Add a mob extension plugin for walking to entities

Adds a new mob extension plugin which creates a walk_to() method on
Mobs to allow walking to another entity (accounting for the size of the
entity) with an optional facing position.

data/plugins/entity/mob/walk-to/plugin.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0"?>
+<plugin>
+    <id>mob-walk-to</id>
+    <version>0.1</version>
+    <name>Mob path generation</name>
+    <description>Adds a mixin for making mobs walk to another entity.</description>
+    <authors>
+        <author>Gary Tierney</author>
+    </authors>
+    <scripts>
+        <script>walk_to.rb</script>
+    </scripts>
+    <dependencies>
+        <dependency>mob-extension</dependency>
+    </dependencies>
+</plugin>

data/plugins/entity/mob/walk-to/walk_to.rb

@@ -0,0 +1,83 @@
+java_import 'org.apollo.game.model.entity.path.AStarPathfindingAlgorithm'
+java_import 'org.apollo.game.model.entity.path.EuclideanHeuristic'
+java_import 'org.apollo.game.model.entity.path.SimplePathfindingAlgorithm'
+java_import 'org.apollo.game.model.entity.obj.GameObject'
+java_import 'org.apollo.game.model.entity.Mob'
+java_import 'org.apollo.game.model.entity.Player'
+java_import 'org.apollo.game.model.entity.EntityType'
+java_import 'org.apollo.game.model.Direction'
+
+##
+# A pathfinder used for simple following (i.e.: An NPC attacking a player).
+SIMPLE_PATH_FINDER = SimplePathfindingAlgorithm.new($world.collision_manager)
+
+##
+# A pathfinder used for precise following (i.e.: A player attacking another player).
+FOLLOW_PATH_FINDER = AStarPathfindingAlgorithm.new($world.collision_manager, EuclideanHeuristic.new)
+
+##
+# The directions that we use as a random offset when not walking to the facing direction.
+OFFSET_DIRECTIONS = Direction::NESW.to_a
+
+module WalkToMobExtension
+  def walk_to(entity, front: false, behind: false)
+    if [front, behind].count { |option| option == true } > 1
+      fail 'Can only specify one of "front" or "behind"'
+    end
+
+    position = self.position
+    target_position = entity.position
+    target_distance = position.get_distance(target_position)
+    target_offset = walk_to_offset(entity)
+    target_offset_direction = OFFSET_DIRECTIONS.sample
+    target_facing_direction = walk_to_facing_direction(entity)
+
+    unless target_facing_direction.nil?
+      if front
+        target_offset_direction = target_facing_direction
+      elsif behind
+        target_offset_direction = target_facing_direction.opposite
+      end
+    end
+
+    target_offset_position = target_position.step(target_offset, target_offset_direction)
+    return if target_offset_position.eql?(position)
+
+    pathfinder = FOLLOW_PATH_FINDER
+    path = pathfinder.find(position, target_offset_position)
+    path.each { |tile| self.walking_queue.add_step(tile) }
+  end
+end
+
+MobExtension::register(WalkToMobExtension)
+
+private
+
+##
+# Gets the number of tiles away from an entity's actual origin that we can
+# walk to.
+def walk_to_offset(entity)
+  case entity.entity_type
+    when EntityType::DYNAMIC_OBJECT, EntityType::STATIC_OBJECT
+      return max(entity.definition.width, entity.definition.length) + 1
+    when EntityType::NPC
+      return entity.definition.size + 1
+    when EntityType::PLAYER
+      return 1
+    else
+      fail "walk_to_offset called with invalid entity type: #{type.to_s}"
+  end
+end
+
+##
+# Gets the direction that an entity is facing, so a mob can walk up infront of them.
+def walk_to_facing_direction(entity)
+  case entity.entity_type
+    when EntityType::DYNAMIC_OBJECT, EntityType::STATIC_OBJECT
+      return Direction::WNES[entity.orientation]
+    when EntityType::NPC, EntityType::PLAYER
+      return entity.last_direction
+    else
+      fail "walk_to_offset called with invalid entity type: #{type.to_s}"
+  end
+end

game/src/main/org/apollo/game/model/entity/Mob.java

@@ -103,6 +103,11 @@ public abstract class Mob extends Entity {
 	 */
 	private Direction firstDirection = Direction.NONE;
 
+	/**
+	 * The last facing direction of this mob.
+	 */
+	private Direction lastDirection = Direction.NORTH;
+
 	/**
 	 * This mob's second movement direction.
 	 */
@@ -196,8 +201,8 @@ public abstract class Mob extends Entity {
 	 */
 	public final Direction[] getDirections() {
 		if (firstDirection != Direction.NONE) {
-			return secondDirection == Direction.NONE ? new Direction[]{ firstDirection }
-				: new Direction[]{ firstDirection, secondDirection };
+			return secondDirection == Direction.NONE ? new Direction[]{firstDirection}
+				: new Direction[]{firstDirection, secondDirection};
 		}
 
 		return Direction.EMPTY_DIRECTION_ARRAY;
@@ -268,6 +273,15 @@ public abstract class Mob extends Entity {
 		return inventory;
 	}
 
+	/**
+	 * Gets the last facing direction of this mob.
+	 *
+	 * @return The last direction this mob was facing.
+	 */
+	public Direction getLastDirection() {
+		return lastDirection;
+	}
+
 	/**
 	 * Gets this mob's local npc {@link List}.
 	 *
@@ -425,6 +439,15 @@ public abstract class Mob extends Entity {
 		blockSet.add(SynchronizationBlock.createInteractingMobBlock(mob.getInteractionIndex()));
 	}
 
+	/**
+	 * Set the last direction this mob was facing.
+	 *
+	 * @param lastDirection The direction to set.
+	 */
+	public void setLastDirection(Direction lastDirection) {
+		this.lastDirection = lastDirection;
+	}
+
 	/**
 	 * Sets the {@link Position} of this mob.
 	 * <p>
@@ -470,7 +493,7 @@ public abstract class Mob extends Entity {
 	 * Gets the number of tiles this mob occupies.
 	 *
 	 * @return The number of tiles this mob occupies.
-     */
+	 */
 	public int size() {
 		return definition.map(NpcDefinition::getSize).orElse(1);
 	}
@@ -548,4 +571,5 @@ public abstract class Mob extends Entity {
 		world.schedule(new SkillNormalizationTask(this));
 	}
 
+
 }

game/src/main/org/apollo/game/model/entity/WalkingQueue.java

@@ -146,6 +146,7 @@ public final class WalkingQueue {
 			} else {
 				previousPoints.add(next);
 				position = new Position(next.getX(), next.getY(), height);
+				mob.setLastDirection(firstDirection);
 
 				if (running) {
 					next = points.poll();
@@ -158,6 +159,7 @@ public final class WalkingQueue {
 						} else {
 							previousPoints.add(next);
 							position = new Position(next.getX(), next.getY(), height);
+							mob.setLastDirection(secondDirection);
 						}
 					}
 				}