Add link previews setting.

Signal/src/ViewControllers/AppSettings/PrivacySettingsTableViewController.m

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import "PrivacySettingsTableViewController.h"
@@ -309,6 +309,17 @@ static NSString *const kSealedSenderInfoURL = @"https://signal.org/blog/sealed-s
                                          }]];
     [contents addSection:unidentifiedDeliveryLearnMoreSection];
 
+    OWSTableSection *linkPreviewsSection = [OWSTableSection new];
+    [linkPreviewsSection
+        addItem:[OWSTableItem switchItemWithText:NSLocalizedString(@"SETTINGS_LINK_PREVIEWS",
+                                                     @"Setting for enabling & disabling link previews.")
+                                            isOn:SSKPreferences.areLinkPreviewsEnabled
+                                          target:weakSelf
+                                        selector:@selector(didToggleLinkPreviewsEnabled:)]];
+    linkPreviewsSection.footerTitle
+        = NSLocalizedString(@"SETTINGS_LINK_PREVIEWS", @"Setting for enabling & disabling link previews.");
+    [contents addSection:linkPreviewsSection];
+
     self.contents = contents;
 }
 
@@ -417,6 +428,12 @@ static NSString *const kSealedSenderInfoURL = @"https://signal.org/blog/sealed-s
     [self.preferences setShouldShowUnidentifiedDeliveryIndicators:sender.isOn];
 }
 
+- (void)didToggleLinkPreviewsEnabled:(UISwitch *)sender
+{
+    OWSLogInfo(@"toggled to: %@", (sender.isOn ? @"ON" : @"OFF"));
+    [SSKPreferences setAreLinkPreviewsEnabledWithValue:sender.isOn];
+}
+
 - (void)show2FASettings
 {
     OWSLogInfo(@"");

Signal/translations/en.lproj/Localizable.strings

@@ -2090,6 +2090,9 @@
 /* table cell label */
 "SETTINGS_LEGAL_TERMS_CELL" = "Terms & Privacy Policy";
 
+/* Setting for enabling & disabling link previews. */
+"SETTINGS_LINK_PREVIEWS" = "Link Previews";
+
 /* Title for settings activity */
 "SETTINGS_NAV_BAR_TITLE" = "Settings";
 

SignalServiceKit/src/Messages/Interactions/OWSLinkPreview.swift

@@ -101,6 +101,9 @@ public class OWSLinkPreview: MTLModel {
         guard OWSLinkPreview.featureEnabled else {
             throw LinkPreviewError.noPreview
         }
+        guard SSKPreferences.areLinkPreviewsEnabled() else {
+            throw LinkPreviewError.noPreview
+        }
         guard let previewProto = dataMessage.preview.first else {
             throw LinkPreviewError.noPreview
         }
@@ -162,6 +165,9 @@ public class OWSLinkPreview: MTLModel {
         guard OWSLinkPreview.featureEnabled else {
             throw LinkPreviewError.noPreview
         }
+        guard SSKPreferences.areLinkPreviewsEnabled() else {
+            throw LinkPreviewError.noPreview
+        }
         let imageAttachmentId = OWSLinkPreview.saveAttachmentIfPossible(inputFilePath: info.imageFilePath,
                                                                         transaction: transaction)
 
@@ -361,6 +367,9 @@ public class OWSLinkPreview: MTLModel {
         guard OWSLinkPreview.featureEnabled else {
             return nil
         }
+        guard SSKPreferences.areLinkPreviewsEnabled() else {
+            return nil
+        }
         guard let body = body else {
             return nil
         }
@@ -407,6 +416,10 @@ public class OWSLinkPreview: MTLModel {
             completion(nil)
             return
         }
+        guard SSKPreferences.areLinkPreviewsEnabled() else {
+            completion(nil)
+            return
+        }
         guard let previewUrl = previewUrl else {
             completion(nil)
             return

SignalServiceKit/src/Util/SSKPreferences.swift

@@ -0,0 +1,28 @@
+//
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
+//
+
+import Foundation
+
+@objc
+public class SSKPreferences: NSObject {
+    // Never instantiate this class.
+    private override init() {}
+
+    private static let collection = "SSKPreferences"
+    private static let areLinkPreviewsEnabledKey = "areLinkPreviewsEnabled"
+
+    @objc
+    public class func areLinkPreviewsEnabled() -> Bool {
+        return OWSPrimaryStorage.dbReadConnection().bool(forKey: areLinkPreviewsEnabledKey,
+                                                         inCollection: collection,
+                                                         defaultValue: true)
+    }
+
+    @objc
+    public class func setAreLinkPreviewsEnabled(value: Bool) {
+        return OWSPrimaryStorage.dbReadWriteConnection().setBool(value,
+                                                                 forKey: areLinkPreviewsEnabledKey,
+                                                                 inCollection: collection)
+    }
+}