Use Siesta framework

Extensions/Array+Next.swift

@@ -0,0 +1,13 @@
+extension Array where Element: Equatable {
+    func next(after element: Element) -> Element? {
+        let idx = firstIndex(of: element)
+
+        if idx == nil {
+            return first
+        }
+
+        let next = index(after: idx!)
+
+        return self[next == endIndex ? startIndex : next]
+    }
+}