const presenceTimestamp = (value) => {
  const timestamp = new Date(value || 0).getTime();
  return Number.isFinite(timestamp) ? timestamp : 0;
};

export function selectCurrentPresenceDevice(devices = []) {
  return devices.filter(Boolean).reduce((current, candidate) => {
    if (!current) return candidate;
    if (Boolean(candidate.isOnline) !== Boolean(current.isOnline)) {
      return candidate.isOnline ? candidate : current;
    }
    return presenceTimestamp(candidate.lastSeenAt) > presenceTimestamp(current.lastSeenAt)
      ? candidate
      : current;
  }, null);
}

export function buildOperatorPresenceRows(users = []) {
  return users.flatMap((user) => {
    const devices = Array.isArray(user?.devices) ? user.devices : [];
    const currentDevice = selectCurrentPresenceDevice(devices);
    if (!currentDevice) return [];

    return [{
      ...currentDevice,
      userId: String(user.userId ?? ''),
      name: user.name || '',
      username: user.username || '',
      departmentName: user.departmentName || '',
      activeDeviceCount: Number(user.activeDeviceCount) || 0,
      deviceCount: Number(user.deviceCount) || devices.length,
      isOnline: Boolean(currentDevice.isOnline),
    }];
  });
}

export function filterOperatorPresenceRows(rows = [], status = 'all') {
  if (status === 'online') return rows.filter((row) => row.isOnline);
  if (status === 'offline') return rows.filter((row) => !row.isOnline);
  return rows;
}

export function getOperatorPresenceCounts(rows = []) {
  const online = rows.filter((row) => row.isOnline).length;
  return {
    total: rows.length,
    online,
    offline: rows.length - online,
  };
}