PlayerHelper.java

package vazkii.botania.common.core.helper;

import java.util.function.Predicate;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.util.EnumHand;

public final class PlayerHelper {

	// Checks if either of the player's hands has an item.
	public static boolean hasAnyHeldItem(EntityPlayer player) {
		return !player.getHeldItemMainhand().isEmpty() || !player.getHeldItemOffhand().isEmpty();
	}

	// Checks main hand, then off hand for this item.
	public static boolean hasHeldItem(EntityPlayer player, Item item) {
		return !player.getHeldItemMainhand().isEmpty() && player.getHeldItemMainhand().getItem() == item
				|| !player.getHeldItemOffhand().isEmpty() && player.getHeldItemOffhand().getItem() == item;
	}

	// Checks main hand, then off hand for this item class.
	public static boolean hasHeldItemClass(EntityPlayer player, Item template) {
		return hasHeldItemClass(player, template.getClass());
	}

	// Checks main hand, then off hand for this item class.
	public static boolean hasHeldItemClass(EntityPlayer player, Class<?> template) {
		return !player.getHeldItemMainhand().isEmpty() && template.isAssignableFrom(player.getHeldItemMainhand().getItem().getClass())
				|| !player.getHeldItemOffhand().isEmpty() && template.isAssignableFrom(player.getHeldItemOffhand().getItem().getClass());
	}

	// Checks main hand, then off hand for this item. Null otherwise.
	public static ItemStack getFirstHeldItem(EntityPlayer player, Item item) {
		ItemStack main = player.getHeldItemMainhand();
		ItemStack offhand = player.getHeldItemOffhand();
		if(!main.isEmpty() && item == main.getItem()) {
			return main;
		} else if(!offhand.isEmpty() && item == offhand.getItem()) {
			return offhand;
		} else return ItemStack.EMPTY;
	}

	// Checks main hand, then off hand for this item class. Null otherwise.
	public static ItemStack getFirstHeldItemClass(EntityPlayer player, Class<?> template) {
		ItemStack main = player.getHeldItemMainhand();
		ItemStack offhand = player.getHeldItemOffhand();
		if(!main.isEmpty() && template.isAssignableFrom(main.getItem().getClass())) {
			return main;
		} else if(!offhand.isEmpty() && template.isAssignableFrom(offhand.getItem().getClass())) {
			return offhand;
		} else return ItemStack.EMPTY;
	}

	public static ItemStack getAmmo(EntityPlayer player, Predicate<ItemStack> ammoFunc) {
		// Mainly from ItemBow.findAmmo
		if (ammoFunc.test(player.getHeldItem(EnumHand.OFF_HAND)))
		{
			return player.getHeldItem(EnumHand.OFF_HAND);
		}
		else if (ammoFunc.test(player.getHeldItem(EnumHand.MAIN_HAND)))
		{
			return player.getHeldItem(EnumHand.MAIN_HAND);
		}
		else
		{
			for (int i = 0; i < player.inventory.getSizeInventory(); ++i)
			{
				ItemStack itemstack = player.inventory.getStackInSlot(i);

				if (ammoFunc.test(itemstack))
				{
					return itemstack;
				}
			}

			return ItemStack.EMPTY;
		}
	}

	public static boolean hasAmmo(EntityPlayer player, Predicate<ItemStack> ammoFunc) {
		return !getAmmo(player, ammoFunc).isEmpty();
	}

	public static void consumeAmmo(EntityPlayer player, Predicate<ItemStack> ammoFunc) {
		ItemStack ammo = getAmmo(player, ammoFunc);
		if(!ammo.isEmpty()) {
			ammo.shrink(1);
		}
	}

	public static boolean hasItem(EntityPlayer player, Predicate<ItemStack> itemFunc) {
		for (int i = 0; i < player.inventory.getSizeInventory(); i++) {
			if (itemFunc.test(player.inventory.getStackInSlot(i)))
				return true;
		}
		return false;
	}

	private PlayerHelper() {}
}