Block focus time in next week's calendar

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

@on_trigger
def run(event):
    cal = build("calendar", "v3", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False)
    monday = (datetime.now(timezone.utc) + timedelta(days=1)).replace(hour=0, minute=0, second=0, microsecond=0)
    busy = cal.freebusy().query(body={"timeMin": monday.isoformat(), "timeMax": (monday + timedelta(days=5)).isoformat(),
                                      "items": [{"id": "primary"}]}).execute()["calendars"]["primary"]["busy"]
    spans = [(datetime.fromisoformat(b["start"].replace("Z", "+00:00")), datetime.fromisoformat(b["end"].replace("Z", "+00:00"))) for b in busy]
    plan = []
    for d in range(5):
        for hour in (9, 11, 14):
            start = monday + timedelta(days=d, hours=hour)
            end = start + timedelta(hours=2)
            if not any(s < end and e > start for s, e in spans):
                cal.events().insert(calendarId="primary", body={"summary": "Focus time", "transparency": "opaque",
                                    "start": {"dateTime": start.isoformat()}, "end": {"dateTime": end.isoformat()}}).execute()
                plan.append(f"{start:%a %H:%M}-{end:%H:%M}")
                break
    notify.slack("Focus blocks next week: " + (", ".join(plan) or "no free 2-hour slots"), channel="#me")
    return {"blocks": len(plan)}