Add event sign-ups to the calendar invite

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
import base64
from email.mime.text import MIMEText
from clickruntime import on_event, credentials

EVENT_ID = "your-event-id"

def send(gmail, to, subject, text, thread=None):
    msg = MIMEText(text)
    msg["to"], msg["subject"] = to, subject
    body = {"raw": base64.urlsafe_b64encode(msg.as_bytes()).decode()}
    if thread:
        body["threadId"] = thread
    gmail.users().messages().send(userId="me", body=body).execute()

@on_event
def handle(event):
    p = event.json or {}
    email, name = p["email"].strip().lower(), p.get("name", "")
    creds = Credentials(credentials.connection("google", "work"))
    cal = build("calendar", "v3", credentials=creds, cache_discovery=False).events()
    ev = cal.get(calendarId="primary", eventId=EVENT_ID).execute()
    guests = ev.get("attendees", [])
    if all(g["email"].lower() != email for g in guests):
        cal.patch(calendarId="primary", eventId=EVENT_ID, sendUpdates="all",
                  body={"attendees": guests + [{"email": email, "displayName": name}]}).execute()
    when = ev["start"].get("dateTime", ev["start"].get("date"))
    send(build("gmail", "v1", credentials=creds, cache_discovery=False), email, f"You're registered: {ev['summary']}",
         f"Hi {name},\n\nYour place at {ev['summary']} is confirmed.\nWhen: {when}\nWhere: {ev.get('location', 'see invite')}\n\nSee you there.")
    return {"guests": len(guests) + 1}