Refactor Gilded Rose to use polymorphic item types

python/gilded_rose.py

@@ -1,39 +1,26 @@
-# -*- coding: utf-8 -*-
-
 class GildedRose(object):
 
     def __init__(self, items):
-        self.items = items
+
+        self.items = [self._create_specific_item(item) for item in items]
+
+    def _create_specific_item(self, item):
+        """
+        :param item: Take param as Item object
+        :return: Specified Item object based on specification.
+        """
+        if item.name.startswith("Aged Brie"):
+            return AgedBrieItem(item.name, item.sell_in, item.quality)
+        elif item.name.startswith("Sulfuras"):
+            return SulfurasItem(item.name, item.sell_in, item.quality)
+        elif item.name.startswith("Backstage"):
+            return BackstagePassItem(item.name, item.sell_in, item.quality)
+        else:
+            return NormalItem(item.name, item.sell_in, item.quality)
 
     def update_quality(self):
         for item in self.items:
-            if item.name != "Aged Brie" and item.name != "Backstage passes to a TAFKAL80ETC concert":
-                if item.quality > 0:
-                    if item.name != "Sulfuras, Hand of Ragnaros":
-                        item.quality = item.quality - 1
-            else:
-                if item.quality < 50:
-                    item.quality = item.quality + 1
-                    if item.name == "Backstage passes to a TAFKAL80ETC concert":
-                        if item.sell_in < 11:
-                            if item.quality < 50:
-                                item.quality = item.quality + 1
-                        if item.sell_in < 6:
-                            if item.quality < 50:
-                                item.quality = item.quality + 1
-            if item.name != "Sulfuras, Hand of Ragnaros":
-                item.sell_in = item.sell_in - 1
-            if item.sell_in < 0:
-                if item.name != "Aged Brie":
-                    if item.name != "Backstage passes to a TAFKAL80ETC concert":
-                        if item.quality > 0:
-                            if item.name != "Sulfuras, Hand of Ragnaros":
-                                item.quality = item.quality - 1
-                    else:
-                        item.quality = item.quality - item.quality
-                else:
-                    if item.quality < 50:
-                        item.quality = item.quality + 1
+            item.update_quality()
 
 
 class Item:
@@ -44,3 +31,54 @@ class Item:
 
     def __repr__(self):
         return "%s, %s, %s" % (self.name, self.sell_in, self.quality)
+
+    def update_quality(self):
+
+        self.sell_in -= 1
+        if self.quality > 0:
+            self.quality -= 1
+
+        if self.sell_in < 0 and self.quality > 0:
+            self.quality -= 1
+
+    def _decrease_quality(self, amount=1):
+        # Setting minimum quality to zero.
+        self.quality = max(0, self.quality - amount)
+
+    def _increase_quality(self, amount=1):
+        # Setting a limit to 50 as described in spec
+        self.quality = min(50, self.quality + amount)
+
+
+class NormalItem(Item):
+    pass
+
+
+class AgedBrieItem(Item):
+    def update_quality(self):
+        self.sell_in -= 1
+        self._increase_quality()  # It increases in quality as per spec
+        if self.sell_in < 0:
+            self._increase_quality()  # It increases in quality by double after sell_in passes as per spec
+
+
+class SulfurasItem(Item):
+    def update_quality(self):
+        # It never changes any attributes
+        pass
+
+
+class BackstagePassItem(Item):
+    def update_quality(self):
+        self.sell_in -= 1
+        self._increase_quality()
+
+        if self.sell_in < 10:
+            self._increase_quality()
+
+        if self.sell_in < 5:
+            self._increase_quality()
+
+        if self.sell_in < 0:
+            self.quality = 0
+