Fix up some checkstyle stuff and include vendor in brand.

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

@@ -28,6 +28,10 @@ public class VelocityCommand implements Command {
 
   private final Map<String, Command> subcommands;
 
+  /**
+   * Initializes the command object for /velocity.
+   * @param server the Velocity server
+   */
   public VelocityCommand(ProxyServer server) {
     this.subcommands = ImmutableMap.<String, Command>builder()
         .put("version", new Info(server))

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

@@ -88,8 +88,9 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
       return true;
     }
 
-    if (PluginMessageUtil.isMCBrand(packet)) {
-      serverConn.getPlayer().getConnection().write(PluginMessageUtil.rewriteMinecraftBrand(packet));
+    if (PluginMessageUtil.isMcBrand(packet)) {
+      PluginMessage rewritten = PluginMessageUtil.rewriteMinecraftBrand(packet, server.getVersion());
+      serverConn.getPlayer().getConnection().write(rewritten);
       return true;
     }
 

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

@@ -160,7 +160,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     VelocityServerConnection serverConn = player.getConnectedServer();
     MinecraftConnection backendConn = serverConn != null ? serverConn.getConnection() : null;
     if (serverConn != null && backendConn != null) {
-      if (PluginMessageUtil.isMCRegister(packet)) {
+      if (PluginMessageUtil.isRegister(packet)) {
         List<String> actuallyRegistered = new ArrayList<>();
         List<String> channels = PluginMessageUtil.getChannels(packet);
         for (String channel : channels) {
@@ -177,12 +177,13 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
               .getProtocolVersion(), actuallyRegistered);
           backendConn.write(newRegisterPacket);
         }
-      } else if (PluginMessageUtil.isMCUnregister(packet)) {
+      } else if (PluginMessageUtil.isUnregister(packet)) {
         List<String> channels = PluginMessageUtil.getChannels(packet);
         knownChannels.removeAll(channels);
         backendConn.write(packet);
-      } else if (PluginMessageUtil.isMCBrand(packet)) {
-        backendConn.write(PluginMessageUtil.rewriteMinecraftBrand(packet));
+      } else if (PluginMessageUtil.isMcBrand(packet)) {
+        PluginMessage rewritten = PluginMessageUtil.rewriteMinecraftBrand(packet, server.getVersion());
+        backendConn.write(rewritten);
       } else if (backendConn.isLegacyForge() && !serverConn.hasCompletedJoin()) {
         if (packet.getChannel().equals(ForgeConstants.FORGE_LEGACY_HANDSHAKE_CHANNEL)) {
           if (!player.getModInfo().isPresent()) {

proxy/src/main/java/com/velocitypowered/proxy/protocol/util/PluginMessageUtil.java

@@ -1,7 +1,11 @@
 package com.velocitypowered.proxy.protocol.util;
 
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
+import com.velocitypowered.api.util.ProxyVersion;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
@@ -24,36 +28,61 @@ public class PluginMessageUtil {
     throw new AssertionError();
   }
 
-  public static boolean isMCBrand(PluginMessage message) {
-    Preconditions.checkNotNull(message, "message");
+  /**
+   * Determines whether or not this is a brand plugin message. This is shown on the client.
+   * @param message the plugin message
+   * @return whether or not this is a brand plugin message
+   */
+  public static boolean isMcBrand(PluginMessage message) {
+    checkNotNull(message, "message");
     return message.getChannel().equals(BRAND_CHANNEL_LEGACY) || message.getChannel()
         .equals(BRAND_CHANNEL);
   }
 
-  public static boolean isMCRegister(PluginMessage message) {
-    Preconditions.checkNotNull(message, "message");
+  /**
+   * Determines whether or not this plugin message is being used to register plugin channels.
+   * @param message the plugin message
+   * @return whether we are registering plugin channels or not
+   */
+  public static boolean isRegister(PluginMessage message) {
+    checkNotNull(message, "message");
     return message.getChannel().equals(REGISTER_CHANNEL_LEGACY) || message.getChannel()
         .equals(REGISTER_CHANNEL);
   }
 
-  public static boolean isMCUnregister(PluginMessage message) {
-    Preconditions.checkNotNull(message, "message");
+  /**
+   * Determines whether or not this plugin message is being used to unregister plugin channels.
+   * @param message the plugin message
+   * @return whether we are unregistering plugin channels or not
+   */
+  public static boolean isUnregister(PluginMessage message) {
+    checkNotNull(message, "message");
     return message.getChannel().equals(UNREGISTER_CHANNEL_LEGACY) || message.getChannel()
         .equals(UNREGISTER_CHANNEL);
   }
 
+  /**
+   * Fetches all the channels in a register or unregister plugin message.
+   * @param message the message to get the channels from
+   * @return the channels, as an immutable list
+   */
   public static List<String> getChannels(PluginMessage message) {
-    Preconditions.checkNotNull(message, "message");
-    Preconditions
-        .checkArgument(isMCRegister(message) || isMCUnregister(message), "Unknown channel type %s",
+    checkNotNull(message, "message");
+    checkArgument(isRegister(message) || isUnregister(message), "Unknown channel type %s",
             message.getChannel());
     String channels = new String(message.getData(), StandardCharsets.UTF_8);
     return ImmutableList.copyOf(channels.split("\0"));
   }
 
+  /**
+   * Constructs a channel (un)register packet.
+   * @param protocolVersion the client/server's protocol version
+   * @param channels the channels to register
+   * @return the plugin message to send
+   */
   public static PluginMessage constructChannelsPacket(int protocolVersion,
       Collection<String> channels) {
-    Preconditions.checkNotNull(channels, "channels");
+    checkNotNull(channels, "channels");
     String channelName = protocolVersion >= ProtocolConstants.MINECRAFT_1_13 ? REGISTER_CHANNEL
         : REGISTER_CHANNEL_LEGACY;
     PluginMessage message = new PluginMessage();
@@ -62,15 +91,24 @@ public class PluginMessageUtil {
     return message;
   }
 
-  public static PluginMessage rewriteMinecraftBrand(PluginMessage message) {
-    Preconditions.checkNotNull(message, "message");
-    Preconditions.checkArgument(isMCBrand(message), "message is not a MC Brand plugin message");
+  /**
+   * Rewrites the brand message to indicate the presence of Velocity.
+   * @param message the plugin message
+   * @param version the proxy version
+   * @return the rewritten plugin message
+   */
+  public static PluginMessage rewriteMinecraftBrand(PluginMessage message, ProxyVersion version) {
+    checkNotNull(message, "message");
+    checkNotNull(version, "version");
+    checkArgument(isMcBrand(message), "message is not a brand plugin message");
+
+    String toAppend = " (" + version.getName() + ")";
 
     byte[] rewrittenData;
     ByteBuf rewrittenBuf = Unpooled.buffer();
     try {
       String currentBrand = ProtocolUtils.readString(Unpooled.wrappedBuffer(message.getData()));
-      ProtocolUtils.writeString(rewrittenBuf, currentBrand + " (Velocity)");
+      ProtocolUtils.writeString(rewrittenBuf, currentBrand + toAppend);
       rewrittenData = new byte[rewrittenBuf.readableBytes()];
       rewrittenBuf.readBytes(rewrittenData);
     } finally {