Add support for dynamic creature spawning

Position of spawn in zone is random instead of a static point

#713

data/conf/zones.xsd

@@ -25,6 +25,7 @@
 					maxOccurs="unbounded"/>
 				<element name="associated" type="Q1:associatedZones" minOccurs="0"
 					maxOccurs="1"/>
+				<element name="spawns" type="Q1:spawnsGroup" minOccurs="0" maxOccurs="1"/>
 			</choice>
 		</sequence>
 		<attribute name="name" type="string"/>
@@ -178,4 +179,27 @@
 		<attribute name="zones" type="string" use="required"></attribute>
 	</complexType>
 
+	<complexType name="spawnsGroup">
+		<choice minOccurs="1" maxOccurs="unbounded">
+			<element name="creatures" type="Q1:creaturesSpawnsGroup" minOccurs="0" maxOccurs="1"/>
+		</choice>
+	</complexType>
+
+	<!--
+		adding a dynamic creature spawner to zone:
+			<spawns>
+				<creatures>
+					<parameter name="bat">15</parameter>
+				</creatures>
+			</spans> 
+
+		"name" attribute is the creature to be spawned, value is the maximum number that can be active
+		at same time
+	-->
+	<complexType name="creaturesSpawnsGroup">
+		<sequence>
+			<element name="parameter" type="Q1:parameterType" minOccurs="1" maxOccurs="unbounded"/>
+		</sequence>
+	</complexType>
+
 </schema>

doc/CHANGES.txt

@@ -34,6 +34,7 @@ Changelog
 - new achievements:
   - 30 Minutes or Less: Deliver 25 hot pizzas
 - Balduin allows requesting different item for Ultimate Collector quest
+- support added for dynamic creature spawning
 
 *web client*
 - fixed text extending past edge of notification bubbles

src/games/stendhal/server/core/config/ZonesXMLLoader.java

@@ -38,6 +38,7 @@
 import games.stendhal.common.tiled.StendhalMapStructure;
 import games.stendhal.server.core.config.zone.AttributesXMLReader;
 import games.stendhal.server.core.config.zone.ConfiguratorXMLReader;
+import games.stendhal.server.core.config.zone.CreatureSpawnsXMLReader;
 import games.stendhal.server.core.config.zone.EntitySetupXMLReader;
 import games.stendhal.server.core.config.zone.PortalSetupXMLReader;
 import games.stendhal.server.core.config.zone.RegionNameSubstitutionHelper;
@@ -60,6 +61,8 @@ public final class ZonesXMLLoader {
 
 	/** Zone attributes reader. */
 	private static final SetupXMLReader attributesReader = new AttributesXMLReader();
+	/** Dynamically spawned creatures. */
+	private static final SetupXMLReader creatureSpawnsReader = new CreatureSpawnsXMLReader();
 	/**
 	 * The ConfiguratorDescriptor XML reader.
 	 */
@@ -419,6 +422,13 @@ public ZoneDesc readZone(final Element element) {
 				continue;
 			} else if (tag.equals("associated")) {
 				desc.setAssociatedZones(child.getAttribute("zones"));
+			} else if (tag.equals("spawns")) {
+				for (final Element spawn: XMLUtil.getElements(child)) {
+					final String spawnType = spawn.getTagName();
+					if ("creatures".equals(spawnType)) {
+						setupDesc = creatureSpawnsReader.read(spawn);
+					}
+				}
 			} else {
 				logger.warn("Zone [" + name + "] has unknown element: " + tag);
 				continue;

src/games/stendhal/server/core/config/zone/CreatureSpawnsXMLReader.java

@@ -0,0 +1,56 @@
+/***************************************************************************
+ *                    Copyright © 2024 - Faiumoni e. V.                    *
+ ***************************************************************************
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+package games.stendhal.server.core.config.zone;
+
+import java.util.Map;
+
+import org.apache.log4j.Logger;
+import org.w3c.dom.Element;
+
+import games.stendhal.common.MathHelper;
+import games.stendhal.server.core.engine.StendhalRPZone;
+import games.stendhal.server.entity.mapstuff.spawner.DynamicCreatureSpawner;
+
+
+/**
+ * Parses info for dynamically spawned creatures.
+ */
+public class CreatureSpawnsXMLReader extends SetupXMLReader {
+
+	private static Logger logger = Logger.getLogger(CreatureSpawnsXMLReader.class);
+
+
+	@Override
+	public SetupDescriptor read(final Element element) {
+		final CreatureSpawnsDescriptor desc = new CreatureSpawnsDescriptor();
+		readParameters(desc, element);
+		return desc;
+	}
+
+	private static class CreatureSpawnsDescriptor extends SetupDescriptor {
+		@Override
+		public void setup(final StendhalRPZone zone) {
+			final DynamicCreatureSpawner spawner = new DynamicCreatureSpawner(zone);
+			final Map<String, String> params = getParameters();
+			for (final String name: params.keySet()) {
+				final int max = MathHelper.parseIntDefault(params.get(name), 0);
+				if (max < 0) {
+					logger.warn("Max must be a positive integer, not registering dynamic spawn for creature \"" + name + "\"");
+					continue;
+				}
+				spawner.register(name, max);
+			}
+			// NOTE: does zone need to know about dynamic spawner?
+			zone.setDynamicSpawner(spawner);
+		}
+	}
+}

src/games/stendhal/server/core/engine/StendhalRPZone.java

@@ -39,6 +39,7 @@
 import games.stendhal.common.Direction;
 import games.stendhal.common.Line;
 import games.stendhal.common.MathHelper;
+import games.stendhal.common.Rand;
 import games.stendhal.common.filter.FilterCriteria;
 import games.stendhal.common.grammar.Grammar;
 import games.stendhal.common.tiled.LayerDefinition;
@@ -64,6 +65,7 @@
 import games.stendhal.server.entity.mapstuff.portal.OneWayPortalDestination;
 import games.stendhal.server.entity.mapstuff.portal.Portal;
 import games.stendhal.server.entity.mapstuff.spawner.CreatureRespawnPoint;
+import games.stendhal.server.entity.mapstuff.spawner.DynamicCreatureSpawner;
 import games.stendhal.server.entity.mapstuff.spawner.PassiveEntityRespawnPoint;
 import games.stendhal.server.entity.mapstuff.spawner.PassiveEntityRespawnPointFactory;
 import games.stendhal.server.entity.mapstuff.spawner.SheepFood;
@@ -73,6 +75,7 @@
 import games.stendhal.server.entity.npc.TrainingDummyFactory;
 import games.stendhal.server.entity.player.Player;
 import games.stendhal.server.util.StringUtils;
+import marauroa.common.Pair;
 import marauroa.common.game.IRPZone;
 import marauroa.common.game.RPObject;
 import marauroa.common.game.RPSlot;
@@ -113,8 +116,12 @@ public class StendhalRPZone extends MarauroaRPZone {
 	 */
 	private final List<SheepFood> sheepFoods;
 
+	/** Statically spawned creatures. */
 	private final List<CreatureRespawnPoint> respawnPoints;
 
+	/** Dynamically spawned creatures. */
+	private DynamicCreatureSpawner dynamicSpawner;
+
 	private final List<PassiveEntityRespawnPoint> plantGrowers;
 
 	private final List<RPEntity> playersAndFriends;
@@ -311,6 +318,30 @@ public void remove(final CreatureRespawnPoint point) {
 		respawnPoints.remove(point);
 	}
 
+	/**
+	 * Retrieves the dynamic creature spawner associated with this zone.
+	 *
+	 * @return
+	 *   Creature spawner instance.
+	 */
+	public DynamicCreatureSpawner getDynamicSpawner() {
+		return dynamicSpawner;
+	}
+
+	/**
+	 * Sets the dynamic creature spawner associated with this zone.
+	 *
+	 * @param spawner
+	 *   Creature spawner instance.
+	 */
+	public void setDynamicSpawner(final DynamicCreatureSpawner spawner) {
+		if (dynamicSpawner != null) {
+			dynamicSpawner.remove();
+		}
+		dynamicSpawner = spawner;
+		dynamicSpawner.init();
+	}
+
 	/**
 	 * Retrieves growers in this zone.
 	 */
@@ -1517,6 +1548,7 @@ public void nextTurn() {
 			os.append("playersAndFriends: " + playersAndFriends.size() + "\n");
 			os.append("portals: " + portals.size() + "\n");
 			os.append("respawnPoints: " + respawnPoints.size() + "\n");
+			os.append("dynamicRespawns: " + dynamicSpawner.maxTotal() + "\n");
 			os.append("sheepFoods: " + sheepFoods.size() + "\n");
 			os.append("objects: " + objects.size() + "\n");
 			logger.info(os);
@@ -1971,4 +2003,24 @@ public boolean passes(final Entity e) {
 		}
 		return (WeatherEntity) entities.get(0);
 	}
+
+	/**
+	 * Attempts to find a position where an entity can be spawned.
+	 *
+	 * @param entity
+	 *   Entity attempting to spawn.
+	 * @return
+	 *   Appropriate position or `null` if none found.
+	 */
+	public Pair<Integer, Integer> getRandomSpawnPosition(final Entity entity) {
+		final short retries = 50;
+		for (short t = 0; t < retries; t++) {
+			final int x = Rand.rand(getWidth());
+			final int y = Rand.rand(getHeight());
+			if (!collides(entity, x, y)) {
+				return new Pair<>(x, y);
+			}
+		}
+		return null;
+	}
 }