app.py

import uvicorn
from fastapi import FastAPI, Depends
from starlette.responses import RedirectResponse
from starlette.middleware.sessions import SessionMiddleware
from authlib.integrations.starlette_client import OAuth, OAuthError
from fastapi import Request
import os
from starlette.config import Config
import gradio as gr

app = FastAPI()

# OAuth settings
GOOGLE_CLIENT_ID = os.environ.get("GOOGLE_CLIENT_ID")
GOOGLE_CLIENT_SECRET = os.environ.get("GOOGLE_CLIENT_SECRET")
SECRET_KEY = os.environ.get("SECRET_KEY")

# Set up OAuth
config_data = {'GOOGLE_CLIENT_ID': GOOGLE_CLIENT_ID, 'GOOGLE_CLIENT_SECRET': GOOGLE_CLIENT_SECRET}
starlette_config = Config(environ=config_data)
oauth = OAuth(starlette_config)
oauth.register(
    name='google',
    server_metadata_url='https://accounts.google.com/.well-known/openid-configuration',
    client_kwargs={'scope': 'openid email profile'},
)

app.add_middleware(SessionMiddleware, secret_key=SECRET_KEY)

# Dependency to get the current user
def get_user(request: Request):
    user = request.session.get('user')
    if user:
        return user['name']
    return None

@app.get('/')
def public(request: Request, user = Depends(get_user)):
    root_url = gr.route_utils.get_root_url(request, "/", None)
    if user:
        return RedirectResponse(url=f'{root_url}/gradio/')
    else:
        return RedirectResponse(url=f'{root_url}/main/')

@app.route('/logout')
async def logout(request: Request):
    request.session.pop('user', None)
    return RedirectResponse(url='/')

@app.route('/login')
async def login(request: Request):
    root_url = gr.route_utils.get_root_url(request, "/login", None)
    redirect_uri = f"{root_url}/auth"
    print("Redirecting to", redirect_uri)
    return await oauth.google.authorize_redirect(request, redirect_uri)

@app.route('/auth')
async def auth(request: Request):
    try:
        access_token = await oauth.google.authorize_access_token(request)
    except OAuthError:
        print("Error getting access token", str(OAuthError))
        return RedirectResponse(url='/')
    request.session['user'] = dict(access_token)["userinfo"]
    print("Redirecting to /gradio")
    return RedirectResponse(url='/gradio')

with gr.Blocks() as login_demo:
    btn = gr.Button("Login")
    _js_redirect = """
    () => {
        url = '/login' + window.location.search;
        window.open(url, '_blank');
    }
    """
    btn.click(None, js=_js_redirect)

app = gr.mount_gradio_app(app, login_demo, path="/main")

def greet(request: gr.Request):
    return f"Welcome to Gradio, {request.username}"

with gr.Blocks() as main_demo:
    m = gr.Markdown("Welcome to Gradio!")
    gr.Button("Logout", link="/logout")
    main_demo.load(greet, None, m)

app = gr.mount_gradio_app(app, main_demo, path="/gradio", auth_dependency=get_user)


if __name__ == '__main__':
    uvicorn.run(app)