Blur link card images when status is sensitive

Closes #412

Tusker/Views/CachedImageView.swift

@@ -46,6 +46,13 @@ class CachedImageView: UIImageView {
         }
     }
     
+    func showOnlyBlurHash(_ blurhash: String, for url: URL) {
+        if url != self.url {
+            self.url = url
+            updateBlurhash(blurhash, for: url)
+        }
+    }
+    
     @objc private func preferencesChanged() {
         if isGrayscale != Preferences.shared.grayscaleImages {
             updateImage()

Tusker/Views/Status/StatusCardView.swift

@@ -30,7 +30,7 @@ class StatusCardView: UIView {
     private var titleLabel: UILabel!
     private var descriptionLabel: UILabel!
     private var domainLabel: UILabel!
-    private var imageView: CachedImageView!
+    private var imageView: StatusCardImageView!
     private var placeholderImageView: UIImageView!
     private var leadingSpacer: UIView!
     private var trailingSpacer: UIView!
@@ -80,7 +80,7 @@ class StatusCardView: UIView {
         vStack.alignment = .leading
         vStack.spacing = 0
         
-        imageView = CachedImageView(cache: .attachments)
+        imageView = StatusCardImageView(cache: .attachments)
         imageView.contentMode = .scaleAspectFill
         imageView.clipsToBounds = true
         
@@ -167,7 +167,18 @@ class StatusCardView: UIView {
         }
         
         if let image = card.image {
-            imageView.update(for: URL(image), blurhash: card.blurhash)
+            if status.sensitive {
+                if let blurhash = card.blurhash {
+                    imageView.blurImage = false
+                    imageView.showOnlyBlurHash(blurhash, for: URL(image)!)
+                } else {
+                    // if we don't have a blurhash, load the image and show it behind a blur
+                    imageView.blurImage = true
+                    imageView.update(for: URL(image), blurhash: nil)
+                }
+            } else {
+                imageView.update(for: URL(image), blurhash: card.blurhash)
+            }
             imageView.isHidden = false
             leadingSpacer.isHidden = true
         } else {
@@ -257,3 +268,25 @@ extension StatusCardView: UIContextMenuInteractionDelegate {
         }
     }
 }
+
+private class StatusCardImageView: CachedImageView {
+    @Lazy private var blurView = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
+    var blurImage = false {
+        didSet {
+            if blurImage {
+                if !_blurView.isInitialized {
+                    blurView.translatesAutoresizingMaskIntoConstraints = false
+                    addSubview(blurView)
+                    NSLayoutConstraint.activate([
+                        blurView.leadingAnchor.constraint(equalTo: leadingAnchor),
+                        blurView.trailingAnchor.constraint(equalTo: trailingAnchor),
+                        blurView.topAnchor.constraint(equalTo: topAnchor),
+                        blurView.bottomAnchor.constraint(equalTo: bottomAnchor),
+                    ])
+                }
+            } else {
+                _blurView.valueIfInitialized?.removeFromSuperview()
+            }
+        }
+    }
+}