Paper/Spigot-API-Patches/0150-Mob-Pathfinding-API.patch

From a9c06c0f1eecb397249a9e0c8881bf848e9168f3 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 9 Sep 2018 12:39:06 -0400
Subject: [PATCH] Mob Pathfinding API

Adds an API to allow plugins to instruct a Mob to Pathfind to a Location or Entity

This does not do anything to stop other AI rules from changing the location, so
it is still up to the plugin to control that or override after another goal changed
the location.

diff --git a/src/main/java/com/destroystokyo/paper/entity/Pathfinder.java b/src/main/java/com/destroystokyo/paper/entity/Pathfinder.java
new file mode 100644
index 000000000..27b6bb696
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/entity/Pathfinder.java
@@ -0,0 +1,168 @@
+package com.destroystokyo.paper.entity;
+
+import org.apache.commons.lang.Validate;
+import org.bukkit.Location;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.Mob;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.List;
+
+/**
+ * Handles pathfinding operations for an Entity
+ */
+public interface Pathfinder {
+
+    /**
+     *
+     * @return The entity that is controlled by this pathfinder
+     */
+    Mob getEntity();
+
+    /**
+     * Instructs the Entity to stop trying to navigate to its current desired location
+     */
+    void stopPathfinding();
+
+    /**
+     * If the entity is currently trying to navigate to a destination, this will return true
+     * @return true if the entity is navigating to a destination
+     */
+    boolean hasDestination();
+
+    /**
+     * @return The location the entity is trying to navigate to, or null if there is no destination
+     */
+    @Nullable PathResult getCurrentDestination();
+
+    /**
+     * Calculates a destination for the Entity to navigate to, but does not set it
+     * as the current target. Useful for calculating what would happen before setting it.
+     * @param loc Location to navigate to
+     * @return The closest Location the Entity can get to for this navigation, or null if no path could be calculated
+     */
+    @Nullable PathResult calculateDestination(Location loc);
+
+    /**
+     * Calculates a destination for the Entity to navigate to to reach the target entity,
+     * but does not set it as the current target.
+     * Useful for calculating what would happen before setting it.
+     *
+     * The behavior of this PathResult is subject to the games pathfinding rules, and may
+     * result in the pathfinding automatically updating to follow the target Entity.
+     *
+     * However, this behavior is not guaranteed, and is subject to the games behavior.
+     *
+     * @param target the Entity to navigate to
+     * @return The closest Location the Entity can get to for this navigation, or null if no path could be calculated
+     */
+    @Nullable PathResult calculateDestination(LivingEntity target);
+
+    /**
+     * Calculates a destination for the Entity to navigate to, and sets it with default speed
+     * as the current target.
+     * @param loc Location to navigate to
+     * @return If the pathfinding was successfully started
+     */
+    default boolean setDestination(@Nonnull Location loc) {
+        return setDestination(loc, 1);
+    }
+
+    /**
+     * Calculates a destination for the Entity to navigate to, with desired speed
+     * as the current target.
+     * @param loc Location to navigate to
+     * @param speed Speed multiplier to navigate at, where 1 is 'normal'
+     * @return If the pathfinding was successfully started
+     */
+    default boolean setDestination(@Nonnull Location loc, double speed) {
+        PathResult path = calculateDestination(loc);
+        return path != null && setDestination(path, speed);
+    }
+
+    /**
+     * Calculates a destination for the Entity to navigate to to reach the target entity,
+     * and sets it with default speed.
+     *
+     * The behavior of this PathResult is subject to the games pathfinding rules, and may
+     * result in the pathfinding automatically updating to follow the target Entity.
+     *
+     * However, this behavior is not guaranteed, and is subject to the games behavior.
+     *
+     * @param target the Entity to navigate to
+     * @return If the pathfinding was successfully started
+     */
+    default boolean setDestination(@Nonnull LivingEntity target) {
+        return setDestination(target, 1);
+    }
+
+    /**
+     * Calculates a destination for the Entity to navigate to to reach the target entity,
+     * and sets it with specified speed.
+     *
+     * The behavior of this PathResult is subject to the games pathfinding rules, and may
+     * result in the pathfinding automatically updating to follow the target Entity.
+     *
+     * However, this behavior is not guaranteed, and is subject to the games behavior.
+     *
+     * @param target the Entity to navigate to
+     * @param speed Speed multiplier to navigate at, where 1 is 'normal'
+     * @return If the pathfinding was successfully started
+     */
+    default boolean setDestination(@Nonnull LivingEntity target, double speed) {
+        PathResult path = calculateDestination(target);
+        return path != null && setDestination(path, speed);
+    }
+
+    /**
+     * Takes the result of a previous pathfinding calculation and sets it
+     * as the active pathfinding with default speed.
+     *
+     * @param path The Path to start following
+     * @return If the pathfinding was successfully started
+     */
+    default boolean setDestination(@Nonnull PathResult path) {
+        return setDestination(path, 1);
+    }
+
+    /**
+     * Takes the result of a previous pathfinding calculation and sets it
+     * as the active pathfinding,
+     *
+     * @param path The Path to start following
+     * @param speed Speed multiplier to navigate at, where 1 is 'normal'
+     * @return If the pathfinding was successfully started
+     */
+    boolean setDestination(@Nonnull PathResult path, double speed);
+
+    /**
+     * Represents the result of a pathfinding calculation
+     */
+    interface PathResult {
+
+        /**
+         * @return The closest point the path can get to the target location
+         */
+        @Nullable Location getLocation();
+
+        /**
+         * All currently calculated points to follow along the path to reach the destination location
+         *
+         * Will return points the entity has already moved past, see {@link #getNextPointIndex()}
+         * @return List of points
+         */
+        List<Location> getPoints();
+
+        /**
+         * @return Returns the index of the current point along the points returned in {@link #getPoints()} the entity
+         * is trying to reach, or null if we are done with this pathfinding.
+         */
+        @Nullable Integer getNextPointIndex();
+
+        /**
+         * @return The next location in the path points the entity is trying to reach, or null if there is no next point
+         */
+        @Nullable Location getNextPointLocation();
+    }
+}
diff --git a/src/main/java/org/bukkit/entity/Mob.java b/src/main/java/org/bukkit/entity/Mob.java
index d029d34ea..48eddcd30 100644
--- a/src/main/java/org/bukkit/entity/Mob.java
+++ b/src/main/java/org/bukkit/entity/Mob.java
@@ -7,6 +7,14 @@ import org.bukkit.loot.Lootable;
  */
 public interface Mob extends LivingEntity, Lootable {
 
+    // Paper start
+    /**
+     * Enables access to control the pathing of an Entity
+     * @return Pathfinding Manager for this entity
+     */
+    com.destroystokyo.paper.entity.Pathfinder getPathfinder();
+    // Paper end
+
     /**
      * Instructs this Mob to set the specified LivingEntity as its target.
      * <p>
-- 
2.18.0