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

/*
 * Minecraft Forge - Forge Development LLC
 * SPDX-License-Identifier: LGPL-2.1-only
 */

package net.minecraftforge.items;

import net.minecraft.world.entity.player.Player;
import net.minecraft.world.Container;
import net.minecraft.world.SimpleContainer;
import net.minecraft.world.inventory.Slot;
import net.minecraft.world.item.ItemStack;
import javax.annotation.Nonnull;

public class SlotItemHandler extends Slot
{
    private static Container emptyInventory = new SimpleContainer(0);
    private final IItemHandler itemHandler;
    private final int index;

    public SlotItemHandler(IItemHandler itemHandler, int index, int xPosition, int yPosition)
    {
        super(emptyInventory, index, xPosition, yPosition);
        this.itemHandler = itemHandler;
        this.index = index;
    }

    @Override
    public boolean mayPlace(@Nonnull ItemStack stack)
    {
        if (stack.isEmpty())
            return false;
        return itemHandler.isItemValid(index, stack);
    }

    @Override
    @Nonnull
    public ItemStack getItem()
    {
        return this.getItemHandler().getStackInSlot(index);
    }

    // Override if your IItemHandler does not implement IItemHandlerModifiable
    @Override
    public void set(@Nonnull ItemStack stack)
    {
        ((IItemHandlerModifiable) this.getItemHandler()).setStackInSlot(index, stack);
        this.setChanged();
    }

    @Override
    public void onQuickCraft(@Nonnull ItemStack oldStackIn, @Nonnull ItemStack newStackIn)
    {

    }

    @Override
    public int getMaxStackSize()
    {
        return this.itemHandler.getSlotLimit(this.index);
    }

    @Override
    public int getMaxStackSize(@Nonnull ItemStack stack)
    {
        ItemStack maxAdd = stack.copy();
        int maxInput = stack.getMaxStackSize();
        maxAdd.setCount(maxInput);

        IItemHandler handler = this.getItemHandler();
        ItemStack currentStack = handler.getStackInSlot(index);
        if (handler instanceof IItemHandlerModifiable) {
            IItemHandlerModifiable handlerModifiable = (IItemHandlerModifiable) handler;

            handlerModifiable.setStackInSlot(index, ItemStack.EMPTY);

            ItemStack remainder = handlerModifiable.insertItem(index, maxAdd, true);

            handlerModifiable.setStackInSlot(index, currentStack);

            return maxInput - remainder.getCount();
        }
        else
        {
            ItemStack remainder = handler.insertItem(index, maxAdd, true);

            int current = currentStack.getCount();
            int added = maxInput - remainder.getCount();
            return current + added;
        }
    }

    @Override
    public boolean mayPickup(Player playerIn)
    {
        return !this.getItemHandler().extractItem(index, 1, true).isEmpty();
    }

    @Override
    @Nonnull
    public ItemStack remove(int amount)
    {
        return this.getItemHandler().extractItem(index, amount, false);
    }

    public IItemHandler getItemHandler()
    {
        return itemHandler;
    }
/* TODO Slot patches
    @Override
    public boolean isSameInventory(Slot other)
    {
        return other instanceof SlotItemHandler && ((SlotItemHandler) other).getItemHandler() == this.itemHandler;
    }*/
}