feat: add oauth2 ui and authorzation code grant handling

packages/better_networking/lib/utils/auth/handle_auth.dart

@@ -1,8 +1,11 @@
 import 'dart:convert';
+import 'dart:io';
 import 'dart:math';
 import 'package:better_networking/utils/auth/jwt_auth_utils.dart';
 import 'package:better_networking/utils/auth/digest_auth_utils.dart';
 import 'package:better_networking/better_networking.dart';
+import 'package:better_networking/utils/auth/oauth2_utils.dart';
+import 'package:flutter/foundation.dart';
 
 Future<HttpRequestModel> handleAuth(
   HttpRequestModel httpRequestModel,
@@ -157,8 +160,54 @@ Future<HttpRequestModel> handleAuth(
       // TODO: Handle this case.
       throw UnimplementedError();
     case APIAuthType.oauth2:
-      // TODO: Handle this case.
-      throw UnimplementedError();
+      final oauth2 = authData.oauth2;
+
+      if (oauth2 == null) {
+        throw Exception("Failed to get OAuth2 Data");
+      }
+
+      if (oauth2.redirectUrl == null) {
+        throw Exception("No Redirect URL found!");
+      }
+
+      //TODO: Create a proper credentials file path, use the existing file utils if needed.
+      final credentialsDir = Directory.systemTemp;
+      final credentialsFile = File(
+        '${credentialsDir.path}/oauth2_credentials.json',
+      );
+
+      switch (oauth2.grantType) {
+        case OAuth2GrantType.authorizationCode:
+          final res = await oAuth2AuthorizationCodeGrantHandler(
+            identifier: oauth2.clientId,
+            secret: oauth2.clientSecret,
+            authorizationEndpoint: Uri.parse(oauth2.authorizationUrl),
+            redirectUrl: Uri.parse(
+              oauth2.redirectUrl ?? "apidash://oauth2/callback",
+            ),
+            tokenEndpoint: Uri.parse(oauth2.accessTokenUrl),
+            credentialsFile: credentialsFile,
+            scope: oauth2.scope,
+          );
+          debugPrint(res.credentials.accessToken);
+
+          // Add the access token to the request headers
+          updatedHeaders.add(
+            NameValueModel(
+              name: 'Authorization',
+              value: 'Bearer ${res.credentials.accessToken}',
+            ),
+          );
+          updatedHeaderEnabledList.add(true);
+
+          break;
+        case OAuth2GrantType.clientCredentials:
+          // TODO: Handle this case.
+          throw UnimplementedError();
+        case OAuth2GrantType.resourceOwnerPassword:
+          // TODO: Handle this case.
+          throw UnimplementedError();
+      }
   }
 
   return httpRequestModel.copyWith(

packages/better_networking/lib/utils/auth/oauth2_utils.dart

@@ -0,0 +1,75 @@
+import 'dart:async';
+import 'dart:developer' show log;
+import 'dart:io';
+import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';
+import 'package:oauth2/oauth2.dart' as oauth2;
+
+Future<oauth2.Client> oAuth2AuthorizationCodeGrantHandler({
+  required String identifier,
+  required String secret,
+  required Uri authorizationEndpoint,
+  required Uri tokenEndpoint,
+  required Uri redirectUrl,
+  required File credentialsFile,
+  String? state,
+  String? scope,
+}) async {
+  if (await credentialsFile.exists()) {
+    try {
+      final json = await credentialsFile.readAsString();
+
+      final credentials = oauth2.Credentials.fromJson(json);
+
+      if (credentials.accessToken.isNotEmpty && !credentials.isExpired) {
+        log('Using existing valid credentials');
+
+        return oauth2.Client(
+          credentials,
+          identifier: identifier,
+          secret: secret,
+        );
+      }
+    } catch (e) {
+      log('Error reading existing credentials: $e');
+    }
+  }
+
+  final grant = oauth2.AuthorizationCodeGrant(
+    identifier,
+    authorizationEndpoint,
+    tokenEndpoint,
+    secret: secret,
+  );
+
+  final authorizationUrl = grant.getAuthorizationUrl(
+    redirectUrl,
+    scopes: scope != null ? [scope] : null,
+    state: state,
+  );
+  log('Generated authorization URL: ${authorizationUrl.toString()}');
+  log('Expected redirect URL: ${redirectUrl.toString()}');
+
+  final uri = await FlutterWebAuth2.authenticate(
+    url: authorizationUrl.toString(),
+    callbackUrlScheme: redirectUrl.scheme,
+    options: const FlutterWebAuth2Options(useWebview: true),
+  );
+
+  try {
+    final client = await grant.handleAuthorizationResponse(
+      Uri.parse(uri).queryParameters,
+    );
+
+    log('OAuth2 authorization successful, saving credentials');
+
+    await credentialsFile.writeAsString(client.credentials.toJson());
+
+    return client;
+  } catch (e) {
+    log('Error handling authorization response: $e');
+
+    log('URI query parameters: ${Uri.parse(uri).queryParameters}');
+
+    rethrow;
+  }
+}

packages/better_networking/lib/utils/utils.dart

@@ -5,3 +5,5 @@ export 'http_response_utils.dart';
 export 'string_utils.dart' hide RandomStringGenerator;
 export 'uri_utils.dart';
 export 'auth/handle_auth.dart';
+export 'auth/oauth2_webview_utils.dart';
+export 'auth/handle_auth_webview.dart';