AgedBrieItemTypes.php

<?php
/**
 * Aged Brie Item Types
 * All items have a SellIn value which denotes the number of days we have to sell the item
 * All items have a Quality value which denotes how valuable the item is
 * At the end of each day our system lowers both values for every item

 * Once the sell by date has passed, Quality degrades twice as fast
 * The Quality of an item is never negative
 * "Aged Brie" actually increases in Quality the older it gets
 * The Quality of an item is never more than 50
 */

namespace App\ItemTypes;

use App\Item;

class AgedBrieItemTypes
{
    public function itemType(Item $item): bool {
        return ($item->name == 'Aged Brie');
    }

    public function nextDay(Item $item) {
        // Initial values
        $quality = 1;
        $sellIn = -1;

        $item->sellIn = $item->sellIn + $sellIn;
        if($item->sellIn < 1) { $quality = 2; }

        // Check that qualty will not exceed 50
        if($item->quality + $quality > 50) { $quality = 50 - $item->quality; }
        $item->quality = $item->quality + $quality;
    }
}