Move filename charset to extensions

Passepartout-iOS/Scenes/Organizer/WizardHostViewController.swift

@@ -33,11 +33,6 @@ class WizardHostViewController: UITableViewController, TableModelHost, Wizard {
     private struct ParsedFile {
         let url: URL
 
-        var filename: String {
-            let raw = url.deletingPathExtension().lastPathComponent
-            return raw.components(separatedBy: AppConstants.Store.filenameCharset.inverted).joined(separator: "_")
-        }
-
         let hostname: String
         
         let configuration: TunnelKitProvider.Configuration
@@ -118,7 +113,7 @@ class WizardHostViewController: UITableViewController, TableModelHost, Wizard {
             return
         }
         if field.text?.isEmpty ?? true {
-            field.text = parsedFile?.filename
+            field.text = parsedFile?.url.normalizedFilename
         }
     }
     
@@ -216,7 +211,7 @@ extension WizardHostViewController {
             let cell = Cells.field.dequeue(from: tableView, for: indexPath)
             cell.caption = L10n.Wizards.Host.Cells.TitleInput.caption
             cell.captionWidth = 100.0
-            cell.allowedCharset = AppConstants.Store.filenameCharset
+            cell.allowedCharset = .filename
             cell.field.placeholder = L10n.Wizards.Host.Cells.TitleInput.placeholder
             cell.field.clearButtonMode = .always
             cell.field.returnKeyType = .done

Passepartout/Sources/AppConstants.swift

@@ -40,16 +40,6 @@ class AppConstants {
         static let providersDirectory = "Providers"
 
         static let hostsDirectory = "Hosts"
-        
-        static let filenameCharset: CharacterSet = {
-            var chars: CharacterSet = .decimalDigits
-            let english = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-            let symbols = "-_"
-            chars.formUnion(CharacterSet(charactersIn: english))
-            chars.formUnion(CharacterSet(charactersIn: english.lowercased()))
-            chars.formUnion(CharacterSet(charactersIn: symbols))
-            return chars
-        }()
     }
     
     class VPN {

Passepartout/Sources/Utils.swift

@@ -201,3 +201,24 @@ extension String {
         }
     }
 }
+
+extension CharacterSet {
+    static let filename: CharacterSet = {
+        var chars: CharacterSet = .decimalDigits
+        let english = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+        let symbols = "-_"
+        chars.formUnion(CharacterSet(charactersIn: english))
+        chars.formUnion(CharacterSet(charactersIn: english.lowercased()))
+        chars.formUnion(CharacterSet(charactersIn: symbols))
+        return chars
+    }()
+}
+
+extension URL {
+    private static let illegalCharacterFallback = "_"
+    
+    var normalizedFilename: String {
+        let filename = deletingPathExtension().lastPathComponent
+        return filename.components(separatedBy: CharacterSet.filename.inverted).joined(separator: URL.illegalCharacterFallback)
+    }
+}