MinecraftForge/src/main/java/net/minecraftforge/items/VanillaHopperItemHandler.java

/*
 * Minecraft Forge
 * Copyright (c) 2016-2019.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation version 2.1
 * of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

package net.minecraftforge.items;

import net.minecraft.item.ItemStack;
import net.minecraft.tileentity.HopperTileEntity;
import net.minecraftforge.items.wrapper.InvWrapper;

import javax.annotation.Nonnull;

public class VanillaHopperItemHandler extends InvWrapper
{
    private final HopperTileEntity hopper;

    public VanillaHopperItemHandler(HopperTileEntity hopper)
    {
        super(hopper);
        this.hopper = hopper;
    }

    @Override
    @Nonnull
    public ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate)
    {
        if (simulate)
        {
            return super.insertItem(slot, stack, simulate);
        }
        else
        {
            boolean wasEmpty = getInv().isEmpty();

            int originalStackSize = stack.getCount();
            stack = super.insertItem(slot, stack, simulate);

            if (wasEmpty && originalStackSize > stack.getCount())
            {
                if (!hopper.mayTransfer())
                {
                    // This cooldown is always set to 8 in vanilla with one exception:
                    // Hopper -> Hopper transfer sets this cooldown to 7 when this hopper
                    // has not been updated as recently as the one pushing items into it.
                    // This vanilla behavior is preserved by VanillaInventoryCodeHooks#insertStack,
                    // the cooldown is set properly by the hopper that is pushing items into this one.
                    hopper.setTransferCooldown(8);
                }
            }

            return stack;
        }
    }
}