   override func viewDidLoad() {
     super.viewDidLoad()
     setNavigationBar()
-    view.backgroundColor = .white
 
+    view.backgroundColor = Style.Colors.white
     view.addSubview(wkWebView)
+
+    let guide = view.safeAreaLayoutGuide
     wkWebView.navigationDelegate = self
-    wkWebView.translatesAutoresizingMaskIntoConstraints = false
-    let guide = view.safeAreaLayoutGuide
-    wkWebView.leadingAnchor.constraint(equalTo: guide.leadingAnchor).isActive = true
-    wkWebView.trailingAnchor.constraint(equalTo: guide.trailingAnchor).isActive = true
-    wkWebView.topAnchor.constraint(equalTo: navBar.bottomAnchor).isActive = true
-    wkWebView.bottomAnchor.constraint(equalTo: guide.bottomAnchor).isActive = true
+    wkWebView.snp.makeConstraints {
+      $0.leading.trailing.equalTo(guide)
+      $0.top.equalTo(navBar.snp.bottom)
+      $0.bottom.equalTo(guide.snp.bottom)
+    }
   }
 
   override func handle(_ url: URL) {

extension FitbitAuthorizeViewController: WKNavigationDelegate {
  func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction,
               decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    //print ("url:\(navigationAction.request.url!)")
    if let url = navigationAction.request.url,
      let fitBitUrl = URL(string: AppConfig.fitbitCallbackUri),
      url.host == fitBitUrl.host {

  }

  func setNavigationBar() {
    view.addSubview(navBar)

    let guide = view.safeAreaLayoutGuide
    navBar.snp.makeConstraints {
      $0.leading.trailing.equalTo(guide)
      $0.top.equalTo(guide.snp.top)
      $0.height.equalTo(44)
    }

    let navItem = UINavigationItem(title: "")
    let doneItem = UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: #selector(done))
