Major improvements to tab complete support.

- Removed half-baked 1.13 support that didn't even work anyway. Perhaps
  in the future we could restore it by rewriting the available commands
  packet.
- Proxy commands now show up in tab complete responses where possible.

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommandManager.java

@@ -66,6 +66,7 @@ public class VelocityCommandManager implements CommandManager {
         if (split.length == 1) {
             return Optional.of(commands.keySet().stream()
                     .filter(cmd -> cmd.regionMatches(true, 0, command, 0, command.length()))
+                    .map(cmd -> "/" + cmd)
                     .collect(Collectors.toList()));
         }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -98,6 +98,8 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
                             }
                         }, connection.getMinecraftConnection().getChannel().eventLoop());
             }
+        } else if (packet instanceof TabCompleteResponse) {
+            playerHandler.handleTabCompleteResponse((TabCompleteResponse) packet);
         } else if (connection.hasCompletedJoin()) {
             // Just forward the packet on. We don't have anything to handle at this time.
             connection.getPlayer().getConnection().write(packet);

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

@@ -36,6 +36,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     private final Set<String> clientPluginMsgChannels = new HashSet<>();
     private final Queue<PluginMessage> loginPluginMessages = new ArrayDeque<>();
     private final VelocityServer server;
+    private TabCompleteRequest outstandingTabComplete;
 
     public ClientPlaySessionHandler(VelocityServer server, ConnectedPlayer player) {
         this.player = player;
@@ -100,32 +101,10 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
         }
 
         if (packet instanceof TabCompleteRequest) {
-            TabCompleteRequest req = (TabCompleteRequest) packet;
+            // Record the request so that the outstanding request can be augmented later.
-            int lastSpace = req.getCommand().indexOf(' ');
+            outstandingTabComplete = (TabCompleteRequest) packet;
-            if (!req.isAssumeCommand() && lastSpace != -1) {
-                String command = req.getCommand().substring(1);
-                try {
-                    Optional<List<String>> offers = server.getCommandManager().offerSuggestions(player, command);
-                    if (offers.isPresent()) {
-                        TabCompleteResponse response = new TabCompleteResponse();
-                        response.setTransactionId(req.getTransactionId());
-                        response.setStart(lastSpace);
-                        response.setLength(req.getCommand().length() - lastSpace);
-
-                        for (String s : offers.get()) {
-                            response.getOffers().add(new TabCompleteResponse.Offer(s, null));
-                        }
-
-                        player.getConnection().write(response);
-                    } else {
             serverConnection.getMinecraftConnection().write(packet);
         }
-                } catch (Exception e) {
-                    logger.error("Unable to provide tab list completions for " + player.getUsername() + " for command '" + req.getCommand() + "'", e);
-                }
-                return;
-            }
-        }
 
         if (packet instanceof PluginMessage) {
             handleClientPluginMessage((PluginMessage) packet);
@@ -327,4 +306,21 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
         this.lastPingID = -1;
         this.lastPingSent = -1;
     }
+
+    public void handleTabCompleteResponse(TabCompleteResponse response) {
+        if (outstandingTabComplete != null) {
+            if (!outstandingTabComplete.isAssumeCommand()) {
+                String command = outstandingTabComplete.getCommand().substring(1);
+                try {
+                    Optional<List<String>> offers = server.getCommandManager().offerSuggestions(player, command);
+                    offers.ifPresent(strings -> response.getOffers().addAll(strings));
+                } catch (Exception e) {
+                    logger.error("Unable to provide tab list completions for {} for command '{}'", player.getUsername(),
+                            command, e);
+                }
+                outstandingTabComplete = null;
+            }
+            player.getConnection().write(response);
+        }
+    }
 }

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

@@ -40,8 +40,7 @@ public enum StateRegistry {
                     map(0x14, MINECRAFT_1_8, false),
                     map(0x01, MINECRAFT_1_9, false),
                     map(0x02, MINECRAFT_1_12, false),
-                    map(0x01, MINECRAFT_1_12_1, false),
+                    map(0x01, MINECRAFT_1_12_1, false));
-                    map(0x05, MINECRAFT_1_13, false));
             SERVERBOUND.register(Chat.class, Chat::new,
                     map(0x01, MINECRAFT_1_8, false),
                     map(0x02, MINECRAFT_1_9, false),
@@ -77,10 +76,9 @@ public enum StateRegistry {
                     map(0x0F, MINECRAFT_1_12, true),
                     map(0x0E, MINECRAFT_1_13, true));
             CLIENTBOUND.register(TabCompleteResponse.class, TabCompleteResponse::new,
-                    map(0x3A, MINECRAFT_1_8, true),
+                    map(0x3A, MINECRAFT_1_8, false),
-                    map(0x0E, MINECRAFT_1_9, true),
+                    map(0x0E, MINECRAFT_1_9, false),
-                    map(0x0E, MINECRAFT_1_12, true),
+                    map(0x0E, MINECRAFT_1_12, false));
-                    map(0x10, MINECRAFT_1_13, true));
             CLIENTBOUND.register(PluginMessage.class, PluginMessage::new,
                     map(0x3F, MINECRAFT_1_8, false),
                     map(0x18, MINECRAFT_1_9, false),

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/TabCompleteRequest.java

@@ -9,20 +9,11 @@ import static com.velocitypowered.proxy.protocol.ProtocolConstants.MINECRAFT_1_1
 import static com.velocitypowered.proxy.protocol.ProtocolConstants.MINECRAFT_1_9;
 
 public class TabCompleteRequest implements MinecraftPacket {
-    private int transactionId;
     private String command;
     private boolean assumeCommand;
     private boolean hasPosition;
     private long position;
 
-    public int getTransactionId() {
-        return transactionId;
-    }
-
-    public void setTransactionId(int transactionId) {
-        this.transactionId = transactionId;
-    }
-
     public String getCommand() {
         return command;
     }
@@ -58,8 +49,7 @@ public class TabCompleteRequest implements MinecraftPacket {
     @Override
     public String toString() {
         return "TabCompleteRequest{" +
-                "transactionId=" + transactionId +
+                "command='" + command + '\'' +
-                ", command='" + command + '\'' +
                 ", assumeCommand=" + assumeCommand +
                 ", hasPosition=" + hasPosition +
                 ", position=" + position +
@@ -68,10 +58,6 @@ public class TabCompleteRequest implements MinecraftPacket {
 
     @Override
     public void decode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        if (protocolVersion >= MINECRAFT_1_13) {
-            this.transactionId = ProtocolUtils.readVarInt(buf);
-            this.command = ProtocolUtils.readString(buf);
-        } else {
         this.command = ProtocolUtils.readString(buf);
         if (protocolVersion >= MINECRAFT_1_9) {
             this.assumeCommand = buf.readBoolean();
@@ -81,14 +67,9 @@ public class TabCompleteRequest implements MinecraftPacket {
             this.position = buf.readLong();
         }
     }
-    }
 
     @Override
     public void encode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        if (protocolVersion >= MINECRAFT_1_13) {
-            ProtocolUtils.writeVarInt(buf, transactionId);
-            ProtocolUtils.writeString(buf, command);
-        } else {
         ProtocolUtils.writeString(buf, command);
         if (protocolVersion >= MINECRAFT_1_9) {
             buf.writeBoolean(assumeCommand);
@@ -98,5 +79,4 @@ public class TabCompleteRequest implements MinecraftPacket {
             buf.writeLong(position);
         }
     }
-    }
 }

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/TabCompleteResponse.java

@@ -4,125 +4,37 @@ import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
-import net.kyori.text.Component;
-import net.kyori.text.serializer.ComponentSerializers;
-import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import static com.velocitypowered.proxy.protocol.ProtocolConstants.MINECRAFT_1_13;
-
 public class TabCompleteResponse implements MinecraftPacket {
-    private int transactionId;
+    private final List<String> offers = new ArrayList<>();
-    private int start;
-    private int length;
-    private final List<Offer> offers = new ArrayList<>();
 
-    public int getTransactionId() {
+    public List<String> getOffers() {
-        return transactionId;
-    }
-
-    public void setTransactionId(int transactionId) {
-        this.transactionId = transactionId;
-    }
-
-    public int getStart() {
-        return start;
-    }
-
-    public void setStart(int start) {
-        this.start = start;
-    }
-
-    public int getLength() {
-        return length;
-    }
-
-    public void setLength(int length) {
-        this.length = length;
-    }
-
-    public List<Offer> getOffers() {
         return offers;
     }
 
     @Override
     public String toString() {
         return "TabCompleteResponse{" +
-                "transactionId=" + transactionId +
+                "offers=" + offers +
-                ", start=" + start +
-                ", length=" + length +
-                ", offers=" + offers +
                 '}';
     }
 
     @Override
     public void decode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        if (protocolVersion >= MINECRAFT_1_13) {
-            this.transactionId = ProtocolUtils.readVarInt(buf);
-            this.start = ProtocolUtils.readVarInt(buf);
-            this.length = ProtocolUtils.readVarInt(buf);
         int offersAvailable = ProtocolUtils.readVarInt(buf);
         for (int i = 0; i < offersAvailable; i++) {
-                String entry = ProtocolUtils.readString(buf);
+            offers.add(ProtocolUtils.readString(buf));
-                Component component = buf.readBoolean() ? ComponentSerializers.JSON.deserialize(ProtocolUtils.readString(buf)) :
-                        null;
-                offers.add(new Offer(entry, component));
-            }
-        } else {
-            int offersAvailable = ProtocolUtils.readVarInt(buf);
-            for (int i = 0; i < offersAvailable; i++) {
-                offers.add(new Offer(ProtocolUtils.readString(buf), null));
-            }
         }
     }
 
     @Override
     public void encode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        if (protocolVersion >= MINECRAFT_1_13) {
-            ProtocolUtils.writeVarInt(buf, transactionId);
-            ProtocolUtils.writeVarInt(buf, start);
-            ProtocolUtils.writeVarInt(buf, length);
         ProtocolUtils.writeVarInt(buf, offers.size());
-            for (Offer offer : offers) {
+        for (String offer : offers) {
-                ProtocolUtils.writeString(buf, offer.entry);
+            ProtocolUtils.writeString(buf, offer);
-                buf.writeBoolean(offer.tooltip != null);
-                if (offer.tooltip != null) {
-                    ProtocolUtils.writeString(buf, ComponentSerializers.JSON.serialize(offer.tooltip));
-                }
-            }
-        } else {
-            ProtocolUtils.writeVarInt(buf, offers.size());
-            for (Offer offer : offers) {
-                ProtocolUtils.writeString(buf, offer.entry);
-            }
-        }
-    }
-
-    public static class Offer {
-        private final String entry;
-        private final Component tooltip;
-
-        public Offer(String entry, @Nullable Component tooltip) {
-            this.entry = entry;
-            this.tooltip = tooltip;
-        }
-
-        public String getEntry() {
-            return entry;
-        }
-
-        public @Nullable Component getTooltip() {
-            return tooltip;
-        }
-
-        @Override
-        public String toString() {
-            return "Offer{" +
-                    "entry='" + entry + '\'' +
-                    ", tooltip=" + tooltip +
-                    '}';
         }
     }
 }