Missing Entity API

Co-authored-by: Nassim Jahnke <nassim@njahnke.dev>
Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>
Co-authored-by: William Blake Galbreath <blake.galbreath@gmail.com>
Co-authored-by: SoSeDiK <mrsosedik@gmail.com>
Co-authored-by: booky10 <boooky10@gmail.com>
Co-authored-by: Amin <amin.haddou@frg.wwschool.de>
Co-authored-by: TrollyLoki <trollyloki@gmail.com>
Co-authored-by: FireInstall <kettnerl@hu-berlin.de>
Co-authored-by: maxcom1 <46265094+maxcom1@users.noreply.github.com>
Co-authored-by: TotalledZebra <Holappa57@gmail.com>

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

@@ -43,7 +43,9 @@ public interface Wither extends Monster, Boss, com.destroystokyo.paper.entity.Ra
      * Returns the wither's current invulnerability ticks.
      *
      * @return amount of invulnerability ticks
+     * @deprecated Duplicate api, use {@link #getInvulnerableTicks()}
      */
+    @Deprecated(forRemoval = true) // Paper
     int getInvulnerabilityTicks();
 
     /**
@@ -52,7 +54,9 @@ public interface Wither extends Monster, Boss, com.destroystokyo.paper.entity.Ra
      * When invulnerability ticks reach 0, the wither will trigger an explosion.
      *
      * @param ticks amount of invulnerability ticks
+     * @deprecated Duplicate api, use {@link #setInvulnerableTicks(int)}
      */
+    @Deprecated(forRemoval = true) // Paper
     void setInvulnerabilityTicks(int ticks);
 
     /**
@@ -64,4 +68,43 @@ public interface Wither extends Monster, Boss, com.destroystokyo.paper.entity.Ra
         LEFT,
         RIGHT
     }
+
+    // Paper start
+    /**
+     * @return whether the wither is charged
+     */
+    boolean isCharged();
+
+    /**
+     * @return ticks the wither is invulnerable for
+     */
+    int getInvulnerableTicks();
+
+    /**
+     * Sets for how long in the future, the wither should be invulnerable.
+     *
+     * @param ticks ticks the wither is invulnerable for
+     */
+    void setInvulnerableTicks(int ticks);
+
+    /**
+     * @return whether the wither can travel through portals
+     */
+    boolean canTravelThroughPortals();
+
+    /**
+     * Sets whether the wither can travel through portals.
+     *
+     * @param value whether the wither can travel through portals
+     */
+    void setCanTravelThroughPortals(boolean value);
+
+    /**
+     * Makes the wither invulnerable for 11 seconds and
+     * sets the health to one third of the max health.
+     * <br>
+     * This is called in vanilla directly after spawning the wither.
+     */
+    void enterInvulnerabilityPhase();
+    // Paper end
 }