From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 27 Apr 2016 22:09:52 -0400
Subject: [PATCH] Optimize Hoppers

* Removes unnecessary extra calls to .update() that are very expensive
* Lots of itemstack cloning removed. Only clone if the item is actually moved
* Return true when a plugin cancels inventory move item event instead of false, as false causes pulls to cycle through all items.
  However, pushes do not exhibit the same behavior, so this is not something plugins could of been relying on.
* Add option (Default on) to cooldown hoppers when they fail to move an item due to full inventory
* Skip subsequent InventoryMoveItemEvents if a plugin does not use the item after first event fire for an iteration by tracking changes to the event via an internal event implementation.
* Don't check for Entities with Inventories if the block above us is also occluding (not just Inventoried)
* Remove Streams from Item Suck In and restore restore 1.12 AABB checks which is simpler and no voxel allocations (was doing TWO Item Suck ins)

diff --git a/src/main/java/io/papermc/paper/event/inventory/PaperInventoryMoveItemEvent.java b/src/main/java/io/papermc/paper/event/inventory/PaperInventoryMoveItemEvent.java
new file mode 100644
index 0000000000000000000000000000000000000000..5c42823726e70ce6c9d0121d074315488e8b3f60
--- /dev/null
+++ b/src/main/java/io/papermc/paper/event/inventory/PaperInventoryMoveItemEvent.java
@@ -0,0 +1,31 @@
+package io.papermc.paper.event.inventory;
+
+import org.bukkit.event.inventory.InventoryMoveItemEvent;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+import org.jetbrains.annotations.NotNull;
+
+@DefaultQualifier(NonNull.class)
+public class PaperInventoryMoveItemEvent extends InventoryMoveItemEvent {
+
+    public boolean calledSetItem;
+    public boolean calledGetItem;
+
+    public PaperInventoryMoveItemEvent(final @NotNull Inventory sourceInventory, final @NotNull ItemStack itemStack, final @NotNull Inventory destinationInventory, final boolean didSourceInitiate) {
+        super(sourceInventory, itemStack, destinationInventory, didSourceInitiate);
+    }
+
+    @Override
+    public ItemStack getItem() {
+        this.calledGetItem = true;
+        return super.getItem();
+    }
+
+    @Override
+    public void setItem(final ItemStack itemStack) {
+        super.setItem(itemStack);
+        this.calledSetItem = true;
+    }
+}
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 3c230ae060998bfb79d5812fef21a80a9df8c8ff..64d0e04b6f9c52d90d0bc185b16a8a4768af4ac1 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1659,6 +1659,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             ServerLevel worldserver = (ServerLevel) iterator.next();
             worldserver.hasPhysicsEvent = org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - BlockPhysicsEvent
             worldserver.hasEntityMoveEvent = io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - Add EntityMoveEvent
+            net.minecraft.world.level.block.entity.HopperBlockEntity.skipHopperEvents = worldserver.paperConfig().hopper.disableMoveEvent || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper - Perf: Optimize Hoppers
 
             this.profiler.push(() -> {
                 String s = String.valueOf(worldserver);
diff --git a/src/main/java/net/minecraft/world/item/ItemStack.java b/src/main/java/net/minecraft/world/item/ItemStack.java
index 86197725f0f2ac1e650297ae7a79907578e0e8f1..312b57b4ef340935f4335989ce1d6a4b8b61532c 100644
--- a/src/main/java/net/minecraft/world/item/ItemStack.java
+++ b/src/main/java/net/minecraft/world/item/ItemStack.java
@@ -809,10 +809,16 @@ public final class ItemStack implements DataComponentHolder {
     }
 
     public ItemStack copy() {
-        if (this.isEmpty()) {
+        // Paper start - Perf: Optimize Hoppers
+        return this.copy(false);
+    }
+
+    public ItemStack copy(boolean originalItem) {
+        if (!originalItem && this.isEmpty()) {
+            // Paper end - Perf: Optimize Hoppers
             return ItemStack.EMPTY;
         } else {
-            ItemStack itemstack = new ItemStack(this.getItem(), this.count, this.components.copy());
+            ItemStack itemstack = new ItemStack(originalItem ? this.item : this.getItem(), this.count, this.components.copy()); // Paper - Perf: Optimize Hoppers
 
             itemstack.setPopTime(this.getPopTime());
             return itemstack;
diff --git a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
index cd3b952a228c09077c2e74183a34ddb32811280b..c0563260277f9f4bd9ff08993b2efb4bca9a0c60 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
@@ -38,6 +38,7 @@ import co.aikar.timings.MinecraftTimings; // Paper
 import co.aikar.timings.Timing; // Paper
 
 public abstract class BlockEntity {
+    static boolean ignoreTileUpdates; // Paper - Perf: Optimize Hoppers
 
     public Timing tickTimer = MinecraftTimings.getTileEntityTimings(this); // Paper
     // CraftBukkit start - data containers
@@ -216,6 +217,7 @@ public abstract class BlockEntity {
 
     public void setChanged() {
         if (this.level != null) {
+            if (ignoreTileUpdates) return; // Paper - Perf: Optimize Hoppers
             BlockEntity.setChanged(this.level, this.worldPosition, this.blockState);
         }
 
diff --git a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
index 92086ca118d55ec49cefa5bf18977f8706e3e4b4..8310d132006043e93c612890514c4c7f3eb1c74d 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
@@ -156,6 +156,43 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     }
 
+    // Paper start - Perf: Optimize Hoppers
+    private static final int HOPPER_EMPTY = 0;
+    private static final int HOPPER_HAS_ITEMS = 1;
+    private static final int HOPPER_IS_FULL = 2;
+
+    private static int getFullState(final HopperBlockEntity tileEntity) {
+        tileEntity.unpackLootTable(null);
+
+        final List<ItemStack> hopperItems = tileEntity.getItems();
+
+        boolean empty = true;
+        boolean full = true;
+
+        for (int i = 0, len = hopperItems.size(); i < len; ++i) {
+            final ItemStack stack = hopperItems.get(i);
+            if (stack.isEmpty()) {
+                full = false;
+                continue;
+            }
+
+            if (!full) {
+                // can't be full
+                return HOPPER_HAS_ITEMS;
+            }
+
+            empty = false;
+
+            if (stack.getCount() != stack.getMaxStackSize()) {
+                // can't be full or empty
+                return HOPPER_HAS_ITEMS;
+            }
+        }
+
+        return empty ? HOPPER_EMPTY : (full ? HOPPER_IS_FULL : HOPPER_HAS_ITEMS);
+    }
+    // Paper end - Perf: Optimize Hoppers
+
     private static boolean tryMoveItems(Level world, BlockPos pos, BlockState state, HopperBlockEntity blockEntity, BooleanSupplier booleansupplier) {
         if (world.isClientSide) {
             return false;
@@ -163,11 +200,12 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             if (!blockEntity.isOnCooldown() && (Boolean) state.getValue(HopperBlock.ENABLED)) {
                 boolean flag = false;
 
-                if (!blockEntity.isEmpty()) {
+                final int fullState = getFullState(blockEntity); // Paper - Perf: Optimize Hoppers
+                if (fullState != HOPPER_EMPTY) { // Paper - Perf: Optimize Hoppers
                     flag = HopperBlockEntity.ejectItems(world, pos, blockEntity);
                 }
 
-                if (!blockEntity.inventoryFull()) {
+                if (fullState != HOPPER_IS_FULL || flag) { // Paper - Perf: Optimize Hoppers
                     flag |= booleansupplier.getAsBoolean();
                 }
 
@@ -198,6 +236,202 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
         return false;
     }
 
+    // Paper start - Perf: Optimize Hoppers
+    private static boolean skipPullModeEventFire;
+    private static boolean skipPushModeEventFire;
+    public static boolean skipHopperEvents;
+
+    private static boolean hopperPush(final Level level, final Container destination, final Direction direction, final HopperBlockEntity hopper) {
+        skipPushModeEventFire = skipHopperEvents;
+        boolean foundItem = false;
+        for (int i = 0; i < hopper.getContainerSize(); ++i) {
+            final ItemStack item = hopper.getItem(i);
+            if (!item.isEmpty()) {
+                foundItem = true;
+                ItemStack origItemStack = item;
+                ItemStack movedItem = origItemStack;
+
+                final int originalItemCount = origItemStack.getCount();
+                final int movedItemCount = Math.min(level.spigotConfig.hopperAmount, originalItemCount);
+                origItemStack.setCount(movedItemCount);
+
+                // We only need to fire the event once to give protection plugins a chance to cancel this event
+                // Because nothing uses getItem, every event call should end up the same result.
+                if (!skipPushModeEventFire) {
+                    movedItem = callPushMoveEvent(destination, movedItem, hopper);
+                    if (movedItem == null) { // cancelled
+                        origItemStack.setCount(originalItemCount);
+                        return false;
+                    }
+                }
+
+                final ItemStack remainingItem = addItem(hopper, destination, movedItem, direction);
+                final int remainingItemCount = remainingItem.getCount();
+                if (remainingItemCount != movedItemCount) {
+                    origItemStack = origItemStack.copy(true);
+                    origItemStack.setCount(originalItemCount);
+                    if (!origItemStack.isEmpty()) {
+                        origItemStack.setCount(originalItemCount - movedItemCount + remainingItemCount);
+                    }
+                    hopper.setItem(i, origItemStack);
+                    destination.setChanged();
+                    return true;
+                }
+                origItemStack.setCount(originalItemCount);
+            }
+        }
+        if (foundItem && level.paperConfig().hopper.cooldownWhenFull) { // Inventory was full - cooldown
+            hopper.setCooldown(level.spigotConfig.hopperTransfer);
+        }
+        return false;
+    }
+
+    private static boolean hopperPull(final Level level, final Hopper hopper, final Container container, ItemStack origItemStack, final int i) {
+        ItemStack movedItem = origItemStack;
+        final int originalItemCount = origItemStack.getCount();
+        final int movedItemCount = Math.min(level.spigotConfig.hopperAmount, originalItemCount);
+        container.setChanged(); // original logic always marks source inv as changed even if no move happens.
+        movedItem.setCount(movedItemCount);
+
+        if (!skipPullModeEventFire) {
+            movedItem = callPullMoveEvent(hopper, container, movedItem);
+            if (movedItem == null) { // cancelled
+                origItemStack.setCount(originalItemCount);
+                // Drastically improve performance by returning true.
+                // No plugin could of relied on the behavior of false as the other call
+                // site for IMIE did not exhibit the same behavior
+                return true;
+            }
+        }
+
+        final ItemStack remainingItem = addItem(container, hopper, movedItem, null);
+        final int remainingItemCount = remainingItem.getCount();
+        if (remainingItemCount != movedItemCount) {
+            origItemStack = origItemStack.copy(true);
+            origItemStack.setCount(originalItemCount);
+            if (!origItemStack.isEmpty()) {
+                origItemStack.setCount(originalItemCount - movedItemCount + remainingItemCount);
+            }
+
+            ignoreTileUpdates = true;
+            container.setItem(i, origItemStack);
+            ignoreTileUpdates = false;
+            container.setChanged();
+            return true;
+        }
+        origItemStack.setCount(originalItemCount);
+
+        if (level.paperConfig().hopper.cooldownWhenFull) {
+            cooldownHopper(hopper);
+        }
+
+        return false;
+    }
+
+    @Nullable
+    private static ItemStack callPushMoveEvent(Container iinventory, ItemStack itemstack, HopperBlockEntity hopper) {
+        final Inventory destinationInventory = getInventory(iinventory);
+        final io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent event = new io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent(hopper.getOwner(false).getInventory(),
+            CraftItemStack.asCraftMirror(itemstack), destinationInventory, true);
+        final boolean result = event.callEvent();
+        if (!event.calledGetItem && !event.calledSetItem) {
+            skipPushModeEventFire = true;
+        }
+        if (!result) {
+            cooldownHopper(hopper);
+            return null;
+        }
+
+        if (event.calledSetItem) {
+            return CraftItemStack.asNMSCopy(event.getItem());
+        } else {
+            return itemstack;
+        }
+    }
+
+    @Nullable
+    private static ItemStack callPullMoveEvent(final Hopper hopper, final Container container, final ItemStack itemstack) {
+        final Inventory sourceInventory = getInventory(container);
+        final Inventory destination = getInventory(hopper);
+
+        // Mirror is safe as no plugins ever use this item
+        final io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent event = new io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent(sourceInventory, CraftItemStack.asCraftMirror(itemstack), destination, false);
+        final boolean result = event.callEvent();
+        if (!event.calledGetItem && !event.calledSetItem) {
+            skipPullModeEventFire = true;
+        }
+        if (!result) {
+            cooldownHopper(hopper);
+            return null;
+        }
+
+        if (event.calledSetItem) {
+            return CraftItemStack.asNMSCopy(event.getItem());
+        } else {
+            return itemstack;
+        }
+    }
+
+    private static Inventory getInventory(final Container container) {
+        final Inventory sourceInventory;
+        if (container instanceof CompoundContainer compoundContainer) {
+            // Have to special-case large chests as they work oddly
+            sourceInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest(compoundContainer);
+        } else if (container instanceof BlockEntity blockEntity) {
+            sourceInventory = blockEntity.getOwner(false).getInventory();
+        } else if (container.getOwner() != null) {
+            sourceInventory = container.getOwner().getInventory();
+        } else {
+            sourceInventory = new CraftInventory(container);
+        }
+        return sourceInventory;
+    }
+
+    private static void cooldownHopper(final Hopper hopper) {
+        if (hopper instanceof HopperBlockEntity blockEntity && blockEntity.getLevel() != null) {
+            blockEntity.setCooldown(blockEntity.getLevel().spigotConfig.hopperTransfer);
+        }
+    }
+
+    private static boolean allMatch(Container iinventory, Direction enumdirection, java.util.function.BiPredicate<ItemStack, Integer> test) {
+        if (iinventory instanceof WorldlyContainer) {
+            for (int i : ((WorldlyContainer) iinventory).getSlotsForFace(enumdirection)) {
+                if (!test.test(iinventory.getItem(i), i)) {
+                    return false;
+                }
+            }
+        } else {
+            int size = iinventory.getContainerSize();
+            for (int i = 0; i < size; i++) {
+                if (!test.test(iinventory.getItem(i), i)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    private static boolean anyMatch(Container iinventory, Direction enumdirection, java.util.function.BiPredicate<ItemStack, Integer> test) {
+        if (iinventory instanceof WorldlyContainer) {
+            for (int i : ((WorldlyContainer) iinventory).getSlotsForFace(enumdirection)) {
+                if (test.test(iinventory.getItem(i), i)) {
+                    return true;
+                }
+            }
+        } else {
+            int size = iinventory.getContainerSize();
+            for (int i = 0; i < size; i++) {
+                if (test.test(iinventory.getItem(i), i)) {
+                    return true;
+                }
+            }
+        }
+        return true;
+    }
+    private static final java.util.function.BiPredicate<ItemStack, Integer> STACK_SIZE_TEST = (itemstack, i) -> itemstack.getCount() >= itemstack.getMaxStackSize();
+    private static final java.util.function.BiPredicate<ItemStack, Integer> IS_EMPTY_TEST = (itemstack, i) -> itemstack.isEmpty();
+    // Paper end - Perf: Optimize Hoppers
+
     private static boolean ejectItems(Level world, BlockPos pos, HopperBlockEntity blockEntity) {
         Container iinventory = HopperBlockEntity.getAttachedContainer(world, pos, blockEntity);
 
@@ -209,47 +443,50 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             if (HopperBlockEntity.isFullContainer(iinventory, enumdirection)) {
                 return false;
             } else {
-                for (int i = 0; i < blockEntity.getContainerSize(); ++i) {
-                    ItemStack itemstack = blockEntity.getItem(i);
-
-                    if (!itemstack.isEmpty()) {
-                        int j = itemstack.getCount();
-                        // CraftBukkit start - Call event when pushing items into other inventories
-                        CraftItemStack oitemstack = CraftItemStack.asCraftMirror(blockEntity.removeItem(i, world.spigotConfig.hopperAmount)); // Spigot
-
-                        Inventory destinationInventory;
-                        // Have to special case large chests as they work oddly
-                        if (iinventory instanceof CompoundContainer) {
-                            destinationInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest((CompoundContainer) iinventory);
-                        } else if (iinventory.getOwner() != null) {
-                            destinationInventory = iinventory.getOwner().getInventory();
-                        } else {
-                            destinationInventory = new CraftInventory(iinventory);
-                        }
-
-                        InventoryMoveItemEvent event = new InventoryMoveItemEvent(blockEntity.getOwner().getInventory(), oitemstack, destinationInventory, true);
-                        world.getCraftServer().getPluginManager().callEvent(event);
-                        if (event.isCancelled()) {
-                            blockEntity.setItem(i, itemstack);
-                            blockEntity.setCooldown(world.spigotConfig.hopperTransfer); // Delay hopper checks // Spigot
-                            return false;
-                        }
-                        ItemStack itemstack1 = HopperBlockEntity.addItem(blockEntity, iinventory, CraftItemStack.asNMSCopy(event.getItem()), enumdirection);
-                        // CraftBukkit end
-
-                        if (itemstack1.isEmpty()) {
-                            iinventory.setChanged();
-                            return true;
-                        }
-
-                        itemstack.setCount(j);
-                        if (j == 1) {
-                            blockEntity.setItem(i, itemstack);
-                        }
-                    }
-                }
-
-                return false;
+                // Paper start - Perf: Optimize Hoppers
+                return hopperPush(world, iinventory, enumdirection, blockEntity);
+                //for (int i = 0; i < blockEntity.getContainerSize(); ++i) {
+                //    ItemStack itemstack = blockEntity.getItem(i);
+
+                //    if (!itemstack.isEmpty()) {
+                //        int j = itemstack.getCount();
+                //        // CraftBukkit start - Call event when pushing items into other inventories
+                //        CraftItemStack oitemstack = CraftItemStack.asCraftMirror(blockEntity.removeItem(i, world.spigotConfig.hopperAmount)); // Spigot
+
+                //        Inventory destinationInventory;
+                //        // Have to special case large chests as they work oddly
+                //        if (iinventory instanceof CompoundContainer) {
+                //            destinationInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest((CompoundContainer) iinventory);
+                //        } else if (iinventory.getOwner() != null) {
+                //            destinationInventory = iinventory.getOwner().getInventory();
+                //        } else {
+                //            destinationInventory = new CraftInventory(iinventory);
+                //        }
+
+                //        InventoryMoveItemEvent event = new InventoryMoveItemEvent(tileentityhopper.getOwner().getInventory(), oitemstack, destinationInventory, true);
+                //        world.getCraftServer().getPluginManager().callEvent(event);
+                //        if (event.isCancelled()) {
+                //            blockEntity.setItem(i, itemstack);
+                //            blockEntity.setCooldown(world.spigotConfig.hopperTransfer); // Delay hopper checks // Spigot
+                //            return false;
+                //        }
+                //        ItemStack itemstack1 = HopperBlockEntity.addItem(blockEntity, iinventory, CraftItemStack.asNMSCopy(event.getItem()), enumdirection);
+                //        // CraftBukkit end
+
+                //        if (itemstack1.isEmpty()) {
+                //            iinventory.setChanged();
+                //            return true;
+                //        }
+
+                //        itemstack.setCount(j);
+                //        if (j == 1) {
+                //            blockEntity.setItem(i, itemstack);
+                //        }
+                //    }
+                //}
+
+                // return false;
+                // Paper end - Perf: Optimize Hoppers
             }
         }
     }
@@ -300,7 +537,6 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                 return false;
             }
         }
-
         return true;
     }
 
@@ -311,6 +547,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
         if (iinventory != null) {
             Direction enumdirection = Direction.DOWN;
+            skipPullModeEventFire = skipHopperEvents; // Paper - Perf: Optimize Hoppers
             int[] aint = HopperBlockEntity.getSlots(iinventory, enumdirection);
             int i = aint.length;
 
@@ -346,44 +583,47 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
         ItemStack itemstack = iinventory.getItem(i);
 
         if (!itemstack.isEmpty() && HopperBlockEntity.canTakeItemFromContainer(ihopper, iinventory, itemstack, i, enumdirection)) {
-            int j = itemstack.getCount();
-            // CraftBukkit start - Call event on collection of items from inventories into the hopper
-            CraftItemStack oitemstack = CraftItemStack.asCraftMirror(iinventory.removeItem(i, world.spigotConfig.hopperAmount)); // Spigot
-
-            Inventory sourceInventory;
-            // Have to special case large chests as they work oddly
-            if (iinventory instanceof CompoundContainer) {
-                sourceInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest((CompoundContainer) iinventory);
-            } else if (iinventory.getOwner() != null) {
-                sourceInventory = iinventory.getOwner().getInventory();
-            } else {
-                sourceInventory = new CraftInventory(iinventory);
-            }
-
-            InventoryMoveItemEvent event = new InventoryMoveItemEvent(sourceInventory, oitemstack, ihopper.getOwner().getInventory(), false);
-
-            Bukkit.getServer().getPluginManager().callEvent(event);
-            if (event.isCancelled()) {
-                iinventory.setItem(i, itemstack);
-
-                if (ihopper instanceof HopperBlockEntity) {
-                    ((HopperBlockEntity) ihopper).setCooldown(world.spigotConfig.hopperTransfer); // Spigot
-                }
-
-                return false;
-            }
-            ItemStack itemstack1 = HopperBlockEntity.addItem(iinventory, ihopper, CraftItemStack.asNMSCopy(event.getItem()), null);
-            // CraftBukkit end
-
-            if (itemstack1.isEmpty()) {
-                iinventory.setChanged();
-                return true;
-            }
-
-            itemstack.setCount(j);
-            if (j == 1) {
-                iinventory.setItem(i, itemstack);
-            }
+            // Paper start - Perf: Optimize Hoppers
+            return hopperPull(world, ihopper, iinventory, itemstack, i);
+        //    int j = itemstack.getCount();
+        //    // CraftBukkit start - Call event on collection of items from inventories into the hopper
+        //    CraftItemStack oitemstack = CraftItemStack.asCraftMirror(iinventory.removeItem(i, world.spigotConfig.hopperAmount)); // Spigot
+
+        //    Inventory sourceInventory;
+        //    // Have to special case large chests as they work oddly
+        //    if (iinventory instanceof CompoundContainer) {
+        //        sourceInventory = new org.bukkit.craftbukkit.inventory.CraftInventoryDoubleChest((CompoundContainer) iinventory);
+        //    } else if (iinventory.getOwner() != null) {
+        //        sourceInventory = iinventory.getOwner().getInventory();
+        //    } else {
+        //        sourceInventory = new CraftInventory(iinventory);
+        //    }
+
+        //    InventoryMoveItemEvent event = new InventoryMoveItemEvent(sourceInventory, oitemstack, ihopper.getOwner().getInventory(), false);
+
+        //    Bukkit.getServer().getPluginManager().callEvent(event);
+        //    if (event.isCancelled()) {
+        //        iinventory.setItem(i, itemstack);
+
+        //        if (ihopper instanceof HopperBlockEntity) {
+        //            ((HopperBlockEntity) ihopper).setCooldown(world.spigotConfig.hopperTransfer); // Spigot
+        //        }
+
+        //        return false;
+        //    }
+        //    ItemStack itemstack1 = HopperBlockEntity.addItem(iinventory, ihopper, CraftItemStack.asNMSCopy(event.getItem()), null);
+        //    // CraftBukkit end
+
+        //    if (itemstack1.isEmpty()) {
+        //        iinventory.setChanged();
+        //        return true;
+        //    }
+
+        //    itemstack.setCount(j);
+        //    if (j == 1) {
+        //        iinventory.setItem(i, itemstack);
+        //    }
+            // Paper end - Perf: Optimize Hoppers
         }
 
         return false;
@@ -392,12 +632,14 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     public static boolean addItem(Container inventory, ItemEntity itemEntity) {
         boolean flag = false;
         // CraftBukkit start
-        InventoryPickupItemEvent event = new InventoryPickupItemEvent(inventory.getOwner().getInventory(), (org.bukkit.entity.Item) itemEntity.getBukkitEntity());
+        if (InventoryPickupItemEvent.getHandlerList().getRegisteredListeners().length > 0) { // Paper - optimize hoppers
+        InventoryPickupItemEvent event = new InventoryPickupItemEvent(getInventory(inventory), (org.bukkit.entity.Item) itemEntity.getBukkitEntity()); // Paper - Perf: Optimize Hoppers; use getInventory() to avoid snapshot creation
         itemEntity.level().getCraftServer().getPluginManager().callEvent(event);
         if (event.isCancelled()) {
             return false;
         }
         // CraftBukkit end
+        } // Paper - Perf: Optimize Hoppers
         ItemStack itemstack = itemEntity.getItem().copy();
         ItemStack itemstack1 = HopperBlockEntity.addItem((Container) null, inventory, itemstack, (Direction) null);
 
@@ -491,7 +733,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                     stack = stack.split(to.getMaxStackSize());
                 }
                 // Spigot end
+                ignoreTileUpdates = true; // Paper - Perf: Optimize Hoppers
                 to.setItem(slot, stack);
+                ignoreTileUpdates = false; // Paper - Perf: Optimize Hoppers
                 stack = leftover; // Paper - Make hoppers respect inventory max stack size
                 flag = true;
             } else if (HopperBlockEntity.canMergeItems(itemstack1, stack)) {
@@ -571,14 +815,20 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     @Nullable
     public static Container getContainerAt(Level world, BlockPos pos) {
-        return HopperBlockEntity.getContainerAt(world, pos, world.getBlockState(pos), (double) pos.getX() + 0.5D, (double) pos.getY() + 0.5D, (double) pos.getZ() + 0.5D);
+        return HopperBlockEntity.getContainerAt(world, pos, world.getBlockState(pos), (double) pos.getX() + 0.5D, (double) pos.getY() + 0.5D, (double) pos.getZ() + 0.5D, true);
     }
 
     @Nullable
     private static Container getContainerAt(Level world, BlockPos pos, BlockState state, double x, double y, double z) {
+        // Paper start - Perf: Optimize Hoppers
+        return HopperBlockEntity.getContainerAt(world, pos, state, x, y, z, false);
+    }
+    @Nullable
+    private static Container getContainerAt(Level world, BlockPos pos, BlockState state, double x, double y, double z, boolean optimizeEntities) {
+        // Paper end - Perf: Optimize Hoppers
         Container iinventory = HopperBlockEntity.getBlockContainer(world, pos, state);
 
-        if (iinventory == null) {
+        if (iinventory == null && (!optimizeEntities || !world.paperConfig().hopper.ignoreOccludingBlocks || !state.getBukkitMaterial().isOccluding())) { // Paper - Perf: Optimize Hoppers
             iinventory = HopperBlockEntity.getEntityContainer(world, x, y, z);
         }
 
@@ -613,13 +863,13 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     @Nullable
     private static Container getEntityContainer(Level world, double x, double y, double z) {
-        List<Entity> list = world.getEntities((Entity) null, new AABB(x - 0.5D, y - 0.5D, z - 0.5D, x + 0.5D, y + 0.5D, z + 0.5D), EntitySelector.CONTAINER_ENTITY_SELECTOR);
+        List<Entity> list = world.getEntitiesOfClass((Class) Container.class, new AABB(x - 0.5D, y - 0.5D, z - 0.5D, x + 0.5D, y + 0.5D, z + 0.5D), EntitySelector.CONTAINER_ENTITY_SELECTOR); // Paper - Perf: Optimize hoppers
 
         return !list.isEmpty() ? (Container) list.get(world.random.nextInt(list.size())) : null;
     }
 
     private static boolean canMergeItems(ItemStack first, ItemStack second) {
-        return first.getCount() <= first.getMaxStackSize() && ItemStack.isSameItemSameComponents(first, second);
+        return first.getCount() < first.getMaxStackSize() && ItemStack.isSameItemSameComponents(first, second); // Paper - Perf: Optimize Hoppers; used to return true for full itemstacks?!
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
index 13c9a68b604d4c7c6e09e72b3cea7ab2214b06ab..e2752752417c50b06f7c15b7d00bda0eaad3b0ae 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/RandomizableContainerBlockEntity.java
@@ -53,7 +53,7 @@ public abstract class RandomizableContainerBlockEntity extends BaseContainerBloc
 
     @Override
     public ItemStack getItem(int slot) {
-        this.unpackLootTable(null);
+        if (slot == 0) this.unpackLootTable(null); // Paper - Perf: Optimize Hoppers
         return super.getItem(slot);
     }
 
