Book appointments only when you're free

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from datetime import datetime, timedelta
from zoneinfo import ZoneInfo
from clickruntime import on_event, credentials

TZ = ZoneInfo("Europe/London")

@on_event
def handle(event):
    req = event.json or {}
    start = datetime.fromisoformat(req["start"]).astimezone(TZ)
    end = start + timedelta(minutes=30)
    if start.weekday() >= 5 or start.hour < 9 or end > start.replace(hour=17, minute=0):
        return {"booked": False, "message": "Please pick a weekday slot between 9am and 5pm."}
    cal = build("calendar", "v3", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False)
    busy = cal.freebusy().query(body={"timeMin": start.isoformat(), "timeMax": end.isoformat(),
                                      "items": [{"id": "primary"}]}).execute()["calendars"]["primary"]["busy"]
    if busy:
        return {"booked": False, "message": "That slot is taken, please choose another."}
    cal.events().insert(calendarId="primary", sendUpdates="all", body={
        "summary": f"Appointment with {req['name']}",
        "start": {"dateTime": start.isoformat()}, "end": {"dateTime": end.isoformat()},
        "attendees": [{"email": req["email"]}],
    }).execute()
    return {"booked": True, "message": f"Booked for {start:%a %d %b %H:%M}."}