Add very basic /npc hologram command

main/src/main/java/net/citizensnpcs/commands/NPCCommands.java

@@ -92,6 +92,7 @@ import net.citizensnpcs.trait.EndermanTrait;
 import net.citizensnpcs.trait.FollowTrait;
 import net.citizensnpcs.trait.GameModeTrait;
 import net.citizensnpcs.trait.Gravity;
+import net.citizensnpcs.trait.HologramTrait;
 import net.citizensnpcs.trait.HorseModifiers;
 import net.citizensnpcs.trait.LookClose;
 import net.citizensnpcs.trait.MountTrait;
@@ -701,6 +702,25 @@ public class NPCCommands {
         Messaging.sendTr(sender, key, npc.getName());
     }
 
+    @Command(
+            aliases = { "npc" },
+            usage = "hologram [text]",
+            desc = "Controls NPC hologram",
+            modifiers = { "hologram" },
+            min = 1,
+            max = -1,
+            permission = "citizens.npc.hologram")
+    public void hologram(CommandContext args, CommandSender sender, NPC npc) {
+        HologramTrait trait = npc.getTrait(HologramTrait.class);
+        if (args.argsLength() == 1) {
+            trait.setText(null);
+            Messaging.sendTr(sender, Messages.HOLOGRAM_TEXT_REMOVED);
+        } else {
+            trait.setText(args.getJoinedStrings(1));
+            Messaging.sendTr(sender, Messages.HOLOGRAM_TEXT_SET);
+        }
+    }
+
     @Command(
             aliases = { "npc" },
             usage = "horse|llama|donkey|mule (--color color) (--type type) (--style style) (-cb)",

main/src/main/java/net/citizensnpcs/npc/CitizensTraitFactory.java

@@ -31,6 +31,7 @@ import net.citizensnpcs.trait.EndermanTrait;
 import net.citizensnpcs.trait.FollowTrait;
 import net.citizensnpcs.trait.GameModeTrait;
 import net.citizensnpcs.trait.Gravity;
+import net.citizensnpcs.trait.HologramTrait;
 import net.citizensnpcs.trait.HorseModifiers;
 import net.citizensnpcs.trait.LookClose;
 import net.citizensnpcs.trait.MountTrait;
@@ -69,6 +70,7 @@ public class CitizensTraitFactory implements TraitFactory {
         registerTrait(TraitInfo.create(GameModeTrait.class));
         registerTrait(TraitInfo.create(Gravity.class));
         registerTrait(TraitInfo.create(HorseModifiers.class));
+        registerTrait(TraitInfo.create(HologramTrait.class));
         registerTrait(TraitInfo.create(Inventory.class));
         registerTrait(TraitInfo.create(LookClose.class));
         registerTrait(TraitInfo.create(OcelotModifiers.class));

main/src/main/java/net/citizensnpcs/trait/HologramTrait.java

@@ -0,0 +1,71 @@
+package net.citizensnpcs.trait;
+
+import org.bukkit.entity.ArmorStand;
+import org.bukkit.entity.EntityType;
+
+import net.citizensnpcs.api.CitizensAPI;
+import net.citizensnpcs.api.npc.MemoryNPCDataStore;
+import net.citizensnpcs.api.npc.NPC;
+import net.citizensnpcs.api.npc.NPCRegistry;
+import net.citizensnpcs.api.persistence.Persist;
+import net.citizensnpcs.api.trait.Trait;
+import net.citizensnpcs.api.trait.TraitName;
+import net.citizensnpcs.api.util.Placeholders;
+
+/**
+ * Persists a hologram attached to the NPC.
+ */
+@TraitName("hologramtrait")
+public class HologramTrait extends Trait {
+    private final NPCRegistry registry = CitizensAPI
+            .createAnonymousNPCRegistry(new MemoryNPCDataStore());
+    private NPC hologramNPC;
+    @Persist
+    private String text;
+
+    public HologramTrait() {
+        super("hologramtrait");
+    }
+
+    @Override
+    public void onDespawn() {
+        if (hologramNPC != null) {
+            hologramNPC.destroy();
+        }
+    }
+
+    @Override
+    public void onSpawn() {
+        hologramNPC = registry.createNPC(EntityType.ARMOR_STAND, "");
+        ArmorStandTrait trait = hologramNPC.getTrait(ArmorStandTrait.class);
+        trait.setVisible(false);
+        trait.setSmall(true);
+        hologramNPC.spawn(npc.getStoredLocation());
+        hologramNPC.getEntity().setInvulnerable(true);
+        hologramNPC.getEntity().setGravity(false);
+    }
+
+    @Override
+    public void run() {
+        if (!npc.isSpawned())
+            return;
+        ArmorStand hologram = (ArmorStand) hologramNPC.getEntity();
+        if (hologram == null)
+            return;
+        if (hologram.getVehicle() == null || hologram.getVehicle() != npc.getEntity()) {
+            if (hologram.getVehicle() != npc.getEntity()) {
+                hologram.leaveVehicle();
+            }
+            npc.getEntity().addPassenger(hologram);
+        }
+        if (text != null && !text.isEmpty()) {
+            hologramNPC.setName(Placeholders.replace(text, null, npc));
+        } else {
+        }
+    }
+
+    public void setText(String text) {
+        this.text = text;
+    }
+
+}

main/src/main/java/net/citizensnpcs/util/Messages.java

@@ -134,6 +134,8 @@ public class Messages {
     public static final String GUIDED_WAYPOINT_EDITOR_ALREADY_TAKEN = "citizens.editors.waypoints.guided.already-taken";
     public static final String GUIDED_WAYPOINT_EDITOR_BEGIN = "citizens.editors.waypoints.guided.begin";
     public static final String GUIDED_WAYPOINT_EDITOR_END = "citizens.editors.waypoints.guided.end";
+    public static final String HOLOGRAM_TEXT_REMOVED = "citizens.commands.npc.hologram.text-removed";
+    public static final String HOLOGRAM_TEXT_SET = "citizens.commands.npc.hologram.text-set";
     public static final String HORSE_CHEST_SET = "citizens.commands.npc.horse.chest-set";
     public static final String HORSE_CHEST_UNSET = "citizens.commands.npc.horse.chest-unset";
     public static final String HORSE_COLOR_SET = "citizens.commands.npc.horse.color-set";

main/src/main/resources/messages_en.properties

@@ -87,6 +87,8 @@ citizens.commands.npc.glowing.unset=[[{0}]] is no longer glowing.
 citizens.commands.npc.glowing.color-set=[[{0}]]''s glowing color set to {1}]].
 citizens.commands.npc.guardian.elder-unset=[[{0}]] is no longer an elder guardian.
 citizens.commands.npc.guardian.elder-set=[[{0}]] is now an elder guardian.
+citizens.commands.npc.hologram.text-set=Set hologram text to [[{0}]].
+citizens.commands.npc.hologram.text-removed=Removed hologram text.
 citizens.commands.npc.horse.chest-set=The horse is now carrying a chest.
 citizens.commands.npc.horse.chest-unset=The horse is no longer carrying a chest.
 citizens.commands.npc.horse.color-set=The horse''s color was set to [[{0}]].