Add Mob Goal API

paper-api/src/main/java/com/destroystokyo/paper/entity/ai/Goal.java

@@ -0,0 +1,63 @@
+package com.destroystokyo.paper.entity.ai;
+
+import java.util.EnumSet;
+import org.bukkit.entity.Mob;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Represents an AI goal of an entity
+ */
+@NullMarked
+public interface Goal<T extends Mob> {
+
+    /**
+     * Checks if this goal should be activated
+     *
+     * @return if this goal should be activated
+     */
+    boolean shouldActivate();
+
+    /**
+     * Checks if this goal should stay active, defaults to {@link Goal#shouldActivate()}
+     *
+     * @return if this goal should stay active
+     */
+    default boolean shouldStayActive() {
+        return this.shouldActivate();
+    }
+
+    /**
+     * Called when this goal gets activated
+     */
+    default void start() {
+    }
+
+    /**
+     * Called when this goal gets stopped
+     */
+    default void stop() {
+    }
+
+    /**
+     * Called each tick the goal is activated
+     */
+    default void tick() {
+    }
+
+    /**
+     * A unique key that identifies this type of goal. Plugins should use their own namespace, not the minecraft
+     * namespace. Additionally, this key also specifies to what mobs this goal can be applied to
+     *
+     * @return the goal key
+     */
+    GoalKey<T> getKey();
+
+    /**
+     * Returns a list of all applicable flags for this goal.<br>
+     * <p>
+     * This method is only called on construction.
+     *
+     * @return the subtypes.
+     */
+    EnumSet<GoalType> getTypes();
+}

paper-api/src/main/java/com/destroystokyo/paper/entity/ai/GoalKey.java

@@ -0,0 +1,59 @@
+package com.destroystokyo.paper.entity.ai;
+
+import com.google.common.base.Objects;
+import java.util.StringJoiner;
+import org.bukkit.NamespacedKey;
+import org.bukkit.entity.Mob;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Used to identify a Goal. Consists of a {@link NamespacedKey} and the type of mob the goal can be applied to
+ *
+ * @param <T> the type of mob the goal can be applied to
+ */
+@NullMarked
+public final class GoalKey<T extends Mob> {
+
+    private final Class<T> entityClass;
+    private final NamespacedKey namespacedKey;
+
+    private GoalKey(Class<T> entityClass, NamespacedKey namespacedKey) {
+        this.entityClass = entityClass;
+        this.namespacedKey = namespacedKey;
+    }
+
+    public Class<T> getEntityClass() {
+        return this.entityClass;
+    }
+
+    public NamespacedKey getNamespacedKey() {
+        return this.namespacedKey;
+    }
+
+    @Override
+    public boolean equals(@Nullable Object o) {
+        if (this == o) return true;
+        if (o == null || this.getClass() != o.getClass()) return false;
+        GoalKey<?> goalKey = (GoalKey<?>) o;
+        return Objects.equal(this.entityClass, goalKey.entityClass) &&
+            Objects.equal(this.namespacedKey, goalKey.namespacedKey);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(this.entityClass, this.namespacedKey);
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", GoalKey.class.getSimpleName() + "[", "]")
+            .add("entityClass=" + this.entityClass)
+            .add("namespacedKey=" + this.namespacedKey)
+            .toString();
+    }
+
+    public static <A extends Mob> GoalKey<A> of(Class<A> entityClass, NamespacedKey namespacedKey) {
+        return new GoalKey<>(entityClass, namespacedKey);
+    }
+}

paper-api/src/main/java/com/destroystokyo/paper/entity/ai/GoalType.java

@@ -0,0 +1,17 @@
+package com.destroystokyo.paper.entity.ai;
+
+/**
+ * Represents the subtype of a goal. Used by minecraft to disable certain types of goals if needed.
+ */
+public enum GoalType {
+
+    MOVE,
+    LOOK,
+    JUMP,
+    TARGET,
+    /**
+     * Used to map vanilla goals, that are a behavior goal but don't have a type set...
+     */
+    UNKNOWN_BEHAVIOR,
+
+}

paper-api/src/main/java/com/destroystokyo/paper/entity/ai/MobGoals.java

@@ -0,0 +1,42 @@
+package com.destroystokyo.paper.entity.ai;
+
+
+import java.util.Collection;
+import org.bukkit.entity.Mob;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Represents a part of the "brain" of a mob. It tracks all tasks (running or not), allows adding and removing goals
+ */
+@NullMarked
+public interface MobGoals {
+
+    <T extends Mob> void addGoal(T mob, int priority, Goal<T> goal);
+
+    <T extends Mob> void removeGoal(T mob, Goal<T> goal);
+
+    <T extends Mob> void removeAllGoals(T mob);
+
+    <T extends Mob> void removeAllGoals(T mob, GoalType type);
+
+    <T extends Mob> void removeGoal(T mob, GoalKey<T> key);
+
+    <T extends Mob> boolean hasGoal(T mob, GoalKey<T> key);
+
+    <T extends Mob> @Nullable Goal<T> getGoal(T mob, GoalKey<T> key);
+
+    <T extends Mob> Collection<Goal<T>> getGoals(T mob, GoalKey<T> key);
+
+    <T extends Mob> Collection<Goal<T>> getAllGoals(T mob);
+
+    <T extends Mob> Collection<Goal<T>> getAllGoals(T mob, GoalType type);
+
+    <T extends Mob> Collection<Goal<T>> getAllGoalsWithout(T mob, GoalType type);
+
+    <T extends Mob> Collection<Goal<T>> getRunningGoals(T mob);
+
+    <T extends Mob> Collection<Goal<T>> getRunningGoals(T mob, GoalType type);
+
+    <T extends Mob> Collection<Goal<T>> getRunningGoalsWithout(T mob, GoalType type);
+}

paper-api/src/main/java/org/bukkit/Bukkit.java

@@ -2584,6 +2584,16 @@ public final class Bukkit {
     public static boolean isStopping() {
         return server.isStopping();
     }
+
+    /**
+     * Returns the {@link com.destroystokyo.paper.entity.ai.MobGoals} manager
+     *
+     * @return the mob goals manager
+     */
+    @NotNull
+    public static com.destroystokyo.paper.entity.ai.MobGoals getMobGoals() {
+        return server.getMobGoals();
+    }
     // Paper end
 
     @NotNull

paper-api/src/main/java/org/bukkit/Server.java

@@ -2250,5 +2250,13 @@ public interface Server extends PluginMessageRecipient, net.kyori.adventure.audi
      * @return true if server is in the process of being shutdown
      */
     boolean isStopping();
+
+    /**
+     * Returns the {@link com.destroystokyo.paper.entity.ai.MobGoals} manager
+     *
+     * @return the mob goals manager
+     */
+    @NotNull
+    com.destroystokyo.paper.entity.ai.MobGoals getMobGoals();
     // Paper end
 }