Move Legendary item logic to legendary-item-behavior

TypeScript/app/update-behaviors/behavior-resolver.spec.ts

@@ -3,6 +3,7 @@ import { getUpdateBehaviorFor } from "./behavior-resolver";
 import { AgedBrieBehavior } from "./implementations/aged-brie/aged-brie-behavior";
 import { LegacyBehavior } from "./implementations/legacy-behavior";
 import { BackstagePassBehavior } from "./implementations/backstage-pass/backstage-pass-behavior";
+import { LegendaryItemBehavior } from "./implementations/legendary-item/legendary-item-behavior";
 
 describe("Behavior resolver", () => {
   it("should correctly resolve Aged Brie", () => {
@@ -19,6 +20,12 @@ describe("Behavior resolver", () => {
     ).toBeInstanceOf(BackstagePassBehavior);
   });
 
+  it("should correctly resolve Legendary Items", () => {
+    expect(
+      getUpdateBehaviorFor(new Item("Sulfuras, Hand of Ragnaros", 0, 0))
+    ).toBeInstanceOf(LegendaryItemBehavior);
+  });
+
   it("should correctly resolve the rest to Legacy behavior", () => {
     expect(
       getUpdateBehaviorFor(new Item("some other item", 0, 0))

TypeScript/app/update-behaviors/behavior-resolver.ts

@@ -3,6 +3,7 @@ import { IUpdateBehavior } from "./update-behavior.interface";
 import { LegacyBehavior } from "./implementations/legacy-behavior";
 import { AgedBrieBehavior } from "./implementations/aged-brie/aged-brie-behavior";
 import { BackstagePassBehavior } from "./implementations/backstage-pass/backstage-pass-behavior";
+import { LegendaryItemBehavior } from "./implementations/legendary-item/legendary-item-behavior";
 
 export function getUpdateBehaviorFor(item: Item): IUpdateBehavior {
   switch (item.name) {
@@ -10,6 +11,8 @@ export function getUpdateBehaviorFor(item: Item): IUpdateBehavior {
       return new AgedBrieBehavior(item);
     case "Backstage passes to a TAFKAL80ETC concert":
       return new BackstagePassBehavior(item);
+    case "Sulfuras, Hand of Ragnaros":
+      return new LegendaryItemBehavior(item);
     default:
       return new LegacyBehavior(item);
   }

TypeScript/app/update-behaviors/implementations/legacy-behavior.spec.ts

@@ -37,18 +37,4 @@ describe("Legacy Behavior", () => {
       quality: 0,
     });
   });
-
-  it("should not change quality of Sulfuras", () => {
-    const behavior = new LegacyBehavior(
-      new Item("Sulfuras, Hand of Ragnaros", 0, 80)
-    );
-
-    const result = behavior.update();
-
-    expect(result).toMatchObject({
-      name: "Sulfuras, Hand of Ragnaros",
-      sellIn: 0,
-      quality: 80,
-    });
-  });
 });

TypeScript/app/update-behaviors/implementations/legacy-behavior.ts

@@ -6,19 +6,13 @@ export class LegacyBehavior implements IUpdateBehavior {
 
   update(): Item {
     if (this.item.quality > 0) {
-      if (this.item.name !== "Sulfuras, Hand of Ragnaros") {
+      this.item.quality = this.item.quality - 1;
-        this.item.quality = this.item.quality - 1;
-      }
     }
 
-    if (this.item.name !== "Sulfuras, Hand of Ragnaros") {
+    this.item.sellIn = this.item.sellIn - 1;
-      this.item.sellIn = this.item.sellIn - 1;
-    }
     if (this.item.sellIn < 0) {
       if (this.item.quality > 0) {
-        if (this.item.name !== "Sulfuras, Hand of Ragnaros") {
+        this.item.quality = this.item.quality - 1;
-          this.item.quality = this.item.quality - 1;
-        }
       }
     }
     return this.item;

TypeScript/app/update-behaviors/implementations/legendary-item/legendary-item-behavior.ts

@@ -0,0 +1,13 @@
+import { config } from "@app/config";
+import { Item } from "@app/item";
+import { IUpdateBehavior } from "@app/update-behaviors/update-behavior.interface";
+
+export class LegendaryItemBehavior implements IUpdateBehavior {
+  constructor(public item: Item) {}
+  update(): Item {
+    if (this.item.quality !== 80) {
+      throw new Error("A Legendary Item cannot have a quality other than 80");
+    }
+    return this.item;
+  }
+}

TypeScript/app/update-behaviors/implementations/legendary-item/legendary-item.spec.ts

@@ -0,0 +1,28 @@
+import { Item } from "@app/item";
+import { LegendaryItemBehavior } from "./legendary-item-behavior";
+
+describe("Legendary Item Behavior", () => {
+  it("should keep items of quality 80 the same", () => {
+    const behavior = new LegendaryItemBehavior(
+      new Item("Sulfuras, Hand of Ragnaros", 0, 80)
+    );
+
+    const result = behavior.update();
+
+    expect(result).toMatchObject({
+      name: "Sulfuras, Hand of Ragnaros",
+      sellIn: 0,
+      quality: 80,
+    });
+  });
+
+  it("should throw an error when a legendary item doesn't have a quality of 80", () => {
+    const behavior = new LegendaryItemBehavior(
+      new Item("Sulfuras, Hand of Ragnaros", 0, 5)
+    );
+
+    expect(() => behavior.update()).toThrow(
+      "A Legendary Item cannot have a quality other than 80"
+    );
+  });
+});