Add link preview & open group metadata warnings

Signal/src/Loki/View Controllers/JoinPublicChatVC.swift

@@ -186,14 +186,22 @@ private final class EnterChatURLVC : UIViewController {
     override func viewDidLoad() {
         // Remove background color
         view.backgroundColor = .clear
-        // Set up explanation label
-        let explanationLabel = UILabel()
-        explanationLabel.textColor = Colors.text.withAlphaComponent(Values.unimportantElementOpacity)
-        explanationLabel.font = .systemFont(ofSize: Values.smallFontSize)
-        explanationLabel.text = NSLocalizedString("Enter an open group URL", comment: "")
-        explanationLabel.numberOfLines = 0
-        explanationLabel.textAlignment = .center
-        explanationLabel.lineBreakMode = .byWordWrapping
+        // Set up top explanation label
+        let topExplanationLabel = UILabel()
+        topExplanationLabel.textColor = Colors.text.withAlphaComponent(Values.unimportantElementOpacity)
+        topExplanationLabel.font = .systemFont(ofSize: Values.smallFontSize)
+        topExplanationLabel.text = NSLocalizedString("Enter an open group URL", comment: "")
+        topExplanationLabel.numberOfLines = 0
+        topExplanationLabel.textAlignment = .center
+        topExplanationLabel.lineBreakMode = .byWordWrapping
+        // Set up bottom explanation label
+        let bottomExplanationLabel = UILabel()
+        bottomExplanationLabel.textColor = Colors.text.withAlphaComponent(Values.unimportantElementOpacity)
+        bottomExplanationLabel.font = .systemFont(ofSize: Values.verySmallFontSize)
+        bottomExplanationLabel.text = NSLocalizedString("Open groups can be joined by anyone and do not provide full metadata protection", comment: "")
+        bottomExplanationLabel.numberOfLines = 0
+        bottomExplanationLabel.textAlignment = .center
+        bottomExplanationLabel.lineBreakMode = .byWordWrapping
         // Next button
         let nextButton = Button(style: .prominentOutline, size: .large)
         nextButton.setTitle(NSLocalizedString("Next", comment: ""), for: UIControl.State.normal)
@@ -205,10 +213,11 @@ private final class EnterChatURLVC : UIViewController {
         nextButtonContainer.pin(.trailing, to: .trailing, of: nextButton, withInset: 80)
         nextButtonContainer.pin(.bottom, to: .bottom, of: nextButton)
         // Set up stack view
-        let stackView = UIStackView(arrangedSubviews: [ chatURLTextField, UIView.spacer(withHeight: Values.smallSpacing), explanationLabel, UIView.vStretchingSpacer(), nextButtonContainer ])
+        let stackView = UIStackView(arrangedSubviews: [ chatURLTextField, UIView.spacer(withHeight: Values.smallSpacing), topExplanationLabel, UIView.vStretchingSpacer(), nextButtonContainer, UIView.spacer(withHeight: Values.smallSpacing), bottomExplanationLabel ])
         stackView.axis = .vertical
         stackView.alignment = .fill
-        stackView.layoutMargins = UIEdgeInsets(top: Values.largeSpacing, left: Values.largeSpacing, bottom: Values.largeSpacing, right: Values.largeSpacing)
+        let bottomSpacing = isSmallScreen ? Values.smallSpacing : Values.largeSpacing
+        stackView.layoutMargins = UIEdgeInsets(top: Values.largeSpacing, left: Values.largeSpacing, bottom: bottomSpacing, right: Values.largeSpacing)
         stackView.isLayoutMarginsRelativeArrangement = true
         view.addSubview(stackView)
         stackView.pin(.leading, to: .leading, of: view)

Signal/src/ViewControllers/AppSettings/PrivacySettingsTableViewController.m

@@ -537,6 +537,18 @@ static NSString *const kSealedSenderInfoURL = @"https://signal.org/blog/sealed-s
 
 - (void)didToggleLinkPreviewsEnabled:(UISwitch *)sender
 {
+    BOOL isOn = sender.isOn;
+    if (isOn) {
+        NSString *title = NSLocalizedString(@"Enable Link Previews?", @"");
+        NSString *message = NSLocalizedString(@"You will not have full metadata protection when sending or receiving link previews.", @"");
+        UIAlertController *alert = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert];
+        [alert addAction:[UIAlertAction actionWithTitle:NSLocalizedString(@"OK", @"") style:UIAlertActionStyleDefault handler:nil]];
+        [alert addAction:[UIAlertAction actionWithTitle:NSLocalizedString(@"Cancel", @"") style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
+            [sender setOn:NO animated:YES];
+            SSKPreferences.areLinkPreviewsEnabled = NO;
+        }]];
+        [self presentViewController:alert animated:YES completion:nil];
+    }
     OWSLogInfo(@"toggled to: %@", (sender.isOn ? @"ON" : @"OFF"));
     SSKPreferences.areLinkPreviewsEnabled = sender.isOn;
 }

Signal/translations/en.lproj/Localizable.strings

@@ -2796,3 +2796,6 @@
 "Please enter a group name" = "Please enter a group name";
 "Please enter a shorter group name" = "Please enter a shorter group name";
 "Please pick at least 2 group members" = "Please pick at least 2 group members";
+"Enable Link Previews?" = "Enable Link Previews?";
+"You will not have full metadata protection when sending or receiving link previews." = "You will not have full metadata protection when sending or receiving link previews.";
+"Open groups can be joined by anyone and do not provide full metadata protection" = "Open groups can be joined by anyone and do not provide full metadata protection";