Add API methods for controlling the spectator camera Entity

Adds #1395

Signed-off-by: Gabriel Harris-Rouquette <[email protected]>

Author: kashike

src/main/java/org/spongepowered/api/entity/living/player/Player.java

@@ -34,8 +34,10 @@
 import org.spongepowered.api.data.type.SkinPart;
 import org.spongepowered.api.data.value.mutable.Value;
 import org.spongepowered.api.effect.Viewer;
+import org.spongepowered.api.entity.Entity;
 import org.spongepowered.api.entity.living.Humanoid;
 import org.spongepowered.api.entity.living.player.gamemode.GameMode;
+import org.spongepowered.api.entity.living.player.gamemode.GameModes;
 import org.spongepowered.api.entity.living.player.tab.TabList;
 import org.spongepowered.api.event.cause.Cause;
 import org.spongepowered.api.item.inventory.Container;
@@ -52,6 +54,8 @@
 import java.util.Optional;
 import java.util.Set;
 
+import javax.annotation.Nullable;
+
 /**
  * A Player represents the in-game entity of a human playing on a server.
  * This is in contrast to User which represents the storage and data
@@ -294,4 +298,20 @@ default Value<GameMode> gameMode() {
      */
     boolean respawnPlayer();
 
+    /**
+     * Gets the {@link Entity} followed by the camera when in the
+     * {@link GameModes#SPECTATOR spectator gamemode}.
+     *
+     * @return The followed entity, if present, {@link Optional#empty()} otherwise
+     */
+    Optional<Entity> getSpectatorTarget();
+
+    /**
+     * Sets the {@link Entity} followed by the camera when in the
+     * {@link GameModes#SPECTATOR spectator gamemode}.
+     *
+     * @param entity The entity to spectate
+     */
+    void setSpectatorTarget(@Nullable Entity entity);
+
 }