Create entity spawner utility class

api/src/main/java/com/bartlomiejpluta/base/util/world/EntitySpawner.java

@@ -0,0 +1,140 @@
+package com.bartlomiejpluta.base.util.world;
+
+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.map.model.GameMap;
+import com.bartlomiejpluta.base.internal.logic.Updatable;
+import com.bartlomiejpluta.base.util.math.Distance;
+import com.bartlomiejpluta.base.util.math.MathUtil;
+import com.bartlomiejpluta.base.util.random.DiceRoller;
+import lombok.NonNull;
+import org.joml.Vector2i;
+import org.joml.Vector2ic;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+import java.util.function.Supplier;
+
+
+public class EntitySpawner implements Updatable {
+   private static final int MAX_REPOSITION_ATTEMPTS = 10;
+   private final Random random = new Random();
+   private final List<Entity> spawnedEntities = new LinkedList<>();
+   private final List<Supplier<Entity>> spawners = new ArrayList<>();
+   private final Vector2ic origin;
+   private final GameMap map;
+   private final ObjectLayer layer;
+   private float maxTime = 10000f;
+   private int range = 4;
+   private int spawnChance = 50;
+   private DiceRoller countRoller = DiceRoller.of("1d4");
+   private Entity awayEntity;
+   private EventType<? extends Event> entityRemoveEvent;
+
+   private float accumulator = 10000f;
+   private float threshold;
+
+   public EntitySpawner(int x, int y, @NonNull GameMap map, @NonNull ObjectLayer layer) {
+      this.origin = new Vector2i(x, y);
+      this.map = map;
+      this.layer = layer;
+      drawThreshold();
+   }
+
+   public EntitySpawner maxTime(float maxTime) {
+      this.maxTime = maxTime;
+      this.accumulator = maxTime;
+      drawThreshold();
+      return this;
+   }
+
+   public EntitySpawner range(int range) {
+      this.range = range;
+      return this;
+   }
+
+   public EntitySpawner spawnChance(int percent) {
+      this.spawnChance = percent;
+      return this;
+   }
+
+   public EntitySpawner count(String dices) {
+      this.countRoller = DiceRoller.of(dices);
+      return this;
+   }
+
+   public EntitySpawner entityAway(@NonNull Entity awayEntity) {
+      this.awayEntity = awayEntity;
+      return this;
+   }
+
+   public EntitySpawner trackEntities(@NonNull EventType<? extends Event> entityRemoveEvent) {
+      this.entityRemoveEvent = entityRemoveEvent;
+      return this;
+   }
+
+   public EntitySpawner spawn(@NonNull Supplier<Entity> spawner) {
+      this.spawners.add(spawner);
+      return this;
+   }
+
+   private void drawThreshold() {
+      threshold = random.nextFloat(maxTime);
+   }
+
+   @Override
+   public void update(float dt) {
+      if (awayEntity != null && awayEntity.manhattanDistance(origin) <= range) {
+         return;
+      }
+
+      accumulator += dt * 1000;
+      if (accumulator >= threshold) {
+         spawn();
+         drawThreshold();
+         accumulator = 0f;
+      }
+   }
+
+   private void spawn() {
+      if (random.nextInt(100) < spawnChance) {
+         return;
+      }
+
+      var count = Math.max(0, countRoller.roll() - spawnedEntities.size());
+      for (int i = 0; i < count; ++i) {
+         var attempts = 0;
+         var coordinates = new Vector2i();
+
+         do {
+            coordinates.x = MathUtil.clamp(origin.x() + random.nextInt(2 * range) - range, 0, map.getColumns() - 1);
+            coordinates.y = MathUtil.clamp(origin.y() + random.nextInt(2 * range) - range, 0, map.getRows() - 1);
+
+            if (!layer.isTileReachable(coordinates)) {
+               ++attempts;
+               continue;
+            }
+
+            if (attempts > MAX_REPOSITION_ATTEMPTS) {
+               return;
+            }
+
+         } while (Distance.manhattan(origin, coordinates) <= range);
+
+         var spawner = spawners.get(random.nextInt(spawners.size()));
+         var entity = spawner.get();
+
+         entity.setCoordinates(coordinates);
+         layer.addEntity(entity);
+
+         if (entityRemoveEvent != null) {
+            spawnedEntities.add(entity);
+            entity.addEventListener(entityRemoveEvent, e -> spawnedEntities.remove(entity));
+         }
+      }
+   }
+}