IItemHandler.java

/*
 * Minecraft Forge
 * Copyright (c) 2016.
 *
 * 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 javax.annotation.Nonnull;

public interface IItemHandler
{
    /**
     * Returns the number of slots available
     *
     * @return The number of slots available
     **/
    int getSlots();

    /**
     * Returns the ItemStack in a given slot.
     *
     * The result's stack size may be greater than the itemstacks max size.
     *
     * If the result is null, then the slot is empty.
     * If the result is not null but the stack size is zero, then it represents
     * an empty slot that will only accept* a specific itemstack.
     *
     * <p/>
     * IMPORTANT: This ItemStack MUST NOT be modified. This method is not for
     * altering an inventories contents. Any implementers who are able to detect
     * modification through this method should throw an exception.
     * <p/>
     * SERIOUSLY: DO NOT MODIFY THE RETURNED ITEMSTACK
     *
     * @param slot Slot to query
     * @return ItemStack in given slot. May be null.
     **/
    @Nonnull
    ItemStack getStackInSlot(int slot);

    /**
     * Inserts an ItemStack into the given slot and return the remainder.
     * The ItemStack should not be modified in this function!
     * Note: This behaviour is subtly different from IFluidHandlers.fill()
     *
     * @param slot     Slot to insert into.
     * @param stack    ItemStack to insert.
     * @param simulate If true, the insertion is only simulated
     * @return The remaining ItemStack that was not inserted (if the entire stack is accepted, then return ItemStack.EMPTY).
     *         May be the same as the input ItemStack if unchanged, otherwise a new ItemStack.
     **/
    @Nonnull
    ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate);

    /**
     * Extracts an ItemStack from the given slot. The returned value must be null
     * if nothing is extracted, otherwise it's stack size must not be greater than amount or the
     * itemstacks getMaxStackSize().
     *
     * @param slot     Slot to extract from.
     * @param amount   Amount to extract (may be greater than the current stacks max limit)
     * @param simulate If true, the extraction is only simulated
     * @return ItemStack extracted from the slot, must be ItemStack.EMPTY, if nothing can be extracted
     **/
    @Nonnull
    ItemStack extractItem(int slot, int amount, boolean simulate);

    /**
     * Retrieves the maximum stack size allowed to exist in the given slot.
     *
     * @param slot Slot to query.
     * @return     The maximum stack size allowed in the slot.
     */
    int getSlotLimit(int slot);
}