Welcome new members when they join a Slack channel

from clickruntime import on_trigger, credentials, http, state, notify

CHANNEL_ID = "C0123BETA"
CHANNEL = "#customers-beta"
WELCOME = ("Start with the beta guide: https://acme.com/beta-guide\n"
           "Post bugs here with a screenshot; <@U0KIMCHEN> answers within a day.")

def slack(method, **params):
    resp = http.get(f"https://slack.com/api/{method}", params=params,
                    headers={"Authorization": f"Bearer {credentials.connection('slack', 'work')}"})
    data = resp.json()
    if not data.get("ok"):
        raise RuntimeError(data.get("error"))
    return data

@on_trigger
def run(event):
    members, cursor = [], None
    while True:
        page = slack("conversations.members", channel=CHANNEL_ID, limit=1000, **({"cursor": cursor} if cursor else {}))
        members += page["members"]
        cursor = page.get("response_metadata", {}).get("next_cursor")
        if not cursor:
            break
    prev = state.get("members")
    state.set("members", members)
    if prev is None:
        return {"baseline": len(members)}
    joined = [m for m in members if m not in set(prev)]
    people = []
    for uid in joined:
        u = slack("users.info", user=uid)["user"]
        if not u.get("is_bot") and not u.get("deleted"):
            people.append(f"<@{uid}>")
    if people:
        notify.slack(f"Welcome {' and '.join([', '.join(people[:-1]), people[-1]] if len(people) > 1 else people)} 👋\n{WELCOME}", channel=CHANNEL)
    return {"joined": len(people)}