@Mod.EventBusSubscriber(modid="planetcore")
public class AnvilHandler {
    @SubscribeEvent
    public static void onAnvilUpdate(AnvilUpdateEvent event) {
        ItemStack stack1 = event.getLeft();
        ItemStack stack2 = event.getRight();

        if (stack1.getItem() instanceof EmeraldBody && stack2.getItem() instanceof EmeraldBody) {
            int finalDamage = stack1.getItemDamage() + stack2.getItemDamage();

            ItemStack finalResult = new ItemStack(ModItems.EMERALD_CHESTPLATE1);
            finalResult.setItemDamage(finalDamage);

            Map<Enchantment, Integer> map = EnchantmentHelper.getEnchantments(stack1);

            EnchantmentHelper.getEnchantments(stack2).forEach((ench, level) -> {
                if (map.containsKey(ench)) {
                    if (map.get(ench) < level)
                        map.replace(ench, level);
                } else {
                    map.put(ench, level);
                }
            });
            event.setCost(4);
            EnchantmentHelper.setEnchantments(map, finalResult);
            event.setOutput(finalResult);
        }
    }
}