Add conjured item functionality

Java/src/main/java/com/gildedrose/AgedBrieItemUpdater.java

@@ -0,0 +1,9 @@
+package com.gildedrose;
+
+public class AgedBrieItemUpdater extends ItemUpdater {
+
+    @Override
+    int getIncrementValue() {
+        return 1;
+    }
+}

Java/src/main/java/com/gildedrose/BackstagePassesItemUpdater.java

@@ -0,0 +1,24 @@
+package com.gildedrose;
+
+public class BackstagePassesItemUpdater extends ItemUpdater {
+
+    @Override
+    public void update(Item item) {
+        updateQuality(item, getIncrementValue());
+        if (item.sellIn <= 10) {
+            updateQuality(item, getIncrementValue());
+        }
+        if (item.sellIn <= 5) {
+            updateQuality(item, getIncrementValue());
+        }
+        updateSellIn(item);
+        if (isExpired(item)) {
+            item.quality = 0;
+        }
+    }
+
+    @Override
+    int getIncrementValue() {
+        return 1;
+    }
+}

Java/src/main/java/com/gildedrose/ConjuredItemUpdater.java

@@ -0,0 +1,9 @@
+package com.gildedrose;
+
+public class ConjuredItemUpdater extends ItemUpdater {
+
+    @Override
+    int getIncrementValue() {
+        return -2;
+    }
+}

Java/src/main/java/com/gildedrose/GildedRose.java

@@ -8,55 +8,9 @@ class GildedRose {
     }
 
     public void updateQuality() {
-        for (int i = 0; i < items.length; i++) {
+        for (Item item : items) {
-            if (!items[i].name.equals("Aged Brie")
+            ItemUpdater itemUpdater = ItemUpdaterFactory.getUpdater(item);
-                    && !items[i].name.equals("Backstage passes to a TAFKAL80ETC concert")) {
+            itemUpdater.update(item);
-                if (items[i].quality > 0) {
-                    if (!items[i].name.equals("Sulfuras, Hand of Ragnaros")) {
-                        items[i].quality = items[i].quality - 1;
-                    }
-                }
-            } else {
-                if (items[i].quality < 50) {
-                    items[i].quality = items[i].quality + 1;
-
-                    if (items[i].name.equals("Backstage passes to a TAFKAL80ETC concert")) {
-                        if (items[i].sellIn < 11) {
-                            if (items[i].quality < 50) {
-                                items[i].quality = items[i].quality + 1;
-                            }
-                        }
-
-                        if (items[i].sellIn < 6) {
-                            if (items[i].quality < 50) {
-                                items[i].quality = items[i].quality + 1;
-                            }
-                        }
-                    }
-                }
-            }
-
-            if (!items[i].name.equals("Sulfuras, Hand of Ragnaros")) {
-                items[i].sellIn = items[i].sellIn - 1;
-            }
-
-            if (items[i].sellIn < 0) {
-                if (!items[i].name.equals("Aged Brie")) {
-                    if (!items[i].name.equals("Backstage passes to a TAFKAL80ETC concert")) {
-                        if (items[i].quality > 0) {
-                            if (!items[i].name.equals("Sulfuras, Hand of Ragnaros")) {
-                                items[i].quality = items[i].quality - 1;
-                            }
-                        }
-                    } else {
-                        items[i].quality = items[i].quality - items[i].quality;
-                    }
-                } else {
-                    if (items[i].quality < 50) {
-                        items[i].quality = items[i].quality + 1;
-                    }
-                }
-            }
         }
     }
 }

Java/src/main/java/com/gildedrose/ItemUpdater.java

@@ -0,0 +1,31 @@
+package com.gildedrose;
+
+import static java.lang.Math.max;
+import static java.lang.Math.min;
+
+public abstract class ItemUpdater {
+    public static final int QUALITY_MIN = 0;
+    public static final int QUALITY_MAX = 50;
+
+    protected void update(Item item){
+        updateQuality(item, getIncrementValue());
+        updateSellIn(item);
+        if (isExpired(item)) {
+            updateQuality(item, getIncrementValue());
+        }
+    }
+
+    abstract int getIncrementValue();
+
+    boolean isExpired(Item item) {
+        return item.sellIn < 0;
+    }
+
+    void updateQuality(Item item, int increment){
+        item.quality = max(QUALITY_MIN, min(QUALITY_MAX, item.quality + increment));
+    }
+
+    final void updateSellIn(Item item) {
+        item.sellIn = (int) max(Integer.MIN_VALUE, min(Integer.MAX_VALUE, ((long) item.sellIn) - 1));
+    }
+}

Java/src/main/java/com/gildedrose/ItemUpdaterFactory.java

@@ -0,0 +1,23 @@
+package com.gildedrose;
+
+public final class ItemUpdaterFactory {
+
+    private ItemUpdaterFactory() {
+        throw new UnsupportedOperationException("Class cannot be instantiated");
+    }
+
+    public static ItemUpdater getUpdater(Item item) {
+        switch (item.name) {
+            case "Aged Brie":
+                return new AgedBrieItemUpdater();
+            case "Backstage passes to a TAFKAL80ETC concert":
+                return new BackstagePassesItemUpdater();
+            case "Sulfuras, Hand of Ragnaros":
+                return new SulfurasItemUpdater();
+            case "Conjured Mana Cake":
+                return new ConjuredItemUpdater();
+            default:
+                return new RegularItemUpdater();
+        }
+    }
+}

Java/src/main/java/com/gildedrose/RegularItemUpdater.java

@@ -0,0 +1,9 @@
+package com.gildedrose;
+
+public class RegularItemUpdater extends ItemUpdater {
+
+    @Override
+    int getIncrementValue() {
+        return -1;
+    }
+}

Java/src/main/java/com/gildedrose/SulfurasItemUpdater.java

@@ -0,0 +1,14 @@
+package com.gildedrose;
+
+public class SulfurasItemUpdater extends ItemUpdater {
+
+    @Override
+    public void update(Item item) {
+        // Don't change legendary item
+    }
+
+    @Override
+    int getIncrementValue() {
+        return 0;
+    }
+}