Cache fetched license content

And show an error message when unable to fetch license URL.

Passepartout-iOS/Scenes/Organizer/CreditsViewController.swift

@@ -64,7 +64,7 @@ class CreditsViewController: UITableViewController, TableModelHost {
         vc.title = cell.leftText
         switch model.row(at: indexPath) {
         case .license:
-            vc.url = licenses[indexPath.row].url
+            vc.license = licenses[indexPath.row]
 
         case .notice:
             vc.text = notices[indexPath.row].statement

Passepartout-iOS/Scenes/Organizer/LabelViewController.swift

@@ -34,7 +34,7 @@ class LabelViewController: UIViewController {
     
     var text: String?
     
-    var url: URL?
+    var license: AppConstants.License?
 
     override func awakeFromNib() {
         super.awakeFromNib()
@@ -47,23 +47,41 @@ class LabelViewController: UIViewController {
 
         activity?.hidesWhenStopped = true
         activity?.applyAccent(Theme.current)
+        scrollView?.applyPrimaryBackground(Theme.current)
+        label?.applyLight(Theme.current)
 
-        if let url = url {
+        if let license = license {
+            
+            // try cache first
+            if let cachedContent = AppConstants.License.cachedContent[license.name] {
+                label?.text = cachedContent
+                return
+            }
+            
             label?.text = nil
             activity?.startAnimating()
 
             DispatchQueue(label: LabelViewController.description(), qos: .background).async { [weak self] in
-                let urlText = try? String(contentsOf: url)
+                let content: String
+                let couldFetch: Bool
+                do {
+                    content = try String(contentsOf: license.url)
+                    couldFetch = true
+                } catch {
+                    content = L10n.Label.License.error
+                    couldFetch = false
+                }
                 DispatchQueue.main.async {
-                    self?.label?.text = urlText
+                    self?.label?.text = content
                     self?.activity?.stopAnimating()
+                    
+                    if couldFetch {
+                        AppConstants.License.cachedContent[license.name] = content
+                    }
                 }
             }
         } else {
             label?.text = text
         }
-
-        scrollView?.applyPrimaryBackground(Theme.current)
-        label?.applyLight(Theme.current)
     }
 }

Passepartout/Resources/en.lproj/Localizable.strings

@@ -208,3 +208,5 @@
 "credits.title" = "Credits";
 "credits.sections.licenses.header" = "Licenses";
 "credits.sections.notices.header" = "Notices";
+
+"label.license.error" = "Unable to download full license content.";

Passepartout/Sources/AppConstants.swift

@@ -175,7 +175,7 @@ class AppConstants {
         let type: String
         
         let url: URL
-
+        
         init(_ name: String, _ type: String, _ urlString: String) {
             self.name = name
             self.type = type
@@ -209,6 +209,8 @@ class AppConstants {
                 "https://raw.githubusercontent.com/SwiftyBeaver/SwiftyBeaver/master/LICENSE"
             )
         ]
+
+        static var cachedContent: [String: String] = [:]
     }
     
     struct Notice {

Passepartout/Sources/SwiftGen+Strings.swift

@@ -293,6 +293,13 @@ internal enum L10n {
     }
   }
 
+  internal enum Label {
+    internal enum License {
+      /// Unable to download full license content.
+      internal static let error = L10n.tr("Localizable", "label.license.error")
+    }
+  }
+
   internal enum Organizer {
     internal enum Alerts {
       internal enum AddHost {