feat: add deeplinking support for oauth login

lib/features/onboarding/view/user_login_with_open_id.dart

@@ -0,0 +1,116 @@
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:shelfsdk/audiobookshelf_api.dart';
+import 'package:vaani/api/api_provider.dart';
+import 'package:vaani/features/onboarding/providers/oauth_provider.dart';
+import 'package:vaani/features/onboarding/view/user_login_with_password.dart';
+import 'package:vaani/main.dart';
+import 'package:vaani/models/error_response.dart';
+import 'package:vaani/router/router.dart';
+import 'package:vaani/settings/constants.dart';
+import 'package:vaani/settings/models/models.dart' as model;
+import 'package:vaani/shared/utils.dart';
+
+class UserLoginWithOpenID extends HookConsumerWidget {
+  UserLoginWithOpenID({
+    super.key,
+    required this.server,
+    required this.addServer,
+    this.openIDButtonText,
+  });
+
+  final Uri server;
+  final model.AudiobookShelfServer Function() addServer;
+  final String? openIDButtonText;
+  final responseErrorHandler = ErrorResponseHandler(name: 'OpenID');
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final serverStatus = ref.watch(serverStatusProvider(server));
+    void openIDLoginFlow() async {
+      appLogger.fine('Clicked Login with OpenID');
+
+      final api = ref.read(audiobookshelfApiProvider(server));
+      final (verifier, challenge) = generateVerifierAndChallenge();
+
+      appLogger.fine('Generated verifier: $verifier\nchallenge: $challenge');
+      final appRedirectUri =
+          '${AppMetadata.appScheme}://${Routes.openIDCallback.fullPath.substring(1)}';
+      final (openIDLoginEndpoint, authCookie) = await api.server.oauth2Request(
+        clientId: AppMetadata.appName,
+        codeChallenge: challenge,
+        // redirectUri: Uri(
+        //   scheme: AppMetadata.appScheme,
+        //   host: Routes.openIDCallback.path.substring(1),
+        // ).toString(),
+        redirectUri: appRedirectUri,
+        responseErrorHandler: responseErrorHandler.storeError,
+      );
+
+      if (openIDLoginEndpoint == null) {
+        if (responseErrorHandler.response.statusCode == 400 &&
+            responseErrorHandler.response.body
+                .toLowerCase()
+                .contains(RegExp(r'invalid.*redirect.*uri'))) {
+          // show error
+          handleServerError(
+            context,
+            responseErrorHandler,
+            title: 'Failed to get OpenID login endpoint\n',
+            body:
+                'Please check that the redirect URI: "$appRedirectUri" is registered with the server.',
+            outLink: server.replace(path: '${Routes.settings.fullPath}/auth'),
+            outLinkText: 'Server settings',
+          );
+          return;
+        }
+
+        // show error
+        handleServerError(
+          context,
+          responseErrorHandler,
+          title: 'Failed to get OpenID login endpoint',
+        );
+        return;
+      }
+
+      // extract the state parameter
+      final oauthState = openIDLoginEndpoint.queryParameters['state'];
+
+      if (oauthState == null) {
+        handleServerError(
+          context,
+          responseErrorHandler,
+          title: 'Failed to get OpenID login endpoint',
+          body: 'No state parameter found in the response',
+        );
+        return;
+      }
+
+      appLogger.fine('Got OpenID login endpoint: $openIDLoginEndpoint');
+
+      // add the flow to the provider
+      ref.read(oauthFlowsProvider.notifier).addFlow(
+            oauthState,
+            verifier: verifier,
+            serverUri: server,
+            cookie: Cookie.fromSetCookieValue(authCookie!),
+          );
+
+      await handleLaunchUrl(
+        openIDLoginEndpoint,
+      );
+    }
+
+    return Column(
+      children: [
+        ElevatedButton(
+          onPressed: openIDLoginFlow,
+          child: Text(openIDButtonText ?? 'Login with OpenID'),
+        ),
+      ],
+    );
+  }
+}