Emulate "trim_pattern" registry in 1.19.4 -> 1.20 if not present (#557)

common/src/main/java/com/viaversion/viabackwards/protocol/protocol1_19_4to1_20/Protocol1_19_4To1_20.java

@@ -18,9 +18,9 @@
 package com.viaversion.viabackwards.protocol.protocol1_19_4to1_20;
 
 import com.viaversion.viabackwards.api.BackwardsProtocol;
-import com.viaversion.viabackwards.api.data.BackwardsMappings;
 import com.viaversion.viabackwards.api.rewriters.SoundRewriter;
 import com.viaversion.viabackwards.api.rewriters.TranslatableRewriter;
+import com.viaversion.viabackwards.protocol.protocol1_19_4to1_20.data.BackwardsMappings;
 import com.viaversion.viabackwards.protocol.protocol1_19_4to1_20.packets.BlockItemPackets1_20;
 import com.viaversion.viabackwards.protocol.protocol1_19_4to1_20.packets.EntityPackets1_20;
 import com.viaversion.viaversion.api.connection.UserConnection;
@@ -29,14 +29,13 @@ import com.viaversion.viaversion.api.type.Type;
 import com.viaversion.viaversion.data.entity.EntityTrackerBase;
 import com.viaversion.viaversion.protocols.protocol1_19_4to1_19_3.ClientboundPackets1_19_4;
 import com.viaversion.viaversion.protocols.protocol1_19_4to1_19_3.ServerboundPackets1_19_4;
-import com.viaversion.viaversion.protocols.protocol1_20to1_19_4.Protocol1_20To1_19_4;
 import com.viaversion.viaversion.rewriter.StatisticsRewriter;
 import com.viaversion.viaversion.rewriter.TagRewriter;
 import java.util.Arrays;
 
 public final class Protocol1_19_4To1_20 extends BackwardsProtocol<ClientboundPackets1_19_4, ClientboundPackets1_19_4, ServerboundPackets1_19_4, ServerboundPackets1_19_4> {
 
-    public static final BackwardsMappings MAPPINGS = new BackwardsMappings("1.20", "1.19.4", Protocol1_20To1_19_4.class);
+    public static final BackwardsMappings MAPPINGS = new BackwardsMappings();
     private final TranslatableRewriter<ClientboundPackets1_19_4> translatableRewriter = new TranslatableRewriter<>(this);
     private final EntityPackets1_20 entityRewriter = new EntityPackets1_20(this);
     private final BlockItemPackets1_20 itemRewriter = new BlockItemPackets1_20(this);

common/src/main/java/com/viaversion/viabackwards/protocol/protocol1_19_4to1_20/data/BackwardsMappings.java

@@ -0,0 +1,49 @@
+/*
+ * This file is part of ViaBackwards - https://github.com/ViaVersion/ViaBackwards
+ * Copyright (C) 2023 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.viabackwards.protocol.protocol1_19_4to1_20.data;
+
+import com.viaversion.viabackwards.api.data.VBMappingDataLoader;
+import com.viaversion.viaversion.api.minecraft.nbt.BinaryTagIO;
+import com.viaversion.viaversion.libs.opennbt.tag.builtin.CompoundTag;
+import com.viaversion.viaversion.protocols.protocol1_20to1_19_4.Protocol1_20To1_19_4;
+
+import java.io.IOException;
+
+public class BackwardsMappings extends com.viaversion.viabackwards.api.data.BackwardsMappings {
+
+    private CompoundTag trimPatternRegistry;
+
+    public BackwardsMappings() {
+        super("1.20", "1.19.4", Protocol1_20To1_19_4.class);
+    }
+
+    @Override
+    protected void loadExtras(CompoundTag data) {
+        super.loadExtras(data);
+
+        try {
+            trimPatternRegistry = BinaryTagIO.readInputStream(VBMappingDataLoader.getResource("trim_pattern-1.19.4.nbt"));
+        } catch (final IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public CompoundTag getTrimPatternRegistry() {
+        return trimPatternRegistry;
+    }
+}

common/src/main/java/com/viaversion/viabackwards/protocol/protocol1_19_4to1_20/packets/EntityPackets1_20.java

@@ -165,7 +165,17 @@ public final class EntityPackets1_20 extends EntityRewriter<ClientboundPackets1_
                 handler(worldDataTrackerHandlerByKey()); // Tracks world height and name for chunk data and entity (un)tracking
                 handler(wrapper -> {
                     final CompoundTag registry = wrapper.get(Type.NBT, 0);
-                    final ListTag values = ((CompoundTag) registry.get("minecraft:trim_pattern")).get("value");
+
+                    ListTag values;
+                    // A 1.20 server can't send this element, and the 1.20 client still works, if the element is missing
+                    // on a 1.19.4 client there is an exception, so in case the 1.20 server doesn't send the element we put in an original 1.20 element
+                    if (registry.contains("minecraft:trim_pattern")) {
+                        values = ((CompoundTag) registry.get("minecraft:trim_pattern")).get("value");
+                    } else {
+                        final CompoundTag trimPatternRegistry = Protocol1_19_4To1_20.MAPPINGS.getTrimPatternRegistry().clone();
+                        registry.put("minecraft:trim_pattern", trimPatternRegistry);
+                        values = trimPatternRegistry.get("value");
+                    }
                     for (final Tag entry : values) {
                         final CompoundTag element = ((CompoundTag) entry).get("element");
                         final StringTag templateItem = element.get("template_item");