Get told when your calendar changes

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from clickruntime import on_trigger, report_fetched, credentials, state, notify

@on_trigger
def run(event):
    cal = build("calendar", "v3", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False)
    token = state.get("sync_token")
    try:
        resp = cal.events().list(calendarId="primary", syncToken=token, showDeleted=True).execute() if token \
            else cal.events().list(calendarId="primary", timeMin="2026-01-01T00:00:00Z", maxResults=2500).execute()
    except HttpError as e:
        if e.resp.status != 410:
            raise
        state.delete("sync_token")  # token expired: start over next run
        report_fetched(0)
        return {"summary": "Sync reset"}
    changes = resp["items"] if token else []
    report_fetched(len(changes))
    state.set("sync_token", resp["nextSyncToken"])
    for e in changes:
        if e["status"] == "cancelled":
            notify.slack(f"Cancelled: {e.get('summary', 'an event')}", channel="#calendar")
        else:
            when = e["start"].get("dateTime", e["start"].get("date"))
            notify.slack(f"Added or moved: {e.get('summary')} – now {when}", channel="#calendar")
    return {"changes": len(changes)}