Text clients a booking confirmation and reminders

from datetime import datetime, timedelta, timezone
from clickruntime import on_event, on_trigger, credentials, http, state

FROM = "+447700900000"
QUIET = range(8, 21)  # only send 08:00–20:59 UTC

def sms(to, body):
    sid = credentials.secret("TWILIO_ACCOUNT_SID")
    http.post(f"https://api.twilio.com/2010-04-01/Accounts/{sid}/Messages.json",
              auth=(sid, credentials.secret("TWILIO_AUTH_TOKEN")), data={"To": to, "From": FROM, "Body": body})

@on_event
def booked(event):
    b = event.json  # {"id", "name", "phone", "start": ISO time}
    bookings = state.get("bookings") or {}
    bookings[b["id"]] = {**b, "sent": []}
    state.set("bookings", bookings)
    sms(b["phone"], f"Hi {b['name']}, you're booked for {b['start'][:16].replace('T', ' ')}. Reply STOP to opt out.")
    return {"stored": b["id"]}

@on_trigger
def reminders(event):
    now = datetime.now(timezone.utc)
    if now.hour not in QUIET:
        return {"skipped": "quiet hours"}
    bookings, sent = state.get("bookings") or {}, 0
    for bid, b in list(bookings.items()):
        start = datetime.fromisoformat(b["start"])
        for label, before in (("day", timedelta(hours=24)), ("soon", timedelta(hours=2))):
            if label not in b["sent"] and now >= start - before and now < start:
                sms(b["phone"], f"Reminder: see you at {start:%H:%M} on {start:%a %d %b}.")
                b["sent"].append(label)
                sent += 1
        if start < now:
            bookings.pop(bid)
    state.set("bookings", bookings)
    return {"sent": sent}