GildedRose-Refactoring-Kata/Java/src/main/java/com/gildedrose/GildedRose.java

package com.gildedrose;

class GildedRose {

    public static final String AGED_BRIE = "Aged Brie";
    public static final String SULFURAS = "Sulfuras, Hand of Ragnaros";
    public static final String BACKSTAGE = "Backstage passes to a TAFKAL80ETC concert";
    public static final String CONJURED = "Conjured Mana Cake";

    private Item[] items;

    public GildedRose(Item... items) {
        this.items = items;
    }

    public void updateQuality() {
        for (Item item : items) {
            updateItemQuality(item);
        }
    }

    private void updateItemQuality(Item item) {
            int degradeRate = item.name.equals(CONJURED) ? -2 : -1;
            if (!item.name.equals(AGED_BRIE)
                    && !item.name.equals(BACKSTAGE)) {
                if (item.quality > 0) {
                    if (!item.name.equals(SULFURAS)) {
                        adjustQuality(item, degradeRate);
                    }
                }
            } else {
                adjustQuality(item, 1);

                if (item.name.equals(BACKSTAGE)) {
                    if (item.sellIn < 11) {
                        adjustQuality(item, 1);
                    }

                    if (item.sellIn < 6) {
                        adjustQuality(item, 1);
                    }
                }
            }

            if (!item.name.equals(SULFURAS)) {
                item.sellIn = item.sellIn - 1;
            }

            if (item.sellIn < 0) {
                if (!item.name.equals(AGED_BRIE)) {
                    if (!item.name.equals(BACKSTAGE)) {
                        if (!item.name.equals(SULFURAS)) {
                            adjustQuality(item, degradeRate);
                        }
                    } else {
                        item.quality = item.quality - item.quality;
                    }
                } else {
                    int adjustment = 1;
                    adjustQuality(item, adjustment);
                }
            }
        }

    public void adjustQuality(Item item, int adjustment) {
        int newQuality = item.quality + adjustment;
        boolean isValid = newQuality <= 50 && newQuality >= 0;
        if (isValid) {
            item.quality = newQuality;
        }
    }

    public Item[] getItems() {
        return items;
    }
}