Let customers book appointments through your Telegram bot

from datetime import datetime, timedelta, timezone
from clickruntime import on_event, credentials, http
CAL = "https://www.googleapis.com/calendar/v3"
def free_slots(h):
    now = datetime.now(timezone.utc).replace(minute=0, second=0, microsecond=0) + timedelta(hours=1)
    busy = http.post(f"{CAL}/freeBusy", headers=h, json={"timeMin": now.isoformat(), "timeMax": (now + timedelta(days=7)).isoformat(),
                     "items": [{"id": "primary"}]}).json()["calendars"]["primary"]["busy"]
    slots = [now + timedelta(hours=i) for i in range(168)]
    return [s for s in slots if s.weekday() < 6 and 9 <= s.hour < 18 and all(
        s + timedelta(hours=1) <= datetime.fromisoformat(b["start"]) or s >= datetime.fromisoformat(b["end"]) for b in busy)][:6]
@on_event
def handle(event):
    u = event.json or {}
    tg = f"https://api.telegram.org/bot{credentials.secret('TELEGRAM_BOT_TOKEN')}"
    h = {"Authorization": f"Bearer {credentials.connection('google', 'work')}"}
    if "callback_query" in u:
        q = u["callback_query"]
        start = datetime.fromisoformat(q["data"])
        if start in free_slots(h):
            http.post(f"{CAL}/calendars/primary/events", headers=h, json={"summary": f"Booking: {q['from'].get('first_name')}",
                      "start": {"dateTime": start.isoformat()}, "end": {"dateTime": (start + timedelta(hours=1)).isoformat()}})
            text = f"You're booked for {start:%A %d %B at %H:%M}. See you then!"
        else:
            text = "Sorry, that time has just gone. Send any message to see fresh times."
        http.post(f"{tg}/sendMessage", json={"chat_id": q["message"]["chat"]["id"], "text": text})
        return {"booked": "You're" in text}
    buttons = [[{"text": f"{s:%a %d %b %H:%M}", "callback_data": s.isoformat()}] for s in free_slots(h)]
    http.post(f"{tg}/sendMessage", json={"chat_id": u["message"]["chat"]["id"], "text": "Pick a time:", "reply_markup": {"inline_keyboard": buttons}})
    return {"offered": len(buttons)}