Paper/paper-server/patches/sources/net/minecraft/world/item/ServerItemCooldowns.java.patch

--- a/net/minecraft/world/item/ServerItemCooldowns.java
+++ b/net/minecraft/world/item/ServerItemCooldowns.java
@@ -11,6 +_,50 @@
         this.player = player;
     }
 
+    // Paper start - Add PlayerItemCooldownEvent
+    private int getCurrentCooldown(final ResourceLocation groupId) {
+        final net.minecraft.world.item.ItemCooldowns.CooldownInstance cooldownInstance = this.cooldowns.get(groupId);
+        if (cooldownInstance == null) {
+            return 0;
+        }
+        return Math.max(0, cooldownInstance.endTime() - this.tickCount);
+    }
+
+    @Override
+    public void addCooldown(ItemStack item, int duration) {
+        final ResourceLocation cooldownGroup = this.getCooldownGroup(item);
+        final io.papermc.paper.event.player.PlayerItemCooldownEvent event = new io.papermc.paper.event.player.PlayerItemCooldownEvent(
+            this.player.getBukkitEntity(),
+            org.bukkit.craftbukkit.inventory.CraftItemType.minecraftToBukkit(item.getItem()),
+            org.bukkit.craftbukkit.util.CraftNamespacedKey.fromMinecraft(cooldownGroup),
+            duration
+        );
+        if (event.callEvent()) {
+            this.addCooldown(cooldownGroup, event.getCooldown(), false);
+        } else {
+            this.player.connection.send(new ClientboundCooldownPacket(cooldownGroup, this.getCurrentCooldown(cooldownGroup)));
+        }
+    }
+
+    @Override
+    public void addCooldown(ResourceLocation groupId, int duration, boolean callEvent) {
+        if (callEvent) {
+            final io.papermc.paper.event.player.PlayerItemGroupCooldownEvent event = new io.papermc.paper.event.player.PlayerItemGroupCooldownEvent(
+                this.player.getBukkitEntity(),
+                org.bukkit.craftbukkit.util.CraftNamespacedKey.fromMinecraft(groupId),
+                duration
+            );
+            if (!event.callEvent()) {
+                this.player.connection.send(new ClientboundCooldownPacket(groupId, this.getCurrentCooldown(groupId)));
+                return;
+            }
+
+            duration = event.getCooldown();
+        }
+        super.addCooldown(groupId, duration, false);
+    }
+    // Paper end - Add PlayerItemCooldownEvent
+
     @Override
     protected void onCooldownStarted(ResourceLocation group, int cooldown) {
         super.onCooldownStarted(group, cooldown);