Catch double bookings before they happen

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from datetime import datetime, timedelta, timezone
from clickruntime import on_trigger, credentials, notify

def declined(e):
    return any(a.get("self") and a.get("responseStatus") == "declined" for a in e.get("attendees", []))

@on_trigger
def run(event):
    cal = build("calendar", "v3", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False)
    now = datetime.now(timezone.utc)
    items = cal.events().list(calendarId="primary", timeMin=now.isoformat(), timeMax=(now + timedelta(days=7)).isoformat(),
                              singleEvents=True, orderBy="startTime").execute()["items"]
    timed = [e for e in items if "dateTime" in e["start"] and not declined(e) and e.get("transparency") != "transparent"]
    clashes = []
    for i, a in enumerate(timed):
        for b in timed[i + 1:]:
            if b["start"]["dateTime"] >= a["end"]["dateTime"]:
                break
            clashes.append(f"{a['start']['dateTime'][:16]}: {a.get('summary')} overlaps {b.get('summary')}")
    if clashes:
        notify.email_me(f"{len(clashes)} overlapping meetings this week", "\n".join(clashes))
    return {"overlaps": len(clashes)}