Add throw back feature for velocity server when connection is unsuccessful

src/main/java/com/sekwah/advancedportals/bukkit/AdvancedPortalsPlugin.java

@@ -27,6 +27,8 @@ public class AdvancedPortalsPlugin extends JavaPlugin {
 
     protected boolean isProxyPluginEnabled = false;
 
+    protected boolean isVelocitySupported = false;
+
     protected boolean forceRegisterProxyChannels = false;
     protected boolean disableProxyWarning = false;
 
@@ -134,6 +136,10 @@ public class AdvancedPortalsPlugin extends JavaPlugin {
         return isProxyPluginEnabled;
     }
 
+    public boolean isVelocitySupported() {
+        return isVelocitySupported;
+    }
+
     private boolean checkIfBungee()
     {
         // we check if the server is Spigot/Paper (because of the spigot.yml file)
@@ -161,6 +167,7 @@ public class AdvancedPortalsPlugin extends JavaPlugin {
             if(Objects.equals(config.get("velocity-support.enabled"),true)
                     || Objects.equals(config.get("proxies.velocity.enabled"),true)) {
                 getLogger().info( "Modern forwarding detected. Enabling proxy features." );
+                isVelocitySupported = true;
                 return true;
             }
         } catch(NoSuchMethodError | NullPointerException e) {

src/main/java/com/sekwah/advancedportals/bukkit/listeners/PluginMessageReceiver.java

@@ -3,9 +3,11 @@ package com.sekwah.advancedportals.bukkit.listeners;
 import com.google.common.io.ByteArrayDataInput;
 import com.google.common.io.ByteStreams;
 import com.sekwah.advancedportals.bukkit.AdvancedPortalsPlugin;
+import com.sekwah.advancedportals.bukkit.PluginMessages;
 import com.sekwah.advancedportals.bukkit.config.ConfigAccessor;
 import com.sekwah.advancedportals.bukkit.config.ConfigHelper;
 import com.sekwah.advancedportals.bukkit.destinations.Destination;
+import com.sekwah.advancedportals.bukkit.portals.Portal;
 import com.sekwah.advancedportals.bungee.BungeeMessages;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.messaging.PluginMessageListener;
@@ -48,6 +50,17 @@ public class PluginMessageReceiver implements PluginMessageListener {
                 );
             }
 
+        } else if (subchannel.equals(BungeeMessages.KNOCKBACK)) {
+            String reason = in.readUTF();
+            String bungeeUUID = in.readUTF();
+
+            Player targetPlayer = this.plugin.getServer().getPlayer(UUID.fromString(bungeeUUID));
+
+            if (targetPlayer != null) {
+                Portal.throwPlayerBack(targetPlayer);
+                player.sendMessage(PluginMessages.customPrefixFail
+                    + "\u00A7c " + reason);
+            }
         }
     }
 

src/main/java/com/sekwah/advancedportals/bukkit/portals/Portal.java

@@ -546,16 +546,24 @@ public class Portal {
 
             }
 
-            ByteArrayDataOutput outForSend = ByteStreams.newDataOutput();
+            if (!plugin.isVelocitySupported() || !doKnockback) {
-            outForSend.writeUTF("Connect");
+                ByteArrayDataOutput outForSend = ByteStreams.newDataOutput();
-            outForSend.writeUTF(bungeeServer);
+                outForSend.writeUTF("Connect");
+                outForSend.writeUTF(bungeeServer);
 
 
+                portal.inPortal.add(player.getUniqueId());
+                player.sendPluginMessage(plugin, "BungeeCord", outForSend.toByteArray());
+                // Down to bungee to sort out the teleporting but yea theoretically they should
+                // warp.
+            } else {
+                ByteArrayDataOutput outForSend = ByteStreams.newDataOutput();
+                outForSend.writeUTF(BungeeMessages.SEND_TO_SERVER_WITH_KNOCKBACK);
+                outForSend.writeUTF(bungeeServer);
 
-            portal.inPortal.add(player.getUniqueId());
+                portal.inPortal.add(player.getUniqueId());
-            player.sendPluginMessage(plugin, "BungeeCord", outForSend.toByteArray());
+                player.sendPluginMessage(plugin, BungeeMessages.CHANNEL_NAME, outForSend.toByteArray());
-            // Down to bungee to sort out the teleporting but yea theoretically they should
+            }
-            // warp.
         } else if (portal.getDestinations().length > 0) {
             ConfigAccessor configDesti = new ConfigAccessor(plugin, "destinations.yml");
             String randomDest = portal.getDestinations()[random.nextInt(portal.getDestinations().length)];

src/main/java/com/sekwah/advancedportals/bungee/BungeeMessages.java

@@ -17,6 +17,10 @@ public class BungeeMessages {
      */
     public static String ENTER_PORTAL = "PortalEnter";
 
+    public static String SEND_TO_SERVER_WITH_KNOCKBACK = "SendToServerWithKnockback";
+
+    public static String KNOCKBACK = "Knockback";
+
     public static String CHANNEL_NAME = "advancedportals:warp";
 
 

src/main/java/com/sekwah/advancedportals/velocity/AdvancedPortalsPlugin.java

@@ -10,12 +10,19 @@ import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.api.event.player.ServerPostConnectEvent;
 import com.velocitypowered.api.event.proxy.ProxyInitializeEvent;
 import com.velocitypowered.api.plugin.Plugin;
+import com.velocitypowered.api.proxy.ConnectionRequestBuilder;
+import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.ProxyServer;
 import com.velocitypowered.api.proxy.ServerConnection;
 import com.velocitypowered.api.proxy.messages.LegacyChannelIdentifier;
+import com.velocitypowered.api.proxy.server.RegisteredServer;
 import org.slf4j.Logger;
 
 import java.util.HashMap;
+import java.util.Optional;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -51,6 +58,21 @@ public class AdvancedPortalsPlugin {
         proxy.getChannelRegistrar().register(AP_CHANNEL);
     }
 
+    private void throwPlayerBack(Player player, String reason) {
+        ByteArrayDataOutput out = ByteStreams.newDataOutput();
+
+        out.writeUTF(BungeeMessages.KNOCKBACK);
+        out.writeUTF(reason);
+        out.writeUTF(player.getUniqueId().toString());
+
+        player.getCurrentServer().ifPresent(serverConnection ->
+            serverConnection.sendPluginMessage(AP_CHANNEL, out.toByteArray())
+        );
+    }
+
+    static class CannotConnectException extends Exception {
+    }
+
     @Subscribe
     public void onPluginMessage(PluginMessageEvent event) {
         if(event.getIdentifier().equals(AP_CHANNEL)) {
@@ -77,6 +99,27 @@ public class AdvancedPortalsPlugin {
                         proxy.getCommandManager().executeAsync(connection.getPlayer(), command);
                     }
 
+                } else if (subChannel.equalsIgnoreCase(BungeeMessages.SEND_TO_SERVER_WITH_KNOCKBACK)) {
+                    String targetServer = in.readUTF();
+                    Optional<RegisteredServer> server = proxy.getServer(targetServer);
+                    Player player = ((ServerConnection) event.getSource()).getPlayer();
+                    if (!server.isPresent()) {
+                        throwPlayerBack(player, "The server is invalid");
+                    } else {
+                        CompletableFuture<ConnectionRequestBuilder.Result> future = player.createConnectionRequest(server.get())
+                            .connect();
+                        proxy.getScheduler().buildTask(this, () -> {
+                            try {
+                                ConnectionRequestBuilder.Result result = future.get();
+                                if (!result.isSuccessful()) {
+                                    throw new CannotConnectException();
+                                }
+                            } catch (CancellationException | InterruptedException | ExecutionException |
+                                     CannotConnectException e) {
+                                throwPlayerBack(player, "Could not connect to the server");
+                            }
+                        }).schedule();
+                    }
                 }
             }
             // So that client packets don't make it through to the servers, always trigger on this channel.