Add context menu previews

Gemini-iOS/BrowserWebViewController.swift

@@ -75,6 +75,7 @@ class BrowserWebViewController: UIViewController {
         webView.backgroundColor = .systemBackground
         webView.isOpaque = false
         webView.navigationDelegate = self
+        webView.uiDelegate = self
         // it is safe to set the delegate of the web view's internal scroll view becuase WebKit takes care of forwarding between its internal delegate and our own
         webView.scrollView.delegate = scrollViewDelegate
         // this doesn't default to .default :S
@@ -247,3 +248,26 @@ extension BrowserWebViewController: WKNavigationDelegate {
         }
     }
 }
+
+extension BrowserWebViewController: WKUIDelegate {
+    func webView(_ webView: WKWebView, contextMenuConfigurationForElement elementInfo: WKContextMenuElementInfo, completionHandler: @escaping (UIContextMenuConfiguration?) -> Void) {
+        guard let url = elementInfo.linkURL,
+              url.scheme == "gemini" else {
+            completionHandler(nil)
+            return
+        }
+        let config = UIContextMenuConfiguration(identifier: nil) {
+            return BrowserWebViewController(navigator: self.navigator, url: url)
+        } actionProvider: { (_) in
+            return nil
+        }
+        completionHandler(config)
+    }
+    
+    func webView(_ webView: WKWebView, contextMenuForElement elementInfo: WKContextMenuElementInfo, willCommitWithAnimator animator: UIContextMenuInteractionCommitAnimating) {
+        animator.preferredCommitStyle = .pop
+        animator.addCompletion {
+            self.navigator.changeURL(elementInfo.linkURL!)
+        }
+    }
+}