Error handling: Introduce a WireGuardAppError protocol to manage errors

The alert strings shall be located next to where the errors are declared.

Signed-off-by: Roopesh Chander <roop@roopc.net>

WireGuard/WireGuard/UI/iOS/ErrorPresenter.swift

@@ -7,8 +7,8 @@ import os.log
 class ErrorPresenter {
     static func errorMessage(for error: Error) -> (String, String) {
 
-        if let tunnelsManagerError = error as? TunnelsManagerError {
-            return errorMessage(forTunnelsManagerError: tunnelsManagerError)
+        if let error = error as? WireGuardAppError {
+            return error.alertText()
         }
 
         switch (error) {
@@ -32,32 +32,6 @@ class ErrorPresenter {
         }
     }
 
-    private static func errorMessage(forTunnelsManagerError error: TunnelsManagerError) -> (String, String) {
-        switch (error) {
-        // Tunnels list management
-        case TunnelsManagerError.tunnelNameEmpty:
-            return ("No name provided", "Can't create tunnel with an empty name")
-        case TunnelsManagerError.tunnelAlreadyExistsWithThatName:
-            return ("Name already exists", "A tunnel with that name already exists")
-        case TunnelsManagerError.vpnSystemErrorOnListingTunnels:
-            return ("Unable to list tunnels", "Internal error")
-        case TunnelsManagerError.vpnSystemErrorOnAddTunnel:
-            return ("Unable to create tunnel", "Internal error")
-        case TunnelsManagerError.vpnSystemErrorOnModifyTunnel:
-            return ("Unable to modify tunnel", "Internal error")
-        case TunnelsManagerError.vpnSystemErrorOnRemoveTunnel:
-            return ("Unable to remove tunnel", "Internal error")
-
-        // Tunnel activation
-        case TunnelsManagerError.tunnelActivationAttemptFailed:
-            return ("Activation failure", "The tunnel could not be activated due to an internal error")
-        case TunnelsManagerError.tunnelActivationFailedInternalError:
-            return ("Activation failure", "The tunnel could not be activated due to an internal error")
-        case TunnelsManagerError.tunnelActivationFailedNoInternetConnection:
-            return ("Activation failure", "No internet connection")
-        }
-    }
-
     static func showErrorAlert(error: Error, from sourceVC: UIViewController?,
                                onDismissal: (() -> Void)? = nil, onPresented: (() -> Void)? = nil) {
         guard let sourceVC = sourceVC else { return }

WireGuard/WireGuard/VPN/TunnelsManager.swift

@@ -16,7 +16,8 @@ protocol TunnelsManagerActivationDelegate: class {
     func tunnelActivationFailed(tunnel: TunnelContainer, error: TunnelsManagerError)
 }
 
-enum TunnelsManagerError: Error {
+enum TunnelsManagerError: WireGuardAppError {
+    // Tunnels list management
     case tunnelNameEmpty
     case tunnelAlreadyExistsWithThatName
     case vpnSystemErrorOnListingTunnels
@@ -24,9 +25,34 @@ enum TunnelsManagerError: Error {
     case vpnSystemErrorOnModifyTunnel
     case vpnSystemErrorOnRemoveTunnel
 
+    // Tunnel activation
     case tunnelActivationAttemptFailed // startTunnel() throwed
     case tunnelActivationFailedInternalError // startTunnel() succeeded, but activation failed
     case tunnelActivationFailedNoInternetConnection // startTunnel() succeeded, but activation failed since no internet
+
+    func alertText() -> (String, String) {
+        switch (self) {
+        case .tunnelNameEmpty:
+            return ("No name provided", "Can't create tunnel with an empty name")
+        case .tunnelAlreadyExistsWithThatName:
+            return ("Name already exists", "A tunnel with that name already exists")
+        case .vpnSystemErrorOnListingTunnels:
+            return ("Unable to list tunnels", "Internal error")
+        case .vpnSystemErrorOnAddTunnel:
+            return ("Unable to create tunnel", "Internal error")
+        case .vpnSystemErrorOnModifyTunnel:
+            return ("Unable to modify tunnel", "Internal error")
+        case .vpnSystemErrorOnRemoveTunnel:
+            return ("Unable to remove tunnel", "Internal error")
+
+        case .tunnelActivationAttemptFailed:
+            return ("Activation failure", "The tunnel could not be activated due to an internal error")
+        case .tunnelActivationFailedInternalError:
+            return ("Activation failure", "The tunnel could not be activated due to an internal error")
+        case .tunnelActivationFailedNoInternetConnection:
+            return ("Activation failure", "No internet connection")
+        }
+    }
 }
 
 enum TunnelsManagerResult<T> {

WireGuard/WireGuard/WireGuardAppError.swift

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018 WireGuard LLC. All Rights Reserved.
+
+protocol WireGuardAppError: Error {
+    func alertText() -> (/* title */ String, /* message */ String)
+}