >= 0 && sid < Block.BLOCK_STATE_REGISTRY.size());
                emit(id, r);
                break;
            }
            case "fog": {
                // 关雾：fogStart/fogEnd 是 levelRenderer 内部状态；
                // 更简单可靠的是加大 renderDistance + 用 BLOCK 光照
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                emit(id, r);
                break;
            }
            case "resolve": {
                // ★ 方块名(+属性) → state id。存档 palette 是名字，网络载荷要 id，
                //   而这个名字→id 的权威映射只有客户端注册表有。
                //   入参: {"cmd":"resolve","blocks":["minecraft:oak_log[axis=y]", ...]}
                JsonArray arr = req.getAsJsonArray("blocks");
                // ★ parseForBlock 要 HolderLookup（不是 Registry）。
                //   用**静态注册表**的 asLookup()：它是方块名→id 的权威来源
                //   （mod 方块也注册在这里），且两代 API 一致。
                //   不用 mc.level.registryAccess() —— 1.21 上它来自 cookie，
                //   只含 worldgen 那批注册表，查 block 会报 "Registry not found"（实测）。
                var reg = BuiltInRegistries.BLOCK.asLookup();
                JsonArray out = new JsonArray();
                int unknown = 0;
                for (JsonElement el : arr) {
                    String spec = el.getAsString();
                    int sid;
                    try {
                        var res = net.minecraft.commands.arguments.blocks.BlockStateParser
                                .parseForBlock(reg, spec, false);
                        sid = Block.getId(res.blockState());
                    } catch (Throwable t) {
                        sid = -1; unknown++;
                    }
                    out.add(sid);
                }
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.add("ids", out);
                r.addProperty("unknown", unknown);
                r.addProperty("total", arr.size());
                emit(id, r);
                break;
            }
            case "debug": {
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("playerPos", mc.player.getX() + "," + mc.player.getY() + "," + mc.player.getZ());
                int pcx = (int)Math.floor(mc.player.getX()) >> 4, pcz = (int)Math.floor(mc.player.getZ()) >> 4;
                r.addProperty("playerChunk", pcx + "," + pcz);
                var cc = (net.minecraft.client.multiplayer.ClientChunkCache) level.getChunkSource();
                r.addProperty("loadedChunks", cc.getLoadedChunksCount());
                r.addProperty("chunksRendered", mc.levelRenderer.countRenderedSections());
                r.addProperty("screenNow", mc.screen != null ? mc.screen.getClass().getSimpleName() : "null");
                r.addProperty("overlayNow", mc.getOverlay() != null ? mc.getOverlay().getClass().getSimpleName() : "null");
                r.addProperty("levelNow", mc.level != null);
                r.addProperty("playerNow", mc.player != null);
                r.addProperty("cameraEntity", mc.getCameraEntity() != null ? "set" : "null");
                r.addProperty("noRender", mc.noRender);
                r.addProperty("hasRenderedAllChunks", mc.levelRenderer.hasRenderedAllSections());
                var got = cc.getChunk(pcx, pcz, net.minecraft.world.level.chunk.status.ChunkStatus.FULL, false);
                r.addProperty("chunkAtPlayer", got != null ? got.getClass().getSimpleName() : "null");
                if (got != null) {
                    // 扫描玩家所在列，找最高的非空气方块
                    int top = Integer.MIN_VALUE;
                    for (int y = level.getMaxBuildHeight() - 1; y >= level.getMinBuildHeight(); y--) {
                        var st = got.getBlockState(new BlockPos(
                                (int)Math.floor(mc.player.getX()) & 15, y, (int)Math.floor(mc.player.getZ()) & 15));
                        if (!st.isAir()) {
                            top = y;
                            r.addProperty("topSolidY", y);
                            r.addProperty("topSolidBlock", BuiltInRegistries.BLOCK.getKey(st.getBlock()).toString());
                            r.addProperty("topSolidProps", st.toString());
                            break;
                        }
                    }
                    if (top == Integer.MIN_VALUE) r.addProperty("topSolidY", "none");
                }
                // viewCenter
                r.addProperty("fogStart", String.valueOf(mc.options.renderDistance().get()));
                emit(id, r);
                break;
            }
            case "viewport": {
                // ★ viewCenter 决定 ClientChunkCache 收哪些区块（超范围会被丢弃）
                int cx = req.get("cx").getAsInt(), cz = req.get("cz").getAsInt();
                if (req.has("radius")) {
                    level.getChunkSource().updateViewRadius(req.get("radius").getAsInt());
                }
                level.getChunkSource().updateViewCenter(cx, cz);
                JsonObject r = new JsonObject();
                r.addProperty("ok", true);
                r.addProperty("viewCenter", cx + "," + cz);
                emit(id, r);
                break;
            }
            case "render": {
                int frames = req.has("frames") ? req.get("frames").getAsInt() : 60;
                String out = req.has("out") ? req.get("out").getAsString() : null;
                if (req.has("width")) width = req.get("width").getAsInt();
                if (req.has("height")) height = req.get("height").getAsInt();
                render(id, frames, out);
                break;
            }
            default:
                emitError(id, "未知命令: " + cmd);
        }
    }

    static JsonObject applyChunk(int cx, int cz, byte[] data) {
        // ★ 官方路径：ClientChunkCache.replaceWithPacketData
        //   内部：new LevelChunk + chunk.replaceWithPacketData(buf, heightmaps, consumer)
        //   与网络包 handleLevelChunkWithLight 完全同一路径
        FriendlyByteBuf buf = new FriendlyByteBuf(io.netty.buffer.Unpooled.wrappedBuffer(data));
        var cache = level.getChunkSource();
        // 显式匿名类而非 lambda：lambda 参数类型推断在此处会失败（实测）
        net.minecraft.network.protocol.game.ClientboundLevelChunkPacketData.BlockEntityTagOutput beOut =
                new net.minecraft.network.protocol.game.ClientboundLevelChunkPacketData.BlockEntityTagOutput() {
                    @Override public void accept(BlockPos bp,
                            net.minecraft.world.level.block.entity.BlockEntityType<?> type,
                            net.minecraft.nbt.CompoundTag tag) { }
                };
        // ★ 参数是 Consumer<BlockEntityTagOutput>（消费这个接口本身），不是该接口的方法签名。
        //   LevelChunk.replaceWithPacketData 内部会调 beOut.accept(...)，这里直接空实现。
        cache.replaceWithPacketData(cx, cz, buf, new net.minecraft.nbt.CompoundTag(), out -> {});
        // 无光照数据 ⇒ 显式全亮，否则地形全黑
        var light = cache.getLightEngine();
        for (int sy = level.getMinSection(); sy < level.getMaxSection(); sy++) {
            DataLayer sky = new DataLayer();
            for (int x = 0; x < 16; x++)
                for (int y = 0; y < 16; y++)
                    for (int z = 0; z < 16; z++) sky.set(x, y, z, 15);
            light.queueSectionData(LightLayer.SKY, net.minecraft.core.SectionPos.of(cx, sy, cz), sky);
            light.queueSectionData(LightLayer.BLOCK, net.minecraft.core.SectionPos.of(cx, sy, cz), sky);
        }
        light.setLightEnabled(new ChunkPos(cx, cz), true);
        int upd = light.runLightUpdates();
        JsonObject r = new JsonObject();
        r.addProperty("lightUpdates", upd);
        return r;
    }

    static void levelRendererAllChanged() {
        mc.levelRenderer.allChanged();
    }

    /** tick + 渲染各帧（区块网格重建队列靠 tick 推进） */
    static void tickFrames(int n) {
        MainTarget target = (MainTarget) mc.getMainRenderTarget();
        for (int f = 0; f < n; f++) {
            try { mc.tick(); } catch (Throwable t) {
                if (f == 0) { System.err.println("[mcfold] tick 异常(第1帧): " + t); t.printStackTrace(System.err); }
            }
            RenderSystem.clear(16640, Minecraft.ON_OSX);
            target.bindWrite(true);
            // ★ 世代差异（1.21+）：render(DeltaTracker, boolean)
            mc.gameRenderer.render(mc.getTimer(), true);
            target.unbindWrite();
            target.blitToScreen(mc.getWindow().getWidth(), mc.getWindow().getHeight());
            mc.getWindow().updateDisplay();
        }
    }

    static void render(Integer id, int frames, String out) throws Exception {
        // ★ 1.21 实测：setLevel 会挂 ReceivingLevelScreen；
        //   若渲染前它有残留，画面就是加载屏（distinctColors 停在 ~199）。
        mc.setScreen(null);
        mc.setOverlay(null);
        tickFrames(frames);

        MainTarget target = (MainTarget) mc.getMainRenderTarget();
        int w = mc.getWindow().getWidth(), h = mc.getWindow().getHeight();
        org.lwjgl.opengl.GL30.glBindFramebuffer(org.lwjgl.opengl.GL30.GL_FRAMEBUFFER, target.frameBufferId);
        GL11.glReadBuffer(org.lwjgl.opengl.GL30.GL_COLOR_ATTACHMENT0);
        var buf = org.lwjgl.BufferUtils.createByteBuffer(w * h * 4);
        GL11.glReadPixels(0, 0, w, h, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, buf);
        org.lwjgl.opengl.GL30.glBindFramebuffer(org.lwjgl.opengl.GL30.GL_FRAMEBUFFER, 0);

        BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        java.util.Set<Integer> colors = new java.util.HashSet<>();
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++) {
                int i = ((h - 1 - y) * w + x) * 4;
                int rgb = ((buf.get(i) & 0xFF) << 16) | ((buf.get(i + 1) & 0xFF) << 8) | (buf.get(i + 2) & 0xFF);
                img.setRGB(x, y, rgb);
                colors.add(rgb);
            }

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ImageIO.write(img, "png", bos);
        byte[] png = bos.toByteArray();
        if (out != null) ImageIO.write(img, "png", new File(out));

        JsonObject r = new JsonObject();
        r.addProperty("ok", true);
        r.addProperty("width", w);
        r.addProperty("height", h);
        r.addProperty("chunksRendered", mc.levelRenderer.countRenderedSections());
        r.addProperty("hasRenderedAllChunks", mc.levelRenderer.hasRenderedAllSections());
        r.addProperty("distinctColors", colors.size());
        JsonArray cam = new JsonArray();
        cam.add(mc.player.getX()); cam.add(mc.player.getY()); cam.add(mc.player.getZ());
        r.add("camera", cam);
        if (out != null) r.addProperty("path", out);
        r.addProperty("image", Base64.getEncoder().encodeToString(png));
        emit(id, r);
    }

    // ---------------- 启动 ----------------

    static void boot(String gameDir, String assets, String assetIdx) throws Exception {
        SharedConstants.tryDetectVersion();
        // ★ 世代差异（1.21+）：enableDataFixerOptimizations() 已被移除（实测映射表无此方法）
        Bootstrap.bootStrap();

        File runDir = new File(gameDir);
        runDir.mkdirs();
        // ★ 世代差异（1.21+）：User(String, UUID, String, Optional, Optional, Type)
        //   1.20.x 是 (String, String sessionId, String, ...)
        User user = new User("mcfold_cam", java.util.UUID.nameUUIDFromBytes("mcfold_cam".getBytes()),
                "mcfold_cam", Optional.empty(), Optional.empty(), User.Type.LEGACY);
        PropertyMap props = new PropertyMap();
        GameConfig cfg = new GameConfig(
            new GameConfig.UserData(user, props, props, Proxy.NO_PROXY),
            new DisplayData(width, height, OptionalInt.empty(), OptionalInt.empty(), false),
            new GameConfig.FolderData(runDir, new File(runDir, "resourcepacks"),
                                      new File(assets), assetIdx),
            new GameConfig.GameData(false, "mcfold", "release", false, false),
            new GameConfig.QuickPlayData(null, null, null, null));

        RenderSystem.initRenderThread();
        RenderSystem.beginInitialization();
        mc = new Minecraft(cfg);
        RenderSystem.finishInitialization();
        System.err.println("[mcfold] Minecraft constructed");

        reloadResources(mc);
        System.err.println("[mcfold] resources reloaded");

        // ★★ 世代差异（1.21+）：注册表经 CommonListenerCookie.receivedRegistries 传入，
        //   并在 ClientPacketListener 构造时赋给 **final** 字段
        //   （实测：1.20.x 是可变 LayeredRegistryAccess，可事后反射替换；
        //          1.21 是 final RegistryAccess$Frozen，反射会抛
        //          "Can not set final ... field"）。
        //   ⇒ 本世代的正确顺序：**先加载注册表，再构造 cookie + listener**。
        //   这比 1.20 的反射注入更干净。
        var packs = net.minecraft.server.packs.repository.ServerPacksSource.createPackRepository(
                new File(runDir, "datapacks").toPath(),
                new net.minecraft.world.level.validation.DirectoryValidator(p -> false));
        packs.reload();
        ResourceManager dataRm = new net.minecraft.server.packs.resources.MultiPackResourceManager(
                net.minecraft.server.packs.PackType.SERVER_DATA,
                java.util.List.of(packs.getPack("vanilla").open()));
        var all = new java.util.ArrayList<RegistryDataLoader.RegistryData<?>>();
        all.addAll(RegistryDataLoader.WORLDGEN_REGISTRIES);
        all.addAll(RegistryDataLoader.DIMENSION_REGISTRIES);
        RegistryAccess.Frozen base = net.minecraft.client.multiplayer.ClientRegistryLayer
                .createRegistryAccess().compositeAccess();
        RegistryAccess.Frozen loaded = RegistryDataLoader.load(dataRm, base, all);
        System.err.println("[mcfold] registries loaded: dimension_type="
                + loaded.registryOrThrow(Registries.DIMENSION_TYPE).size());

        Connection conn = new Connection(PacketFlow.CLIENTBOUND);
        GameProfile profile = new GameProfile(UUID.randomUUID(), "mcfold_cam");
        WorldSessionTelemetryManager telemetry = new WorldSessionTelemetryManager(
                TelemetryEventSender.DISABLED, false, Duration.ZERO, "");
        var cookie = new net.minecraft.client.multiplayer.CommonListenerCookie(
                profile,
                telemetry,
                loaded,                                  // ← 注册表从这里进
                net.minecraft.world.flag.FeatureFlags.DEFAULT_FLAGS,
                null, null, null,
                java.util.Map.of(), null, false, java.util.Map.of(),
                net.minecraft.server.ServerLinks.EMPTY);
        ClientPacketListener listener = new ClientPacketListener(mc, conn, cookie);
        System.err.println("[mcfold] listener ok, registryAccess dims="
                + listener.registryAccess().registryOrThrow(Registries.DIMENSION_TYPE).size());

        Holder<DimensionType> dimHolder = loaded.registryOrThrow(Registries.DIMENSION_TYPE)
                .getHolderOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, ResourceLocation.parse("minecraft:overworld")));
        var levelData = new ClientLevel.ClientLevelData(Difficulty.NORMAL, false, false);
        level = new ClientLevel(listener, levelData, Level.OVERWORLD, dimHolder,
                Math.max(8, mc.options.renderDistance().get()), 8,
                () -> InactiveProfiler.INSTANCE, mc.levelRenderer, false, 0L);
        // ★ 世代差异（1.21+）：setLevel(ClientLevel, ReceivingLevelScreen$Reason)
        //   1.20.x 只有一个参数。这是本文件与 gen_1_20 的差异之一。
        // 枚举值实测：NETHER_PORTAL / END_PORTAL / OTHER（没有 LEVEL_LOAD）
        // 我们不是经传送门进入世界 ⇒ OTHER
        mc.setLevel(level, net.minecraft.client.gui.screens.ReceivingLevelScreen.Reason.OTHER);

        var player = new net.minecraft.client.player.LocalPlayer(mc, level, listener,
                new net.minecraft.stats.StatsCounter(), new net.minecraft.client.ClientRecipeBook(), false, false);
        player.setPos(8.0, 70.0, 8.0);
        mc.player = player;
        mc.setCameraEntity(player);
        mc.gameMode = new net.minecraft.client.multiplayer.MultiPlayerGameMode(mc, listener);

        net.minecraft.client.renderer.McfoldBridge.reloadShaders(mc.gameRenderer, mc.getResourceManager());

        // ★★ 世代差异（1.21+，编译期看不出）：
        //   GameRenderer.render(DeltaTracker,boolean) 里有门禁
        //       boolean ok = minecraft.isGameLoadFinished();
        //       if (ok && renderLevel && level != null) renderLevel(...);
        //   而 gameLoadFinished 只在 **reloadResourcePacks 的回调**
        //   （onResourceLoadFinished）里被置 true。
        //   我们不跑异步 reload（会死锁）⇒ 该位恒 false ⇒ 世界永不渲染
        //   （症状：画面停在 Mojang 加载屏，distinctColors≈199，chunksRendered=0）。
        //   1.20.x 无此门禁，所以 gen_1_20 不受影响。
        net.minecraft.client.renderer.McfoldBridge.markGameLoadFinished(mc);

        mc.setOverlay(null);
        mc.setScreen(null);
        mc.options.setCameraType(net.minecraft.client.CameraType.THIRD_PERSON_BACK);
        System.err.println("[mcfold] boot done");
    }

    /**
     * 把 blockstate 里的 model 引用规范化成 jar 里实际存在的路径。
     *
     * 实测两类写法：
     *   "ns:block/foo"  → models/block/foo.json          （createbigcannons 风格，正确）
     *   "ns:foo"        → models/foo.json（不存在！）    （MTS 风格，实际在 models/block/foo.json）
     * 所以先原样查，再试补 "block/"。
     */
    static String normalizeModelPath(java.util.zip.ZipFile zf, String model) {
        int i = model.indexOf(':');
        String ns = i > 0 ? model.substring(0, i) : "minecraft";
        String path = i > 0 ? model.substring(i + 1) : model;
        if (zf.getEntry("assets/" + ns + "/models/" + path + ".json") != null) return model;
        if (zf.getEntry("assets/" + ns + "/models/block/" + path + ".json") != null) {
            return ns + ":block/" + path;
        }
        return model;   // 都不存在 → 保持原样（会显示 missing，但至少不误导）
    }

    /**
     * 生成一个「blockstates 覆盖包」：把 mod 的变体键统一改写成 ""。
     *
     * ★ 为什么需要（实测根因）：
     *   我们的占位方块只有 defaultBlockState（变体键 ""），
     *   而 mod 的 blockstates 常用属性键（如 "normal"、"facing=north"）⇒ 匹配不上
     *   ⇒ missing model ⇒ 画面上是紫黑棋盘格。
     *   例：createbigcannons:steel_block 的键是 ""（渲染正常，测过），
     *       mts:...fancydirt_block 的键是 "normal"（棋盘格）。
     *
     * 做法：读每个 mod jar 的 assets/<ns>/blockstates/*.json，取第一个 variant 的 model，
     *       改写成 {"variants":{"":{"model":"<那个 model>"}}}，打进一个 zip。
     *       该 zip 作为**最后选中**的资源包，优先级最高，从而覆盖原 blockstates。
     *       模型/贴图仍由原 jar 提供（不动）。
     */
    static File buildBlockstateOverlay(java.util.List<File> jars, java.nio.file.Path outDir) throws Exception {
        File overlay = new File(outDir.toFile(), "mcfold-blockstate-overlay.zip");
        java.util.TreeMap<String, byte[]> entries = new java.util.TreeMap<>();
        entries.put("pack.mcmeta",
                ("{\"pack\":{\"description\":\"mcfold blockstate overlay\",\"pack_format\":15}}")
                        .getBytes(java.nio.charset.StandardCharsets.UTF_8));
        int rewritten = 0;
        for (File jar : jars) {
            try (java.util.zip.ZipFile zf = new java.util.zip.ZipFile(jar)) {
                var en = zf.entries();
                while (en.hasMoreElements()) {
                    var e = en.nextElement();
                    String nm = e.getName();
                    if (!nm.startsWith("assets/") || !nm.contains("/blockstates/")
                            || !nm.endsWith(".json")) continue;
                    String text;
                    try (var in = zf.getInputStream(e)) {
                        text = new String(in.readAllBytes(), java.nio.charset.StandardCharsets.UTF_8);
                    }
                    JsonObject root;
                    try { root = JsonParser.parseString(text).getAsJsonObject(); }
                    catch (Throwable t) { continue; }
                    if (!root.has("variants") || !root.get("variants").isJsonObject()) continue;

                    // 取第一个 variant 的第一个 model —— 只求外观，不求语义
                    String model = null;
                    for (var ve : root.getAsJsonObject("variants").entrySet()) {
                        JsonElement v = ve.getValue();
                        JsonElement one = v.isJsonArray() ? (v.getAsJsonArray().size() > 0
                                ? v.getAsJsonArray().get(0) : null) : v;
                        if (one != null && one.isJsonObject() && one.getAsJsonObject().has("model")) {
                            model = one.getAsJsonObject().get("model").getAsString();
                            break;
                        }
                    }
                    if (model == null) continue;
                    // ★ 规范化 model 路径（实测根因）：
                    //   MTS 写 "mts:mtsofficialpack.fancydirt_block"（缺 block/），
                    //   而文件在 models/block/... ⇒ MC 找不到 ⇒ missing model ⇒ 棋盘格。
                    //   createbigcannons 写 "createbigcannons:block/steel_block"（有 block/），正常。
                    //   策略：先按原样看 jar 里有没有；没有就试补 block/ 前缀。
                    model = normalizeModelPath(zf, model);
                    String out = "{\"variants\":{\"\":{\"model\":\"" + model + "\"}}}";
                    entries.put(nm, out.getBytes(java.nio.charset.StandardCharsets.UTF_8));
                    rewritten++;
                }
            }
        }
        if (rewritten == 0) return null;
        try (var zos = new java.util.zip.ZipOutputStream(
                new java.io.FileOutputStream(overlay))) {
            for (var kv : entries.entrySet()) {
                zos.putNextEntry(new java.util.zip.ZipEntry(kv.getKey()));
                zos.write(kv.getValue());
                zos.closeEntry();
            }
        }
        System.err.println("[mcfold] overlay: 重写 " + rewritten + " 个 blockstates → " + overlay);
        return overlay;
    }

    /**
     * 加载 mod：扫 jar → 注册占位方块 → 挂资源包（外观）。
     *
     * ★ 全部在 Java 侧完成（用户 2026-09-25 定向）：Java 自己读 jar、自己注册、
     *   自己挂资源包。Python 只传目录路径。
     *
     * 原理（见 scaffold/MOD-BLOCKS.md）：方块**渲染**只需要
     *   (a) 注册表里有这个名字（拿 state id）
     *   (b) 资源包里有它的 blockstates/models/textures
     * 与方块行为无关 ⇒ 零 mod 加载器也能正确显示。
     */
    static JsonObject loadMods(String dir) {
        JsonObject out = new JsonObject();
        File d = new File(dir);
        File[] jars = d.listFiles((f, n) -> n.endsWith(".jar"));
        if (jars == null || jars.length == 0) {
            out.addProperty("ok", true);
            out.addProperty("mods", 0);
            out.addProperty("blocksRegistered", 0);
            return out;
        }

        // ── 1. 解冻 BLOCK 注册表（frozen=false + 恢复 intrusiveHolders）──
        //    两个字段都必须处理：只清 frozen 会抛 "can't create intrusive holders"
        Object blockReg = BuiltInRegistries.BLOCK;
        try {
            for (Class<?> c = blockReg.getClass(); c != null; c = c.getSuperclass()) {
                try {
                    var f = c.getDeclaredField("frozen");
                    f.setAccessible(true);
                    f.setBoolean(blockReg, false);
                } catch (NoSuchFieldException ignore) { }
                try {
                    var f = c.getDeclaredField("unregisteredIntrusiveHolders");
                    f.setAccessible(true);
                    if (f.get(blockReg) == null) f.set(blockReg, new java.util.IdentityHashMap<>());
                } catch (NoSuchFieldException ignore) { }
            }
        } catch (Throwable t) {
            System.err.println("[mcfold] 解冻失败: " + t);
        }

        int mods = 0, blocksAdded = 0, skipped = 0;
        JsonArray detail = new JsonArray();
        for (File jar : jars) {
            JsonObject m = new JsonObject();
            m.addProperty("jar", jar.getName());
            int n = 0, skip = 0;
            try (java.util.zip.ZipFile zf = new java.util.zip.ZipFile(jar)) {
                var en = zf.entries();
                java.util.Set<String> seen = new java.util.LinkedHashSet<>();
                while (en.hasMoreElements()) {
                    String name = en.nextElement().getName();
                    // 方块名来源：assets/<ns>/blockstates/<name>.json（权威，见 P5 实测）
                    java.util.regex.Matcher mm = java.util.regex.Pattern
                            .compile("^assets/([^/]+)/blockstates/(.+)\\.json$").matcher(name);
                    if (!mm.matches()) continue;
                    String ns = mm.group(1), blk = mm.group(2);
                    if (!seen.add(ns + ":" + blk)) continue;
                    // ★ 世代差异（1.21+）：ResourceLocation 构造变 private → 静态工厂
                    ResourceLocation rl = ResourceLocation.fromNamespaceAndPath(ns, blk);
                    try {
                        if (BuiltInRegistries.BLOCK.containsKey(rl)) { skip++; continue; }
                        // ★ 世代差异（1.21+）：Properties.copy(Block) 已移除，只有 of()
                        Block b = new Block(BlockBehaviour.Properties.of());
                        Registry.register(BuiltInRegistries.BLOCK, rl, b);
                        // ★ BlockState 不会自动进 BLOCK_STATE_REGISTRY（实测 state id 会是 0）
                        Block.BLOCK_STATE_REGISTRY.add(b.defaultBlockState());
                        n++;
                    } catch (Throwable t) {
                        skip++;
                    }
                }
                mods++;
            } catch (Throwable t) {
                m.addProperty("error", String.valueOf(t));
            }
            m.addProperty("blocksRegistered", n);
            m.addProperty("skipped", skip);
            blocksAdded += n;
            skipped += skip;
            detail.add(m);
        }

        // ── 2. 挂资源包（外观：blockstates/models/textures）──
        //    把 mod jar 作为资源包加入并选中，然后重载资源管理器。
        int packsAdded = 0;
        try {
            var repo = mc.getResourcePackRepository();
            java.nio.file.Path rpDir = mc.getResourcePackDirectory();
            for (File jar : jars) {
                // ★ 必须是 .zip 后缀：FolderRepositorySource 只认
                //   isDirectory+pack.mcmeta 或 **.zip**（实测它不看 .jar）
                String base = jar.getName().replaceAll("\\.jar$", "");
                File dst = new File(rpDir.toFile(), "mcfold-" + base + ".zip");
                if (!dst.isFile()) java.nio.file.Files.copy(jar.toPath(), dst.toPath(),
                        java.nio.file.StandardCopyOption.REPLACE_EXISTING);
            }
            // ★ 生成 blockstates 覆盖包并放进资源包目录
            //   （把 mod 的属性变体键改写成 "" —— 占位方块只有 defaultBlockState）
            java.util.List<File> jarList = new java.util.ArrayList<>();
            for (File j : jars) jarList.add(j);
            File overlay = buildBlockstateOverlay(jarList, rpDir);
            if (overlay != null) {
                File od = new File(rpDir.toFile(), "zzz-mcfold-blockstate-overlay.zip");
                java.nio.file.Files.copy(overlay.toPath(), od.toPath(),
                        java.nio.file.StandardCopyOption.REPLACE_EXISTING);
            }
            repo.reload();
            // 诊断（放进响应，stderr 会被后续日志冲掉）
            out.addProperty("packDir", rpDir.toString());
            JsonArray avail = new JsonArray();
            for (String ai : repo.getAvailableIds()) avail.add(ai);
            out.add("availableIds", avail);
            JsonArray compat = new JsonArray();
            for (var pk2 : repo.getAvailablePacks()) {
                JsonObject po = new JsonObject();
                po.addProperty("id", pk2.getId());
                po.addProperty("compat", String.valueOf(pk2.getCompatibility()));
                compat.add(po);
            }
            out.add("availablePacks", compat);
            var sel = new java.util.LinkedHashSet<>(repo.getSelectedIds());
            // 先加 mod 包（提供 models/textures），再加 overlay（覆盖 blockstates）
            java.util.List<String> overlayIds = new java.util.ArrayList<>();
            for (String packId : repo.getAvailableIds()) {
                if (packId.contains("zzz-mcfold-blockstate-overlay")) { overlayIds.add(packId); continue; }
                if (packId.contains("mcfold-")) { sel.add(packId); packsAdded++; }
            }
            sel.addAll(overlayIds);   // 最后 = 最高优先级
            JsonArray selArr = new JsonArray();
            for (String si : sel) selArr.add(si);
            out.add("selectedIds", selArr);
            repo.setSelected(sel);

            // 用新 pack 列表重建 resource manager（照官方 createReload 内部做法），
            // 再手工驱动 listener（不能 join Minecraft.reloadResourcePacks，会死锁）
            java.util.List<net.minecraft.server.packs.PackResources> packs = new java.util.ArrayList<>();
            for (var pk : repo.getSelectedPacks()) packs.add(pk.open());
            var rmF = Minecraft.class.getDeclaredField("resourceManager");
            rmF.setAccessible(true);
            var rm = (net.minecraft.server.packs.resources.ReloadableResourceManager) rmF.get(mc);
            var resF = net.minecraft.server.packs.resources.ReloadableResourceManager.class
                    .getDeclaredField("resources");
            resF.setAccessible(true);
            resF.set(rm, new net.minecraft.server.packs.resources.MultiPackResourceManager(
                    net.minecraft.server.packs.PackType.CLIENT_RESOURCES, packs));
            reloadResources(mc);
            net.minecraft.client.renderer.McfoldBridge.reloadShaders(mc.gameRenderer, mc.getResourceManager());
            mc.levelRenderer.allChanged();

            // ★ 自验证：重载后 mod 资源是否真的可读（TOO_OLD 是否阻止加载）
            ResourceManager rm2 = mc.getResourceManager();
            System.err.println("[mcfold] resourceManager=" + rm2.getClass().getSimpleName()
                    + " namespaces=" + rm2.getNamespaces());
            JsonArray check = new JsonArray();
            for (File jar : jars) {
                try (java.util.zip.ZipFile zf = new java.util.zip.ZipFile(jar)) {
                    var en2 = zf.entries();
                    while (en2.hasMoreElements()) {
                        String nm = en2.nextElement().getName();
                        java.util.regex.Matcher m2 = java.util.regex.Pattern
                                .compile("^assets/([^/]+)/(blockstates/.+\\.json)$").matcher(nm);
                        if (!m2.matches()) continue;
                        // ★ 世代差异（1.21+）：构造 private → 静态工厂
                        ResourceLocation rid = ResourceLocation.fromNamespaceAndPath(
                                m2.group(1), m2.group(2));
                        JsonObject co = new JsonObject();
                        co.addProperty("id", rid.toString());
                        var got2 = rm2.getResource(rid);
                        co.addProperty("readable", got2.isPresent());
                        if (got2.isPresent()) {
                            try (var in2 = got2.get().open()) {
                                co.addProperty("bytes", in2.readAllBytes().length);
                            }
                        }
                        check.add(co);
                        break;   // 每个 jar 只查一个样本
                    }
                } catch (Throwable ignore) { }
            }
            out.add("resourceCheck", check);
        } catch (Throwable t) {
            out.addProperty("packError", String.valueOf(t));
            System.err.println("[mcfold] 资源包挂载失败: " + t);
        }

        out.addProperty("ok", true);
        out.addProperty("mods", mods);
        out.addProperty("blocksRegistered", blocksAdded);
        out.addProperty("skipped", skipped);
        out.addProperty("packsAdded", packsAdded);
        out.add("detail", detail);
        return out;
    }

    /** 同步驱动各 reload listener（不能 join Minecraft 的 reloadResourcePacks：等主循环 → 死锁）*/
    static void reloadResources(Minecraft mc) throws Exception {
        var rmF = Minecraft.class.getDeclaredField("resourceManager");
        rmF.setAccessible(true);
        var rm = (net.minecraft.server.packs.resources.ReloadableResourceManager) rmF.get(mc);
        mc.getResourcePackRepository().reload();

        var barrier = new net.minecraft.server.packs.resources.PreparableReloadListener.PreparationBarrier() {
            @Override public <T> java.util.concurrent.CompletableFuture<T> wait(T t) {
                return java.util.concurrent.CompletableFuture.completedFuture(t);
            }
        };
        var prof = InactiveProfiler.INSTANCE;
        java.util.concurrent.Executor sync = Runnable::run;

        for (var listener : reloadListeners(rm)) {
            String name = listener.getName();
            try {
                var fut = listener.reload(barrier, rm, prof, prof, sync, sync);
                long deadline = System.currentTimeMillis() + 60_000;
                while (!fut.isDone() && System.currentTimeMillis() < deadline) Thread.sleep(10);
                if (fut.isDone()) fut.join();
                else System.err.println("[mcfold]   TIMEOUT " + name);
            } catch (Throwable e) {
                System.err.println("[mcfold]   FAILED " + name + ": " + e);
            }
        }
    }

    @SuppressWarnings("unchecked")
    static java.util.List<net.minecraft.server.packs.resources.PreparableReloadListener> reloadListeners(Object rm) throws Exception {
        for (var f : rm.getClass().getDeclaredFields()) {
            if (java.util.List.class.isAssignableFrom(f.getType())) {
                f.setAccessible(true);
                Object v = f.get(rm);
                if (v instanceof java.util.List<?> l && !l.isEmpty()
                        && l.get(0) instanceof net.minecraft.server.packs.resources.PreparableReloadListener) {
                    return (java.util.List<net.minecraft.server.packs.resources.PreparableReloadListener>) l;
                }
            }
        }
        throw new IllegalStateException("reload listeners not found");
    }

    // ---------------- 工具 ----------------

    static byte[] decode(String b64) {
        return Base64.getDecoder().decode(b64);
    }

    static String arg(String[] a, String key, String def) {
        for (int i = 0; i < a.length - 1; i++) if (a[i].equals(key)) return a[i + 1];
        return def;
    }

    static synchronized void emit(Integer id, JsonObject obj) {
        if (id != null) obj.addProperty("id", id);
        OUT.println(GSON.toJson(obj));
        OUT.flush();
    }

    static void emitError(Integer id, String msg) {
        JsonObject o = new JsonObject();
        o.addProperty("ok", false);
        o.addProperty("error", msg);
        emit(id, o);
    }

    static void event(String name, JsonObject payload) {
        JsonObject o = new JsonObject();
        o.addProperty("event", name);
        if (payload != null) o.add("payload", payload);
        OUT.println(GSON.toJson(o));
        OUT.flush();
    }
}