function hideUsername($username) {
    $username = ltrim($username, '@');
    $len = mb_strlen($username);
    
    if ($len <= 4) {
        // Juda qisqa username - faqat birinchi va oxirgi harf
        return '@' . mb_substr($username, 0, 1) . '***' . mb_substr($username, -1);
    } elseif ($len <= 6) {
        // Qisqa username - 2 ta ko'rsatib qolganini yashirish
        return '@' . mb_substr($username, 0, 2) . '****' . mb_substr($username, -1);
    } else {
        // Normal username - boshi va oxiridan 2-3 ta ko'rsatish
        $show_start = 2;
        $show_end = 2;
        $hidden_len = $len - $show_start - $show_end;
        return '@' . mb_substr($username, 0, $show_start) . str_repeat('*', min($hidden_len, 4)) . mb_substr($username, -$show_end);
    }
}