minecraft-src/net/minecraft/world/Container.java

package net.minecraft.world;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.Predicate;
import net.minecraft.core.BlockPos;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.item.Item;
import net.minecraft.world.item.ItemStack;
import net.minecraft.world.level.Level;
import net.minecraft.world.level.block.entity.BlockEntity;

public interface Container extends Clearable, Iterable<ItemStack> {
	float DEFAULT_DISTANCE_BUFFER = 4.0F;

	/**
	 * Returns the number of slots in the inventory.
	 */
	int getContainerSize();

	boolean isEmpty();

	/**
	 * Returns the stack in the given slot.
	 */
	ItemStack getItem(int slot);

	/**
	 * Removes up to a specified number of items from an inventory slot and returns them in a new stack.
	 */
	ItemStack removeItem(int slot, int amount);

	/**
	 * Removes a stack from the given slot and returns it.
	 */
	ItemStack removeItemNoUpdate(int slot);

	/**
	 * Sets the given item stack to the specified slot in the inventory (can be crafting or armor sections).
	 */
	void setItem(int slot, ItemStack stack);

	/**
	 * Returns the maximum stack size for an inventory slot. Seems to always be 64, possibly will be extended.
	 */
	default int getMaxStackSize() {
		return 99;
	}

	default int getMaxStackSize(ItemStack stack) {
		return Math.min(this.getMaxStackSize(), stack.getMaxStackSize());
	}

	/**
	 * For block entities, ensures the chunk containing the block entity is saved to disk later - the game won't think it hasn't changed and skip it.
	 */
	void setChanged();

	/**
	 * Don't rename this method to canInteractWith due to conflicts with Container
	 */
	boolean stillValid(Player player);

	default void startOpen(Player player) {
	}

	default void stopOpen(Player player) {
	}

	/**
	 * Returns {@code true} if automation is allowed to insert the given stack (ignoring stack size) into the given slot. For guis use Slot.isItemValid
	 */
	default boolean canPlaceItem(int slot, ItemStack stack) {
		return true;
	}

	/**
	 * {@return {@code true} if the given stack can be extracted into the target inventory}
	 * 
	 * @param target the container into which the item should be extracted
	 * @param slot the slot from which to extract the item
	 * @param stack the item to extract
	 */
	default boolean canTakeItem(Container target, int slot, ItemStack stack) {
		return true;
	}

	/**
	 * Returns the total amount of the specified item in this inventory. This method does not check for nbt.
	 */
	default int countItem(Item item) {
		int i = 0;

		for (ItemStack itemStack : this) {
			if (itemStack.getItem().equals(item)) {
				i += itemStack.getCount();
			}
		}

		return i;
	}

	/**
	 * Returns {@code true} if any item from the passed set exists in this inventory.
	 */
	default boolean hasAnyOf(Set<Item> set) {
		return this.hasAnyMatching(itemStack -> !itemStack.isEmpty() && set.contains(itemStack.getItem()));
	}

	default boolean hasAnyMatching(Predicate<ItemStack> predicate) {
		for (ItemStack itemStack : this) {
			if (predicate.test(itemStack)) {
				return true;
			}
		}

		return false;
	}

	static boolean stillValidBlockEntity(BlockEntity blockEntity, Player player) {
		return stillValidBlockEntity(blockEntity, player, 4.0F);
	}

	static boolean stillValidBlockEntity(BlockEntity blockEntity, Player player, float distance) {
		Level level = blockEntity.getLevel();
		BlockPos blockPos = blockEntity.getBlockPos();
		if (level == null) {
			return false;
		} else {
			return level.getBlockEntity(blockPos) != blockEntity ? false : player.canInteractWithBlock(blockPos, distance);
		}
	}

	default Iterator<ItemStack> iterator() {
		return new Container.ContainerIterator(this);
	}

	public static class ContainerIterator implements Iterator<ItemStack> {
		private final Container container;
		private int index;
		private final int size;

		public ContainerIterator(Container container) {
			this.container = container;
			this.size = container.getContainerSize();
		}

		public boolean hasNext() {
			return this.index < this.size;
		}

		public ItemStack next() {
			if (!this.hasNext()) {
				throw new NoSuchElementException();
			} else {
				return this.container.getItem(this.index++);
			}
		}
	}
}