FreeFreshMilkWhenByAmericanoEspresso.php

<?php

use Foo\Cart;
use Foo\CartItem;
use Foo\FreshMilk;
use Foo\ThisConditionReturnItemInterface;

class FreeFreshMilkWhenByAmericanoEspresso implements ThisConditionReturnItemInterface
{
    $needToBuyBothToGetFreeFreshMilk = false;
        
    public function setNeedToBuyBothToGetFreeFreshMilk(bool $flag)
    {
        $this->needToBuyBothToGetFreeFreshMilk = $flag;
    }

    public function getItem(Cart $cart): CartItem
    {
        $amoutOfAmericano = $cart->items->find('Americano')->count();
        $amoutOfEspresso = $cart->items->find('Espresso')->count();
        
        $amoutOfFreshMilkFromAmericano = $amoutOfAmericano / 2;
        $amoutOfFreshMilkFromEspresso = $amoutOfEspresso / 2;
        
        if ($this->needToBuyBothToGetFreeFreshMilk) {
            $amoutOfFreshMilk = min($amoutOfFreshMilkFromAmericano, $amoutOfFreshMilkFromEspresso);
        } else {
            $amoutOfFreshMilk = max($amoutOfFreshMilkFromAmericano, $amoutOfFreshMilkFromEspresso);
        }
        
        return new CartItem(new FreshMilk, ['quantity' => $amoutOfFreshMilk, 'price' => 0]);
    }
}