Events Espresso Add new registration

<?php

/**
 * Add new registration
 *
 * @return WP_Error|boolean|EE_Registration
 */
function add_new_registration($data, $check_referer = true, $reg_number = 1, $quantity = 1)
{

    if ($check_referer && !check_ajax_referer('add_new_registration', false, false)) {
        return new WP_Error("invalid_token", "Invalid  or expired session");
    }

    extract($data);

    if (isset($quantity) && $quantity > 0) {
        $quantity = $quantity;
    } else {
        $quantity = 1;
    }

    if (!EE_Registry::instance()->CAP->current_user_can('ee_edit_registrations', 'espresso_registrations_new_registration', $event_id)) {

        return new WP_Error("permission_denied", "Permission Denied");
    }

    if (empty($first_name)) {
        return new WP_Error("first_name", "First Name is required");
    }

    if (empty($last_name)) {
        return new WP_Error("last_name", "Last Name is required");
    }

    global $wpdb;

    $ticket = EEM_Ticket::instance()->get_one_by_ID($ticket_id);

    if (!$ticket instanceof EE_Ticket) {

        $event = EEM_Event::instance()->get_one_by_ID($event_id);

        if (!$event instanceof EE_Event) {
            return new WP_Error('ticket', 'Invalid Ticket');
        }

        $ticket = reset($event->tickets());

        if (!$ticket instanceof EE_Ticket) {
            return new WP_Error('ticket', 'Invalid Ticket');
        }
    }

    $registration_processor = EE_Registry::instance()->load_class('Registration_Processor');

    $payment_method = EEM_Payment_Method::instance()->get_one_by_slug('other');
    $transaction = EE_Transaction::new_instance(array(
        'TXN_timestamp' => time(), //unix timestamp
        'TXN_total' => 0, //txn_total
        'TXN_paid' => 0, //txn_paid
        'STS_ID' => EEM_Transaction::complete_status_code, //sts_id
        'TXN_session_data' => null, //dump of txn session object (we're just going to leave blank here)
        'TXN_hash_salt' => null, //hash salt blank as well
        'PMD_ID' => $payment_method->ID(),
    ));

    $transaction->save();

    $total_line_item = $transaction->total_line_item();
    $line_item = \EEH_Line_Item::add_ticket_purchase(
        $total_line_item,
        $ticket,
        $quantity
    );

    $total_line_item->save_this_and_descendants_to_txn($transaction->ID());

    EEH_Line_Item::apply_taxes($total_line_item);

    for ($i = 1; $i <= $quantity; $i++) {

        $registration = (new \EventEspresso\core\domain\services\registration\CreateRegistrationService())->create(
            $ticket->get_related_event(),
            $transaction,
            $ticket,
            $line_item,
            $i,
            $quantity
        );

        $attendee = EE_Attendee::new_instance(array(
            'ATT_fname' => !empty($first_name) ? $first_name : '',
            'ATT_lname' => !empty($last_name) ? $last_name : '',
            'ATT_email' => !empty($email) ? $email : '',
            'ATT_phone' => $phone,
        ));

        if (!empty($other_questions)) {

            foreach ($other_questions as $question_id => $value) {

                $where_conditions = array(
                    'QST_ID' => $question_id,
                    'REG_ID' => $registration->ID(),
                );
                $possibly_new_values = array(
                    'ANS_value' => $value,
                );
                $answer = EEM_Answer::instance()->get_one(array($where_conditions));
                if ($answer instanceof EE_Answer) {
                    $success = $answer->save($possibly_new_values);
                } else {
                    //insert it then
                    $cols_n_vals = array_merge($where_conditions, $possibly_new_values);
                    $answer = EE_Answer::new_instance($cols_n_vals);
                    $success = $answer->save();
                }
            }
        }

        $attendee->save();
        $attendee->_add_relation_to($registration, 'Registration');

        $total_line_item->save_this_and_descendants_to_txn();

        $grand_total = $total_line_item->recalculate_total_including_taxes();

        $payment = EE_Payment::new_instance(
            array(
                'TXN_ID' => $transaction->ID(),
                'STS_ID' => 'PAP',
                'PAY_source' => EEM_Payment_Method::scope_admin,
                'PMD_ID' => $payment_method->ID(),
                'PAY_amount' => $grand_total,
            ));

        $payment->save();

        $registration_processor->update_registration_final_prices($transaction);

        if ($registration->set_status(EEM_Registration::status_id_approved)) {
            $registration->save();
        }

    }

    /** @type EE_Transaction_Payments $transaction_payments */
    $transaction_payments = EE_Registry::instance()->load_class('Transaction_Payments');
    // maybe update status, and make sure to save transaction if not done already
    if (!$transaction_payments->calculate_total_payments_and_update_status($transaction)) {
        $transaction->save();
    }

    return $registration;
}