Add requirements for mods and see mods in use if so

src/main/java/me/libraryaddict/disguise/utilities/modded/ModdedManager.java

@@ -1,10 +1,18 @@
 package me.libraryaddict.disguise.utilities.modded;
 
+import com.comphenix.protocol.utility.StreamSerializer;
+import lombok.Getter;
+import me.libraryaddict.disguise.LibsDisguises;
 import me.libraryaddict.disguise.disguisetypes.DisguiseType;
 import me.libraryaddict.disguise.utilities.parser.DisguisePerm;
 import me.libraryaddict.disguise.utilities.reflection.ReflectionManager;
+import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
+import org.bukkit.entity.Player;
+import org.bukkit.metadata.FixedMetadataValue;
+import org.bukkit.plugin.messaging.PluginMessageListener;
 
+import java.io.*;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map;
@@ -12,8 +20,52 @@ import java.util.Map;
 /**
  * Created by libraryaddict on 14/04/2020.
  */
-public class ModdedManager {
+public class ModdedManager implements PluginMessageListener {
+    @Getter
     private static final HashMap<NamespacedKey, CustomEntity> entities = new HashMap<>();
+    @Getter
+    private static byte[] fmlHandshake;
+
+    public ModdedManager(ArrayList<String> channels) {
+        if (getEntities().isEmpty()) {
+            return;
+        }
+
+        if (getEntities().values().stream().noneMatch(e -> e.getMod() != null)) {
+            return;
+        }
+
+        Bukkit.getMessenger().registerOutgoingPluginChannel(LibsDisguises.getInstance(), "fml:handshake");
+        Bukkit.getMessenger().registerIncomingPluginChannel(LibsDisguises.getInstance(), "fml:handshake", this);
+
+        ByteArrayOutputStream stream = new ByteArrayOutputStream();
+        DataOutputStream output = new DataOutputStream(stream);
+
+        StreamSerializer s = StreamSerializer.getDefault();
+
+        try {
+            // Packet id 1
+            s.serializeVarInt(output, 1);
+            // We have no mods to declare
+            s.serializeVarInt(output, 0);
+
+            // We want to declare some channels
+            s.serializeVarInt(output, channels.size());
+
+            for (String channel : channels) {
+                s.serializeString(output, channel.substring(0, channel.indexOf("|")));
+                s.serializeString(output, channel.substring(channel.indexOf("|") + 1));
+            }
+
+            // We have no resources to declare
+            s.serializeVarInt(output, 0);
+        }
+        catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        fmlHandshake = stream.toByteArray();
+    }
 
     public static void registerCustomEntity(NamespacedKey name, CustomEntity entity, boolean register) {
         if (entities.keySet().stream().anyMatch(n -> n.toString().equalsIgnoreCase(name.toString()))) {
@@ -68,4 +120,54 @@ public class ModdedManager {
 
         return perms;
     }
+
+    @Override
+    public void onPluginMessageReceived(String channel, Player player, byte[] bytes) {
+        if (player.hasMetadata("forge_mods")) {
+            return;
+        }
+
+        DataInputStream stream = new DataInputStream(new ByteArrayInputStream(bytes));
+
+        try {
+            StreamSerializer s = StreamSerializer.getDefault();
+            int packetId = s.deserializeVarInt(stream);
+
+            if (packetId != 2) {
+                return;
+            }
+
+            int count = s.deserializeVarInt(stream);
+
+            ArrayList<String> mods = new ArrayList<>();
+
+            for (int i = 0; i < count; i++) {
+                mods.add(s.deserializeString(stream, 256));
+            }
+
+            player.setMetadata("forge_mods", new FixedMetadataValue(LibsDisguises.getInstance(), mods));
+
+            for (CustomEntity e : getEntities().values()) {
+                if (e.getMod() == null) {
+                    continue;
+                }
+
+                if (mods.contains(e.getMod().toLowerCase())) {
+                    continue;
+                }
+
+                // TODO Idk, something because they don't have a mod?
+
+                if (e.getRequired() == null) {
+                    continue;
+                }
+
+                player.kickPlayer(e.getRequired());
+                break;
+            }
+        }
+        catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
 }