Command system rewrite using Drink and Maven support.

src/main/java/net/nuggetmc/ai/npc/NPCManager.java

@@ -0,0 +1,153 @@
+package net.nuggetmc.ai.npc;
+
+import io.netty.channel.*;
+import net.minecraft.server.v1_16_R3.PacketPlayOutEntityMetadata;
+import net.minecraft.server.v1_16_R3.PacketPlayOutNamedEntitySpawn;
+import net.minecraft.server.v1_16_R3.PacketPlayOutPlayerInfo;
+import net.minecraft.server.v1_16_R3.PlayerConnection;
+import net.nuggetmc.ai.PlayerAI;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_16_R3.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerJoinEvent;
+import org.bukkit.event.player.PlayerQuitEvent;
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class NPCManager implements Listener {
+
+    private PlayerAI plugin;
+
+    private final Set<NPC> npcs = new HashSet<>();
+    private final Map<Integer, NPC> npcConnections = new HashMap<>();
+
+    public Set<NPC> fetch() {
+        return npcs;
+    }
+
+    public void add(NPC npc) {
+        npcs.add(npc);
+
+        Bukkit.getScheduler().runTaskLater(PlayerAI.getInstance(), () -> {
+            npcConnections.put(npc.getId(), npc);
+        }, 10);
+    }
+
+    public NPCManager(PlayerAI instance) {
+        plugin = instance;
+    }
+
+    public void reset() {
+        for (NPC npc : npcs) {
+            npc.despawn();
+        }
+
+        npcs.clear();
+        npcConnections.clear();
+    }
+
+    @EventHandler
+    public void onJoin(PlayerJoinEvent event) {
+        PlayerConnection connection = ((CraftPlayer) event.getPlayer()).getHandle().playerConnection;
+
+        for (NPC npc : npcs) {
+            npc.render(connection, true);
+        }
+
+        injectPlayer(event.getPlayer());
+    }
+
+    public void connectAll() {
+        for (Player player : Bukkit.getOnlinePlayers()) {
+            injectPlayer(player);
+        }
+    }
+
+    @EventHandler
+    public void onQuit(PlayerQuitEvent event) {
+        removePlayer(event.getPlayer());
+    }
+
+    public void disconnectAll() {
+        for (Player player : Bukkit.getOnlinePlayers()) {
+            removePlayer(player);
+        }
+    }
+
+    private void injectPlayer(Player player) {
+        ChannelDuplexHandler channelDuplexHandler = new ChannelDuplexHandler() {
+
+            @Override
+            public void channelRead(ChannelHandlerContext channelHandlerContext, Object packet) throws Exception {
+                super.channelRead(channelHandlerContext, packet);
+            }
+
+            @Override
+            public void write(ChannelHandlerContext channelHandlerContext, Object packet, ChannelPromise channelPromise) throws Exception {
+                if (packet instanceof PacketPlayOutNamedEntitySpawn) {
+                    renderNPC(player, (PacketPlayOutNamedEntitySpawn) packet);
+                }
+
+                super.write(channelHandlerContext, packet, channelPromise);
+            }
+        };
+
+        ChannelPipeline pipeline = ((CraftPlayer) player).getHandle().playerConnection.networkManager.channel.pipeline();
+
+        try {
+            pipeline.addBefore("packet_handler", player.getName(), channelDuplexHandler);
+        } catch (IllegalArgumentException ignore) { }
+    }
+
+    private void renderNPC(Player player, PacketPlayOutNamedEntitySpawn packet) {
+        PlayerConnection connection = ((CraftPlayer) player).getHandle().playerConnection;
+        Field field;
+
+        try {
+            field = packet.getClass().getDeclaredField("a");
+        } catch (NoSuchFieldException e) {
+            return;
+        }
+
+        field.setAccessible(true);
+
+        Object obj;
+
+        try {
+            obj = field.get(packet);
+        } catch (IllegalAccessException e) {
+            return;
+        }
+
+        if (!(obj instanceof Integer)) return;
+        int n = (int) obj;
+
+        NPC npc = npcConnections.get(n);
+        if (npc == null) return;
+
+        connection.sendPacket(new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.ADD_PLAYER, npc));
+        connection.sendPacket(new PacketPlayOutEntityMetadata(npc.getId(), npc.getDataWatcher(), true));
+
+        PacketPlayOutPlayerInfo noTabPacket = new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.REMOVE_PLAYER, npc);
+
+        Bukkit.getScheduler().runTaskLater(plugin, () -> {
+            if (!connection.isDisconnected()) {
+                connection.sendPacket(noTabPacket);
+            }
+        }, 5);
+    }
+
+    public void removePlayer(Player player) {
+        Channel channel = ((CraftPlayer) player).getHandle().playerConnection.networkManager.channel;
+        channel.eventLoop().submit(() -> {
+            channel.pipeline().remove(player.getName());
+            return null;
+        });
+    }
+}