refactored the credential checking logic into a shared helper function to reduce code duplication

auth/oauth_callback_server.py

@@ -15,7 +15,7 @@ import socket
 from fastapi import FastAPI, Request
 import uvicorn
 
-from auth.google_auth import handle_auth_callback, CONFIG_CLIENT_SECRETS_PATH
+from auth.google_auth import handle_auth_callback, check_client_secrets
 from auth.scopes import OAUTH_STATE_TO_SESSION_ID_MAP, SCOPES
 from auth.oauth_responses import create_error_response, create_success_response, create_server_error_response
 
@@ -60,11 +60,9 @@ class MinimalOAuthServer:
 
             try:
                 # Check if we have credentials available (environment variables or file)
-                from auth.google_auth import load_client_secrets_from_env
-                env_config = load_client_secrets_from_env()
-                if not env_config and not os.path.exists(CONFIG_CLIENT_SECRETS_PATH):
-                    logger.error(f"OAuth client credentials not found. No environment variables set and no file at {CONFIG_CLIENT_SECRETS_PATH}")
-                    return create_server_error_response("OAuth client credentials not found. Please set GOOGLE_OAUTH_CLIENT_ID and GOOGLE_OAUTH_CLIENT_SECRET environment variables or provide client_secret.json file.")
+                error_message = check_client_secrets()
+                if error_message:
+                    return create_server_error_response(error_message)
 
                 logger.info(f"OAuth callback: Received code (state: {state}). Attempting to exchange for tokens.")