PaperMC/Spigot-API-Patches/0147-Mob-Pathfinding-API.patch

From b1cb593f47c8e02a87189db2ac57ca0eb2886a1a 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.

You can use EntityPathfindEvent to cancel new pathfinds from overriding your current.

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..8b90a9053
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/entity/Pathfinder.java
@@ -0,0 +1,170 @@
+package com.destroystokyo.paper.entity;
+
+import org.bukkit.Location;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.Mob;
+
+import java.util.List;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Handles pathfinding operations for an Entity
+ */
+public interface Pathfinder {
+
+    /**
+     *
+     * @return The entity that is controlled by this pathfinder
+     */
+    @NotNull
+    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 hasPath();
+
+    /**
+     * @return The location the entity is trying to navigate to, or null if there is no destination
+     */
+    @Nullable
+    PathResult getCurrentPath();
+
+    /**
+     * 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 findPath(@NotNull 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 findPath(@NotNull 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 moveTo(@NotNull Location loc) {
+        return moveTo(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 moveTo(@NotNull Location loc, double speed) {
+        PathResult path = findPath(loc);
+        return path != null && moveTo(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 moveTo(@NotNull LivingEntity target) {
+        return moveTo(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 moveTo(@NotNull LivingEntity target, double speed) {
+        PathResult path = findPath(target);
+        return path != null && moveTo(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 moveTo(@NotNull PathResult path) {
+        return moveTo(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 moveTo(@NotNull PathResult path, double speed);
+
+    /**
+     * Represents the result of a pathfinding calculation
+     */
+    interface PathResult {
+
+        /**
+         * 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
+         */
+        @NotNull
+        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.
+         */
+        int 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 getNextPoint();
+
+        /**
+         * @return The closest point the path can get to the target location
+         */
+        @Nullable Location getFinalPoint();
+    }
+}
diff --git a/src/main/java/org/bukkit/entity/Mob.java b/src/main/java/org/bukkit/entity/Mob.java
index 838440ff8..afdc103fe 100644
--- a/src/main/java/org/bukkit/entity/Mob.java
+++ b/src/main/java/org/bukkit/entity/Mob.java
@@ -1,6 +1,7 @@
 package org.bukkit.entity;
 
 import org.bukkit.loot.Lootable;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -8,6 +9,15 @@ import org.jetbrains.annotations.Nullable;
  */
 public interface Mob extends LivingEntity, Lootable {
 
+    // Paper start
+    /**
+     * Enables access to control the pathing of an Entity
+     * @return Pathfinding Manager for this entity
+     */
+    @NotNull
+    com.destroystokyo.paper.entity.Pathfinder getPathfinder();
+    // Paper end
+
     /**
      * Instructs this Mob to set the specified LivingEntity as its target.
      * <p>
-- 
2.21.0