# retoor <retoor@molodetz.nl>
import json
import threading
import time
from datetime import datetime, timedelta, timezone

from molodetz import config
from molodetz.database import db, get_service_state, now_iso, update_user

_lock = threading.Lock()
_last_write = {}


def touch(uid):
    if not uid:
        return
    now = time.monotonic()
    throttle = max(1, config.PRESENCE_TIMEOUT_SECONDS // 2)
    with _lock:
        if now - _last_write.get(uid, 0) < throttle:
            return
        _last_write[uid] = now
    update_user(uid, last_seen_at=now_iso())


def compute_roster():
    if "users" not in db.tables:
        return []
    window = config.PRESENCE_TIMEOUT_SECONDS + config.PRESENCE_ONLINE_MARGIN_SECONDS
    cutoff = (datetime.now(timezone.utc) - timedelta(seconds=window)).isoformat()
    rows = db.query(
        "SELECT uid FROM users WHERE last_seen_at >= :cutoff AND deleted_at IS NULL "
        "ORDER BY last_seen_at DESC LIMIT :limit",
        cutoff=cutoff,
        limit=config.PRESENCE_TRACK_LIMIT,
    )
    return [row["uid"] for row in rows]


def published_roster():
    row = get_service_state("presence")
    if row and row.get("metrics"):
        try:
            metrics = json.loads(row["metrics"])
        except ValueError:
            metrics = {}
        if "roster" in metrics:
            return metrics["roster"]
    return compute_roster()


def online_uids(limit=None):
    return published_roster()[: limit or config.PRESENCE_ONLINE_LIMIT]