Implement 1.9->1.8 command block translation

common/src/main/java/com/viaversion/viarewind/protocol/v1_9to1_8/Protocol1_9To1_8.java

@@ -26,6 +26,7 @@
 import com.viaversion.viarewind.protocol.v1_9to1_8.rewriter.WorldPacketRewriter1_9;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.BlockPlaceDestroyTracker;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.BossBarStorage;
+import com.viaversion.viarewind.protocol.v1_9to1_8.storage.CommandBlockStateStorage;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.CooldownStorage;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.EntityTracker1_9;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.LevitationStorage;
@@ -89,6 +90,7 @@ public void init(UserConnection connection) {
         connection.put(new CooldownStorage());
         connection.put(new BlockPlaceDestroyTracker());
         connection.put(new BossBarStorage(connection));
+        connection.put(new CommandBlockStateStorage());
     }
 
     @Override

common/src/main/java/com/viaversion/viarewind/protocol/v1_9to1_8/data/CommandBlockState.java

@@ -0,0 +1,165 @@
+/*
+ * This file is part of ViaRewind - https://github.com/ViaVersion/ViaRewind
+ * Copyright (C) 2018-2026 ViaVersion and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.viaversion.viarewind.protocol.v1_9to1_8.data;
+
+import com.viaversion.nbt.tag.CompoundTag;
+import com.viaversion.nbt.tag.NumberTag;
+import com.viaversion.nbt.tag.StringTag;
+
+public final class CommandBlockState {
+
+    public static final int COMMAND_BLOCK_COMMAND_LIMIT = 32500;
+
+    private static final String IMPULSE = "IMPULSE";
+    private static final String REPEAT = "REPEAT";
+    private static final String CHAIN = "CHAIN";
+    private static final String CONDITIONAL = "CONDITIONAL";
+    private static final String UNCONDITIONAL = "UNCONDITIONAL";
+    private static final String ALWAYS_ACTIVE = "ALWAYSACTIVE";
+    private static final String REDSTONE = "REDSTONE";
+
+    private CommandBlockState() {
+    }
+
+    public static boolean isCommandBlock(final int blockState) {
+        return isImpulse(blockState) || isRepeat(blockState) || isChain(blockState);
+    }
+
+    public static void decorateCommand(final CompoundTag tag, final int blockState) {
+        if (tag == null || !isCommandBlock(blockState)) {
+            return;
+        }
+
+        final StringTag commandTag = tag.getStringTag("Command");
+        if (commandTag == null) {
+            return;
+        }
+
+        final Mode mode = mode(blockState);
+        final boolean conditional = (blockState & 8) != 0;
+        final boolean automatic = booleanTag(tag, "auto");
+        if (mode == Mode.REDSTONE && !conditional && !automatic) {
+            return;
+        }
+
+        final String prefix = mode.prefix + ' ' + (conditional ? CONDITIONAL : UNCONDITIONAL) + ' ' + (automatic ? ALWAYS_ACTIVE : REDSTONE) + ' ';
+        final String command = commandTag.getValue();
+        if (!parseDecoratedCommand(command).prefixed() && prefix.length() + command.length() <= COMMAND_BLOCK_COMMAND_LIMIT) {
+            commandTag.setValue(prefix + command);
+        }
+    }
+
+    public static ParsedCommand parseDecoratedCommand(final String command) {
+        final int first = command.indexOf(' ');
+        if (first == -1) {
+            return ParsedCommand.defaultState(command);
+        }
+        final int second = command.indexOf(' ', first + 1);
+        if (second == -1) {
+            return ParsedCommand.defaultState(command);
+        }
+        final int third = command.indexOf(' ', second + 1);
+        if (third == -1) {
+            return ParsedCommand.defaultState(command);
+        }
+
+        final Mode mode = Mode.fromPrefix(command.substring(0, first));
+        if (mode == null) {
+            return ParsedCommand.defaultState(command);
+        }
+
+        final String conditionalToken = command.substring(first + 1, second);
+        final boolean conditional;
+        if (CONDITIONAL.equalsIgnoreCase(conditionalToken)) {
+            conditional = true;
+        } else if (UNCONDITIONAL.equalsIgnoreCase(conditionalToken)) {
+            conditional = false;
+        } else {
+            return ParsedCommand.defaultState(command);
+        }
+
+        final String automaticToken = command.substring(second + 1, third);
+        final boolean automatic;
+        if (ALWAYS_ACTIVE.equalsIgnoreCase(automaticToken)) {
+            automatic = true;
+        } else if (REDSTONE.equalsIgnoreCase(automaticToken)) {
+            automatic = false;
+        } else {
+            return ParsedCommand.defaultState(command);
+        }
+
+        return new ParsedCommand(command.substring(third + 1), mode.serverName, conditional, automatic, true);
+    }
+
+    private static boolean booleanTag(final CompoundTag tag, final String key) {
+        final NumberTag numberTag = tag.getNumberTag(key);
+        return numberTag != null && numberTag.asByte() != 0;
+    }
+
+    private static Mode mode(final int blockState) {
+        if (isRepeat(blockState)) {
+            return Mode.AUTO;
+        }
+        if (isChain(blockState)) {
+            return Mode.SEQUENCE;
+        }
+        return Mode.REDSTONE;
+    }
+
+    private static boolean isImpulse(final int blockState) {
+        return blockState >= 2192 && blockState <= 2207;
+    }
+
+    private static boolean isRepeat(final int blockState) {
+        return blockState >= 3360 && blockState <= 3375;
+    }
+
+    private static boolean isChain(final int blockState) {
+        return blockState >= 3376 && blockState <= 3391;
+    }
+
+    public record ParsedCommand(String command, String mode, boolean conditional, boolean automatic, boolean prefixed) {
+
+        private static ParsedCommand defaultState(final String command) {
+            return new ParsedCommand(command, Mode.REDSTONE.serverName, false, false, false);
+        }
+    }
+
+    private enum Mode {
+        REDSTONE(IMPULSE, "REDSTONE"),
+        AUTO(REPEAT, "AUTO"),
+        SEQUENCE(CHAIN, "SEQUENCE");
+
+        private final String prefix;
+        private final String serverName;
+
+        Mode(final String prefix, final String serverName) {
+            this.prefix = prefix;
+            this.serverName = serverName;
+        }
+
+        private static Mode fromPrefix(final String prefix) {
+            for (final Mode mode : values()) {
+                if (mode.prefix.equalsIgnoreCase(prefix)) {
+                    return mode;
+                }
+            }
+            return null;
+        }
+    }
+}

common/src/main/java/com/viaversion/viarewind/protocol/v1_9to1_8/rewriter/BlockItemPacketRewriter1_9.java

@@ -26,8 +26,11 @@
 import com.viaversion.viarewind.api.rewriter.VRBlockItemRewriter;
 import com.viaversion.viarewind.protocol.v1_9to1_8.Protocol1_9To1_8;
 import com.viaversion.viarewind.protocol.v1_9to1_8.data.PotionIdMappings1_8;
+import com.viaversion.viarewind.protocol.v1_9to1_8.storage.CommandBlockStateStorage;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.WindowTracker;
 import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.minecraft.BlockChangeRecord;
+import com.viaversion.viaversion.api.minecraft.BlockPosition;
 import com.viaversion.viaversion.api.minecraft.item.Item;
 import com.viaversion.viaversion.api.protocol.remapper.PacketHandlers;
 import com.viaversion.viaversion.api.type.Types;
@@ -59,8 +62,8 @@ public BlockItemPacketRewriter1_9(Protocol1_9To1_8 protocol) {
 
     @Override
     protected void registerPackets() {
-        registerBlockChange(ClientboundPackets1_9.BLOCK_UPDATE);
-        registerMultiBlockChange(ClientboundPackets1_9.CHUNK_BLOCKS_UPDATE);
+        registerBlockChangeWithCommandBlockStorage(ClientboundPackets1_9.BLOCK_UPDATE);
+        registerMultiBlockChangeWithCommandBlockStorage(ClientboundPackets1_9.CHUNK_BLOCKS_UPDATE);
         registerSetCreativeModeSlot(ServerboundPackets1_8.SET_CREATIVE_MODE_SLOT);
 
         protocol.registerClientbound(ClientboundPackets1_9.CONTAINER_CLOSE, wrapper -> {
@@ -184,6 +187,46 @@ public void register() {
         });
     }
 
+    private void registerBlockChangeWithCommandBlockStorage(final ClientboundPackets1_9 packetType) {
+        protocol.registerClientbound(packetType, new PacketHandlers() {
+            @Override
+            public void register() {
+                map(Types.BLOCK_POSITION1_8); // Block Position
+                map(Types.VAR_INT); // Block
+
+                handler(wrapper -> {
+                    final int blockState = wrapper.get(Types.VAR_INT, 0);
+                    wrapper.user().get(CommandBlockStateStorage.class).storeOrRemove(wrapper.get(Types.BLOCK_POSITION1_8, 0), blockState);
+                    wrapper.set(Types.VAR_INT, 0, handleBlockId(blockState));
+                });
+            }
+        });
+    }
+
+    private void registerMultiBlockChangeWithCommandBlockStorage(final ClientboundPackets1_9 packetType) {
+        protocol.registerClientbound(packetType, new PacketHandlers() {
+            @Override
+            public void register() {
+                map(Types.INT); // Chunk X
+                map(Types.INT); // Chunk Z
+                map(Types.BLOCK_CHANGE_ARRAY);
+
+                handler(wrapper -> {
+                    final int chunkX = wrapper.get(Types.INT, 0);
+                    final int chunkZ = wrapper.get(Types.INT, 1);
+                    final CommandBlockStateStorage storage = wrapper.user().get(CommandBlockStateStorage.class);
+
+                    for (BlockChangeRecord record : wrapper.get(Types.BLOCK_CHANGE_ARRAY, 0)) {
+                        final int blockState = record.getBlockId();
+                        final BlockPosition position = new BlockPosition((chunkX << 4) + record.getSectionX(), record.getY(), (chunkZ << 4) + record.getSectionZ());
+                        storage.storeOrRemove(position, blockState);
+                        record.setBlockId(handleBlockId(blockState));
+                    }
+                });
+            }
+        });
+    }
+
     @Override
     protected void registerRewrites() {
         enchantmentRewriter = new LegacyEnchantmentRewriter(nbtTagName());

common/src/main/java/com/viaversion/viarewind/protocol/v1_9to1_8/rewriter/PlayerPacketRewriter1_9.java

@@ -23,6 +23,7 @@
 import com.viaversion.viarewind.ViaRewind;
 import com.viaversion.viarewind.api.type.RewindTypes;
 import com.viaversion.viarewind.protocol.v1_9to1_8.Protocol1_9To1_8;
+import com.viaversion.viarewind.protocol.v1_9to1_8.data.CommandBlockState;
 import com.viaversion.viarewind.protocol.v1_9to1_8.provider.InventoryProvider;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.BlockPlaceDestroyTracker;
 import com.viaversion.viarewind.protocol.v1_9to1_8.storage.BossBarStorage;
@@ -524,7 +525,39 @@ public void register() {
                             pageTag.setValue(ChatUtil.jsonToLegacy(value));
                         }
                     } else if (channel.equals("MC|AdvCdm")) {
-                        wrapper.set(Types.STRING, 0, "MC|AdvCmd");
+                        final byte type = wrapper.read(Types.BYTE);
+                        if (type == 0) {
+                            final int x = wrapper.read(Types.INT);
+                            final int y = wrapper.read(Types.INT);
+                            final int z = wrapper.read(Types.INT);
+                            final CommandBlockState.ParsedCommand command = CommandBlockState.parseDecoratedCommand(wrapper.read(Types.STRING));
+                            final boolean trackOutput = wrapper.read(Types.BOOLEAN);
+                            if (command.prefixed()) {
+                                wrapper.set(Types.STRING, 0, "MC|AutoCmd");
+                                wrapper.write(Types.INT, x);
+                                wrapper.write(Types.INT, y);
+                                wrapper.write(Types.INT, z);
+                                wrapper.write(Types.STRING, command.command());
+                                wrapper.write(Types.BOOLEAN, trackOutput);
+                                wrapper.write(Types.STRING, command.mode());
+                                wrapper.write(Types.BOOLEAN, command.conditional());
+                                wrapper.write(Types.BOOLEAN, command.automatic());
+                            } else {
+                                wrapper.set(Types.STRING, 0, "MC|AdvCmd");
+                                wrapper.write(Types.BYTE, type);
+                                wrapper.write(Types.INT, x);
+                                wrapper.write(Types.INT, y);
+                                wrapper.write(Types.INT, z);
+                                wrapper.write(Types.STRING, command.command());
+                                wrapper.write(Types.BOOLEAN, trackOutput);
+                            }
+                        } else {
+                            wrapper.set(Types.STRING, 0, "MC|AdvCmd");
+                            wrapper.write(Types.BYTE, type);
+                            wrapper.passthrough(Types.INT); // Entity id
+                            wrapper.passthrough(Types.STRING); // Command
+                            wrapper.passthrough(Types.BOOLEAN); // Track output
+                        }
                     }
                 });
             }

common/src/main/java/com/viaversion/viarewind/protocol/v1_9to1_8/rewriter/WorldPacketRewriter1_9.java

@@ -22,7 +22,9 @@
 import com.viaversion.nbt.tag.Tag;
 import com.viaversion.viarewind.ViaRewind;
 import com.viaversion.viarewind.protocol.v1_9to1_8.Protocol1_9To1_8;
+import com.viaversion.viarewind.protocol.v1_9to1_8.data.CommandBlockState;
 import com.viaversion.viarewind.protocol.v1_9to1_8.data.EffectIdMappings1_8;
+import com.viaversion.viarewind.protocol.v1_9to1_8.storage.CommandBlockStateStorage;
 import com.viaversion.viaversion.api.minecraft.BlockPosition;
 import com.viaversion.viaversion.api.minecraft.Environment;
 import com.viaversion.viaversion.api.minecraft.chunks.BaseChunk;
@@ -57,6 +59,12 @@ public void register() {
                 map(Types.NAMED_COMPOUND_TAG); // Tag
                 handler(wrapper -> {
                     final CompoundTag tag = wrapper.get(Types.NAMED_COMPOUND_TAG, 0);
+                    final short action = wrapper.get(Types.UNSIGNED_BYTE, 0);
+
+                    if (action == 2) {
+                        final BlockPosition position = wrapper.get(Types.BLOCK_POSITION1_8, 0);
+                        CommandBlockState.decorateCommand(tag, wrapper.user().get(CommandBlockStateStorage.class).state(position));
+                    }
 
                     if (tag.remove("SpawnData") instanceof CompoundTag spawnData) {
                         final Tag id = spawnData.remove("id");
@@ -111,9 +119,11 @@ public void register() {
             public void register() {
                 handler(wrapper -> {
                     final Environment environment = wrapper.user().getClientWorld(Protocol1_9To1_8.class).getEnvironment();
+                    final CommandBlockStateStorage commandBlockStates = wrapper.user().get(CommandBlockStateStorage.class);
 
                     final int chunkX = wrapper.read(Types.INT);
                     final int chunkZ = wrapper.read(Types.INT);
+                    commandBlockStates.unloadChunk(chunkX, chunkZ);
 
                     wrapper.write(ChunkType1_8.forEnvironment(environment), new BaseChunk(chunkX, chunkZ, true, false, 0, new ChunkSection[16], null, new ArrayList<>()));
                 });
@@ -125,8 +135,23 @@ public void register() {
             public void register() {
                 handler(wrapper -> {
                     final Environment environment = wrapper.user().getClientWorld(Protocol1_9To1_8.class).getEnvironment();
+                    final CommandBlockStateStorage commandBlockStates = wrapper.user().get(CommandBlockStateStorage.class);
 
                     Chunk chunk = wrapper.read(ChunkType1_9_1.forEnvironment(environment));
+                    final Chunk originalChunk = chunk;
+
+                    chunk.getBlockEntities().forEach(nbt -> {
+                        if (!nbt.contains("x") || !nbt.contains("y") || !nbt.contains("z")) {
+                            return;
+                        }
+
+                        final BlockPosition position = new BlockPosition((int) nbt.get("x").getValue(), (int) nbt.get("y").getValue(), (int) nbt.get("z").getValue());
+                        final int blockState = blockStateAt(originalChunk, position);
+                        if (CommandBlockState.isCommandBlock(blockState)) {
+                            commandBlockStates.storeOrRemove(position, blockState);
+                            CommandBlockState.decorateCommand(nbt, blockState);
+                        }
+                    });
 
                     for (ChunkSection section : chunk.getSections()) {
                         if (section == null) continue;
@@ -267,4 +292,18 @@ public void register() {
             }
         });
     }
+
+    private static int blockStateAt(final Chunk chunk, final BlockPosition position) {
+        final int sectionY = position.y() >> 4;
+        if (sectionY < 0 || sectionY >= chunk.getSections().length) {
+            return -1;
+        }
+
+        final ChunkSection section = chunk.getSections()[sectionY];
+        if (section == null) {
+            return -1;
+        }
+
+        return section.palette(PaletteType.BLOCKS).idAt(position.x() & 0xF, position.y() & 0xF, position.z() & 0xF);
+    }
 }