refactor(auth): Revamp account linking flow

- Use nested routes for linking
- Improve redirection logic
- Remove query parameter context

Author: fulleni

lib/authentication/view/authentication_page.dart

@@ -132,10 +132,9 @@ class AuthenticationPage extends StatelessWidget {
                             ? null
                             : () {
                                 context.goNamed(
-                                  Routes.requestCodeName,
-                                  queryParameters: isLinkingContext
-                                      ? {'context': 'linking'}
-                                      : const {},
+                                  isLinkingContext
+                                      ? Routes.linkingRequestCodeName
+                                      : Routes.requestCodeName,
                                 );
                               },
                         label: Text(l10n.authenticationEmailSignInButton),

lib/authentication/view/request_code_page.dart

@@ -85,10 +85,10 @@ class _RequestCodeView extends StatelessWidget {
             } else if (state is AuthenticationCodeSentSuccess) {
               // Navigate to the code verification page on success, passing the email
               context.goNamed(
-                Routes.verifyCodeName,
+                isLinkingContext
+                    ? Routes.linkingVerifyCodeName
+                    : Routes.verifyCodeName,
                 pathParameters: {'email': state.email},
-                queryParameters:
-                    isLinkingContext ? {'context': 'linking'} : const {},
               );
             }
           },

lib/router/router.dart

@@ -135,15 +135,24 @@ GoRouter createRouter({
           appStatus == AppStatus.authenticated) {
         print('  Redirect Decision: User is $appStatus.');
 
-          final isLinkingContext =
-              state.uri.queryParameters['context'] == 'linking';
+          final isLinkingContextQueryPresent = state.uri.queryParameters['context'] == 'linking';
+          final isLinkingPathSegmentPresent = currentLocation.contains('/linking/');
+
+          // Determine if the current location is part of any linking flow (either via query or path segment)
+          final isAnyLinkingContext = isLinkingContextQueryPresent || isLinkingPathSegmentPresent;
 
           // If an authenticated/anonymous user is on any authentication-related path:
           if (currentLocation.startsWith(authenticationPath)) {
-            // Allow navigation within auth paths if the linking context is active
-            if (isLinkingContext) {
+            print('    Debug: Auth path detected. Current Location: $currentLocation');
+            print('    Debug: URI Query Parameters: ${state.uri.queryParameters}');
+            print('    Debug: isLinkingContextQueryPresent: $isLinkingContextQueryPresent');
+            print('    Debug: isLinkingPathSegmentPresent: $isLinkingPathSegmentPresent');
+            print('    Debug: isAnyLinkingContext evaluated to: $isAnyLinkingContext');
+
+            // Allow navigation within auth paths if any linking context is active
+            if (isAnyLinkingContext) {
               print(
-                '    Action: $appStatus user on auth path ($currentLocation) with linking context. Allowing navigation.',
+                '    Action: $appStatus user on auth linking path ($currentLocation). Allowing navigation.',
               );
               return null;
             } else {
@@ -207,24 +216,41 @@ GoRouter createRouter({
           );
         },
         routes: [
+          // Nested route for account linking flow (defined first for priority)
           GoRoute(
-            path: Routes.requestCode, // Use new path
-            name: Routes.requestCodeName, // Use new name
-            builder: (context, state) {
-              // Extract the linking context flag from 'extra', default to false.
-              final isLinking = (state.extra as bool?) ?? false;
-              return RequestCodePage(isLinkingContext: isLinking);
-            },
+            path: Routes.accountLinking, // This is 'linking'
+            name: Routes.accountLinkingName, // Name for the linking segment
+            builder: (context, state) => const SizedBox.shrink(), // Placeholder
+            routes: [
+              GoRoute(
+                path: Routes.requestCode, // Path: /authentication/linking/request-code
+                name: Routes.linkingRequestCodeName,
+                builder: (context, state) =>
+                    const RequestCodePage(isLinkingContext: true),
+              ),
+              GoRoute(
+                path: '${Routes.verifyCode}/:email', // Path: /authentication/linking/verify-code/:email
+                name: Routes.linkingVerifyCodeName,
+                builder: (context, state) {
+                  final email = state.pathParameters['email']!;
+                  return EmailCodeVerificationPage(email: email);
+                },
+              ),
+            ],
+          ),
+          // Non-linking authentication routes (defined after linking routes)
+          GoRoute(
+            path: Routes.requestCode,
+            name: Routes.requestCodeName,
+            builder: (context, state) =>
+                const RequestCodePage(isLinkingContext: false),
           ),
           GoRoute(
-            path:
-                '${Routes.verifyCode}/:email', // Use new path with email parameter
-            name: Routes.verifyCodeName, // Use new name
+            path: '${Routes.verifyCode}/:email',
+            name: Routes.verifyCodeName,
             builder: (context, state) {
-              final email = state.pathParameters['email']!; // Extract email
-              return EmailCodeVerificationPage(
-                email: email,
-              ); // Use renamed page
+              final email = state.pathParameters['email']!;
+              return EmailCodeVerificationPage(email: email);
             },
           ),
         ],

lib/router/routes.dart

@@ -58,6 +58,12 @@ abstract final class Routes {
   static const verifyCode = 'verify-code';
   static const verifyCodeName = 'verifyCode';
 
+  // Linking-specific authentication routes
+  static const linkingRequestCode = 'linking/request-code';
+  static const linkingRequestCodeName = 'linkingRequestCode';
+  static const linkingVerifyCode = 'linking/verify-code';
+  static const linkingVerifyCodeName = 'linkingVerifyCode';
+
   // --- Settings Sub-Routes (relative to /account/settings) ---
   static const settingsAppearance = 'appearance';
   static const settingsAppearanceName = 'settingsAppearance';

pubspec.lock

@@ -1082,10 +1082,10 @@ packages:
     dependency: transitive
     description:
       name: watcher
-      sha256: "69da27e49efa56a15f8afe8f4438c4ec02eff0a117df1b22ea4aad194fe1c104"
+      sha256: "0b7fd4a0bbc4b92641dbf20adfd7e3fd1398fe17102d94b674234563e110088a"
       url: "https://pub.dev"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.2"
   web:
     dependency: transitive
     description: