Add WardenAngerChangeEvent

Adding a event which gets called when a warden is angered by
another entity.

paper-api/src/main/java/io/papermc/paper/event/entity/WardenAngerChangeEvent.java

@@ -0,0 +1,103 @@
+package io.papermc.paper.event.entity;
+
+import com.google.common.base.Preconditions;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Warden;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.entity.EntityEvent;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Range;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Called when a Warden's anger level has changed due to another entity.
+ * <p>
+ * If the event is cancelled, the warden's anger level will not change.
+ */
+@NullMarked
+public class WardenAngerChangeEvent extends EntityEvent implements Cancellable {
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+
+    private final Entity target;
+    private final int oldAnger;
+    private int newAnger;
+
+    private boolean cancelled;
+
+    @ApiStatus.Internal
+    public WardenAngerChangeEvent(final Warden warden, final Entity target, final int oldAnger, final int newAnger) {
+        super(warden);
+        this.target = target;
+        this.oldAnger = oldAnger;
+        this.newAnger = newAnger;
+    }
+
+    /**
+     * Gets the entity which triggered this anger update.
+     *
+     * @return triggering entity
+     */
+    public Entity getTarget() {
+        return this.target;
+    }
+
+    /**
+     * Gets the old anger level.
+     *
+     * @return old anger level
+     * @see Warden#getAnger(Entity)
+     */
+    public @Range(from = 0, to = 150) int getOldAnger() {
+        return this.oldAnger;
+    }
+
+    /**
+     * Gets the new anger level resulting from this event.
+     *
+     * @return new anger level
+     * @see Warden#getAnger(Entity)
+     */
+    public @Range(from = 0, to = 150) int getNewAnger() {
+        return this.newAnger;
+    }
+
+    /**
+     * Sets the new anger level resulting from this event.
+     * <p>
+     * The anger of a warden is capped at 150.
+     *
+     * @param newAnger the new anger level, max 150
+     * @throws IllegalArgumentException if newAnger is greater than 150
+     * @see Warden#setAnger(Entity, int)
+     */
+    public void setNewAnger(final @Range(from = 0, to = 150) int newAnger) {
+        Preconditions.checkArgument(newAnger <= 150, "newAnger must not be greater than 150");
+        this.newAnger = newAnger;
+    }
+
+    @Override
+    public Warden getEntity() {
+        return (Warden) super.getEntity();
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return this.cancelled;
+    }
+
+    @Override
+    public void setCancelled(final boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+}