SPIGOT-4753: Add Pose API

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/entity/Entity.java

@@ -571,4 +571,16 @@ public interface Entity extends Metadatable, CommandSender, Nameable, Persistent
      */
     @NotNull
     BlockFace getFacing();
+
+    /**
+     * Gets the entity's current pose.
+     *
+     * <b>Note that the pose is only updated at the end of a tick, so may be
+     * inconsistent with other methods. eg {@link Player#isSneaking()} being
+     * true does not imply the current pose will be {@link Pose#SNEAKING}</b>
+     *
+     * @return current pose
+     */
+    @NotNull
+    Pose getPose();
 }

paper-api/src/main/java/org/bukkit/entity/Pose.java

@@ -0,0 +1,37 @@
+package org.bukkit.entity;
+
+/**
+ * Represents an entity body pose.
+ */
+public enum Pose {
+
+    /**
+     * Entity is standing normally.
+     *
+     */
+    STANDING,
+    /**
+     * Entity is gliding.
+     */
+    FALL_FLYING,
+    /**
+     * Entity is sleeping.
+     */
+    SLEEPING,
+    /**
+     * Entity is swimming.
+     */
+    SWIMMING,
+    /**
+     * Entity is riptiding with a trident.
+     */
+    SPIN_ATTACK,
+    /**
+     * Entity is sneaking.
+     */
+    SNEAKING,
+    /**
+     * Entity is dead.
+     */
+    DYING;
+}

paper-api/src/main/java/org/bukkit/event/entity/EntityPoseChangeEvent.java

@@ -0,0 +1,44 @@
+package org.bukkit.event.entity;
+
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Pose;
+import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Called when an entity changes its pose.
+ *
+ * @see Entity#getPose()
+ */
+public class EntityPoseChangeEvent extends EntityEvent {
+
+    private static final HandlerList handlers = new HandlerList();
+    //
+    private final Pose pose;
+
+    public EntityPoseChangeEvent(@NotNull Entity who, @NotNull Pose pose) {
+        super(who);
+        this.pose = pose;
+    }
+
+    /**
+     * Gets the entity's new pose.
+     *
+     * @return the new pose
+     */
+    @NotNull
+    public Pose getPose() {
+        return pose;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}