Generate Bungeecord Channel

Generate BungeeCord Channel Handler / 產生 BungeeCord 頻道處理器

技能名稱 / Skill Name

generate-bungeecord-channel

目的 / Purpose

為 Waterfall proxy plugin 產生完整的 plugin messaging 處理類別，含頻道註冊、入站訊息解析、proxy 向後端回應以及 BungeeCord 內建 sub-channel 攔截範例。

觸發條件 / Triggers

• 「BungeeCord channel」
• 「PluginMessageEvent on Waterfall」
• 「plugin messaging BungeeCord」
• 「自訂頻道 Waterfall」
• 「proxy backend communication Waterfall」
• 「ByteStreams BungeeCord」

輸入參數 / Inputs

輸出產物 / Outputs

• messaging/WaterfallMessagingHandler.java — 完整處理器類別（實作 Listener）

代碼範本 / Code Template

package {plugin_package}.messaging;

import com.google.common.io.ByteArrayDataInput;
import com.google.common.io.ByteArrayDataOutput;
import com.google.common.io.ByteStreams;
import net.md_5.bungee.api.ProxyServer;
import net.md_5.bungee.api.chat.TextComponent;
import net.md_5.bungee.api.config.ServerInfo;
import net.md_5.bungee.api.connection.ProxiedPlayer;
import net.md_5.bungee.api.connection.Server;
import net.md_5.bungee.api.event.PluginMessageEvent;
import net.md_5.bungee.api.plugin.Listener;
import net.md_5.bungee.api.plugin.Plugin;
import net.md_5.bungee.event.EventHandler;

import java.util.function.Consumer;
import java.util.logging.Logger;

public class WaterfallMessagingHandler implements Listener {

    private static final String CUSTOM_CHANNEL = "{channel_name}";
    private static final String BUNGEE_CHANNEL  = "BungeeCord";

    private final Plugin plugin;
    private final Logger logger;

    public WaterfallMessagingHandler(Plugin plugin) {
        this.plugin = plugin;
        this.logger = plugin.getLogger();
    }

    /** Call in onEnable(). */
    public void register() {
        plugin.getProxy().registerChannel(CUSTOM_CHANNEL);
        plugin.getProxy().getPluginManager().registerListener(plugin, this);
    }

    /** Call in onDisable(). */
    public void unregister() {
        plugin.getProxy().unregisterChannel(CUSTOM_CHANNEL);
    }

    @EventHandler
    public void onPluginMessage(PluginMessageEvent event) {
        String tag = event.getTag();

        if (CUSTOM_CHANNEL.equals(tag)) {
            // Only handle messages from backend servers
            if (!(event.getSender() instanceof Server)) return;
            handleCustomMessage(event);
        } else if (BUNGEE_CHANNEL.equals(tag)) {
            handleBungeeCordMessage(event);
        }
    }

    // --- Custom Channel Handlers ---

    private void handleCustomMessage(PluginMessageEvent event) {
        ByteArrayDataInput in = ByteStreams.newDataInput(event.getData());
        String action = in.readUTF();

        switch (action) {
            case "BROADCAST" -> {
                String message = in.readUTF();
                plugin.getProxy().broadcast(new TextComponent("§6[Network] §f" + message));
                event.setCancelled(true);   // handled internally — don't forward
            }
            case "MOVE_PLAYER" -> {
                String playerName   = in.readUTF();
                String targetServer = in.readUTF();
                movePlayer(playerName, targetServer);
                event.setCancelled(true);
            }
            case "GET_PLAYER_COUNT" -> {
                int count = plugin.getProxy().getOnlineCount();
                respondToBackend(event, "PLAYER_COUNT_RESPONSE",
                    out -> out.writeInt(count));
                event.setCancelled(true);
            }
            default -> logger.warning("Unknown custom action from backend: " + action);
        }
    }

    // --- BungeeCord Built-in Channel Intercept ---

    private void handleBungeeCordMessage(PluginMessageEvent event) {
        ByteArrayDataInput in = ByteStreams.newDataInput(event.getData());
        String subChannel = in.readUTF();

        switch (subChannel) {
            case "Connect" -> {
                String targetServer = in.readUTF();
                logger.info("[Audit] BungeeCord Connect request → " + targetServer);
                // Do NOT cancel — let Waterfall process the Connect normally
            }
            // Most BungeeCord sub-channels should NOT be cancelled
            // Only intercept if you are fully replacing Waterfall's handling
        }
    }

    // --- Helpers ---

    private void movePlayer(String playerName, String targetServer) {
        ProxiedPlayer player = plugin.getProxy().getPlayer(playerName);
        if (player == null) {
            logger.warning("Move failed: player '" + playerName + "' not found.");
            return;
        }
        ServerInfo server = plugin.getProxy().getServerInfo(targetServer);
        if (server == null) {
            logger.warning("Move failed: server '" + targetServer + "' not found.");
            return;
        }
        player.connect(server);
    }

    private void respondToBackend(PluginMessageEvent event,
                                   String responseAction,
                                   Consumer<ByteArrayDataOutput> writer) {
        // Route the response via the player who is on the requesting backend
        if (!(event.getReceiver() instanceof ProxiedPlayer player)) return;

        ByteArrayDataOutput out = ByteStreams.newDataOutput();
        out.writeUTF(responseAction);
        writer.accept(out);
        player.sendData(CUSTOM_CHANNEL, out.toByteArray());
    }

    /**
     * Send from proxy → specific backend server (requires at least one player on that server).
     */
    public void sendToServer(String serverName, String action,
                              Consumer<ByteArrayDataOutput> writer) {
        plugin.getProxy().getPlayers().stream()
            .filter(p -> p.getServer() != null
                && serverName.equals(p.getServer().getInfo().getName()))
            .findFirst()
            .ifPresent(p -> {
                ByteArrayDataOutput out = ByteStreams.newDataOutput();
                out.writeUTF(action);
                writer.accept(out);
                p.sendData(CUSTOM_CHANNEL, out.toByteArray());
            });
    }
}

Register in main class:

private WaterfallMessagingHandler messagingHandler;

@Override
public void onEnable() {
    messagingHandler = new WaterfallMessagingHandler(this);
    messagingHandler.register();
}

@Override
public void onDisable() {
    if (messagingHandler != null) messagingHandler.unregister();
}

Backend (Paper) side:

// onEnable():
getServer().getMessenger().registerIncomingPluginChannel(
    this, "{channel_name}",
    (channel, player, data) -> { /* handle response */ }
);
getServer().getMessenger().registerOutgoingPluginChannel(this, "{channel_name}");

// Send to proxy:
ByteArrayDataOutput out = ByteStreams.newDataOutput();
out.writeUTF("BROADCAST");
out.writeUTF("Hello from backend!");
player.sendPluginMessage(this, "{channel_name}", out.toByteArray());

BungeeCord Sub-Channel Reference

失敗回退 / Fallback

• 在 Waterfall 不要使用 MinecraftChannelIdentifier（那是 Velocity 的類別），頻道名稱直接用字串。
• 若未呼叫 event.setCancelled(true)，Waterfall 會將訊息轉發給玩家——對於在 proxy 內部處理的訊息，必須 cancel。
• 不要 cancel 內建 BungeeCord sub-channel（如 Connect、GetServer），除非你要完全取代 Waterfall 的處理邏輯。
• sendToServer() 需要目標伺服器上至少有一位玩家，否則無法路由。