Add PlayerAttackCooldownEvent. (SPIGOT-7880)

Signed-off-by: ShreyasAyyengar <shreyas.ayyengar@gmail.com>

src/main/java/org/bukkit/event/player/PlayerAttackCooldownEvent.java

@@ -0,0 +1,64 @@
+package org.bukkit.event.player;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Called when a player's attack cooldown ticker starts.
+ * <p>
+ * Warning: <b>Cancelling this event has no impact on the cooldown graphic displayed to the client.</b> If cancelled,
+ * Bukkit will not reset the cooldown ticker, but the client will still display the cooldown graphic regardless.
+ */
+public class PlayerAttackCooldownEvent extends PlayerEvent implements Cancellable {
+    private static final HandlerList handlers = new HandlerList();
+    private boolean cancelled;
+    private final AttackCooldownCause cause;
+
+    public PlayerAttackCooldownEvent(@NotNull Player who, @NotNull AttackCooldownCause cause) {
+        super(who);
+        this.cause = cause;
+    }
+
+    @NotNull
+    public AttackCooldownCause getCause() {
+        return cause;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return cancelled;
+    }
+
+    @Override
+    public void setCancelled(boolean cancelled) {
+        this.cancelled = cancelled;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+
+    public enum AttackCooldownCause {
+        /**
+         * Indicates the player switched items
+         */
+        ITEM_SWITCH,
+        /**
+         * Indicates the player attacked an entity
+         */
+        ATTACK_ENTITY,
+        /**
+         * Indicates the player swung their arm
+         */
+        SWING
+    }
+}