Add a super simple follow trait

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

@@ -73,6 +73,7 @@ import net.citizensnpcs.trait.Anchors;
 import net.citizensnpcs.trait.ArmorStandTrait;
 import net.citizensnpcs.trait.Controllable;
 import net.citizensnpcs.trait.CurrentLocation;
+import net.citizensnpcs.trait.FollowTrait;
 import net.citizensnpcs.trait.Gravity;
 import net.citizensnpcs.trait.HorseModifiers;
 import net.citizensnpcs.trait.LookClose;
@@ -509,6 +510,24 @@ public class NPCCommands {
         Messaging.sendTr(sender, flyable ? Messages.FLYABLE_SET : Messages.FLYABLE_UNSET, npc.getName());
     }
 
+    @Command(
+            aliases = { "npc" },
+            usage = "follow (player name) (-p[rotect])",
+            desc = "Toggles NPC following you",
+            modifiers = { "follow" },
+            min = 1,
+            max = 1,
+            permission = "citizens.npc.follow")
+    public void follow(CommandContext args, Player sender, NPC npc) throws CommandException {
+        boolean protect = args.hasFlag('p');
+        String name = sender.getName();
+        if (args.argsLength() > 1) {
+            name = args.getString(1);
+        }
+        boolean following = npc.getTrait(FollowTrait.class).toggle(name, protect);
+        Messaging.sendTr(sender, following ? Messages.FOLLOW_SET : Messages.FOLLOW_UNSET, npc.getName(), name);
+    }
+
     @Command(
             aliases = { "npc" },
             usage = "gamemode [gamemode]",

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

@@ -24,6 +24,7 @@ import net.citizensnpcs.trait.Anchors;
 import net.citizensnpcs.trait.ArmorStandTrait;
 import net.citizensnpcs.trait.Controllable;
 import net.citizensnpcs.trait.CurrentLocation;
+import net.citizensnpcs.trait.FollowTrait;
 import net.citizensnpcs.trait.Gravity;
 import net.citizensnpcs.trait.HorseModifiers;
 import net.citizensnpcs.trait.LookClose;
@@ -53,11 +54,12 @@ public class CitizensTraitFactory implements TraitFactory {
         registerTrait(TraitInfo.create(ArmorStandTrait.class));
         registerTrait(TraitInfo.create(Anchors.class));
         registerTrait(TraitInfo.create(Controllable.class));
+        registerTrait(TraitInfo.create(CurrentLocation.class));
         registerTrait(TraitInfo.create(Equipment.class));
+        registerTrait(TraitInfo.create(FollowTrait.class));
         registerTrait(TraitInfo.create(Gravity.class));
         registerTrait(TraitInfo.create(HorseModifiers.class));
         registerTrait(TraitInfo.create(Inventory.class));
-        registerTrait(TraitInfo.create(CurrentLocation.class));
         registerTrait(TraitInfo.create(LookClose.class));
         registerTrait(TraitInfo.create(OcelotModifiers.class));
         registerTrait(TraitInfo.create(Owner.class));

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

@@ -0,0 +1,68 @@
+package net.citizensnpcs.trait;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.entity.EntityDamageByEntityEvent;
+
+import net.citizensnpcs.api.persistence.Persist;
+import net.citizensnpcs.api.trait.Trait;
+import net.citizensnpcs.api.trait.TraitName;
+
+@TraitName("followtrait")
+public class FollowTrait extends Trait {
+    @Persist
+    private boolean active = false;
+    @Persist
+    private String followingName;
+    private Player player;
+    @Persist("protect")
+    private boolean protect;
+
+    public FollowTrait() {
+        super("followtrait");
+    }
+
+    private boolean isActive() {
+        return active && npc.isSpawned() && player != null && npc.getEntity().getWorld().equals(player.getWorld());
+    }
+
+    @EventHandler
+    public void onEntityDamage(EntityDamageByEntityEvent event) {
+        if (isActive() && event.getEntity().equals(player)) {
+            npc.getNavigator().setTarget(event.getDamager(), true);
+        }
+    }
+
+    @Override
+    public void run() {
+        if (player == null || !player.isValid()) {
+            if (followingName == null)
+                return;
+            player = Bukkit.getPlayerExact(followingName);
+            if (player == null) {
+                return;
+            }
+        }
+        if (!isActive()) {
+            return;
+        }
+        if (!npc.getNavigator().isNavigating()) {
+            npc.getNavigator().setTarget(player, false);
+        }
+    }
+
+    public boolean toggle(String name, boolean protect) {
+        this.protect = protect;
+        if (name.equalsIgnoreCase(this.followingName) || this.followingName == null) {
+            this.active = !active;
+        }
+        this.followingName = name;
+        if (npc.getNavigator().isNavigating() && player != null
+                && player == npc.getNavigator().getEntityTarget().getTarget()) {
+            npc.getNavigator().cancelNavigation();
+        }
+        this.player = null;
+        return this.active;
+    }
+}

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

@@ -80,6 +80,9 @@ public class Messages {
     public static final String FAILED_TO_REMOVE = "citizens.commands.trait.failed-to-remove";
     public static final String FLYABLE_SET = "citizens.commands.npc.flyable.set";
     public static final String FLYABLE_UNSET = "citizens.commands.npc.flyable.unset";
+    public static final String FOLLOW_PLAYER_NOT_INGAME = "citizens.commands.npc.follow.player-not-ingame";
+    public static final String FOLLOW_SET = "citizens.commands.npc.follow.set";
+    public static final String FOLLOW_UNSET = "citizens.commands.npc.follow.unset";
     public static final String FROM_ENTITY_NOT_FOUND = "citizens.commands.npc.tpto.from-not-found";
     public static final String GAMEMODE_DESCRIBE = "citizens.commands.npc.gamemode.describe";
     public static final String GAMEMODE_INVALID = "citizens.commands.npc.gamemode.invalid";

main/src/main/resources/messages_en.properties

@@ -39,6 +39,8 @@ citizens.commands.npc.create.no-player-for-spawn=No player could be found by tha
 citizens.commands.npc.despawn.despawned=You despawned [[{0}]].
 citizens.commands.npc.flyable.set=[[{0}]] is now flyable.
 citizens.commands.npc.flyable.unset=[[{0}]] is no longer flyable.
+citizens.commands.npc.follow.set=[[{0}]] is now following [[{1}]]. 
+citizens.commands.npc.follow.unset=[[{0}]] is no longer following anyone.
 citizens.commands.npc.gamemode.describe={0}''s gamemode is [[{1}]].
 citizens.commands.npc.gamemode.invalid={0} is not a valid gamemode.
 citizens.commands.npc.gamemode.set=Gamemode set to [[{0}]].