Error handling: Use WireGuardAppError and WireGuardResult throughout the app

WireGuard/WireGuard/UI/iOS/ErrorPresenter.swift

@@ -5,37 +5,10 @@ import UIKit
 import os.log
 
 class ErrorPresenter {
-    static func errorMessage(for error: Error) -> (String, String) {
-
-        if let error = error as? WireGuardAppError {
-            return error.alertText()
-        }
-
-        switch (error) {
-
-        // Importing a zip file
-        case ZipArchiveError.cantOpenInputZipFile:
-            return ("Unable to read zip archive", "The zip archive could not be read.")
-        case ZipArchiveError.badArchive:
-            return ("Unable to read zip archive", "Bad or corrupt zip archive.")
-        case ZipImporterError.noTunnelsInZipArchive:
-            return ("No tunnels in zip archive", "No .conf tunnel files were found inside the zip archive.")
-
-        // Exporting a zip file
-        case ZipArchiveError.cantOpenOutputZipFileForWriting:
-            return ("Unable to create zip archive", "Could not create a zip file in the app's document directory.")
-        case ZipExporterError.noTunnelsToExport:
-            return ("Nothing to export", "There are no tunnels to export")
-
-        default:
-            return ("Error", error.localizedDescription)
-        }
-    }
-
-    static func showErrorAlert(error: Error, from sourceVC: UIViewController?,
+    static func showErrorAlert(error: WireGuardAppError, from sourceVC: UIViewController?,
                                onDismissal: (() -> Void)? = nil, onPresented: (() -> Void)? = nil) {
         guard let sourceVC = sourceVC else { return }
-        let (title, message) = ErrorPresenter.errorMessage(for: error)
+        let (title, message) = error.alertText()
         let okAction = UIAlertAction(title: "OK", style: .default) { (_) in
             onDismissal?()
         }

WireGuard/WireGuard/UI/iOS/TunnelsListTableViewController.swift

@@ -165,11 +165,12 @@ class TunnelsListTableViewController: UIViewController {
     func importFromFile(url: URL) {
         guard let tunnelsManager = tunnelsManager else { return }
         if (url.pathExtension == "zip") {
-            ZipImporter.importConfigFiles(from: url) { (configs, error) in
-                if let error = error {
+            ZipImporter.importConfigFiles(from: url) { [weak self] result in
+                if let error = result.error {
                     ErrorPresenter.showErrorAlert(error: error, from: self)
                     return
                 }
+                let configs: [TunnelConfiguration?] = result.value!
                 tunnelsManager.addMultiple(tunnelConfigurations: configs.compactMap { $0 }) { [weak self] (numberSuccessful) in
                     if numberSuccessful == configs.count {
                         return

WireGuard/WireGuard/ZipArchive/ZipArchive.swift

@@ -3,10 +3,21 @@
 
 import Foundation
 
-enum ZipArchiveError: Error {
+enum ZipArchiveError: WireGuardAppError {
     case cantOpenInputZipFile
     case cantOpenOutputZipFileForWriting
     case badArchive
+
+    func alertText() -> (String, String) {
+        switch (self) {
+        case .cantOpenInputZipFile:
+            return ("Unable to read zip archive", "The zip archive could not be read.")
+        case .cantOpenOutputZipFileForWriting:
+            return ("Unable to create zip archive", "Could not open zip file for writing.")
+        case .badArchive:
+            return ("Unable to read zip archive", "Bad or corrupt zip archive.")
+        }
+    }
 }
 
 class ZipArchive {

WireGuard/WireGuard/ZipArchive/ZipExporter.swift

@@ -3,12 +3,20 @@
 
 import UIKit
 
-enum ZipExporterError: Error {
+enum ZipExporterError: WireGuardAppError {
     case noTunnelsToExport
+
+    func alertText() -> (String, String) {
+        switch (self) {
+        case .noTunnelsToExport:
+            return ("Nothing to export", "There are no tunnels to export")
+        }
+    }
 }
 
 class ZipExporter {
-    static func exportConfigFiles(tunnelConfigurations: [TunnelConfiguration], to url: URL, completion: @escaping (Error?) -> Void)  {
+    static func exportConfigFiles(tunnelConfigurations: [TunnelConfiguration], to url: URL,
+                                  completion: @escaping (WireGuardAppError?) -> Void)  {
 
         guard (!tunnelConfigurations.isEmpty) else {
             completion(ZipExporterError.noTunnelsToExport)
@@ -27,9 +35,11 @@ class ZipExporter {
             }
             do {
                 try ZipArchive.archive(inputs: inputsToArchiver, to: url)
-            } catch (let e) {
-                DispatchQueue.main.async { completion(e) }
+            } catch (let error as WireGuardAppError) {
+                DispatchQueue.main.async { completion(error) }
                 return
+            } catch {
+                fatalError()
             }
             DispatchQueue.main.async { completion(nil) }
         }

WireGuard/WireGuard/ZipArchive/ZipImporter.swift

@@ -3,12 +3,19 @@
 
 import UIKit
 
-enum ZipImporterError: Error {
+enum ZipImporterError: WireGuardAppError {
     case noTunnelsInZipArchive
+
+    func alertText() -> (String, String) {
+        switch (self) {
+        case .noTunnelsInZipArchive:
+            return ("No tunnels in zip archive", "No .conf tunnel files were found inside the zip archive.")
+        }
+    }
 }
 
 class ZipImporter {
-    static func importConfigFiles(from url: URL, completion: @escaping ([TunnelConfiguration?], Error?) -> Void) {
+    static func importConfigFiles(from url: URL, completion: @escaping (WireGuardResult<[TunnelConfiguration?]>) -> Void) {
         DispatchQueue.global(qos: .userInitiated).async {
             var unarchivedFiles: [(fileName: String, contents: Data)]
             do {
@@ -26,9 +33,11 @@ class ZipImporter {
                 if (unarchivedFiles.isEmpty) {
                     throw ZipImporterError.noTunnelsInZipArchive
                 }
-            } catch (let error) {
-                DispatchQueue.main.async { completion([], error) }
+            } catch (let error as WireGuardAppError) {
+                DispatchQueue.main.async { completion(.failure(error)) }
                 return
+            } catch {
+                fatalError()
             }
 
             unarchivedFiles.sort { $0.fileName < $1.fileName }
@@ -45,7 +54,7 @@ class ZipImporter {
                 }
                 configs[i] = tunnelConfig
             }
-            DispatchQueue.main.async { completion(configs, nil) }
+            DispatchQueue.main.async { completion(.success(configs)) }
         }
     }
 }