#798: Add PrepareGrindstoneEvent and refactor related events to use PrepareInventoryResultEvent

By: FreeSoccerHDX <freesoccerhdx@gmail.com>

paper-api/src/main/java/org/bukkit/event/inventory/PrepareAnvilEvent.java

@@ -10,14 +10,12 @@ import org.jetbrains.annotations.Nullable;
 /**
  * Called when an item is put in a slot for repair by an anvil.
  */
-public class PrepareAnvilEvent extends InventoryEvent {
+public class PrepareAnvilEvent extends PrepareInventoryResultEvent {
 
     private static final HandlerList handlers = new HandlerList();
-    private ItemStack result;
 
     public PrepareAnvilEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
-        super(inventory);
+        super(inventory, result);
-        this.result = result;
     }
 
     @NotNull
@@ -26,20 +24,6 @@ public class PrepareAnvilEvent extends InventoryEvent {
         return (AnvilInventory) super.getInventory();
     }
 
-    /**
-     * Get result item, may be null.
-     *
-     * @return result item
-     */
-    @Nullable
-    public ItemStack getResult() {
-        return result;
-    }
-
-    public void setResult(@Nullable ItemStack result) {
-        this.result = result;
-    }
-
     @NotNull
     @Override
     public HandlerList getHandlers() {

paper-api/src/main/java/org/bukkit/event/inventory/PrepareGrindstoneEvent.java

@@ -0,0 +1,37 @@
+package org.bukkit.event.inventory;
+
+import org.bukkit.event.HandlerList;
+import org.bukkit.inventory.GrindstoneInventory;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Called when an item is put in a slot for repair or unenchanting in a grindstone.
+ */
+public class PrepareGrindstoneEvent extends PrepareInventoryResultEvent {
+
+    private static final HandlerList handlers = new HandlerList();
+
+    public PrepareGrindstoneEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
+        super(inventory, result);
+    }
+
+    @NotNull
+    @Override
+    public GrindstoneInventory getInventory() {
+        return (GrindstoneInventory) super.getInventory();
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

paper-api/src/main/java/org/bukkit/event/inventory/PrepareInventoryResultEvent.java

@@ -0,0 +1,51 @@
+package org.bukkit.event.inventory;
+
+import org.bukkit.event.HandlerList;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Called when an item is put in a slot and the result is calculated.
+ */
+public class PrepareInventoryResultEvent extends InventoryEvent {
+
+    private static final HandlerList handlers = new HandlerList();
+    private ItemStack result;
+
+    public PrepareInventoryResultEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
+        super(inventory);
+        this.result = result;
+    }
+
+    /**
+     * Get result item, may be null.
+     *
+     * @return result item
+     */
+    @Nullable
+    public ItemStack getResult() {
+        return result;
+    }
+
+    /**
+     * Set result item, may be null.
+     *
+     * @param result result item
+     */
+    public void setResult(@Nullable ItemStack result) {
+        this.result = result;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

paper-api/src/main/java/org/bukkit/event/inventory/PrepareSmithingEvent.java

@@ -10,14 +10,12 @@ import org.jetbrains.annotations.Nullable;
 /**
  * Called when an item is put in a slot for upgrade by a Smithing Table.
  */
-public class PrepareSmithingEvent extends InventoryEvent {
+public class PrepareSmithingEvent extends PrepareInventoryResultEvent {
 
     private static final HandlerList handlers = new HandlerList();
-    private ItemStack result;
 
     public PrepareSmithingEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
-        super(inventory);
+        super(inventory, result);
-        this.result = result;
     }
 
     @NotNull
@@ -26,20 +24,6 @@ public class PrepareSmithingEvent extends InventoryEvent {
         return (SmithingInventory) super.getInventory();
     }
 
-    /**
-     * Get result item, may be null.
-     *
-     * @return result item
-     */
-    @Nullable
-    public ItemStack getResult() {
-        return result;
-    }
-
-    public void setResult(@Nullable ItemStack result) {
-        this.result = result;
-    }
-
     @NotNull
     @Override
     public HandlerList getHandlers() {