acknowledge seen messages to server when running proxy commands

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftSessionHandler.java

@@ -50,6 +50,7 @@
 import com.velocitypowered.proxy.protocol.packet.TabCompleteRequest;
 import com.velocitypowered.proxy.protocol.packet.TabCompleteResponse;
 import com.velocitypowered.proxy.protocol.packet.UpsertPlayerInfo;
+import com.velocitypowered.proxy.protocol.packet.chat.ChatAcknowledgement;
 import com.velocitypowered.proxy.protocol.packet.chat.PlayerChatCompletion;
 import com.velocitypowered.proxy.protocol.packet.chat.SystemChat;
 import com.velocitypowered.proxy.protocol.packet.chat.keyed.KeyedPlayerChat;
@@ -314,4 +315,8 @@ default boolean handle(StartUpdate packet) {
   default boolean handle(PingIdentify pingIdentify) {
     return false;
   }
+
+  default boolean handle(ChatAcknowledgement chatAcknowledgement) {
+    return false;
+  }
 }

proxy/src/main/java/com/velocitypowered/proxy/protocol/StateRegistry.java

@@ -75,6 +75,7 @@
 import com.velocitypowered.proxy.protocol.packet.TabCompleteRequest;
 import com.velocitypowered.proxy.protocol.packet.TabCompleteResponse;
 import com.velocitypowered.proxy.protocol.packet.UpsertPlayerInfo;
+import com.velocitypowered.proxy.protocol.packet.chat.ChatAcknowledgement;
 import com.velocitypowered.proxy.protocol.packet.chat.PlayerChatCompletion;
 import com.velocitypowered.proxy.protocol.packet.chat.SystemChat;
 import com.velocitypowered.proxy.protocol.packet.chat.keyed.KeyedPlayerChat;
@@ -184,6 +185,10 @@ public enum StateRegistry {
           map(0x03, MINECRAFT_1_12, false),
           map(0x02, MINECRAFT_1_12_1, false),
           map(0x03, MINECRAFT_1_14, MINECRAFT_1_18_2, false));
+      serverbound.register(
+              ChatAcknowledgement.class,
+              ChatAcknowledgement::new,
+              map(0x03, MINECRAFT_1_19_3, false));
       serverbound.register(KeyedPlayerCommand.class, KeyedPlayerCommand::new,
           map(0x03, MINECRAFT_1_19, false),
           map(0x04, MINECRAFT_1_19_1, MINECRAFT_1_19_1, false));

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/ChatAcknowledgement.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2023 Velocity 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 <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.protocol.packet.chat;
+
+import com.velocitypowered.api.network.ProtocolVersion;
+import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
+import com.velocitypowered.proxy.protocol.MinecraftPacket;
+import com.velocitypowered.proxy.protocol.ProtocolUtils;
+import io.netty.buffer.ByteBuf;
+
+public class ChatAcknowledgement implements MinecraftPacket {
+    int offset;
+
+    public ChatAcknowledgement(int offset) {
+        this.offset = offset;
+    }
+
+    public ChatAcknowledgement() {
+    }
+
+    @Override
+    public void decode(ByteBuf buf, ProtocolUtils.Direction direction, ProtocolVersion protocolVersion) {
+        offset = ProtocolUtils.readVarInt(buf);
+    }
+
+    @Override
+    public void encode(ByteBuf buf, ProtocolUtils.Direction direction, ProtocolVersion protocolVersion) {
+        ProtocolUtils.writeVarInt(buf, offset);
+    }
+
+    @Override
+    public boolean handle(MinecraftSessionHandler handler) {
+        return handler.handle(this);
+    }
+
+    @Override
+    public String toString() {
+        return "ChatAcknowledgement{" +
+                "offset=" + offset +
+                '}';
+    }
+}

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/LastSeenMessages.java

@@ -50,6 +50,10 @@ public boolean isEmpty() {
     return acknowledged.isEmpty();
   }
 
+  public int getOffset() {
+    return this.offset;
+  }
+
   @Override
   public String toString() {
     return "LastSeenMessages{" +

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/session/SessionCommandHandler.java

@@ -18,8 +18,10 @@
 package com.velocitypowered.proxy.protocol.packet.chat.session;
 
 import com.velocitypowered.api.event.command.CommandExecuteEvent;
+import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import com.velocitypowered.proxy.protocol.packet.chat.ChatAcknowledgement;
 import com.velocitypowered.proxy.protocol.packet.chat.CommandHandler;
 import java.util.concurrent.CompletableFuture;
 import net.kyori.adventure.text.Component;
@@ -52,6 +54,10 @@ public void handlePlayerCommandInternal(SessionPlayerCommand packet) {
               "A proxy plugin caused an illegal protocol state. "
                   + "Contact your network administrator."));
         }
+        // We seemingly can't actually do this if signed args exist, if not, we can probs keep stuff happy
+        if (player.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_19_3) >= 0) {
+          return CompletableFuture.completedFuture(new ChatAcknowledgement(packet.lastSeenMessages.getOffset()));
+        }
         return CompletableFuture.completedFuture(null);
       }
 
@@ -102,6 +108,9 @@ public void handlePlayerCommandInternal(SessionPlayerCommand packet) {
                 .toServer();
           }
         }
+        if (player.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_19_3) >= 0) {
+          return new ChatAcknowledgement(packet.lastSeenMessages.getOffset());
+        }
         return null;
       });
     }, packet.command, packet.timeStamp);