PlayerItemInventory.java

package openmods.inventory;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.ItemStack;
import openmods.Log;
import openmods.utils.ItemUtils;

public class PlayerItemInventory extends ItemInventory {

	private final EntityPlayer player;
	private final int inventorySlot;
	private final int selfId = System.identityHashCode(this);

	private boolean isValid = true;

	private static final String TAG_INV = "openedInGui";

	private static void setGuiId(ItemStack stack, int id) {
		ItemUtils.getItemTag(stack).setInteger(TAG_INV, id);
	}

	private static int getGuiId(ItemStack stack) {
		return ItemUtils.getItemTag(stack).getInteger(TAG_INV);
	}

	// Potentially unsecure: player can switch item before inventory opens
	public PlayerItemInventory(EntityPlayer player, int size) {
		this(player, size, player.inventory.currentItem);
	}

	public PlayerItemInventory(EntityPlayer player, int size, int inventorySlot) {
		super(player.inventory.getStackInSlot(inventorySlot), size);
		this.player = player;
		this.inventorySlot = inventorySlot;
		setGuiId(containerStack, selfId);
	}

	private void invalidate(EntityPlayer player) {
		Log.info("Player %s tried to trigger item duplication bug", player);
		this.isValid = false;
	}

	@Override
	public boolean isUseableByPlayer(EntityPlayer player) {
		if (!(player == this.player && player.inventory.currentItem == inventorySlot)) {
			invalidate(player);
			return false;
		}

		if (!player.worldObj.isRemote) {
			final ItemStack currentItem = player.inventory.getCurrentItem();
			if (currentItem == null || !currentItem.isItemEqual(containerStack) || getGuiId(currentItem) != selfId) {
				invalidate(player);
				return false;
			}
		}

		return true;
	}

	@Override
	public void onInventoryChanged(int slotNumber) {
		super.onInventoryChanged(slotNumber);
		if (isValid)
			player.inventory.setInventorySlotContents(inventorySlot, containerStack);
	}
}