afterhours-shift-manager/src/weekly_post.py

"""Lambda handler — posts the weekly on-call schedule to Slack every Monday at 7am ET."""

import logging
import os
from datetime import datetime, timedelta
from zoneinfo import ZoneInfo

import boto3
from slack_sdk import WebClient

from src.blocks import build_week_schedule
from src.schedule import ShiftSchedule

logger = logging.getLogger()
logger.setLevel(logging.INFO)

EASTERN = ZoneInfo("America/New_York")


def handler(event, context):
    now = datetime.now(EASTERN)

    # DST guard — same pattern as the 3CX scheduler
    if now.hour != 7:
        logger.info("ET hour is %d, not 7am — skipping (wrong DST rule fired)", now.hour)
        return {"skipped": True}

    ssm = boto3.client("ssm")
    bot_token = ssm.get_parameter(
        Name=os.environ["SLACK_BOT_TOKEN_PARAM"], WithDecryption=True
    )["Parameter"]["Value"]
    channel_id = ssm.get_parameter(
        Name=os.environ["SHIFT_CHANNEL_PARAM"], WithDecryption=True
    )["Parameter"]["Value"]

    schedule = ShiftSchedule()
    slack = WebClient(token=bot_token)

    # Show this week (Monday = today)
    blocks = build_week_schedule(schedule, start_date=now)

    slack.chat_postMessage(
        channel=channel_id,
        blocks=blocks,
        text=f"After-Hours Schedule — Week of {now.strftime('%b %-d')}",
    )

    logger.info("Posted weekly schedule to channel %s", channel_id)
    return {"posted": True, "channel": channel_id}