Add Google one-tap authentication example

.gitignore

@@ -10,3 +10,4 @@ venv
 .nicegui/
 *.sqlite*
 .DS_Store
+.env

examples/google-one-tap-auth/main.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+import os
+
+import httpx
+from dotenv import load_dotenv
+from fastapi import Form, HTTPException, Request
+from fastapi.responses import RedirectResponse
+
+from nicegui import Client, app, core, ui
+
+# Get your Google Client ID from the Google Cloud Console
+# https://developers.google.com/identity/gsi/web/guides/get-google-api-clientid#get_your_google_api_client_id
+# and pass it as an environment variable (or write it to an .env file)
+load_dotenv()
+GOOGLE_CLIENT_ID = os.environ.get('GOOGLE_CLIENT_ID', '')
+
+
+@ui.page('/')
+def main_page(request: Request):
+    assert request.url.hostname
+    assert core.air
+    assert core.air.remote_url
+    if 'on-air.io' not in request.url.hostname:
+        return RedirectResponse(core.air.remote_url)
+
+    if not GOOGLE_CLIENT_ID:
+        ui.label('Please set the GOOGLE_CLIENT_ID environment variable')
+        return
+
+    ui.add_head_html('<script src="https://accounts.google.com/gsi/client" async defer></script>')
+    ui.html(f'''
+        <div id="g_id_onload"
+            data-client_id="{GOOGLE_CLIENT_ID}"
+            data-login_uri="{core.air.remote_url}auth/google">
+        </div>''')
+    ui.label('Sign in with Google One Tap')
+
+
+@app.post('/auth/google')
+async def google_auth(request: Request, credential: str = Form(...)):
+    async with httpx.AsyncClient() as http_client:
+        response = await http_client.get(f'https://oauth2.googleapis.com/tokeninfo?id_token={credential}')
+    if response.status_code != 200:
+        raise HTTPException(status_code=400, detail='Invalid token')
+    user_data = response.json()
+    with Client(ui.page('')) as nicegui_client:
+        ui.label(f'Welcome {user_data["name"]}!')
+    return nicegui_client.build_response(request, 404)
+
+# NOTE we use NiceGUI On Air (https://nicegui.io/documentation/section_configuration_deployment#nicegui_on_air)
+# to make the local server available to google one-tap auth
+# if you deploy your app on a server, you can remove the whole On Air part
+ui.run(on_air=True, storage_secret='THIS_NEEDS_TO_BE_CHANGED')