Implement event system scaffolding

api/src/main/java/com/bartlomiejpluta/base/api/entity/Entity.java

@@ -1,6 +1,7 @@
 package com.bartlomiejpluta.base.api.entity;
 
 import com.bartlomiejpluta.base.api.animation.Animated;
+import com.bartlomiejpluta.base.api.event.Reactive;
 import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
 import com.bartlomiejpluta.base.api.move.Direction;
 import com.bartlomiejpluta.base.api.move.Movable;
@@ -9,7 +10,7 @@ import com.bartlomiejpluta.base.internal.render.Renderable;
 
 import java.util.concurrent.CompletableFuture;
 
-public interface Entity extends Movable, Animated, Renderable, Updatable {
+public interface Entity extends Reactive, Movable, Animated, Renderable, Updatable {
 
    Direction getFaceDirection();
 

api/src/main/java/com/bartlomiejpluta/base/api/entity/EntityStepInListener.java

@@ -1,7 +0,0 @@
-package com.bartlomiejpluta.base.api.entity;
-
-import com.bartlomiejpluta.base.api.move.Movement;
-
-public interface EntityStepInListener extends Entity {
-   void onEntityStepIn(Movement movement, Entity entity);
-}

api/src/main/java/com/bartlomiejpluta/base/api/entity/EntityStepOutListener.java

@@ -1,7 +0,0 @@
-package com.bartlomiejpluta.base.api.entity;
-
-import com.bartlomiejpluta.base.api.move.Movement;
-
-public interface EntityStepOutListener extends Entity {
-   void onEntityStepOut(Movement movement, Entity entity);
-}

api/src/main/java/com/bartlomiejpluta/base/api/event/Event.java

@@ -0,0 +1,5 @@
+package com.bartlomiejpluta.base.api.event;
+
+public interface Event {
+   EventType<? extends Event> getType();
+}

api/src/main/java/com/bartlomiejpluta/base/api/event/EventType.java

@@ -0,0 +1,10 @@
+package com.bartlomiejpluta.base.api.event;
+
+import lombok.EqualsAndHashCode;
+import lombok.RequiredArgsConstructor;
+
+@EqualsAndHashCode
+@RequiredArgsConstructor
+public final class EventType<E extends Event> {
+   private final String type;
+}

api/src/main/java/com/bartlomiejpluta/base/api/event/Reactive.java

@@ -0,0 +1,11 @@
+package com.bartlomiejpluta.base.api.event;
+
+import java.util.function.Consumer;
+
+public interface Reactive {
+   <E extends Event> void handleEvent(E event);
+
+   <E extends Event> void addEventListener(EventType<E> type, Consumer<E> listener);
+
+   <E extends Event> void removeEventListener(EventType<E> type, Consumer<E> listener);
+}

api/src/main/java/com/bartlomiejpluta/base/api/map/layer/object/ObjectLayer.java

@@ -1,6 +1,7 @@
 package com.bartlomiejpluta.base.api.map.layer.object;
 
 import com.bartlomiejpluta.base.api.entity.Entity;
+import com.bartlomiejpluta.base.api.event.Event;
 import com.bartlomiejpluta.base.api.map.layer.base.Layer;
 import com.bartlomiejpluta.base.api.move.Movement;
 import org.joml.Vector2ic;
@@ -24,8 +25,5 @@ public interface ObjectLayer extends Layer {
 
    void pushMovement(Movement movement);
 
-   // Notifiers
-   void notifyEntityStepIn(Movement movement, Entity entity);
-
-   void notifyEntityStepOut(Movement movement, Entity entity);
+   void fireEvent(Event event);
 }

api/src/main/java/com/bartlomiejpluta/base/api/move/EntityMovement.java

@@ -27,7 +27,7 @@ public final class EntityMovement implements Movement {
    public boolean perform() {
       var result = object.move(this);
       if (result) {
-         object.getLayer().notifyEntityStepOut(this, object);
+         object.getLayer().fireEvent(new MoveEvent(MoveEvent.Action.BEGIN, object, this));
       }
 
       return result;
@@ -40,6 +40,6 @@ public final class EntityMovement implements Movement {
 
    @Override
    public void onFinish() {
-      object.getLayer().notifyEntityStepIn(this, object);
+      object.getLayer().fireEvent(new MoveEvent(MoveEvent.Action.END, object, this));
    }
 }

api/src/main/java/com/bartlomiejpluta/base/api/move/MoveEvent.java

@@ -0,0 +1,23 @@
+package com.bartlomiejpluta.base.api.move;
+
+import com.bartlomiejpluta.base.api.event.Event;
+import com.bartlomiejpluta.base.api.event.EventType;
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@Getter
+@RequiredArgsConstructor
+public final class MoveEvent implements Event {
+   public enum Action {BEGIN, END}
+
+   private final Action action;
+   private final Movable movable;
+   private final Movement movement;
+
+   @Override
+   public EventType<? extends Event> getType() {
+      return TYPE;
+   }
+
+   public static EventType<MoveEvent> TYPE = new EventType<>("MOVE_EVENT");
+}

api/src/main/java/com/bartlomiejpluta/base/lib/entity/EntityDelegate.java

@@ -2,6 +2,8 @@ package com.bartlomiejpluta.base.lib.entity;
 
 import com.bartlomiejpluta.base.api.camera.Camera;
 import com.bartlomiejpluta.base.api.entity.Entity;
+import com.bartlomiejpluta.base.api.event.Event;
+import com.bartlomiejpluta.base.api.event.EventType;
 import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
 import com.bartlomiejpluta.base.api.move.Direction;
 import com.bartlomiejpluta.base.api.move.EntityMovement;
@@ -14,6 +16,7 @@ import org.joml.Vector2fc;
 import org.joml.Vector2ic;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.function.Consumer;
 
 public abstract class EntityDelegate implements Entity {
    protected final Entity entity;
@@ -267,6 +270,21 @@ public abstract class EntityDelegate implements Entity {
       entity.setZIndex(zIndex);
    }
 
+   @Override
+   public <E extends Event> void handleEvent(E event) {
+      entity.handleEvent(event);
+   }
+
+   @Override
+   public <E extends Event> void addEventListener(EventType<E> type, Consumer<E> listener) {
+      entity.addEventListener(type, listener);
+   }
+
+   @Override
+   public <E extends Event> void removeEventListener(EventType<E> type, Consumer<E> listener) {
+      entity.removeEventListener(type, listener);
+   }
+
    @Override
    public CompletableFuture<Void> performInstantAnimation() {
       return entity.performInstantAnimation();

engine/src/main/java/com/bartlomiejpluta/base/engine/world/entity/model/DefaultEntity.java

@@ -1,6 +1,8 @@
 package com.bartlomiejpluta.base.engine.world.entity.model;
 
 import com.bartlomiejpluta.base.api.entity.Entity;
+import com.bartlomiejpluta.base.api.event.Event;
+import com.bartlomiejpluta.base.api.event.EventType;
 import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
 import com.bartlomiejpluta.base.api.move.Direction;
 import com.bartlomiejpluta.base.api.move.EntityMovement;
@@ -17,10 +19,9 @@ import org.joml.Vector2f;
 import org.joml.Vector2fc;
 import org.joml.Vector2i;
 
-import java.util.LinkedList;
-import java.util.Map;
-import java.util.Queue;
+import java.util.*;
 import java.util.concurrent.CompletableFuture;
+import java.util.function.Consumer;
 
 import static java.util.Objects.requireNonNull;
 
@@ -33,6 +34,8 @@ public class DefaultEntity extends MovableSprite implements Entity {
    private final Vector2f entityScale = new Vector2f(1, 1);
    private Vector2fc entitySetSize;
 
+   private final Map<EventType<?>, List<Consumer<? extends Event>>> listeners = new HashMap<>();
+
    @Getter
    @Setter
    private int zIndex = 0;
@@ -233,6 +236,42 @@ public class DefaultEntity extends MovableSprite implements Entity {
       return entityScale.y;
    }
 
+   @SuppressWarnings("unchecked")
+   @Override
+   public <E extends Event> void handleEvent(E event) {
+      var list = listeners.get(event.getType());
+      if (list != null) {
+         for (var listener : list) {
+            ((Consumer<E>) listener).accept(event);
+         }
+      }
+   }
+
+   @Override
+   public <E extends Event> void addEventListener(EventType<E> type, Consumer<E> listener) {
+      var list = this.listeners.get(type);
+
+      if (list != null) {
+         list.add(listener);
+      } else {
+         list = new ArrayList<>();
+         list.add(listener);
+         listeners.put(type, list);
+      }
+   }
+
+   @Override
+   public <E extends Event> void removeEventListener(EventType<E> type, Consumer<E> listener) {
+      var list = this.listeners.get(type);
+
+      if (list != null) {
+         list.remove(listener);
+         if (list.isEmpty()) {
+            this.listeners.remove(type);
+         }
+      }
+   }
+
    @Override
    public void update(float dt) {
       super.update(dt);

engine/src/main/java/com/bartlomiejpluta/base/engine/world/map/layer/object/DefaultObjectLayer.java

@@ -3,8 +3,7 @@ package com.bartlomiejpluta.base.engine.world.map.layer.object;
 import com.bartlomiejpluta.base.api.ai.NPC;
 import com.bartlomiejpluta.base.api.camera.Camera;
 import com.bartlomiejpluta.base.api.entity.Entity;
-import com.bartlomiejpluta.base.api.entity.EntityStepInListener;
-import com.bartlomiejpluta.base.api.entity.EntityStepOutListener;
+import com.bartlomiejpluta.base.api.event.Event;
 import com.bartlomiejpluta.base.api.input.KeyEvent;
 import com.bartlomiejpluta.base.api.input.KeyEventHandler;
 import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
@@ -20,7 +19,6 @@ import org.joml.Vector2ic;
 
 import java.util.ArrayList;
 import java.util.LinkedList;
-import java.util.List;
 import java.util.Queue;
 
 import static java.lang.Float.compare;
@@ -31,10 +29,6 @@ public class DefaultObjectLayer extends BaseLayer implements ObjectLayer, KeyEve
    @Getter
    private final ArrayList<Entity> entities = new ArrayList<>();
 
-   private final List<EntityStepInListener> stepInListeners = new ArrayList<>();
-   private final List<EntityStepOutListener> stepOutListeners = new ArrayList<>();
-   private final List<KeyEventHandler> keyEventHandlers = new ArrayList<>();
-
    @Getter
    private final PassageAbility[][] passageMap;
 
@@ -58,18 +52,6 @@ public class DefaultObjectLayer extends BaseLayer implements ObjectLayer, KeyEve
          layer.entities.remove(entity);
       }
 
-      if (entity instanceof EntityStepInListener) {
-         stepInListeners.add((EntityStepInListener) entity);
-      }
-
-      if (entity instanceof EntityStepOutListener) {
-         stepOutListeners.add((EntityStepOutListener) entity);
-      }
-
-      if (entity instanceof KeyEventHandler) {
-         keyEventHandlers.add((KeyEventHandler) entity);
-      }
-
       entity.setStepSize(stepSize.x(), stepSize.y());
       entities.add(entity);
 
@@ -80,18 +62,6 @@ public class DefaultObjectLayer extends BaseLayer implements ObjectLayer, KeyEve
    public void removeEntity(Entity entity) {
       entities.remove(entity);
 
-      if (entity instanceof EntityStepInListener) {
-         stepInListeners.remove(entity);
-      }
-
-      if (entity instanceof EntityStepOutListener) {
-         stepOutListeners.remove(entity);
-      }
-
-      if (entity instanceof KeyEventHandler) {
-         keyEventHandlers.remove(entity);
-      }
-
       entity.onRemove(this);
    }
 
@@ -149,7 +119,6 @@ public class DefaultObjectLayer extends BaseLayer implements ObjectLayer, KeyEve
 
       while (!movements.isEmpty()) {
          var movement = movements.poll();
-         var from = movement.getFrom();
          var to = movement.getTo();
          if (isTileReachable(to)) {
             movement.perform();
@@ -189,26 +158,19 @@ public class DefaultObjectLayer extends BaseLayer implements ObjectLayer, KeyEve
 
    @Override
    public void handleKeyEvent(KeyEvent event) {
-      for (var handler : keyEventHandlers) {
-         if (event.isConsumed()) {
-            return;
-         }
 
-         handler.handleKeyEvent(event);
-      }
    }
 
+   @SuppressWarnings("ForLoopReplaceableByForEach")
    @Override
-   public void notifyEntityStepIn(Movement movement, Entity entity) {
-      for (var listener : stepInListeners) {
-         listener.onEntityStepIn(movement, entity);
-      }
-   }
-
-   @Override
-   public void notifyEntityStepOut(Movement movement, Entity entity) {
-      for (var listener : stepOutListeners) {
-         listener.onEntityStepOut(movement, entity);
+   public void fireEvent(Event event) {
+      // Disclaimer
+      // For the sake of an easy adding and removing
+      // entities from the entity.update() method inside
+      // the loop, the loop itself has been implemented
+      // as plain old C-style for loop.
+      for (int i = 0; i < entities.size(); ++i) {
+         entities.get(i).handleEvent(event);
       }
    }
 }