From aaa385d397a65620583b197fb235a5518cdde053 Mon Sep 17 00:00:00 2001
From: Konstantin Pavlov <git@konstantinpavlov.net>
Date: Sun, 30 Jun 2019 06:31:16 +0200
Subject: [PATCH] quality rules

---
 .../main/java/com/gildedrose/GildedRose.java  | 22 +++++++++++++
 .../com/gildedrose/rules/QualityRule.java     | 32 +++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 Java/src/main/java/com/gildedrose/rules/QualityRule.java

diff --git a/Java/src/main/java/com/gildedrose/GildedRose.java b/Java/src/main/java/com/gildedrose/GildedRose.java
index 188319c8..c25a6c95 100644
--- a/Java/src/main/java/com/gildedrose/GildedRose.java
+++ b/Java/src/main/java/com/gildedrose/GildedRose.java
@@ -1,10 +1,19 @@
 package com.gildedrose;
 
+import com.gildedrose.rules.QualityRule;
+import com.gildedrose.rules.SulfurasQualityRule;
 import lombok.val;
 
+import java.util.List;
+
 class GildedRose {
     Item[] items;
 
+    private final List<QualityRule> rules = List.of(
+            new SulfurasQualityRule(),
+            new QualityRule()
+    );
+
     public GildedRose(Item[] items) {
         this.items = items;
     }
@@ -17,6 +26,18 @@ class GildedRose {
     }
 
     private void processItem(final Item item) {
+
+        var newQuality = rules.stream()
+                .reduce(new QualityRule.Result(item.quality, false),
+                        (q, rule) -> {
+                            if (q.isFinalValue() || !rule.shouldApply(item.name)) {
+                                return q;
+                            } else {
+                                return rule.calculateQuality(q.getQuality());
+                            }
+                        },
+                        (a, b) -> b).getQuality();
+
         if (!item.name.equals("Aged Brie")
                 && !item.name.equals("Backstage passes to a TAFKAL80ETC concert")) {
             if (item.quality > 0) {
@@ -64,6 +85,7 @@ class GildedRose {
             }
         }
 
+        item.quality = newQuality;
         item.sellIn = newSellIn;
     }
 
diff --git a/Java/src/main/java/com/gildedrose/rules/QualityRule.java b/Java/src/main/java/com/gildedrose/rules/QualityRule.java
new file mode 100644
index 00000000..61f2bac5
--- /dev/null
+++ b/Java/src/main/java/com/gildedrose/rules/QualityRule.java
@@ -0,0 +1,32 @@
+package com.gildedrose.rules;
+
+import static java.lang.Integer.max;
+
+public class QualityRule {
+
+    public boolean shouldApply(String itemName) {
+        return true;
+    }
+
+    public Result calculateQuality(int oldQuality) {
+        return new Result(max(oldQuality - 1, 0), false);
+    }
+
+    public static class Result {
+        final int quality;
+        final boolean isFinalValue;
+
+        public Result(int quality, boolean isFinalValue) {
+            this.quality = quality;
+            this.isFinalValue = isFinalValue;
+        }
+
+        public int getQuality() {
+            return quality;
+        }
+
+        public boolean isFinalValue() {
+            return isFinalValue;
+        }
+    }
+}