derp/plugins/alert.py

"""Plugin: keyword alert subscriptions across multiple platforms."""

from __future__ import annotations

import asyncio
import json
import logging
import re
import sqlite3
import urllib.request
from datetime import datetime, timezone
from html.parser import HTMLParser
from pathlib import Path

from derp.http import urlopen as _urlopen
from derp.plugin import command, event

_log = logging.getLogger(__name__)

# -- Constants ---------------------------------------------------------------

_NAME_RE = re.compile(r"^[a-z0-9][a-z0-9-]{0,19}$")
_MAX_KEYWORD_LEN = 100
_MAX_SEEN = 200
_DEFAULT_INTERVAL = 300
_MAX_INTERVAL = 3600
_FETCH_TIMEOUT = 15
_MAX_TITLE_LEN = 80
_MAX_SUBS = 20
_YT_SEARCH_URL = "https://www.youtube.com/youtubei/v1/search"
_YT_CLIENT_VERSION = "2.20250101.00.00"
_GQL_URL = "https://gql.twitch.tv/gql"
_GQL_CLIENT_ID = "kimne78kx3ncx6brgo4mv6wki5h1ko"
_SEARX_URL = "https://searx.mymx.me/search"
_REDDIT_SEARCH_URL = "https://old.reddit.com/search.json"
_MASTODON_INSTANCES = [
    "mastodon.social",
    "fosstodon.org",
    "hachyderm.io",
    "infosec.exchange",
]
_MASTODON_TAG_TIMEOUT = 4

# -- Module-level tracking ---------------------------------------------------

_pollers: dict[str, asyncio.Task] = {}
_subscriptions: dict[str, dict] = {}
_errors: dict[str, int] = {}

# -- History database --------------------------------------------------------

_DB_PATH = Path("data/alert_history.db")
_conn: sqlite3.Connection | None = None


def _db() -> sqlite3.Connection:
    """Lazy-init the history database connection and schema."""
    global _conn
    if _conn is not None:
        return _conn
    _DB_PATH.parent.mkdir(parents=True, exist_ok=True)
    _conn = sqlite3.connect(str(_DB_PATH))
    _conn.execute("""
        CREATE TABLE IF NOT EXISTS results (
            id       INTEGER PRIMARY KEY AUTOINCREMENT,
            channel  TEXT NOT NULL,
            alert    TEXT NOT NULL,
            backend  TEXT NOT NULL,
            item_id  TEXT NOT NULL,
            title    TEXT NOT NULL,
            url      TEXT NOT NULL,
            date     TEXT NOT NULL DEFAULT '',
            found_at TEXT NOT NULL
        )
    """)
    _conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_results_alert ON results(channel, alert)"
    )
    _conn.commit()
    return _conn


def _save_result(channel: str, alert: str, backend: str, item: dict) -> None:
    """Persist a matched result to the history database."""
    db = _db()
    db.execute(
        "INSERT INTO results (channel, alert, backend, item_id, title, url, date, found_at)"
        " VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
        (
            channel,
            alert,
            backend,
            item.get("id", ""),
            item.get("title", ""),
            item.get("url", ""),
            item.get("date", ""),
            datetime.now(timezone.utc).isoformat(),
        ),
    )
    db.commit()


# -- Pure helpers ------------------------------------------------------------

def _state_key(channel: str, name: str) -> str:
    """Build composite state key."""
    return f"{channel}:{name}"


def _validate_name(name: str) -> bool:
    """Check name against allowed pattern."""
    return bool(_NAME_RE.match(name))


def _truncate(text: str, max_len: int = _MAX_TITLE_LEN) -> str:
    """Truncate text with ellipsis if needed."""
    if len(text) <= max_len:
        return text
    return text[: max_len - 3].rstrip() + "..."


_DATE_PROPS = {
    "article:published_time", "og:article:published_time",
    "og:updated_time", "date", "dc.date", "dcterms.date",
    "sailthru.date",
}


class _OGParser(HTMLParser):
    """Extract og:title, og:description, and published date from <meta> tags."""

    def __init__(self):
        super().__init__()
        self.og_title = ""
        self.og_description = ""
        self.published = ""

    def handle_starttag(self, tag: str, attrs: list[tuple[str, str | None]]) -> None:
        if tag != "meta":
            return
        attr_map = {k.lower(): (v or "") for k, v in attrs}
        prop = attr_map.get("property", "").lower()
        name = attr_map.get("name", "").lower()
        content = attr_map.get("content", "")
        if prop == "og:title":
            self.og_title = content
        elif prop == "og:description":
            self.og_description = content
        if not self.published and content:
            if prop in _DATE_PROPS or name in _DATE_PROPS:
                self.published = content


_OG_TIMEOUT = 10
_OG_MAX_BYTES = 64 * 1024  # Only read first 64 KB (OG tags are in <head>)


def _parse_date(raw: str) -> str:
    """Try to extract a YYYY-MM-DD date from a raw date string."""
    m = re.search(r"\d{4}-\d{2}-\d{2}", raw)
    return m.group(0) if m else ""


def _strip_html(text: str) -> str:
    """Remove HTML tags from text."""
    return re.sub(r"<[^>]+>", "", text).strip()


def _fetch_og(url: str) -> tuple[str, str, str]:
    """Fetch og:title, og:description, and published date from a URL.

    Returns (og_title, og_description, date). Empty strings on failure.
    """
    try:
        req = urllib.request.Request(url, method="GET")
        req.add_header("User-Agent", "Mozilla/5.0 (compatible; derp-bot)")
        resp = _urlopen(req, timeout=_OG_TIMEOUT)
        raw = resp.read(_OG_MAX_BYTES)
        resp.close()
        html = raw.decode("utf-8", errors="replace")
        parser = _OGParser()
        parser.feed(html)
        date = _parse_date(parser.published)
        return parser.og_title, parser.og_description, date
    except Exception as exc:
        _log.debug("og fetch failed for %s: %s", url, exc)
        return "", "", ""


# -- YouTube InnerTube search (blocking) ------------------------------------

def _extract_videos(obj: object, depth: int = 0) -> list[dict]:
    """Recursively walk YouTube JSON to find video results.

    Finds all objects containing both 'videoId' and 'title' keys.
    Resilient to YouTube rearranging wrapper layers.
    """
    if depth > 20:
        return []
    results = []
    if isinstance(obj, dict):
        video_id = obj.get("videoId")
        title_obj = obj.get("title")
        if isinstance(video_id, str) and video_id and title_obj is not None:
            if isinstance(title_obj, dict):
                runs = title_obj.get("runs", [])
                title = "".join(r.get("text", "") for r in runs if isinstance(r, dict))
            elif isinstance(title_obj, str):
                title = title_obj
            else:
                title = ""
            if title:
                # Extract relative publish time (e.g. "2 days ago")
                pub_obj = obj.get("publishedTimeText")
                date = ""
                if isinstance(pub_obj, dict):
                    date = pub_obj.get("simpleText", "")
                elif isinstance(pub_obj, str):
                    date = pub_obj
                results.append({
                    "id": video_id,
                    "title": title,
                    "url": f"https://www.youtube.com/watch?v={video_id}",
                    "date": date,
                    "extra": "",
                })
        for val in obj.values():
            results.extend(_extract_videos(val, depth + 1))
    elif isinstance(obj, list):
        for item in obj:
            results.extend(_extract_videos(item, depth + 1))
    return results


def _search_youtube(keyword: str) -> list[dict]:
    """Search YouTube via InnerTube API. Blocking."""
    payload = json.dumps({
        "context": {
            "client": {
                "clientName": "WEB",
                "clientVersion": _YT_CLIENT_VERSION,
            },
        },
        "query": keyword,
    }).encode()

    req = urllib.request.Request(_YT_SEARCH_URL, data=payload, method="POST")
    req.add_header("Content-Type", "application/json")

    resp = urllib.request.urlopen(req, timeout=_FETCH_TIMEOUT)
    raw = resp.read()
    resp.close()

    data = json.loads(raw)
    videos = _extract_videos(data)
    # Deduplicate by videoId (same video can appear in multiple sections)
    seen_ids: set[str] = set()
    unique: list[dict] = []
    for v in videos:
        if v["id"] not in seen_ids:
            seen_ids.add(v["id"])
            unique.append(v)
    return unique


# -- Twitch GQL search (blocking) ------------------------------------------

def _search_twitch(keyword: str) -> list[dict]:
    """Search Twitch via public GQL. Blocking."""
    query = (
        'query{searchFor(userQuery:"'
        + keyword.replace("\\", "\\\\").replace('"', '\\"')
        + '",options:{targets:[{index:STREAM},{index:VOD}]})'
        "{streams{items{id broadcaster{login displayName}title game{name}"
        "viewersCount}}videos{items{id owner{login displayName}title"
        " game{name}viewCount}}}}"
    )
    body = json.dumps({"query": query}).encode()

    req = urllib.request.Request(_GQL_URL, data=body, method="POST")
    req.add_header("Client-Id", _GQL_CLIENT_ID)
    req.add_header("Content-Type", "application/json")

    resp = _urlopen(req, timeout=_FETCH_TIMEOUT)
    raw = resp.read()
    resp.close()

    data = json.loads(raw)
    results: list[dict] = []

    try:
        search = data["data"]["searchFor"]
    except (KeyError, TypeError):
        return results
    if not search:
        return results

    # Live streams
    streams = search.get("streams") or {}
    for item in streams.get("items") or []:
        stream_id = str(item.get("id", ""))
        if not stream_id:
            continue
        broadcaster = item.get("broadcaster") or {}
        login = broadcaster.get("login", "")
        display = broadcaster.get("displayName", login)
        title = item.get("title", "")
        game = (item.get("game") or {}).get("name", "")
        line = f"{display} is live: {title}"
        if game:
            line += f" ({game})"
        results.append({
            "id": f"stream:{stream_id}",
            "title": line,
            "url": f"https://twitch.tv/{login}",
            "date": "",
            "extra": "",
        })

    # VODs
    videos = search.get("videos") or {}
    for item in videos.get("items") or []:
        vod_id = str(item.get("id", ""))
        if not vod_id:
            continue
        title = item.get("title", "")
        results.append({
            "id": f"vod:{vod_id}",
            "title": title,
            "url": f"https://twitch.tv/videos/{vod_id}",
            "date": "",
            "extra": "",
        })

    return results


# -- SearXNG search (blocking) ----------------------------------------------

def _search_searx(keyword: str) -> list[dict]:
    """Search SearXNG. Blocking."""
    import urllib.parse

    params = urllib.parse.urlencode({"q": keyword, "format": "json"})
    url = f"{_SEARX_URL}?{params}"

    req = urllib.request.Request(url, method="GET")
    resp = urllib.request.urlopen(req, timeout=_FETCH_TIMEOUT)
    raw = resp.read()
    resp.close()

    data = json.loads(raw)
    results: list[dict] = []
    for item in data.get("results", []):
        item_url = item.get("url", "")
        title = item.get("title", "")
        date = _parse_date(item.get("publishedDate") or "")
        results.append({
            "id": item_url,
            "title": title,
            "url": item_url,
            "date": date,
            "extra": "",
        })
    return results


# -- Reddit search (blocking) ------------------------------------------------

def _search_reddit(keyword: str) -> list[dict]:
    """Search Reddit via JSON API. Blocking."""
    import urllib.parse

    params = urllib.parse.urlencode({
        "q": keyword, "sort": "new", "limit": "25", "t": "week",
    })
    url = f"{_REDDIT_SEARCH_URL}?{params}"

    req = urllib.request.Request(url, method="GET")
    req.add_header("User-Agent", "derp-bot/1.0 (IRC keyword alert)")

    resp = _urlopen(req, timeout=_FETCH_TIMEOUT)
    raw = resp.read()
    resp.close()

    data = json.loads(raw)
    results: list[dict] = []
    for child in (data.get("data") or {}).get("children") or []:
        post = child.get("data") or {}
        post_id = post.get("name", "")
        permalink = post.get("permalink", "")
        title = post.get("title", "")
        created = post.get("created_utc")
        date = ""
        if created:
            try:
                date = datetime.fromtimestamp(
                    float(created), tz=timezone.utc,
                ).strftime("%Y-%m-%d")
            except (ValueError, OSError):
                pass
        results.append({
            "id": post_id,
            "title": title,
            "url": f"https://www.reddit.com{permalink}" if permalink else "",
            "date": date,
            "extra": "",
        })
    return results


# -- Mastodon/Fediverse search (blocking) -----------------------------------

def _search_mastodon(keyword: str) -> list[dict]:
    """Search Mastodon instances via public hashtag timeline. Blocking."""
    import urllib.parse

    # Sanitize keyword to alphanumeric for hashtag search
    hashtag = re.sub(r"[^a-zA-Z0-9]", "", keyword).lower()
    if not hashtag:
        return []

    results: list[dict] = []
    seen_urls: set[str] = set()

    for instance in _MASTODON_INSTANCES:
        tag_url = (
            f"https://{instance}/api/v1/timelines/tag/"
            f"{urllib.parse.quote(hashtag, safe='')}"
        )
        req = urllib.request.Request(tag_url, method="GET")
        req.add_header("User-Agent", "derp-bot/1.0 (IRC keyword alert)")
        try:
            resp = _urlopen(req, timeout=_MASTODON_TAG_TIMEOUT)
            raw = resp.read()
            resp.close()
        except Exception as exc:
            _log.debug("mastodon %s failed: %s", instance, exc)
            continue

        try:
            statuses = json.loads(raw)
        except json.JSONDecodeError:
            continue

        if not isinstance(statuses, list):
            continue

        for status in statuses:
            status_url = status.get("url") or status.get("uri", "")
            if not status_url or status_url in seen_urls:
                continue
            seen_urls.add(status_url)

            acct = (status.get("account") or {}).get("acct", "")
            content = _strip_html(status.get("content", ""))
            title = f"@{acct}: {_truncate(content, 60)}" if acct else content
            date = _parse_date(status.get("created_at", ""))
            results.append({
                "id": status_url,
                "title": title,
                "url": status_url,
                "date": date,
                "extra": "",
            })

    return results


# -- Backend registry -------------------------------------------------------

_BACKENDS: dict[str, callable] = {
    "yt": _search_youtube,
    "tw": _search_twitch,
    "sx": _search_searx,
    "rd": _search_reddit,
    "ft": _search_mastodon,
}


# -- State helpers -----------------------------------------------------------

def _save(bot, key: str, data: dict) -> None:
    """Persist subscription data to bot.state."""
    bot.state.set("alert", key, json.dumps(data))


def _load(bot, key: str) -> dict | None:
    """Load subscription data from bot.state."""
    raw = bot.state.get("alert", key)
    if raw is None:
        return None
    try:
        return json.loads(raw)
    except json.JSONDecodeError:
        return None


def _delete(bot, key: str) -> None:
    """Remove subscription data from bot.state."""
    bot.state.delete("alert", key)


# -- Polling -----------------------------------------------------------------

async def _poll_once(bot, key: str, announce: bool = True) -> None:
    """Single poll cycle for one alert subscription (all backends)."""
    data = _subscriptions.get(key)
    if data is None:
        data = _load(bot, key)
    if data is None:
        return
    _subscriptions[key] = data

    keyword = data["keyword"]
    now = datetime.now(timezone.utc).isoformat()
    data["last_poll"] = now

    had_error = False
    loop = asyncio.get_running_loop()

    for tag, backend in _BACKENDS.items():
        try:
            items = await loop.run_in_executor(None, backend, keyword)
        except Exception as exc:
            data["last_error"] = f"{tag}: {exc}"
            had_error = True
            continue

        seen_set = set(data.get("seen", {}).get(tag, []))
        seen_list = list(data.get("seen", {}).get(tag, []))
        new_items = [item for item in items if item["id"] not in seen_set]

        # Filter: only announce results that actually contain the keyword
        # Check title/URL first, then fall back to og:title/og:description
        kw_lower = keyword.lower()
        matched = []
        for item in new_items:
            title_l = item.get("title", "").lower()
            url_l = item.get("url", "").lower()
            if kw_lower in title_l or kw_lower in url_l:
                # Fetch OG tags for date if backend didn't provide one
                if not item.get("date") and item.get("url"):
                    _, _, og_date = await loop.run_in_executor(
                        None, _fetch_og, item["url"],
                    )
                    if og_date:
                        item["date"] = og_date
                matched.append(item)
                continue
            # Fetch OG tags for items that didn't match on title/URL
            item_url = item.get("url", "")
            if item_url:
                og_title, og_desc, og_date = await loop.run_in_executor(
                    None, _fetch_og, item_url,
                )
                if (kw_lower in og_title.lower()
                        or kw_lower in og_desc.lower()):
                    if og_title and len(og_title) > len(item.get("title", "")):
                        item["title"] = og_title
                    if og_date and not item.get("date"):
                        item["date"] = og_date
                    matched.append(item)

        if announce and matched:
            channel = data["channel"]
            name = data["name"]
            for item in matched:
                title = _truncate(item["title"]) if item["title"] else "(no title)"
                url = item["url"]
                date = item.get("date", "")
                line = f"[{name}/{tag}]"
                if date:
                    line += f" ({date})"
                line += f" {title}"
                if url:
                    line += f" -- {url}"
                await bot.send(channel, line)
                _save_result(channel, name, tag, item)

        for item in new_items:
            seen_list.append(item["id"])
        if len(seen_list) > _MAX_SEEN:
            seen_list = seen_list[-_MAX_SEEN:]
        data.setdefault("seen", {})[tag] = seen_list

    if had_error:
        _errors[key] = _errors.get(key, 0) + 1
    else:
        data["last_error"] = ""
        _errors[key] = 0

    _subscriptions[key] = data
    _save(bot, key, data)


async def _poll_loop(bot, key: str) -> None:
    """Infinite poll loop for one alert subscription."""
    try:
        while True:
            data = _subscriptions.get(key) or _load(bot, key)
            if data is None:
                return
            interval = data.get("interval", _DEFAULT_INTERVAL)
            errs = _errors.get(key, 0)
            if errs >= 5:
                interval = min(interval * 2, _MAX_INTERVAL)
            await asyncio.sleep(interval)
            await _poll_once(bot, key, announce=True)
    except asyncio.CancelledError:
        pass


def _start_poller(bot, key: str) -> None:
    """Create and track a poller task."""
    existing = _pollers.get(key)
    if existing and not existing.done():
        return
    task = asyncio.create_task(_poll_loop(bot, key))
    _pollers[key] = task


def _stop_poller(key: str) -> None:
    """Cancel and remove a poller task."""
    task = _pollers.pop(key, None)
    if task and not task.done():
        task.cancel()
    _subscriptions.pop(key, None)
    _errors.pop(key, 0)


# -- Restore on connect -----------------------------------------------------

def _restore(bot) -> None:
    """Rebuild pollers from persisted state."""
    for key in bot.state.keys("alert"):
        existing = _pollers.get(key)
        if existing and not existing.done():
            continue
        data = _load(bot, key)
        if data is None:
            continue
        _subscriptions[key] = data
        _start_poller(bot, key)


@event("001")
async def on_connect(bot, message):
    """Restore alert subscription pollers on connect."""
    _restore(bot)


# -- Command handler ---------------------------------------------------------

@command("alert", help="Alert: !alert add|del|list|check|history")
async def cmd_alert(bot, message):
    """Per-channel keyword alert subscriptions across platforms.

    Usage:
        !alert add <name> <keyword...>   Add keyword alert (admin)
        !alert del <name>                Remove alert (admin)
        !alert list                      List alerts
        !alert check <name>              Force-poll now
        !alert history <name> [n]        Show recent results (default 5)
    """
    parts = message.text.split(None, 3)
    if len(parts) < 2:
        await bot.reply(message, "Usage: !alert <add|del|list|check|history> [args]")
        return

    sub = parts[1].lower()

    # -- list (any user, channel only) ----------------------------------------
    if sub == "list":
        if not message.is_channel:
            await bot.reply(message, "Use this command in a channel")
            return
        channel = message.target
        prefix = f"{channel}:"
        subs = []
        for key in bot.state.keys("alert"):
            if key.startswith(prefix):
                data = _load(bot, key)
                if data:
                    name = data["name"]
                    err = data.get("last_error", "")
                    if err:
                        subs.append(f"{name} (error)")
                    else:
                        subs.append(name)
        if not subs:
            await bot.reply(message, "No alerts in this channel")
            return
        await bot.reply(message, f"Alerts: {', '.join(subs)}")
        return

    # -- check (any user, channel only) ---------------------------------------
    if sub == "check":
        if not message.is_channel:
            await bot.reply(message, "Use this command in a channel")
            return
        if len(parts) < 3:
            await bot.reply(message, "Usage: !alert check <name>")
            return
        name = parts[2].lower()
        channel = message.target
        key = _state_key(channel, name)
        data = _load(bot, key)
        if data is None:
            await bot.reply(message, f"No alert '{name}' in this channel")
            return
        _subscriptions[key] = data
        await _poll_once(bot, key, announce=True)
        data = _subscriptions.get(key, data)
        if data.get("last_error"):
            await bot.reply(message, f"{name}: error -- {data['last_error']}")
        else:
            await bot.reply(message, f"{name}: checked")
        return

    # -- history (any user, channel only) ------------------------------------
    if sub == "history":
        if not message.is_channel:
            await bot.reply(message, "Use this command in a channel")
            return
        if len(parts) < 3:
            await bot.reply(message, "Usage: !alert history <name> [n]")
            return
        name = parts[2].lower()
        channel = message.target
        key = _state_key(channel, name)
        if _load(bot, key) is None:
            await bot.reply(message, f"No alert '{name}' in this channel")
            return
        limit = 5
        if len(parts) >= 4:
            try:
                limit = max(1, min(int(parts[3]), 20))
            except ValueError:
                limit = 5
        db = _db()
        rows = db.execute(
            "SELECT backend, title, url, date, found_at FROM results"
            " WHERE channel = ? AND alert = ? ORDER BY id DESC LIMIT ?",
            (channel, name, limit),
        ).fetchall()
        if not rows:
            await bot.reply(message, f"{name}: no history yet")
            return
        for backend, title, url, date, found_at in reversed(rows):
            ts = found_at[:10]
            title = _truncate(title) if title else "(no title)"
            line = f"[{name}/{backend}] ({date or ts}) {title}"
            if url:
                line += f" -- {url}"
            await bot.reply(message, line)
        return

    # -- add (admin, channel only) -------------------------------------------
    if sub == "add":
        if not bot._is_admin(message):
            await bot.reply(message, "Permission denied: add requires admin")
            return
        if not message.is_channel:
            await bot.reply(message, "Use this command in a channel")
            return
        if len(parts) < 4:
            await bot.reply(message, "Usage: !alert add <name> <keyword...>")
            return

        name = parts[2].lower()
        keyword = parts[3]

        if not _validate_name(name):
            await bot.reply(
                message,
                "Invalid name (lowercase alphanumeric + hyphens, 1-20 chars)",
            )
            return

        if len(keyword) > _MAX_KEYWORD_LEN:
            await bot.reply(message, f"Keyword too long (max {_MAX_KEYWORD_LEN} chars)")
            return

        irc_channel = message.target
        key = _state_key(irc_channel, name)

        if _load(bot, key) is not None:
            await bot.reply(message, f"Alert '{name}' already exists in this channel")
            return

        ch_prefix = f"{irc_channel}:"
        count = sum(1 for k in bot.state.keys("alert") if k.startswith(ch_prefix))
        if count >= _MAX_SUBS:
            await bot.reply(message, f"Alert limit reached ({_MAX_SUBS})")
            return

        # Seed: query all backends to populate seen lists (prevents flood)
        loop = asyncio.get_running_loop()
        seen: dict[str, list[str]] = {}
        for tag, backend in _BACKENDS.items():
            try:
                items = await loop.run_in_executor(None, backend, keyword)
                ids = [item["id"] for item in items]
                if len(ids) > _MAX_SEEN:
                    ids = ids[-_MAX_SEEN:]
                seen[tag] = ids
            except Exception:
                seen[tag] = []

        now = datetime.now(timezone.utc).isoformat()
        data = {
            "keyword": keyword,
            "name": name,
            "channel": irc_channel,
            "interval": _DEFAULT_INTERVAL,
            "added_by": message.nick,
            "added_at": now,
            "last_poll": now,
            "last_error": "",
            "seen": seen,
        }
        _save(bot, key, data)
        _subscriptions[key] = data
        _start_poller(bot, key)

        counts = ", ".join(f"{len(seen.get(t, []))} {t}" for t in _BACKENDS)
        await bot.reply(
            message,
            f"Alert '{name}' added for: {keyword} ({counts} existing)",
        )
        return

    # -- del (admin, channel only) -------------------------------------------
    if sub == "del":
        if not bot._is_admin(message):
            await bot.reply(message, "Permission denied: del requires admin")
            return
        if not message.is_channel:
            await bot.reply(message, "Use this command in a channel")
            return
        if len(parts) < 3:
            await bot.reply(message, "Usage: !alert del <name>")
            return

        name = parts[2].lower()
        channel = message.target
        key = _state_key(channel, name)

        if _load(bot, key) is None:
            await bot.reply(message, f"No alert '{name}' in this channel")
            return

        _stop_poller(key)
        _delete(bot, key)
        await bot.reply(message, f"Removed '{name}'")
        return

    await bot.reply(message, "Usage: !alert <add|del|list|check|history> [args]")