RetroHolograms - A quick and simple Hologram API for Spigot 1.7.10 Protocol Hack (supports 1.7 and 1.8)

Hologram.java

package com.mrpowergamerbr.sparklycore.utils.hologram;

import java.lang.ref.WeakReference;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.List;

import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.craftbukkit.v1_7_R4.entity.CraftPlayer;
import org.bukkit.entity.EntityType;
import org.bukkit.entity.Player;

import com.comphenix.protocol.wrappers.WrappedDataWatcher;
import com.comphenix.protocol.wrappers.WrappedWatchableObject;
import com.mrpowergamerbr.packetwrapper.AbstractPacket;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerAttachEntity;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerEntityDestroy;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerEntityMetadata;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerEntityTeleport;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerSpawnEntity;
import com.mrpowergamerbr.packetwrapper.WrapperPlayServerSpawnEntityLiving;

import lombok.*;
import me.mrpowergamerbr.sparklycore.utils.collections.WeakArrayList;

/**
 * Class to spawn holograms in 1.7.10 Protocol Hack
 * @author Leonardo
 *
 */
public class Hologram {
    int horseId = 0; // Also used as the Armor Stand ID
    int witherSkullId = 0;
    String line;
    @Getter
    Location location;
    @Getter
    @Setter
    WeakArrayList<Player> viewers = new WeakArrayList<Player>();
    @Getter
    @Setter
    ViewHandler vh;
    
    public Hologram(Location location, String line) {
        this.location = location;
        this.line = line;
        horseId = getId();
        witherSkullId = getId();
    }

    public void setViewHandler(ViewHandler vh) {
        this.vh = vh;
    }
    
    private static int getId() {
        try {
            Field field = Class.forName(
                    "net.minecraft.server." + Bukkit.getServer().getClass().getName().split("\\.")[3] + ".Entity")
                    .getDeclaredField("entityCount");
            field.setAccessible(true);
            int id = field.getInt(null);
            field.set(null, id + 1);
            return id;
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return -1;
    }

    public void setLine(String line) {
        this.line = line;
        
        for (WeakReference<Player> p : viewers.getItems()) {
            if (p.get() != null) {
                CraftPlayer craftPlayer = (CraftPlayer) p.get();
                int protocol = craftPlayer.getHandle().playerConnection.networkManager.getVersion();
                List<AbstractPacket> packets = null;

                if (protocol >= 47) {
                    packets = generateMetadataPackets18(p.get());
                } else {
                    packets = generateMetadataPackets17(p.get());
                }

                for (AbstractPacket packet : packets) {
                    packet.sendPacket(p.get());
                }
            }
        }
    }
    
    public String getLineForPlayer(Player p) {
        if (vh != null) {
            return vh.onView(this, p, line);
        }
        return line;
    }
    
    private List<AbstractPacket> generateMetadataPackets17(Player p) {
        WrapperPlayServerEntityMetadata metadata = new WrapperPlayServerEntityMetadata();
        metadata.setEntityId(horseId);
        WrappedWatchableObject wwo = new WrappedWatchableObject(10, getLineForPlayer(p));
        metadata.setEntityMetadata(Arrays.asList(wwo));
        
        return Arrays.asList(metadata);
    }
    
    private List<AbstractPacket> generateMetadataPackets18(Player p) {
        WrapperPlayServerEntityMetadata metadata = new WrapperPlayServerEntityMetadata();
        metadata.setEntityId(horseId);
        WrappedWatchableObject wwo = new WrappedWatchableObject(2, getLineForPlayer(p));
        metadata.setEntityMetadata(Arrays.asList(wwo));
        
        return Arrays.asList(metadata);
    }
    
    public void addEveryoneAsViewer() {
        for (Player p : Bukkit.getOnlinePlayers()) {
            viewers.add(p);
        }
    }

    public void addViewer(Player p) {
        viewers.add(p);

        spawnForPlayer(p);
    }

    public void removeViewer(Player p) {
        viewers.remove(p);

        despawnForPlayer(p);
    }

    public void spawnForAll() {
        if (line == null) {
            throw new RuntimeException("Line is null!");
        }

        for (WeakReference<Player> p : viewers.getItems()) {
            if (p.get() != null) {
                spawnForPlayer(p.get());
            }
        }
    }

    public void spawnForPlayer(Player p) {
        if (!p.getLocation().getWorld().equals(location.getWorld())) {
            return;
        }
        CraftPlayer craftPlayer = (CraftPlayer) p;
        int protocol = craftPlayer.getHandle().playerConnection.networkManager.getVersion();
        List<AbstractPacket> packets = null;

        if (protocol >= 47) {
            packets = generateSpawnPackets18(p);
        } else {
            packets = generateSpawnPackets17(p);
        }

        for (AbstractPacket packet : packets) {
            packet.sendPacket(p);
        }
    }

    private List<AbstractPacket> generateSpawnPackets17(Player p) {
        // Create the wither skull packet first
        WrapperPlayServerSpawnEntity skull = new WrapperPlayServerSpawnEntity();
        skull.setEntityID(witherSkullId);

        skull.setX(location.getX());
        skull.setY(location.getY() + 56.28);
        skull.setZ(location.getZ());
        skull.setType(66); // Wither skull type

        // Now the horse packet
        WrapperPlayServerSpawnEntityLiving horse = new WrapperPlayServerSpawnEntityLiving();
        horse.setEntityID(horseId);
        horse.setType(EntityType.HORSE);
        horse.setX(location.getX());
        horse.setY(location.getY());
        horse.setZ(location.getZ());

        WrappedDataWatcher wdw = new WrappedDataWatcher(); // Create the data watcher
        wdw.setObject(10, line); // And set the horse name to the hologram text
        wdw.setObject(11, (byte) 1); // Always show nametag
        wdw.setObject(12, -1700000);

        horse.setMetadata(wdw);
        // And, finally, the mount 
        WrapperPlayServerAttachEntity attach = new WrapperPlayServerAttachEntity();
        attach.setVehicleId(witherSkullId);
        attach.setEntityId(horseId);

        List<AbstractPacket> packets = Arrays.asList(skull, horse, attach);

        return packets;
    }

    private List<AbstractPacket> generateSpawnPackets18(Player p) {
        // Because Armor Stand is a living entity...
        WrapperPlayServerSpawnEntityLivingWorkaround armorStand = new WrapperPlayServerSpawnEntityLivingWorkaround();

        armorStand.setEntityID(horseId);
        armorStand.setX(location.getX());
        armorStand.setY(location.getY() + 1.52);
        armorStand.setZ(location.getZ());
        armorStand.setType(30); // Armor Stand ID

        WrappedDataWatcher wdw = new WrappedDataWatcher(); // Create the data watcher
        wdw.setObject(0, (byte) 0x20); // Invisible
        wdw.setObject(2, line); // And set the armor stand name to the hologram text
        wdw.setObject(3, (byte) 1); // Always show nametag
        wdw.setObject(10, (byte) 0x16); // Zero Bounding Box (Marker)
        
        armorStand.setMetadata(wdw);

        List<AbstractPacket> packets = Arrays.asList(armorStand);
        return packets;
    }

    public void despawnForPlayer(Player p) {
        WrapperPlayServerEntityDestroy remove = new WrapperPlayServerEntityDestroy();

        remove.setEntities(new int[] { horseId }); // Do we need to add the witherSkullId too?

        remove.sendPacket(p);
    }

    public void despawnForAll() {
        WrapperPlayServerEntityDestroy remove = new WrapperPlayServerEntityDestroy();

        remove.setEntities(new int[] { horseId }); // Do we need to add the witherSkullId too?

        for (WeakReference<Player> p : viewers.getItems()) {
            if (p.get() != null) {
                remove.sendPacket(p.get());
            }
        }
    }
    
    public void teleport(Location l) {
        for (WeakReference<Player> p : viewers.getItems()) {
            if (p.get() != null) {
                teleport(p.get(), l);
            }
        }
    }
    
    public void teleport(Player p, Location l) {
        this.location = l;
        
        CraftPlayer craftPlayer = (CraftPlayer) p;
        int protocol = craftPlayer.getHandle().playerConnection.networkManager.getVersion();
        
        WrapperPlayServerEntityTeleport teleport = new WrapperPlayServerEntityTeleport();
        teleport.setEntityID(protocol >= 47 ? horseId : witherSkullId);
        teleport.setX(l.getX());
        teleport.setY(l.getY() + (protocol >= 47 ? 1.42 : 56.28));
        teleport.setZ(l.getZ());
        
        teleport.sendPacket(p);
    }
    
    public Hologram addLineBelow(String line) {
        Hologram hologram = new Hologram(getLocation().clone().add(0, -0.285, 0), line);
        return hologram;
    }
    
    public Hologram addLineAbove(String line) {
        Hologram hologram = new Hologram(getLocation().clone().add(0, 0.285, 0), line);
        return hologram;
    }
}

class ViewHandler {
    public String onView(Hologram hologram, Player player, String string) {
        return string;
    }
}