feature: handled adding elements when queue is not empty

hbarcelos · hbarcelos · commit a1b4a3e194e1 · 2020-02-05T11:38:01.000-03:00
diff --git a/round-linked-queue.js b/round-linked-queue.js
@@ -18,17 +18,29 @@ class RoundLinkedQueue {
   }
 
   get first() {
-    return this._first;
+    return this._first.data;
   }
 
   get last() {
-    return this._last;
+    return this._last.data;
   }
 
   add(element) {
-    this._root = element;
-    this._first = element;
-    this._last = element;
+    const node = {
+      data: element,
+      next: null,
+    };
+
+    if (!this._root) {
+      this._root = node;
+      this._first = node;
+      this._last = node;
+    } else {
+      const previousLast = this._last;
+      previousLast.next = node;
+
+      this._last = node;
+    }
 
     this._length += 1;
   }
diff --git a/round-linked-queue.test.js b/round-linked-queue.test.js
@@ -37,5 +37,22 @@ describe("Round-Queue", () => {
       // Length should've been increased by 1
       expect(queue.length).to.equal(originalLength + 1);
     });
+
+    it("Should add an element to the end of a non-empty queue", () => {
+      const queue = new RoundQueue(3);
+      const previousElement = 1;
+      const elementToAdd = 2;
+      // Make the queue non-empty
+      queue.add(previousElement);
+
+      queue.add(elementToAdd);
+
+      // Element should've been added to the end of the queue
+      expect(queue.last).to.equal(elementToAdd, "last not properly set");
+      // But the first pointer must remain the first element added
+      expect(queue.first).to.equal(previousElement, "first not properly set");
+      // Length should've been increased by 2
+      expect(queue.length).to.equal(2, "length not properly set");
+    });
   });
 });
