SPIGOT-5950: Add PrepareSmithingEvent event

By: jameslfc19 <jameslfc19@gmail.com>

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

@@ -0,0 +1,53 @@
+package org.bukkit.event.inventory;
+
+import org.bukkit.event.HandlerList;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.SmithingInventory;
+import org.jetbrains.annotations.NotNull;
+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 {
+
+    private static final HandlerList handlers = new HandlerList();
+    private ItemStack result;
+
+    public PrepareSmithingEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
+        super(inventory);
+        this.result = result;
+    }
+
+    @NotNull
+    @Override
+    public SmithingInventory getInventory() {
+        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() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}