SPIGOT-1934: Expand EnderDragon API - adds dragon phases

By: Matthew <stteg@hotmail.com>

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

@@ -5,4 +5,74 @@ package org.bukkit.entity;
  */
 public interface EnderDragon extends ComplexLivingEntity {
 
+    /**
+     * Represents a phase or action that an Ender Dragon can perform.
+     */
+    enum Phase {
+        /**
+         * The dragon will circle outside the ring of pillars if ender
+         * crystals remain or inside the ring if not.
+         */
+        CIRCLING,
+        /**
+         * The dragon will fly towards a targetted player and shoot a
+         * fireball when within 64 blocks.
+         */
+        STRAFING,
+        /**
+         * The dragon will fly towards the empty portal (approaching
+         * from the other side, if applicable).
+         */
+        FLY_TO_PORTAL,
+        /**
+         * The dragon will land on on the portal. If the dragon is not near
+         * the portal, it will fly to it before mounting.
+         */
+        LAND_ON_PORTAL,
+        /**
+         * The dragon will leave the portal.
+         */
+        LEAVE_PORTAL,
+        /**
+         * The dragon will attack with dragon breath at its current location.
+         */
+        BREATH_ATTACK,
+        /**
+         * The dragon will search for a player to attack with dragon breath.
+         * If no player is close enough to the dragon for 5 seconds, the 
+         * dragon will charge at a player within 150 blocks or will take off 
+         * and begin circling if no player is found.
+         */
+        SEARCH_FOR_BREATH_ATTACK_TARGET,
+        /**
+         * The dragon will roar before performing a breath attack.
+         */
+        ROAR_BEFORE_ATTACK,
+        /**
+         * The dragon will charge a player.
+         */
+        CHARGE_PLAYER,
+        /**
+         * The dragon will fly to the vicinity of the portal and die.
+         */
+        DYING,
+        /**
+         * The dragon will hover at its current location, not performing any actions.
+         */
+        HOVER
+    }
+
+    /**
+     * Gets the current phase that the dragon is performing.
+     *
+     * @return the current phase
+     */
+    Phase getPhase();
+
+    /**
+     * Sets the next phase for the dragon to perform.
+     *
+     * @param phase the next phase
+     */
+    void setPhase(Phase phase);
 }

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

@@ -0,0 +1,76 @@
+package org.bukkit.event.entity;
+
+import org.apache.commons.lang.Validate;
+import org.bukkit.entity.EnderDragon;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+
+/**
+ * Called when an EnderDragon switches controller phase.
+ */
+public class EnderDragonChangePhaseEvent extends EntityEvent implements Cancellable {
+
+    private static final HandlerList handlers = new HandlerList();
+    private boolean cancel;
+    private final EnderDragon.Phase currentPhase;
+    private EnderDragon.Phase newPhase;
+
+    public EnderDragonChangePhaseEvent(EnderDragon enderDragon, EnderDragon.Phase currentPhase, EnderDragon.Phase newPhase) {
+        super(enderDragon);
+        this.currentPhase = currentPhase;
+        this.setNewPhase(newPhase);
+    }
+
+    @Override
+    public EnderDragon getEntity() {
+        return (EnderDragon) entity;
+    }
+
+    /**
+     * Gets the current phase that the dragon is in. This method will return null 
+     * when a dragon is first spawned and hasn't yet been assigned a phase.
+     * 
+     * @return the current dragon phase
+     */
+    public EnderDragon.Phase getCurrentPhase() {
+        return currentPhase;
+    }
+
+    /**
+     * Gets the new phase that the dragon will switch to.
+     * 
+     * @return the new dragon phase
+     */
+    public EnderDragon.Phase getNewPhase() {
+        return newPhase;
+    }
+
+    /**
+     * Sets the new phase for the ender dragon.
+     * 
+     * @param newPhase the new dragon phase
+     */
+    public void setNewPhase(EnderDragon.Phase newPhase) {
+        Validate.notNull(newPhase, "New dragon phase cannot be null");
+        this.newPhase = newPhase;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return cancel;
+    }
+
+    @Override
+    public void setCancelled(boolean cancel) {
+        this.cancel = cancel;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}