[CraftBukkit/Spigot] Send a new title of the currently opened inventory.

InventoryTitleHelper

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.bukkit.inventory.Inventory;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * A inventory helper that allows you to change the title of the current
 * opened inventory.
 */
public class InventoryTitleHelper {
	// Methods
	private static Method m_Player_GetHandle;
	private static Method m_PlayerConnection_sendPacket;
	private static Method m_CraftChatMessage_fromString;
	private static Method m_EntityPlayer_updateInventory;
	
	// Fields
	private static Field f_EntityPlayer_playerConnection;
	private static Field f_EntityPlayer_activeContainer;
	private static Field f_Container_windowId;
	
	// Constructors
	private static Constructor<?> c_PacketOpenWindow;
	
	// The version of the server (nms version like v1_5_R3)
	private static String nms_version;
	private static String nms_package;
	private static String crb_package;

	/**
	 * Sends a new inventory title to the client.
	 * 
	 * @param player the player
	 * @param title the new title
	 */
	public static void sendInventoryTitle(Player player, String title) {
		checkNotNull(player, "player");
		
		try {
			sendInventoryTitle0(player, title);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private static void sendInventoryTitle0(Player player, String title) throws Exception {
		Inventory inventory = player.getOpenInventory().getTopInventory();
		if (inventory == null) {
			return;
		}
		if (m_Player_GetHandle == null) {
			m_Player_GetHandle = player.getClass().getMethod("getHandle");
		}
		Object nms_EntityPlayer = m_Player_GetHandle.invoke(player);
		if (f_EntityPlayer_playerConnection == null) {
			f_EntityPlayer_playerConnection = nms_EntityPlayer.getClass().getField("playerConnection");
		}
		Object nms_PlayerConnection = f_EntityPlayer_playerConnection.get(nms_EntityPlayer);
		if (f_EntityPlayer_activeContainer == null) {
			f_EntityPlayer_activeContainer = nms_EntityPlayer.getClass().getField("activeContainer");
		}
		Object nms_Container = f_EntityPlayer_activeContainer.get(nms_EntityPlayer);
		if (f_Container_windowId == null) {
			f_Container_windowId = nms_Container.getClass().getField("windowId");
		}
		int windowId = f_Container_windowId.getInt(nms_Container);
		String version = getNmsVersion();
		if (version.startsWith("v1_5_") || version.startsWith("v1_6_")) {
			sendPacket15a16a17(nms_PlayerConnection, nms_EntityPlayer, nms_Container, windowId, inventory, title, false);
		} else if (version.startsWith("v1_7_")) {
			sendPacket15a16a17(nms_PlayerConnection, nms_EntityPlayer, nms_Container, windowId, inventory, title, true);
		} else if (version.equals("v1_8_R1") || version.equals("v1_8_R2")) {
			sendPacket18(nms_PlayerConnection, nms_EntityPlayer, nms_Container, windowId, inventory, title);
		}
	}

	private static void sendPacket15a16a17(Object nms_playerConnection, Object nms_EntityPlayer, Object nms_Container, int windowId, Inventory inventory, String title, boolean flag) throws Exception {
		if (c_PacketOpenWindow == null) {
			if (flag) {
				c_PacketOpenWindow = findNmsClass("PacketPlayOutOpenWindow").getConstructor(int.class, int.class, String.class, int.class, boolean.class);
			} else {
				c_PacketOpenWindow = findNmsClass("Packet100OpenWindow").getConstructor(int.class, int.class, String.class, int.class, boolean.class);
			}
		}
		
		int id;
		int size;
		
		switch (inventory.getType()) {
			case ANVIL:
				id = 8;
				size = 9;
				break;
			case BEACON:
				id = 7;
				size = 1;
				break;
			case BREWING:
				id = 5;
				size = 4;
				break;
			case CRAFTING:
				return;
			case CREATIVE:
				return;
			case DISPENSER:
				id = 3;
				size = 9;
				break;
			case DROPPER:
				id = 10;
				size = 9;
				break;
			case ENCHANTING:
				id = 4;
				size = 9;
				break;
			case ENDER_CHEST:
			case CHEST:
				id = 0;
				size = inventory.getSize();
				break;
			case FURNACE:
				id = 2;
				size = 2;
				break;
			case HOPPER:
				id = 9;
				size = 5;
				break;
			case MERCHANT:
				id = 6;
				size = 3;
				break;
			case PLAYER:
				return;
			case WORKBENCH:
				id = 1;
				size = 9;
				break;
			default:
				return;
		}
		
		if (title != null && title.length() > 32) {
			title = title.substring(0, 32);
		}
		
		if (m_EntityPlayer_updateInventory == null) {
			m_EntityPlayer_updateInventory = nms_EntityPlayer.getClass().getMethod("updateInventory", findNmsClass("Container"));
		}
		
		Object packet = c_PacketOpenWindow.newInstance(windowId, id, title != null ? title : "", size, true);
		sendPacket(nms_playerConnection, packet);
		
		m_EntityPlayer_updateInventory.invoke(nms_EntityPlayer, nms_Container);
	}

	private static void sendPacket18(Object nms_playerConnection, Object nms_EntityPlayer, Object nms_Container, int windowId, Inventory inventory, String title) throws Exception {
		if (c_PacketOpenWindow == null) {
			c_PacketOpenWindow = findNmsClass("PacketPlayOutOpenWindow").getConstructor(int.class, String.class, findNmsClass("IChatBaseComponent"), int.class);
		}
		
		String id;
		int size = 0;
		
		switch (inventory.getType()) {
			case ANVIL:
				id = "minecraft:anvil";
				break;
			case BEACON:
				id = "minecraft:beacon";
				break;
			case BREWING:
				id = "minecraft:brewing_stand";
				break;
			case CRAFTING:
				return;
			case CREATIVE:
				return;
			case DISPENSER:
				id = "minecraft:dispenser";
				break;
			case DROPPER:
				id = "minecraft:dropper";
				break;
			case ENCHANTING:
				id = "minecraft:enchanting_table";
				break;
			case ENDER_CHEST:
			case CHEST:
				id = "minecraft:chest";
				size = inventory.getSize();
				break;
			case FURNACE:
				id = "minecraft:furnace";
				break;
			case HOPPER:
				id = "minecraft:hopper";
				break;
			case MERCHANT:
				id = "minecraft:villager";
				size = 3;
				break;
			case PLAYER:
				return;
			case WORKBENCH:
				id = "minecraft:crafting_table";
				break;
			default:
				return;
		}
		
		if (m_CraftChatMessage_fromString == null) {
			m_CraftChatMessage_fromString = findCrbClass("util.CraftChatMessage").getMethod("fromString", String.class);
		}
		if (m_EntityPlayer_updateInventory == null) {
			m_EntityPlayer_updateInventory = nms_EntityPlayer.getClass().getMethod("updateInventory", findNmsClass("Container"));
		}
		
		Object nms_title = ((Object[]) m_CraftChatMessage_fromString.invoke(null, title))[0];
		Object nms_packet = c_PacketOpenWindow.newInstance(windowId, id, nms_title, size);
		sendPacket(nms_playerConnection, nms_packet);
		
		m_EntityPlayer_updateInventory.invoke(nms_EntityPlayer, nms_Container);
	}
	
	private static void sendPacket(Object playerConnection, Object packet) throws Exception {
		if (m_PlayerConnection_sendPacket == null) {
			m_PlayerConnection_sendPacket = playerConnection.getClass().getMethod("sendPacket", findNmsClass("Packet"));
		}
		m_PlayerConnection_sendPacket.invoke(playerConnection, packet);
	}
	
	private static String getNmsVersion() {
		if (nms_version == null) {
			nms_version = Bukkit.getServer().getClass().getPackage().getName().replace("org.bukkit.craftbukkit.", "");
		}
		
		return nms_version;
	}
	
	private static String getNmsPackage() {
		if (nms_package == null) {
			nms_package = "net.minecraft.server." + getNmsVersion();
		}
		
		return nms_package;
	}
	
	private static String getCrbPackage() {
		if (crb_package == null) {
			crb_package = "org.bukkit.craftbukkit." + getNmsVersion();
		}
		
		return crb_package;
	}
	
	private static Class<?> findNmsClass(String name) throws Exception {
		return Class.forName(getNmsPackage() + "." + name);
	}
	
	private static Class<?> findCrbClass(String name) throws Exception {
		return Class.forName(getCrbPackage() + "." + name);
	}
}