Implement simple follow & attack AI for enemies

src/main/java/com/bartlomiejpluta/demo/ai/SimpleEnemyAI.java

@@ -0,0 +1,43 @@
+package com.bartlomiejpluta.demo.ai;
+
+import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
+
+import com.bartlomiejpluta.base.util.pathfinder.*;
+import com.bartlomiejpluta.base.api.ai.*;
+import com.bartlomiejpluta.base.lib.ai.*;
+
+import com.bartlomiejpluta.demo.entity.Enemy;
+import com.bartlomiejpluta.demo.entity.Character;
+
+public class SimpleEnemyAI extends FollowEntityAI<Enemy, Character> {
+	private static final int ASTAR_MAX_NODES = 100;
+	private static final int IDLE_MOVEMENT_INTERVAL = 4;
+	private final AI idle;
+	private final int range;
+
+	public SimpleEnemyAI(Enemy enemy, Character target, int range) {
+		super(new AstarPathFinder(ASTAR_MAX_NODES), enemy, target);
+		this.range = range;
+		this.idle = new RandomMovementAI(enemy, IDLE_MOVEMENT_INTERVAL);
+	}
+
+	@Override
+	protected boolean sees(Enemy enemy, Character target, ObjectLayer layer, int distance) {
+		return distance < range;
+	}
+
+	@Override
+	protected void interact(Enemy enemy, Character target, ObjectLayer layer, float dt) {
+		enemy.attack();
+	}
+
+	@Override
+	protected void follow(Enemy enemy, Character target, ObjectLayer layer, float dt) {
+		// noop
+	}
+
+	@Override
+	protected void idle(Enemy enemy, Character target, ObjectLayer layer, float dt) {
+		idle.nextActivity(layer, dt);
+	}
+}

src/main/java/com/bartlomiejpluta/demo/entity/Enemy.java

@@ -1,17 +1,21 @@
 package com.bartlomiejpluta.demo.entity;
 
 import lombok.*;
+
 import com.bartlomiejpluta.base.api.context.Context;
 import com.bartlomiejpluta.base.api.entity.Entity;
 import com.bartlomiejpluta.base.api.ai.AI;
 import com.bartlomiejpluta.base.api.ai.NPC;
+import com.bartlomiejpluta.base.api.move.MoveEvent;
 
 import com.bartlomiejpluta.base.lib.ai.NoopAI;
 
 import com.bartlomiejpluta.demo.runner.DemoRunner;
 import com.bartlomiejpluta.demo.database.model.EnemyModel;
-
 import com.bartlomiejpluta.demo.world.weapon.MeleeWeapon;
+import com.bartlomiejpluta.demo.event.EnemyDiedEvent;
+import com.bartlomiejpluta.demo.ai.*;
+
 
 public class Enemy extends Character implements NPC {
 	private final EnemyModel template;
@@ -41,10 +45,23 @@ public class Enemy extends Character implements NPC {
 		setZIndex(-1);
 
 		ai = NoopAI.INSTANCE;
+
+		getLayer().handleEvent(new EnemyDiedEvent(this));
 	}
 
 	@Override
 	public String toString() {
 		return template.getName() + "@" + hashCode();
 	}
+
+	public Enemy followAndAttack(Character target, int range) {
+		var ai = new SimpleEnemyAI(this, target, range);
+
+		addEventListener(MoveEvent.TYPE, e -> ai.recomputePath());
+		addEventListener(EnemyDiedEvent.TYPE, e -> ai.recomputePath());
+
+		this.ai = ai;
+
+		return this;
+	}
 }

src/main/java/com/bartlomiejpluta/demo/event/EnemyDiedEvent.java

@@ -0,0 +1,20 @@
+package com.bartlomiejpluta.demo.event;
+
+import lombok.*;
+
+import com.bartlomiejpluta.base.api.event.*;
+import com.bartlomiejpluta.base.lib.event.*;
+import com.bartlomiejpluta.demo.entity.Enemy;
+
+@Getter
+@RequiredArgsConstructor
+public class EnemyDiedEvent extends BaseEvent {
+	public static final EventType<EnemyDiedEvent> TYPE = new EventType<>("ENEMY_DIED_EVENT");
+
+	private final Enemy enemy;
+
+	@Override
+	public EventType<EnemyDiedEvent> getType() {
+		return TYPE;
+	}
+}

src/main/java/com/bartlomiejpluta/demo/map/BaseMapHandler.java

@@ -75,9 +75,10 @@ public abstract class BaseMapHandler implements MapHandler {
 		cameraController.update();
 	}
 
-	public void enemy(int x, int y, @NonNull String id) {
+	public Enemy enemy(int x, int y, @NonNull String id) {
 		var enemy = new Enemy(context, runner.getEnemyDAO().get(id));
 		enemy.setCoordinates(x, y);
 		mainLayer.addEntity(enemy);
+		return enemy;
 	}
 }