--- a/net/minecraft/world/inventory/GrindstoneMenu.java
+++ b/net/minecraft/world/inventory/GrindstoneMenu.java
@@ -1,6 +1,7 @@
 package net.minecraft.world.inventory;
 
 import it.unimi.dsi.fastutil.objects.Object2IntMap.Entry;
+import java.util.Iterator;
 import net.minecraft.core.Holder;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.server.level.ServerLevel;
@@ -9,7 +10,6 @@
 import net.minecraft.world.SimpleContainer;
 import net.minecraft.world.entity.ExperienceOrb;
 import net.minecraft.world.entity.player.Inventory;
-import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.Items;
 import net.minecraft.world.item.enchantment.Enchantment;
@@ -18,8 +18,30 @@
 import net.minecraft.world.level.Level;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.phys.Vec3;
+// CraftBukkit start
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.inventory.CraftInventoryGrindstone;
+import org.bukkit.craftbukkit.inventory.CraftInventoryView;
+import org.bukkit.entity.Player;
+// CraftBukkit end
 
 public class GrindstoneMenu extends AbstractContainerMenu {
+
+    // CraftBukkit start
+    private CraftInventoryView bukkitEntity = null;
+    private Player player;
+
+    @Override
+    public CraftInventoryView getBukkitView() {
+        if (this.bukkitEntity != null) {
+            return this.bukkitEntity;
+        }
+
+        CraftInventoryGrindstone inventory = new CraftInventoryGrindstone(this.repairSlots, this.resultSlots);
+        this.bukkitEntity = new CraftInventoryView(this.player, inventory, this);
+        return this.bukkitEntity;
+    }
+    // CraftBukkit end
     public static final int MAX_NAME_LENGTH = 35;
     public static final int INPUT_SLOT = 0;
     public static final int ADDITIONAL_SLOT = 1;
@@ -28,30 +50,39 @@
     private static final int INV_SLOT_END = 30;
     private static final int USE_ROW_SLOT_START = 30;
     private static final int USE_ROW_SLOT_END = 39;
-    private final Container resultSlots = new ResultContainer();
-    final Container repairSlots = new SimpleContainer(2) {
-        @Override
-        public void setChanged() {
-            super.setChanged();
-            GrindstoneMenu.this.slotsChanged(this);
-        }
-    };
+    private final Container resultSlots;
+    final Container repairSlots;
     private final ContainerLevelAccess access;
 
     public GrindstoneMenu(int syncId, Inventory playerInventory) {
         this(syncId, playerInventory, ContainerLevelAccess.NULL);
     }
 
-    public GrindstoneMenu(int syncId, Inventory playerInventory, ContainerLevelAccess context) {
+    public GrindstoneMenu(int syncId, Inventory playerInventory, final ContainerLevelAccess context) {
         super(MenuType.GRINDSTONE, syncId);
+        this.resultSlots = new ResultContainer(this.createBlockHolder(context)); // Paper - Add missing InventoryHolders
+        this.repairSlots = new SimpleContainer(this.createBlockHolder(context), 2) { // Paper - Add missing InventoryHolders
+            @Override
+            public void setChanged() {
+                super.setChanged();
+                GrindstoneMenu.this.slotsChanged(this);
+            }
+
+            // CraftBukkit start
+            @Override
+            public Location getLocation() {
+                return context.getLocation();
+            }
+            // CraftBukkit end
+        };
         this.access = context;
-        this.addSlot(new Slot(this.repairSlots, 0, 49, 19) {
+        this.addSlot(new Slot(this.repairSlots, 0, 49, 19) { // CraftBukkit - decompile error
             @Override
             public boolean mayPlace(ItemStack stack) {
                 return stack.isDamageableItem() || EnchantmentHelper.hasAnyEnchantments(stack);
             }
         });
-        this.addSlot(new Slot(this.repairSlots, 1, 49, 40) {
+        this.addSlot(new Slot(this.repairSlots, 1, 49, 40) { // CraftBukkit - decompile error
             @Override
             public boolean mayPlace(ItemStack stack) {
                 return stack.isDamageableItem() || EnchantmentHelper.hasAnyEnchantments(stack);
@@ -64,55 +95,64 @@
             }
 
             @Override
-            public void onTake(Player player, ItemStack stack) {
-                context.execute((world, pos) -> {
+            public void onTake(net.minecraft.world.entity.player.Player player, ItemStack stack) {
+                context.execute((world, blockposition) -> {
                     if (world instanceof ServerLevel) {
-                        ExperienceOrb.award((ServerLevel)world, Vec3.atCenterOf(pos), this.getExperienceAmount(world));
+                        ExperienceOrb.award((ServerLevel) world, Vec3.atCenterOf(blockposition), this.getExperienceAmount(world), org.bukkit.entity.ExperienceOrb.SpawnReason.GRINDSTONE, player); // Paper
                     }
 
-                    world.levelEvent(1042, pos, 0);
+                    world.levelEvent(1042, blockposition, 0);
                 });
                 GrindstoneMenu.this.repairSlots.setItem(0, ItemStack.EMPTY);
                 GrindstoneMenu.this.repairSlots.setItem(1, ItemStack.EMPTY);
             }
 
             private int getExperienceAmount(Level world) {
-                int i = 0;
-                i += this.getExperienceFromItem(GrindstoneMenu.this.repairSlots.getItem(0));
-                i += this.getExperienceFromItem(GrindstoneMenu.this.repairSlots.getItem(1));
-                if (i > 0) {
-                    int j = (int)Math.ceil((double)i / 2.0);
-                    return j + world.random.nextInt(j);
+                int j = 0;
+
+                j += this.getExperienceFromItem(GrindstoneMenu.this.repairSlots.getItem(0));
+                j += this.getExperienceFromItem(GrindstoneMenu.this.repairSlots.getItem(1));
+                if (j > 0) {
+                    int k = (int) Math.ceil((double) j / 2.0D);
+
+                    return k + world.random.nextInt(k);
                 } else {
                     return 0;
                 }
             }
 
             private int getExperienceFromItem(ItemStack stack) {
-                int i = 0;
-                ItemEnchantments itemEnchantments = EnchantmentHelper.getEnchantmentsForCrafting(stack);
+                int j = 0;
+                ItemEnchantments itemenchantments = EnchantmentHelper.getEnchantmentsForCrafting(stack);
+                Iterator iterator = itemenchantments.entrySet().iterator();
+
+                while (iterator.hasNext()) {
+                    Entry<Holder<Enchantment>> entry = (Entry) iterator.next();
+                    Holder<Enchantment> holder = (Holder) entry.getKey();
+                    int k = entry.getIntValue();
 
-                for (Entry<Holder<Enchantment>> entry : itemEnchantments.entrySet()) {
-                    Holder<Enchantment> holder = entry.getKey();
-                    int j = entry.getIntValue();
                     if (!holder.is(EnchantmentTags.CURSE)) {
-                        i += holder.value().getMinCost(j);
+                        j += ((Enchantment) holder.value()).getMinCost(k);
                     }
                 }
 
-                return i;
+                return j;
             }
         });
 
-        for (int i = 0; i < 3; i++) {
-            for (int j = 0; j < 9; j++) {
-                this.addSlot(new Slot(playerInventory, j + i * 9 + 9, 8 + j * 18, 84 + i * 18));
+        int j;
+
+        for (j = 0; j < 3; ++j) {
+            for (int k = 0; k < 9; ++k) {
+                this.addSlot(new Slot(playerInventory, k + j * 9 + 9, 8 + k * 18, 84 + j * 18));
             }
         }
 
-        for (int k = 0; k < 9; k++) {
-            this.addSlot(new Slot(playerInventory, k, 8 + k * 18, 142));
+        for (j = 0; j < 9; ++j) {
+            this.addSlot(new Slot(playerInventory, j, 8 + j * 18, 142));
         }
+
+        this.player = (Player) playerInventory.player.getBukkitEntity(); // CraftBukkit
     }
 
     @Override
@@ -120,23 +160,29 @@
         super.slotsChanged(inventory);
         if (inventory == this.repairSlots) {
             this.createResult();
+            org.bukkit.craftbukkit.event.CraftEventFactory.callPrepareResultEvent(this, RESULT_SLOT); // Paper - Add PrepareResultEvent
         }
+
     }
 
     private void createResult() {
-        this.resultSlots.setItem(0, this.computeResult(this.repairSlots.getItem(0), this.repairSlots.getItem(1)));
+        org.bukkit.craftbukkit.event.CraftEventFactory.callPrepareGrindstoneEvent(this.getBukkitView(), this.computeResult(this.repairSlots.getItem(0), this.repairSlots.getItem(1))); // CraftBukkit
+        this.sendAllDataToRemote(); // CraftBukkit - SPIGOT-6686: Always send completed inventory to stay in sync with client
         this.broadcastChanges();
     }
 
     private ItemStack computeResult(ItemStack firstInput, ItemStack secondInput) {
-        boolean bl = !firstInput.isEmpty() || !secondInput.isEmpty();
-        if (!bl) {
+        boolean flag = !firstInput.isEmpty() || !secondInput.isEmpty();
+
+        if (!flag) {
             return ItemStack.EMPTY;
         } else if (firstInput.getCount() <= 1 && secondInput.getCount() <= 1) {
-            boolean bl2 = !firstInput.isEmpty() && !secondInput.isEmpty();
-            if (!bl2) {
-                ItemStack itemStack = !firstInput.isEmpty() ? firstInput : secondInput;
-                return !EnchantmentHelper.hasAnyEnchantments(itemStack) ? ItemStack.EMPTY : this.removeNonCursesFrom(itemStack.copy());
+            boolean flag1 = !firstInput.isEmpty() && !secondInput.isEmpty();
+
+            if (!flag1) {
+                ItemStack itemstack2 = !firstInput.isEmpty() ? firstInput : secondInput;
+
+                return !EnchantmentHelper.hasAnyEnchantments(itemstack2) ? ItemStack.EMPTY : this.removeNonCursesFrom(itemstack2.copy());
             } else {
                 return this.mergeItems(firstInput, secondInput);
             }
@@ -153,50 +199,59 @@
             int j = firstInput.getMaxDamage() - firstInput.getDamageValue();
             int k = secondInput.getMaxDamage() - secondInput.getDamageValue();
             int l = j + k + i * 5 / 100;
-            int m = 1;
+            byte b0 = 1;
+
             if (!firstInput.isDamageableItem()) {
                 if (firstInput.getMaxStackSize() < 2 || !ItemStack.matches(firstInput, secondInput)) {
                     return ItemStack.EMPTY;
                 }
 
-                m = 2;
+                b0 = 2;
             }
 
-            ItemStack itemStack = firstInput.copyWithCount(m);
-            if (itemStack.isDamageableItem()) {
-                itemStack.set(DataComponents.MAX_DAMAGE, i);
-                itemStack.setDamageValue(Math.max(i - l, 0));
+            ItemStack itemstack2 = firstInput.copyWithCount(b0);
+
+            if (itemstack2.isDamageableItem()) {
+                itemstack2.set(DataComponents.MAX_DAMAGE, i);
+                itemstack2.setDamageValue(Math.max(i - l, 0));
             }
 
-            this.mergeEnchantsFrom(itemStack, secondInput);
-            return this.removeNonCursesFrom(itemStack);
+            this.mergeEnchantsFrom(itemstack2, secondInput);
+            return this.removeNonCursesFrom(itemstack2);
         }
     }
 
     private void mergeEnchantsFrom(ItemStack target, ItemStack source) {
-        EnchantmentHelper.updateEnchantments(target, components -> {
-            ItemEnchantments itemEnchantments = EnchantmentHelper.getEnchantmentsForCrafting(source);
+        EnchantmentHelper.updateEnchantments(target, (itemenchantments_a) -> {
+            ItemEnchantments itemenchantments = EnchantmentHelper.getEnchantmentsForCrafting(source);
+            Iterator iterator = itemenchantments.entrySet().iterator();
 
-            for (Entry<Holder<Enchantment>> entry : itemEnchantments.entrySet()) {
-                Holder<Enchantment> holder = entry.getKey();
-                if (!holder.is(EnchantmentTags.CURSE) || components.getLevel(holder) == 0) {
-                    components.upgrade(holder, entry.getIntValue());
+            while (iterator.hasNext()) {
+                Entry<Holder<Enchantment>> entry = (Entry) iterator.next();
+                Holder<Enchantment> holder = (Holder) entry.getKey();
+
+                if (!holder.is(EnchantmentTags.CURSE) || itemenchantments_a.getLevel(holder) == 0) {
+                    itemenchantments_a.upgrade(holder, entry.getIntValue());
                 }
             }
+
         });
     }
 
     private ItemStack removeNonCursesFrom(ItemStack item) {
-        ItemEnchantments itemEnchantments = EnchantmentHelper.updateEnchantments(
-            item, components -> components.removeIf(enchantment -> !enchantment.is(EnchantmentTags.CURSE))
-        );
-        if (item.is(Items.ENCHANTED_BOOK) && itemEnchantments.isEmpty()) {
+        ItemEnchantments itemenchantments = EnchantmentHelper.updateEnchantments(item, (itemenchantments_a) -> {
+            itemenchantments_a.removeIf((holder) -> {
+                return !holder.is(EnchantmentTags.CURSE);
+            });
+        });
+
+        if (item.is(Items.ENCHANTED_BOOK) && itemenchantments.isEmpty()) {
             item = item.transmuteCopy(Items.BOOK);
         }
 
         int i = 0;
 
-        for (int j = 0; j < itemEnchantments.size(); j++) {
+        for (int j = 0; j < itemenchantments.size(); ++j) {
             i = AnvilMenu.calculateIncreasedRepairCost(i);
         }
 
@@ -205,60 +260,66 @@
     }
 
     @Override
-    public void removed(Player player) {
+    public void removed(net.minecraft.world.entity.player.Player player) {
         super.removed(player);
-        this.access.execute((world, pos) -> this.clearContainer(player, this.repairSlots));
+        this.access.execute((world, blockposition) -> {
+            this.clearContainer(player, this.repairSlots);
+        });
     }
 
     @Override
-    public boolean stillValid(Player player) {
+    public boolean stillValid(net.minecraft.world.entity.player.Player player) {
+        if (!this.checkReachable) return true; // CraftBukkit
         return stillValid(this.access, player, Blocks.GRINDSTONE);
     }
 
     @Override
-    public ItemStack quickMoveStack(Player player, int slot) {
-        ItemStack itemStack = ItemStack.EMPTY;
-        Slot slot2 = this.slots.get(slot);
-        if (slot2 != null && slot2.hasItem()) {
-            ItemStack itemStack2 = slot2.getItem();
-            itemStack = itemStack2.copy();
-            ItemStack itemStack3 = this.repairSlots.getItem(0);
-            ItemStack itemStack4 = this.repairSlots.getItem(1);
+    public ItemStack quickMoveStack(net.minecraft.world.entity.player.Player player, int slot) {
+        ItemStack itemstack = ItemStack.EMPTY;
+        Slot slot1 = (Slot) this.slots.get(slot);
+
+        if (slot1 != null && slot1.hasItem()) {
+            ItemStack itemstack1 = slot1.getItem();
+
+            itemstack = itemstack1.copy();
+            ItemStack itemstack2 = this.repairSlots.getItem(0);
+            ItemStack itemstack3 = this.repairSlots.getItem(1);
+
             if (slot == 2) {
-                if (!this.moveItemStackTo(itemStack2, 3, 39, true)) {
+                if (!this.moveItemStackTo(itemstack1, 3, 39, true)) {
                     return ItemStack.EMPTY;
                 }
 
-                slot2.onQuickCraft(itemStack2, itemStack);
+                slot1.onQuickCraft(itemstack1, itemstack);
             } else if (slot != 0 && slot != 1) {
-                if (!itemStack3.isEmpty() && !itemStack4.isEmpty()) {
+                if (!itemstack2.isEmpty() && !itemstack3.isEmpty()) {
                     if (slot >= 3 && slot < 30) {
-                        if (!this.moveItemStackTo(itemStack2, 30, 39, false)) {
+                        if (!this.moveItemStackTo(itemstack1, 30, 39, false)) {
                             return ItemStack.EMPTY;
                         }
-                    } else if (slot >= 30 && slot < 39 && !this.moveItemStackTo(itemStack2, 3, 30, false)) {
+                    } else if (slot >= 30 && slot < 39 && !this.moveItemStackTo(itemstack1, 3, 30, false)) {
                         return ItemStack.EMPTY;
                     }
-                } else if (!this.moveItemStackTo(itemStack2, 0, 2, false)) {
+                } else if (!this.moveItemStackTo(itemstack1, 0, 2, false)) {
                     return ItemStack.EMPTY;
                 }
-            } else if (!this.moveItemStackTo(itemStack2, 3, 39, false)) {
+            } else if (!this.moveItemStackTo(itemstack1, 3, 39, false)) {
                 return ItemStack.EMPTY;
             }
 
-            if (itemStack2.isEmpty()) {
-                slot2.setByPlayer(ItemStack.EMPTY);
+            if (itemstack1.isEmpty()) {
+                slot1.setByPlayer(ItemStack.EMPTY);
             } else {
-                slot2.setChanged();
+                slot1.setChanged();
             }
 
-            if (itemStack2.getCount() == itemStack.getCount()) {
+            if (itemstack1.getCount() == itemstack.getCount()) {
                 return ItemStack.EMPTY;
             }
 
-            slot2.onTake(player, itemStack2);
+            slot1.onTake(player, itemstack1);
         }
 
-        return itemStack;
+        return itemstack;
     }
 }
