One comment per user per post but be able to reply to existing comments

So after some time I done exactly what I wanted and I thought it would be nice to share.

So in functions.php add

function c_parent_comment_counter($pid,$uid){

    global $wpdb;
    $query = "SELECT COUNT(comment_post_id) AS count FROM $wpdb->comments WHERE <code>comment_approved</code> = 1 AND <code>comment_post_ID</code> = $pid AND <code>user_id</code> = $uid AND <code>comment_parent</code> = 0";
    $parents = $wpdb->get_row($query);
    return $parents->count;
}

and in comments.php

global $current_user, $post;
$number_of_parents = c_parent_comment_counter($post->ID,$current_user->ID);
echo "parents: ".$number_of_parents;
if ( $number_of_parents >= 1 ) {
    echo '<nav class="withcomment">';
    comment_form( array( 'title_reply' => __( 'Reply' ) ) );
    echo '</nav>';
} else {
    echo '<span class="withoutcomment">' . comment_form( array( 'title_reply' => __( 'Your opinion' ) ) ) . '</span>';
}
?>

in style.css

.withcomment {
    display: none;
}

This will count how many parent comments a user added and if its one or more it will hide the form. if its 0 it will show the form. but when you click the reply button the form will show and you will be able to reply to any comment.
THIS IS NOT HACK PROOF!!!