from __future__ import annotations

import hashlib
import hmac
import json
import logging

logger = logging.getLogger(__name__)


def verify_rocketchat_webhook_signature(
    payload: bytes,
    signature_header: str,
    secret: str,
) -> bool:
    if not signature_header or not secret:
        return False
    expected = hmac.new(
        secret.encode("utf-8"),
        payload,
        hashlib.sha256,
    ).hexdigest()
    computed = signature_header.replace("sha256=", "")
    return hmac.compare_digest(computed, expected)


def parse_rocketchat_incoming_webhook(body: dict) -> dict | None:
    channel = body.get("channel", body.get("channel_id", ""))
    text = body.get("text", body.get("payload", {}).get("text", ""))
    username = body.get("username", body.get("user_name", ""))
    if not channel or not text:
        return None
    return {
        "channel": channel,
        "text": text,
        "username": username,
        "icon_emoji": body.get("icon_emoji", ""),
        "attachments": body.get("attachments", []),
        "raw": body,
    }


async def handle_rocketchat_webhook(
    request_body: bytes,
    headers: dict,
    webhook_secret: str = "",
) -> dict | None:
    try:
        body = json.loads(request_body.decode("utf-8"))
    except (json.JSONDecodeError, UnicodeDecodeError):
        body = {}

    signature = headers.get("X-RocketChat-Signature", "")
    if webhook_secret and not verify_rocketchat_webhook_signature(request_body, signature, webhook_secret):
        logger.warning("Rocket.Chat webhook signature verification failed")
        return None

    parsed = parse_rocketchat_incoming_webhook(body)
    if not parsed:
        return None

    logger.info(
        "Rocket.Chat webhook received from %s in channel %s",
        parsed.get("username", "unknown"),
        parsed.get("channel", "unknown"),
    )
    return parsed