Update/chat order queue (#801)

* Implement chat queue for ordered chat.

* Update system to handle spoofed chat as well.

* Fix checkstyle erroring on bad indentation.

* Fix ChatQueue to use whenComplete instead of thenRun

* Merge upstream.

* Checkstyle

* Deny denied commands.

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -58,6 +58,7 @@ import com.velocitypowered.proxy.protocol.packet.TabCompleteRequest;
 import com.velocitypowered.proxy.protocol.packet.TabCompleteResponse;
 import com.velocitypowered.proxy.protocol.packet.TabCompleteResponse.Offer;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatBuilder;
+import com.velocitypowered.proxy.protocol.packet.chat.ChatQueue;
 import com.velocitypowered.proxy.protocol.packet.chat.LegacyChat;
 import com.velocitypowered.proxy.protocol.packet.chat.PlayerChat;
 import com.velocitypowered.proxy.protocol.packet.chat.PlayerCommand;
@@ -139,10 +140,10 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
   }
 
   private void processCommandMessage(String message, @Nullable SignedChatCommand signedCommand,
-                                     MinecraftPacket original) {
-    server.getCommandManager().callCommandEvent(player, message)
+                                     MinecraftPacket original, Instant passedTimestamp) {
+    this.player.getChatQueue().queuePacket(server.getCommandManager().callCommandEvent(player, message)
         .thenComposeAsync(event -> processCommandExecuteResult(message,
-            event.getResult(), signedCommand))
+            event.getResult(), signedCommand, passedTimestamp))
         .whenComplete((ignored, throwable) -> {
           if (server.getConfiguration().isLogCommandExecutions()) {
             logger.info("{} -> executed command /{}", player, message);
@@ -154,7 +155,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
           player.sendMessage(Component.translatable("velocity.command.generic-error",
               NamedTextColor.RED));
           return null;
-        });
+        }), passedTimestamp);
   }
 
   private void processPlayerChat(String message, @Nullable SignedChatMessage signedMessage,
@@ -163,48 +164,61 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     if (smc == null) {
       return;
     }
-    PlayerChatEvent event = new PlayerChatEvent(player, message);
-    server.getEventManager().fire(event)
-        .thenAcceptAsync(pme -> {
+
+    if (signedMessage == null) {
+      PlayerChatEvent event = new PlayerChatEvent(player, message);
+      callChat(original, event, null).thenAccept(smc::write);
+    } else {
+      Instant messageTimestamp = signedMessage.getExpiryTemporal();
+      PlayerChatEvent event = new PlayerChatEvent(player, message);
+      this.player.getChatQueue().queuePacket(callChat(original, event, signedMessage), messageTimestamp);
+    }
+  }
+
+  private CompletableFuture<MinecraftPacket> callChat(MinecraftPacket original, PlayerChatEvent event,
+                                                      @Nullable SignedChatMessage signedMessage) {
+    return server.getEventManager().fire(event)
+        .thenApply(pme -> {
           PlayerChatEvent.ChatResult chatResult = pme.getResult();
           if (chatResult.isAllowed()) {
             Optional<String> eventMsg = pme.getResult().getMessage();
             if (eventMsg.isPresent()) {
               String messageNew = eventMsg.get();
               if (player.getIdentifiedKey() != null) {
-                if (!messageNew.equals(signedMessage.getMessage())) {
+                if (signedMessage != null && !messageNew.equals(signedMessage.getMessage())) {
                   if (player.getIdentifiedKey().getKeyRevision().compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
                     // Bad, very bad.
                     logger.fatal("A plugin tried to change a signed chat message. "
-                            + "This is no longer possible in 1.19.1 and newer. "
-                            + "Disconnecting player " + player.getUsername());
+                        + "This is no longer possible in 1.19.1 and newer. "
+                        + "Disconnecting player " + player.getUsername());
                     player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
-                           + "Contact your network administrator."));
+                        + "Contact your network administrator."));
                   } else {
                     logger.warn("A plugin changed a signed chat message. The server may not accept it.");
-                    smc.write(ChatBuilder.builder(player.getProtocolVersion())
-                            .message(messageNew).toServer());
+                    return ChatBuilder.builder(player.getProtocolVersion())
+                        .message(messageNew).toServer();
                   }
                 } else {
-                  smc.write(original);
+                  return original;
                 }
               } else {
-                smc.write(ChatBuilder.builder(player.getProtocolVersion())
-                        .message(messageNew).toServer());
+                return ChatBuilder.builder(player.getProtocolVersion())
+                    .message(messageNew).toServer();
               }
             } else {
-              smc.write(original);
+              return original;
             }
           } else {
             if (player.getIdentifiedKey().getKeyRevision().compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
               logger.fatal("A plugin tried to cancel a signed chat message."
-                      + " This is no longer possible in 1.19.1 and newer. "
-                      + "Disconnecting player " + player.getUsername());
+                  + " This is no longer possible in 1.19.1 and newer. "
+                  + "Disconnecting player " + player.getUsername());
               player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
-                      + "Contact your network administrator."));
+                  + "Contact your network administrator."));
             }
           }
-        }, smc.eventLoop())
+          return null;
+        })
         .exceptionally((ex) -> {
           logger.error("Exception while handling player chat for {}", player, ex);
           return null;
@@ -260,12 +274,12 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     if (!packet.isUnsigned()) {
       SignedChatCommand signedCommand = packet.signedContainer(player.getIdentifiedKey(), player.getUniqueId(), false);
       if (signedCommand != null) {
-        processCommandMessage(packet.getCommand(), signedCommand, packet);
+        processCommandMessage(packet.getCommand(), signedCommand, packet, packet.getTimestamp());
         return true;
       }
     }
 
-    processCommandMessage(packet.getCommand(), null, packet);
+    processCommandMessage(packet.getCommand(), null, packet, packet.getTimestamp());
     return true;
   }
 
@@ -303,7 +317,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     }
 
     if (msg.startsWith("/")) {
-      processCommandMessage(msg.substring(1), null, packet);
+      processCommandMessage(msg.substring(1), null, packet, Instant.now());
     } else {
       processPlayerChat(msg, null, packet);
     }
@@ -723,77 +737,72 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
   }
 
 
-  private CompletableFuture<Void> processCommandExecuteResult(String originalCommand,
-                                                              CommandResult result,
-                                                              @Nullable SignedChatCommand signedCommand) {
+  private CompletableFuture<MinecraftPacket> processCommandExecuteResult(String originalCommand,
+                                                                         CommandResult result,
+                                                                         @Nullable SignedChatCommand signedCommand,
+                                                                         Instant passedTimestamp) {
     IdentifiedKey playerKey = player.getIdentifiedKey();
     if (result == CommandResult.denied() && playerKey != null) {
       if (signedCommand != null && playerKey.getKeyRevision()
           .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
         logger.fatal("A plugin tried to deny a command with signable component(s). "
-                + "This is not supported. "
-                + "Disconnecting player " + player.getUsername());
+            + "This is not supported. "
+            + "Disconnecting player " + player.getUsername());
         player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
-                + "Contact your network administrator."));
+            + "Contact your network administrator."));
       }
       return CompletableFuture.completedFuture(null);
     }
 
-    MinecraftConnection smc;
-    try {
-      smc = player.ensureAndGetCurrentServer().ensureConnected();
-    } catch (Exception ex) {
-      player.disconnect(Component.translatable("velocity.error.player-connection-error",
-          NamedTextColor.RED));
-      return CompletableFuture.completedFuture(null);
-    }
-
     String commandToRun = result.getCommand().orElse(originalCommand);
     if (result.isForwardToServer()) {
       ChatBuilder write = ChatBuilder
           .builder(player.getProtocolVersion())
+          .timestamp(passedTimestamp)
           .asPlayer(player);
 
       if (signedCommand != null && commandToRun.equals(signedCommand.getBaseCommand())) {
         write.message(signedCommand);
       } else {
         if (signedCommand != null && playerKey != null && playerKey.getKeyRevision()
-                .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
+            .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
           logger.fatal("A plugin tried to change a command with signed component(s). "
-                  + "This is not supported. "
-                  + "Disconnecting player " + player.getUsername());
+              + "This is not supported. "
+              + "Disconnecting player " + player.getUsername());
           player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
-                  + "Contact your network administrator."));
+              + "Contact your network administrator."));
           return CompletableFuture.completedFuture(null);
         }
         write.message("/" + commandToRun);
       }
-      return CompletableFuture.runAsync(() -> smc.write(write.toServer()), smc.eventLoop());
+      return CompletableFuture.completedFuture(write.toServer());
     } else {
       return server.getCommandManager().executeImmediatelyAsync(player, commandToRun)
-          .thenAcceptAsync(hasRun -> {
+          .thenApply(hasRun -> {
             if (!hasRun) {
               ChatBuilder write = ChatBuilder
                   .builder(player.getProtocolVersion())
+                  .timestamp(passedTimestamp)
                   .asPlayer(player);
 
               if (signedCommand != null && commandToRun.equals(signedCommand.getBaseCommand())) {
                 write.message(signedCommand);
               } else {
                 if (signedCommand != null && playerKey != null && playerKey.getKeyRevision()
-                        .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
+                    .compareTo(IdentifiedKey.Revision.LINKED_V2) >= 0) {
                   logger.fatal("A plugin tried to change a command with signed component(s). "
-                          + "This is not supported. "
-                          + "Disconnecting player " + player.getUsername());
+                      + "This is not supported. "
+                      + "Disconnecting player " + player.getUsername());
                   player.disconnect(Component.text("A proxy plugin caused an illegal protocol state. "
-                          + "Contact your network administrator."));
-                  return;
+                      + "Contact your network administrator."));
+                  return null;
                 }
                 write.message("/" + commandToRun);
               }
-              smc.write(write.toServer());
+              return write.toServer();
             }
-          }, smc.eventLoop());
+            return null;
+          });
     }
   }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -66,6 +66,7 @@ import com.velocitypowered.proxy.protocol.packet.KeepAlive;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackRequest;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatBuilder;
+import com.velocitypowered.proxy.protocol.packet.chat.ChatQueue;
 import com.velocitypowered.proxy.protocol.packet.chat.LegacyChat;
 import com.velocitypowered.proxy.protocol.packet.title.GenericTitlePacket;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
@@ -155,19 +156,20 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   private @Nullable ResourcePackInfo pendingResourcePack;
   private @Nullable ResourcePackInfo appliedResourcePack;
   private final @NotNull Pointers pointers = Player.super.pointers().toBuilder()
-          .withDynamic(Identity.UUID, this::getUniqueId)
-          .withDynamic(Identity.NAME, this::getUsername)
-          .withDynamic(Identity.DISPLAY_NAME, () -> Component.text(this.getUsername()))
-          .withDynamic(Identity.LOCALE, this::getEffectiveLocale)
-          .withStatic(PermissionChecker.POINTER, getPermissionChecker())
-          .withStatic(FacetPointers.TYPE, Type.PLAYER)
-          .build();
+      .withDynamic(Identity.UUID, this::getUniqueId)
+      .withDynamic(Identity.NAME, this::getUsername)
+      .withDynamic(Identity.DISPLAY_NAME, () -> Component.text(this.getUsername()))
+      .withDynamic(Identity.LOCALE, this::getEffectiveLocale)
+      .withStatic(PermissionChecker.POINTER, getPermissionChecker())
+      .withStatic(FacetPointers.TYPE, Type.PLAYER)
+      .build();
   private @Nullable String clientBrand;
   private @Nullable Locale effectiveLocale;
   private @Nullable IdentifiedKey playerKey;
+  private ChatQueue chatQueue;
 
   ConnectedPlayer(VelocityServer server, GameProfile profile, MinecraftConnection connection,
-      @Nullable InetSocketAddress virtualHost, boolean onlineMode, @Nullable IdentifiedKey playerKey) {
+                  @Nullable InetSocketAddress virtualHost, boolean onlineMode, @Nullable IdentifiedKey playerKey) {
     this.server = server;
     this.profile = profile;
     this.connection = connection;
@@ -183,6 +185,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
       this.tabList = new VelocityTabListLegacy(this, server);
     }
     this.playerKey = playerKey;
+    this.chatQueue = new ChatQueue(this);
+  }
+
+  ChatQueue getChatQueue() {
+    return chatQueue;
   }
 
   @Override
@@ -220,6 +227,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   /**
    * Makes sure the player is connected to a server and returns the server they are connected to.
+   *
    * @return the server the player is connected to
    */
   public VelocityServerConnection ensureAndGetCurrentServer() {
@@ -320,21 +328,21 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     Component translated = translateMessage(message);
 
     connection.write(ChatBuilder.builder(this.getProtocolVersion())
-            .component(translated).forIdentity(identity).toClient());
+        .component(translated).forIdentity(identity).toClient());
   }
 
   @Override
   public void sendMessage(@NonNull Identity identity, @NonNull Component message,
-      @NonNull MessageType type) {
+                          @NonNull MessageType type) {
     Preconditions.checkNotNull(message, "message");
     Preconditions.checkNotNull(type, "type");
 
     Component translated = translateMessage(message);
 
     connection.write(ChatBuilder.builder(this.getProtocolVersion())
-            .component(translated).forIdentity(identity)
-            .setType(type == MessageType.CHAT ? ChatBuilder.ChatType.CHAT : ChatBuilder.ChatType.SYSTEM)
-            .toClient());
+        .component(translated).forIdentity(identity)
+        .setType(type == MessageType.CHAT ? ChatBuilder.ChatType.CHAT : ChatBuilder.ChatType.SYSTEM)
+        .toClient());
   }
 
   @Override
@@ -345,7 +353,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     if (playerVersion.compareTo(ProtocolVersion.MINECRAFT_1_11) >= 0) {
       // Use the title packet instead.
       GenericTitlePacket pkt = GenericTitlePacket.constructTitlePacket(
-              GenericTitlePacket.ActionType.SET_ACTION_BAR, playerVersion);
+          GenericTitlePacket.ActionType.SET_ACTION_BAR, playerVersion);
       pkt.setComponent(ProtocolUtils.getJsonChatSerializer(playerVersion)
           .serialize(translated));
       connection.write(pkt);
@@ -465,7 +473,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public void clearTitle() {
     if (this.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_8) >= 0) {
       connection.write(GenericTitlePacket.constructTitlePacket(
-              GenericTitlePacket.ActionType.HIDE, this.getProtocolVersion()));
+          GenericTitlePacket.ActionType.HIDE, this.getProtocolVersion()));
     }
   }
 
@@ -473,7 +481,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public void resetTitle() {
     if (this.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_8) >= 0) {
       connection.write(GenericTitlePacket.constructTitlePacket(
-                      GenericTitlePacket.ActionType.RESET, this.getProtocolVersion()));
+          GenericTitlePacket.ActionType.RESET, this.getProtocolVersion()));
     }
   }
 
@@ -497,7 +505,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   private ConnectionRequestBuilder createConnectionRequest(RegisteredServer server,
-      @Nullable VelocityServerConnection previousConnection) {
+                                                           @Nullable VelocityServerConnection previousConnection) {
     return new ConnectionRequestBuilderImpl(server, previousConnection);
   }
 
@@ -532,7 +540,8 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   /**
    * Disconnects the player from the proxy.
-   * @param reason the reason for disconnecting the player
+   *
+   * @param reason      the reason for disconnecting the player
    * @param duringLogin whether the disconnect happened during login
    */
   public void disconnect0(Component reason, boolean duringLogin) {
@@ -559,12 +568,13 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   /**
    * Handles unexpected disconnects.
-   * @param server the server we disconnected from
+   *
+   * @param server    the server we disconnected from
    * @param throwable the exception
-   * @param safe whether or not we can safely reconnect to a new server
+   * @param safe      whether or not we can safely reconnect to a new server
    */
   public void handleConnectionException(RegisteredServer server, Throwable throwable,
-      boolean safe) {
+                                        boolean safe) {
     if (!isActive()) {
       // If the connection is no longer active, it makes no sense to try and recover it.
       return;
@@ -597,12 +607,13 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   /**
    * Handles unexpected disconnects.
-   * @param server the server we disconnected from
+   *
+   * @param server     the server we disconnected from
    * @param disconnect the disconnect packet
-   * @param safe whether or not we can safely reconnect to a new server
+   * @param safe       whether or not we can safely reconnect to a new server
    */
   public void handleConnectionException(RegisteredServer server, Disconnect disconnect,
-      boolean safe) {
+                                        boolean safe) {
     if (!isActive()) {
       // If the connection is no longer active, it makes no sense to try and recover it.
       return;
@@ -628,7 +639,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   private void handleConnectionException(RegisteredServer rs,
-      @Nullable Component kickReason, Component friendlyReason, boolean safe) {
+                                         @Nullable Component kickReason, Component friendlyReason, boolean safe) {
     if (!isActive()) {
       // If the connection is no longer active, it makes no sense to try and recover it.
       return;
@@ -661,7 +672,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   private void handleKickEvent(KickedFromServerEvent originalEvent, Component friendlyReason,
-      boolean kickedFromCurrent) {
+                               boolean kickedFromCurrent) {
     server.getEventManager().fire(originalEvent)
         .thenAcceptAsync(event -> {
           // There can't be any connection in flight now.
@@ -696,7 +707,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
                     // Impossible/nonsensical cases
                     case ALREADY_CONNECTED:
                     case CONNECTION_IN_PROGRESS:
-                    // Fatal case
+                      // Fatal case
                     case CONNECTION_CANCELLED:
                       Component fallbackMsg = res.getMessageComponent();
                       if (fallbackMsg == null) {
@@ -753,7 +764,6 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
    * server.
    *
    * @param current the "current" server that the player is on, useful as an override
-   *
    * @return the next server to try
    */
   private Optional<RegisteredServer> getNextServerToTry(@Nullable RegisteredServer current) {
@@ -897,8 +907,16 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     Preconditions.checkArgument(input.length() <= LegacyChat.MAX_SERVERBOUND_MESSAGE_LENGTH,
         "input cannot be greater than " + LegacyChat.MAX_SERVERBOUND_MESSAGE_LENGTH
             + " characters in length");
-    ensureBackendConnection().write(ChatBuilder.builder(getProtocolVersion())
-            .asPlayer(this).message(input).toServer());
+    if (getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_19) >= 0) {
+      this.chatQueue.hijack(ChatBuilder.builder(getProtocolVersion()).asPlayer(this).message(input),
+          (instant, item) -> {
+            item.timestamp(instant);
+            return item.toServer();
+          });
+    } else {
+      ensureBackendConnection().write(ChatBuilder.builder(getProtocolVersion())
+          .asPlayer(this).message(input).toServer());
+    }
   }
 
   @Override
@@ -943,7 +961,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
         while (!outstandingResourcePacks.isEmpty()) {
           queued = outstandingResourcePacks.peek();
           if (queued.getShouldForce() && getProtocolVersion()
-                  .compareTo(ProtocolVersion.MINECRAFT_1_17) >= 0) {
+              .compareTo(ProtocolVersion.MINECRAFT_1_17) >= 0) {
             break;
           }
           onResourcePackResponse(PlayerResourcePackStatusEvent.Status.DECLINED);
@@ -985,19 +1003,19 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public boolean onResourcePackResponse(PlayerResourcePackStatusEvent.Status status) {
     final boolean peek = status == PlayerResourcePackStatusEvent.Status.ACCEPTED;
     final ResourcePackInfo queued = peek
-            ? outstandingResourcePacks.peek() : outstandingResourcePacks.poll();
+        ? outstandingResourcePacks.peek() : outstandingResourcePacks.poll();
 
     server.getEventManager().fire(new PlayerResourcePackStatusEvent(this, status, queued))
-            .thenAcceptAsync(event -> {
-              if (event.getStatus() == PlayerResourcePackStatusEvent.Status.DECLINED
-                      && event.getPackInfo() != null && event.getPackInfo().getShouldForce()
-                      && (!event.isOverwriteKick() || event.getPlayer()
-                              .getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_17) >= 0)
-              ) {
-                event.getPlayer().disconnect(Component
-                        .translatable("multiplayer.requiredTexturePrompt.disconnect"));
-              }
-            });
+        .thenAcceptAsync(event -> {
+          if (event.getStatus() == PlayerResourcePackStatusEvent.Status.DECLINED
+              && event.getPackInfo() != null && event.getPackInfo().getShouldForce()
+              && (!event.isOverwriteKick() || event.getPlayer()
+              .getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_17) >= 0)
+          ) {
+            event.getPlayer().disconnect(Component
+                .translatable("multiplayer.requiredTexturePrompt.disconnect"));
+          }
+        });
 
     switch (status) {
       case ACCEPTED:
@@ -1023,7 +1041,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
 
     return queued != null
-            && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
+        && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
   }
 
   /**
@@ -1061,6 +1079,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   /**
    * Return all the plugin message channels "known" to the client.
+   *
    * @return the channels
    */
   public Collection<String> getKnownChannels() {
@@ -1085,7 +1104,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     private final @Nullable VelocityRegisteredServer previousServer;
 
     ConnectionRequestBuilderImpl(RegisteredServer toConnect,
-        @Nullable VelocityServerConnection previousConnection) {
+                                 @Nullable VelocityServerConnection previousConnection) {
       this.toConnect = Preconditions.checkNotNull(toConnect, "info");
       this.previousServer = previousConnection == null ? null : previousConnection.getServer();
     }
@@ -1103,7 +1122,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
         return Optional.of(ConnectionRequestBuilder.Status.CONNECTION_IN_PROGRESS);
       }
       if (connectedServer != null
-              && connectedServer.getServer().getServerInfo().equals(server.getServerInfo())) {
+          && connectedServer.getServer().getServerInfo().equals(server.getServerInfo())) {
         return Optional.of(ALREADY_CONNECTED);
       }
       return Optional.empty();

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

@@ -31,6 +31,7 @@ import net.kyori.adventure.identity.Identity;
 import net.kyori.adventure.text.Component;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
 
 public class ChatBuilder {
 
@@ -43,11 +44,13 @@ public class ChatBuilder {
 
   private @Nullable Player sender;
   private @Nullable Identity senderIdentity;
+  private @NotNull Instant timestamp;
 
   private ChatType type = ChatType.CHAT;
 
   private ChatBuilder(ProtocolVersion version) {
     this.version = version;
+    this.timestamp = Instant.now();
   }
 
   public static ChatBuilder builder(ProtocolVersion version) {
@@ -115,6 +118,11 @@ public class ChatBuilder {
     return this;
   }
 
+  public ChatBuilder timestamp(Instant timestamp) {
+    this.timestamp = timestamp;
+    return this;
+  }
+
   public ChatBuilder asServer() {
     this.sender = null;
     return this;
@@ -153,7 +161,7 @@ public class ChatBuilder {
       } else {
         // Well crap
         if (message.startsWith("/")) {
-          return new PlayerCommand(message.substring(1), ImmutableList.of(), Instant.now());
+          return new PlayerCommand(message.substring(1), ImmutableList.of(), timestamp);
         } else {
           // This will produce an error on the server, but needs to be here.
           return new PlayerChat(message);

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

@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2018 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.proxy.connection.MinecraftConnection;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import com.velocitypowered.proxy.protocol.MinecraftPacket;
+import java.time.Instant;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.BiConsumer;
+
+/**
+ * A precisely ordered queue which allows for outside entries into the ordered queue through piggybacking timestamps.
+ */
+public class ChatQueue {
+  private final Object internalLock;
+  private final ConnectedPlayer player;
+  private CompletableFuture<WrappedPacket> packetFuture;
+
+  /**
+   * Instantiates a {@link ChatQueue} for a specific {@link ConnectedPlayer}.
+   *
+   * @param player the {@link ConnectedPlayer} to maintain the queue for.
+   */
+  public ChatQueue(ConnectedPlayer player) {
+    this.player = player;
+    this.packetFuture = CompletableFuture.completedFuture(new WrappedPacket(Instant.EPOCH, null));
+    this.internalLock = new Object();
+  }
+
+  /**
+   * Queues a packet sent from the player - all packets must wait until this processes to send their packets.
+   * <br />
+   * This maintains order on the server-level for the client insertions of commands and messages. All entries are locked
+   * through an internal object lock.
+   *
+   * @param nextPacket the {@link CompletableFuture} which will provide the next-processed packet.
+   * @param timestamp  the {@link Instant} timestamp of this packet so we can allow piggybacking.
+   */
+  public void queuePacket(CompletableFuture<MinecraftPacket> nextPacket, Instant timestamp) {
+    synchronized (internalLock) { // wait for the lock to resolve - we don't want to drop packets
+      MinecraftConnection smc = player.ensureAndGetCurrentServer().ensureConnected();
+
+      CompletableFuture<WrappedPacket> nextInLine = WrappedPacket.wrap(timestamp, nextPacket);
+      awaitChat(smc, this.packetFuture, nextInLine); // we await chat, binding `this.packetFuture` -> `nextInLine`
+      this.packetFuture = nextInLine;
+    }
+  }
+
+  /**
+   * Hijacks the latest sent packet's timestamp to provide an in-order packet without polling the physical, or prior
+   * packets sent through the stream.
+   *
+   * @param packet        the {@link MinecraftPacket} to send.
+   * @param instantMapper the {@link InstantPacketMapper} which maps the prior timestamp and current packet to a new
+   *                      packet.
+   * @param <K>           the type of base to expect when mapping the packet.
+   * @param <V>           the type of packet for instantMapper type-checking.
+   */
+  public <K, V extends MinecraftPacket> void hijack(K packet, InstantPacketMapper<K, V> instantMapper) {
+    synchronized (internalLock) {
+      CompletableFuture<K> trueFuture = CompletableFuture.completedFuture(packet);
+      MinecraftConnection smc = player.ensureAndGetCurrentServer().ensureConnected();
+
+      this.packetFuture = hijackCurrentPacket(smc, this.packetFuture, trueFuture, instantMapper);
+    }
+  }
+
+  private static BiConsumer<WrappedPacket, Throwable> writePacket(MinecraftConnection connection) {
+    return (wrappedPacket, throwable) -> {
+      if (wrappedPacket != null && !connection.isClosed()) {
+        wrappedPacket.write(connection);
+      }
+    };
+  }
+
+  private static <T extends MinecraftPacket> void awaitChat(
+      MinecraftConnection connection,
+      CompletableFuture<WrappedPacket> binder,
+      CompletableFuture<WrappedPacket> future
+  ) {
+    // the binder will run -> then the future will get the `write packet` caller
+    binder.whenComplete((ignored1, ignored2) -> future.whenComplete(writePacket(connection)));
+  }
+
+  private static <K, V extends MinecraftPacket> CompletableFuture<WrappedPacket> hijackCurrentPacket(
+      MinecraftConnection connection,
+      CompletableFuture<WrappedPacket> binder,
+      CompletableFuture<K> future,
+      InstantPacketMapper<K, V> packetMapper
+  ) {
+    CompletableFuture<WrappedPacket> awaitedFuture = new CompletableFuture<>();
+    // the binder will complete -> then the future will get the `write packet` caller
+    binder.whenComplete((previous, ignored) -> {
+      // map the new packet into a better "designed" packet with the hijacked packet's timestamp
+      WrappedPacket.wrap(previous.timestamp, future.thenApply(item -> packetMapper.map(previous.timestamp, item)))
+          .whenCompleteAsync(writePacket(connection), connection.eventLoop())
+          .whenComplete((packet, throwable) -> awaitedFuture.complete(throwable != null ? null : packet));
+    });
+    return awaitedFuture;
+  }
+
+  /**
+   * Provides an {@link Instant} based timestamp mapper from an existing object to create a packet.
+   *
+   * @param <K> The base object type to map.
+   * @param <V> The resulting packet type.
+   */
+  public interface InstantPacketMapper<K, V extends MinecraftPacket> {
+    /**
+     * Maps a value into a packet with it and a timestamp.
+     *
+     * @param nextInstant   the {@link Instant} timestamp to use for tracking.
+     * @param currentObject the current item to map to the packet.
+     * @return The resulting packet from the mapping.
+     */
+    V map(Instant nextInstant, K currentObject);
+  }
+
+  private static class WrappedPacket {
+    private final Instant timestamp;
+    private final MinecraftPacket packet;
+
+    private WrappedPacket(Instant timestamp, MinecraftPacket packet) {
+      this.timestamp = timestamp;
+      this.packet = packet;
+    }
+
+    public void write(MinecraftConnection connection) {
+      if (packet != null) {
+        connection.write(packet);
+      }
+    }
+
+    private static CompletableFuture<WrappedPacket> wrap(Instant timestamp,
+                                                         CompletableFuture<MinecraftPacket> nextPacket) {
+      return nextPacket
+          .thenApply(pkt -> new WrappedPacket(timestamp, pkt))
+          .exceptionally(ignored -> new WrappedPacket(timestamp, null));
+    }
+  }
+}