"""Slack interactivity Lambda: drill-down modals behind API Gateway.

Fronted by the ``apm-wo.seahaven.com`` HTTP API (Slack interactivity request URL).
Verifies the Slack request signature, then for a category/site drill button reads
the day's ``details.json``, filters it, and opens a WO-list modal via ``views.open``
within Slack's 3-second ``trigger_id`` window. WO rows link to Grafana only — no
APM deep-links (see Phase 4 decisions).
"""

from __future__ import annotations

import base64
import json
from datetime import datetime, timezone
from urllib.parse import parse_qs

import blockkit
import slackio

_FILTER_FIELD = {"drill_category": "category", "drill_site": "site"}


def _raw_body(event: dict) -> str:
    body = event.get("body") or ""
    if event.get("isBase64Encoded"):
        body = base64.b64decode(body).decode("utf-8")
    return body


def _headers(event: dict) -> dict:
    # API Gateway HTTP API lowercases header names; be defensive either way.
    return {k.lower(): v for k, v in (event.get("headers") or {}).items()}


def handler(event, context):
    """Verify the Slack signature and open the requested drill-down modal."""
    body = _raw_body(event)
    headers = _headers(event)
    timestamp = headers.get("x-slack-request-timestamp", "")
    signature = headers.get("x-slack-signature", "")

    if not slackio.verify_signature(body, timestamp, signature):
        print("Rejected: invalid Slack signature.")
        return {"statusCode": 401, "body": "invalid signature"}

    parsed = parse_qs(body)
    payload = json.loads(parsed.get("payload", ["{}"])[0])
    if payload.get("type") != "block_actions":
        return {"statusCode": 200, "body": ""}

    action = (payload.get("actions") or [{}])[0]
    # action_id is qualified for Slack uniqueness, e.g. "drill_category:Report /
    # Docs Needed" — match on the prefix before ":"; the filter value is in `value`.
    action_kind = (action.get("action_id") or "").split(":", 1)[0]
    field = _FILTER_FIELD.get(action_kind)
    value = action.get("value")
    trigger_id = payload.get("trigger_id")
    if not field or not value or not trigger_id:
        return {"statusCode": 200, "body": ""}

    # The daily post is same-day; default the drill to today's snapshot.
    dt = datetime.now(timezone.utc).strftime("%Y-%m-%d")
    details = slackio.read_meta_json(dt, "details.json") or []
    wos = [d for d in details if d.get(field) == value]

    view = blockkit.build_wo_modal(
        title=f"{value} ({len(wos)})",
        wos=wos,
        dashboard_url=slackio.get_dashboard_url(),
    )
    slackio.web_client().views_open(trigger_id=trigger_id, view=view)
    return {"statusCode": 200, "body": ""}