Get warned when payments look unusual

from datetime import datetime, timezone
import stripe
from clickruntime import on_trigger, credentials, state, notify

@on_trigger
def run(event):
    stripe.api_key = credentials.secret("STRIPE_API_KEY")
    now = datetime.now(timezone.utc)
    start = int(now.replace(hour=0, minute=0, second=0, microsecond=0).timestamp())
    charges = sum(1 for c in stripe.Charge.list(created={"gte": start}, limit=100).auto_paging_iter() if c.paid)
    refunds = sum(1 for _ in stripe.Refund.list(created={"gte": start}, limit=100).auto_paging_iter())
    key = f"{now:%a}-{now.hour}"  # usual counts by this hour on this weekday
    usual = state.get("usual") or {}
    base = usual.get(key)
    alerts = []
    if base and base["charges"] >= 4 and charges < base["charges"] / 2:
        alerts.append(f"charges {charges} vs usual {base['charges']:.0f}")
    if base and refunds >= 2 and refunds > base["refunds"] * 2:
        alerts.append(f"refunds {refunds} vs usual {base['refunds']:.0f}")
    if alerts and state.get("alerted_day") != now.date().isoformat():
        notify.email_me("Unusual Stripe activity today", "\n".join(alerts))
        state.set("alerted_day", now.date().isoformat())
    usual[key] = {"charges": charges if not base else base["charges"] * 0.75 + charges * 0.25,
                  "refunds": refunds if not base else base["refunds"] * 0.75 + refunds * 0.25}
    state.set("usual", usual)
    return {"charges": charges, "refunds": refunds, "alerts": alerts}