Polymorphism refactoring

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

@@ -1,12 +1,18 @@
 package com.gildedrose;
 
-import static com.gildedrose.Inventory.BACKSTAGE_PASS;
-import static com.gildedrose.Inventory.LEGENDARY;
-import static com.gildedrose.service.InventoryHelper.*;
+import com.gildedrose.domain.*;
+import com.gildedrose.service.InventoryItem;
+
 import static java.util.stream.IntStream.range;
 import static java.util.stream.Stream.of;
 
 class GildedRose {
+
+    private static final String AGED_BRIE = "Aged Brie";
+    private static final String LEGENDARY = "Sulfuras, Hand of Ragnaros";
+    private static final String CONJURED_ITEM = "Conjured Mana Cake";
+    private static final String BACKSTAGE_PASS = "Backstage passes to a TAFKAL80ETC concert";
+
     Item[] items;
 
     GildedRose(Item[] items) {
@@ -15,29 +21,39 @@ class GildedRose {
 
     void updateQuality() {
         of(items).forEach(item -> {
-            // legendary items should not be sold
-            if (itemNotLegendary(item)) item.sellIn--;
+            InventoryItem inventoryItem = inventoryFromItem(item);
+
+            // reduce sellIn
+            item.sellIn = inventoryItem.reduceSellIn();
 
             // increase quality when quality decrease is inverted
-            if (includesItems(item, getInventoriesWithInvertedQualityDecrease())) {
-                increaseQualityBelowMaximum(item);
-
-                // increase backstage passes
-                increaseBackstagePass(item);
+            if (inventoryItem.qualityDecreaseInverted()) {
+                item.quality = inventoryItem.increaseQualityBelowMaximum();
             }
-            // decrease average (non-legendary) items
-            else if (itemNotLegendary(item)) {
-                // decrease quality based on their decrease amount
-                range(0, getQualityDecreaseAmount(item)).forEach(i -> decreaseQualityAboveZero(item));
+
+            // decrease quality based on their decrease amount
+            else {
+                range(0, inventoryItem.qualityDecreaseAmount()).forEach(i -> item.quality = inventoryItem.decreaseQualityAboveZero());
             }
 
             if (item.sellIn < 0) {
-                // increase quality when aged brie
-                if (itemAgedBrie(item)) increaseQualityBelowMaximum(item);
-
-                    // when not aged brie, backstage pass or legendary, decrease quality above zero
-                else decreaseQualityAboveZeroItemsOtherThan(item, BACKSTAGE_PASS, LEGENDARY);
+                item.quality = inventoryItem.handleQualityAfterSellIn();
             }
         });
     }
+
+    private InventoryItem inventoryFromItem(Item item) {
+        switch (item.name) {
+            case AGED_BRIE:
+                return new AgedBrie(item);
+            case LEGENDARY:
+                return new Legendary(item);
+            case CONJURED_ITEM:
+                return new ConjuredItem(item);
+            case BACKSTAGE_PASS:
+                return new BackstagePass(item);
+            default:
+                return new DefaultItem(item);
+        }
+    }
 }

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

@@ -1,17 +0,0 @@
-package com.gildedrose;
-
-import lombok.AllArgsConstructor;
-import lombok.Getter;
-
-@Getter
-@AllArgsConstructor
-public enum Inventory {
-    AGED_BRIE("Aged Brie", true, 1),
-    LEGENDARY("Sulfuras, Hand of Ragnaros", false, 0),
-    CONJURED("Conjured Mana Cake", false, 2),
-    BACKSTAGE_PASS("Backstage passes to a TAFKAL80ETC concert", true, 1);
-
-    private String name;
-    private boolean qualityDecreaseInverted;
-    private int qualityDecrease;
-}

Java/src/main/java/com/gildedrose/domain/AgedBrie.java

@@ -0,0 +1,29 @@
+package com.gildedrose.domain;
+
+import com.gildedrose.Item;
+import com.gildedrose.service.InventoryItem;
+
+public class AgedBrie extends InventoryItem {
+
+    public AgedBrie(Item item) {
+        setName(item.name);
+        setSellIn(item.sellIn);
+        setQuality(item.quality);
+    }
+
+    @Override
+    public boolean qualityDecreaseInverted() {
+        return true;
+    }
+
+    @Override
+    public int qualityDecreaseAmount() {
+        return 1;
+    }
+
+    @Override
+    public int handleQualityAfterSellIn() {
+        quality = increaseQualityBelowMaximum();
+        return quality;
+    }
+}

Java/src/main/java/com/gildedrose/domain/BackstagePass.java

@@ -0,0 +1,53 @@
+package com.gildedrose.domain;
+
+import com.gildedrose.Item;
+import com.gildedrose.service.InventoryItem;
+
+public class BackstagePass extends InventoryItem {
+
+    public BackstagePass(Item item) {
+        setName(item.name);
+        setSellIn(item.sellIn);
+        setQuality(item.quality);
+    }
+
+    @Override
+    public boolean qualityDecreaseInverted() {
+        return true;
+    }
+
+    @Override
+    public int qualityDecreaseAmount() {
+        return 1;
+    }
+
+    @Override
+    public int handleQualityAfterSellIn() {
+        quality = 0;
+        return quality;
+    }
+
+    @Override
+    public int increaseQualityBelowMaximum() {
+        quality = increaseQualityIfNotMaximum();
+
+        // increase backstage pass further when sellIn date approaches
+        quality = increaseBackstagePass();
+        return quality;
+    }
+
+    private int increaseBackstagePass() {
+        if (sellIn < 10) {
+            quality = increaseQualityIfNotMaximum();
+
+            if (sellIn < 5) {
+                quality = increaseQualityIfNotMaximum();
+            }
+        }
+        return quality;
+    }
+
+    private int increaseQualityIfNotMaximum() {
+        return super.increaseQualityBelowMaximum();
+    }
+}

Java/src/main/java/com/gildedrose/domain/ConjuredItem.java

@@ -0,0 +1,29 @@
+package com.gildedrose.domain;
+
+import com.gildedrose.Item;
+import com.gildedrose.service.InventoryItem;
+
+public class ConjuredItem extends InventoryItem {
+
+    public ConjuredItem(Item item) {
+        setName(item.name);
+        setSellIn(item.sellIn);
+        setQuality(item.quality);
+    }
+
+    @Override
+    public boolean qualityDecreaseInverted() {
+        return false;
+    }
+
+    @Override
+    public int qualityDecreaseAmount() {
+        return 2;
+    }
+
+    @Override
+    public int handleQualityAfterSellIn() {
+        quality = decreaseQualityAboveZero();
+        return quality;
+    }
+}

Java/src/main/java/com/gildedrose/domain/DefaultItem.java

@@ -0,0 +1,29 @@
+package com.gildedrose.domain;
+
+import com.gildedrose.Item;
+import com.gildedrose.service.InventoryItem;
+
+public class DefaultItem extends InventoryItem {
+
+    public DefaultItem(Item item) {
+        setName(item.name);
+        setSellIn(item.sellIn);
+        setQuality(item.quality);
+    }
+
+    @Override
+    public boolean qualityDecreaseInverted() {
+        return false;
+    }
+
+    @Override
+    public int qualityDecreaseAmount() {
+        return 1;
+    }
+
+    @Override
+    public int handleQualityAfterSellIn() {
+        quality = decreaseQualityAboveZero();
+        return quality;
+    }
+}

Java/src/main/java/com/gildedrose/domain/Legendary.java

@@ -0,0 +1,39 @@
+package com.gildedrose.domain;
+
+import com.gildedrose.Item;
+import com.gildedrose.service.InventoryItem;
+
+public class Legendary extends InventoryItem {
+
+    public Legendary(Item item) {
+        super();
+        setName(item.name);
+        setSellIn(item.sellIn);
+        setQuality(item.quality);
+    }
+
+    @Override
+    public boolean qualityDecreaseInverted() {
+        return false;
+    }
+
+    @Override
+    public int qualityDecreaseAmount() {
+        return 0;
+    }
+
+    @Override
+    public int handleQualityAfterSellIn() {
+        return quality;
+    }
+
+    @Override
+    public int decreaseQualityAboveZero() {
+        return quality;
+    }
+
+    @Override
+    public int reduceSellIn() {
+        return sellIn;
+    }
+}

Java/src/main/java/com/gildedrose/service/InventoryHelper.java

@@ -1,64 +0,0 @@
-package com.gildedrose.service;
-
-import com.gildedrose.Inventory;
-import com.gildedrose.Item;
-
-import static com.gildedrose.Inventory.*;
-import static java.util.stream.Stream.of;
-
-public class InventoryHelper {
-    private static final int MAX_QUALITY = 50;
-
-    public static Inventory[] getInventoriesWithInvertedQualityDecrease() {
-        return of(Inventory.values())
-            .filter(Inventory::isQualityDecreaseInverted)
-            .distinct()
-            .toArray(Inventory[]::new);
-    }
-
-    public static void decreaseQualityAboveZeroItemsOtherThan(Item item, Inventory... inventories) {
-        if (!includesItems(item, inventories)) {
-            decreaseQualityAboveZero(item);
-        } else if (itemNotLegendary(item)) item.quality = 0;
-    }
-
-    public static boolean includesItems(Item item, Inventory... inventories) {
-        return of(inventories).anyMatch(inventory -> item.name.equals(inventory.getName()));
-    }
-
-    public static boolean itemNotLegendary(Item item) {
-        return !item.name.equals(LEGENDARY.getName());
-    }
-
-    public static boolean itemAgedBrie(Item item) {
-        return item.name.equals(AGED_BRIE.getName());
-    }
-
-    public static int getQualityDecreaseAmount(Item item) {
-        return of(Inventory.values())
-            .filter(inventory -> inventory.getName().equals(item.name))
-            .findFirst()
-            .map(Inventory::getQualityDecrease)
-            .orElse(1);
-    }
-
-    public static void decreaseQualityAboveZero(Item item) {
-        item.quality = item.quality > 0 ? item.quality - 1 : 0;
-    }
-
-    public static void increaseQualityBelowMaximum(Item item) {
-        if (item.quality < MAX_QUALITY) {
-            item.quality++;
-        }
-    }
-
-    public static void increaseBackstagePass(Item item) {
-        if (item.name.equals(BACKSTAGE_PASS.getName()) && item.sellIn < 10) {
-            increaseQualityBelowMaximum(item);
-
-            if (item.sellIn < 5) {
-                increaseQualityBelowMaximum(item);
-            }
-        }
-    }
-}

Java/src/main/java/com/gildedrose/service/InventoryItem.java

@@ -0,0 +1,37 @@
+package com.gildedrose.service;
+
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@NoArgsConstructor
+@Setter
+public abstract class InventoryItem {
+    private static final int MAX_QUALITY = 50;
+
+    public String name;
+    public int quality;
+    public int sellIn;
+
+    public abstract boolean qualityDecreaseInverted();
+
+    public abstract int qualityDecreaseAmount();
+
+    public abstract int handleQualityAfterSellIn();
+
+    public int decreaseQualityAboveZero() {
+        quality = quality > 0 ? quality - 1 : 0;
+        return quality;
+    }
+
+    public int increaseQualityBelowMaximum() {
+        if (quality < MAX_QUALITY) {
+            quality++;
+        }
+        return quality;
+    }
+
+    public int reduceSellIn() {
+        sellIn--;
+        return sellIn;
+    }
+}