"""Lambda handler — announces a new release to the shift channel.

Invoked by the release workflow (``.github/workflows/release.yaml``) once a
minor or major version has been tagged *and* the new code has deployed
successfully. The event carries the version and notes already extracted from
CHANGELOG.md by the workflow, so this function never reads the changelog file
itself (it ships only in the slack-bot package, not here).

Event shape (the frozen contract between release.yaml and this function):
    {"version": "1.10.0", "notes": "<markdown>", "date_label": "June 11, 2026"}
"""

import logging
import os

from slack_sdk import WebClient

from shared.blocks import build_release_announcement_blocks
from shared.secrets import get_secret

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


def handler(event, context):
    event = event or {}
    version = event.get("version")
    notes = event.get("notes")
    date_label = event.get("date_label", "")

    if not version or not notes:
        raise ValueError("event requires non-empty 'version' and 'notes'")

    bot_token = get_secret(os.environ["SLACK_BOT_TOKEN_SECRET"])
    channel_id = os.environ["SHIFT_CHANNEL"]
    slack = WebClient(token=bot_token)

    blocks = build_release_announcement_blocks(version, notes, date_label)
    result = slack.chat_postMessage(
        channel=channel_id,
        blocks=blocks,
        text=f"What's New — v{version}",
    )
    logger.info("Announced v%s to %s (ts=%s)", version, channel_id, result["ts"])
    return {"announced": True, "version": version, "ts": result["ts"]}