From c2994ce63c27e73bfcfc72ce3bbac4abcb7da70c Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Wed, 18 Feb 2026 12:39:31 +0700
Subject: [PATCH] REFACTOR: extract helper methods and domain constants

---
 lib/gilded_rose.dart | 52 +++++++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 22 deletions(-)

diff --git a/lib/gilded_rose.dart b/lib/gilded_rose.dart
index 413c60f..604c119 100644
--- a/lib/gilded_rose.dart
+++ b/lib/gilded_rose.dart
@@ -11,6 +11,20 @@ class Item {
   String toString() => '$name, $sellIn, $quality';
 }
 
+/// Quality bounds - domain constraints
+const int _minQuality = 0;
+const int _maxQuality = 50;
+const int _legendaryQuality = 80; // unused, just for documentation
+
+/// Helper methods for quality management
+void _degradeQuality(Item item, int amount) {
+  item.quality = (item.quality - amount).clamp(_minQuality, _maxQuality);
+}
+
+void _improveQuality(Item item, int amount) {
+  item.quality = (item.quality + amount).clamp(_minQuality, _maxQuality);
+}
+
 /// Strategy pattern: Each item type has its own update behavior
 abstract class ItemUpdater {
   void update(Item item);
@@ -20,15 +34,13 @@ class NormalItemUpdater implements ItemUpdater {
   @override
   void update(Item item) {
     // Quality decreases by 1 each day
-    if (item.quality > 0) {
-      item.quality -= 1;
-    }
+    _degradeQuality(item, 1);
 
     item.sellIn -= 1;
 
     // After sell-by date, quality degrades twice as fast
-    if (item.sellIn < 0 && item.quality > 0) {
-      item.quality -= 1;
+    if (item.sellIn < 0) {
+      _degradeQuality(item, 1);
     }
   }
 }
@@ -37,15 +49,13 @@ class AgedBrieUpdater implements ItemUpdater {
   @override
   void update(Item item) {
     // Quality increases as it ages
-    if (item.quality < 50) {
-      item.quality += 1;
-    }
+    _improveQuality(item, 1);
 
     item.sellIn -= 1;
 
     // After sell-by date, quality increases twice as fast
-    if (item.sellIn < 0 && item.quality < 50) {
-      item.quality += 1;
+    if (item.sellIn < 0) {
+      _improveQuality(item, 1);
     }
   }
 }
@@ -53,26 +63,24 @@ class AgedBrieUpdater implements ItemUpdater {
 class BackstagePassUpdater implements ItemUpdater {
   @override
   void update(Item item) {
-    // Quality increases as concert approaches
-    if (item.quality < 50) {
-      item.quality += 1;
+    // Base quality increase
+    _improveQuality(item, 1);
 
-      // 10 days or less: +2 quality/day
-      if (item.sellIn < 11 && item.quality < 50) {
-        item.quality += 1;
-      }
+    // 10 days or less: +1 additional
+    if (item.sellIn <= 10) {
+      _improveQuality(item, 1);
+    }
 
-      // 5 days or less: +3 quality/day
-      if (item.sellIn < 6 && item.quality < 50) {
-        item.quality += 1;
-      }
+    // 5 days or less: +1 additional (total +3/day)
+    if (item.sellIn <= 5) {
+      _improveQuality(item, 1);
     }
 
     item.sellIn -= 1;
 
     // After concert, quality drops to 0
     if (item.sellIn < 0) {
-      item.quality = 0;
+      item.quality = _minQuality;
     }
   }
 }