apply coupon code to primary attendee only

gistfile1.txt

function apply_coupon_to_primary_attendee_only ($ext_att_data_source) {
    global $wpdb;
    $attendee = $wpdb->get_row('SELECT * FROM ' . EVENTS_ATTENDEE_TABLE . ' WHERE id=' . $ext_att_data_source['attendee_id'], ARRAY_A);
    if ($attendee['is_primary'] != 1) {
        $wpdb->update(EVENTS_ATTENDEE_TABLE,
                array('final_price'=>$attendee['orig_price']),
                array('id'=>$attendee['id']),
                array('%f'),
                array('%d'));
    }
}

add_action('action_hook_espresso_save_attendee_data', 'apply_coupon_to_primary_attendee_only');

// bug in 3.1.36.1.P. need to change line 572 of includes/process-registration/add_attendees_to_db.php from
// $ext_att_data_source['attendee_id'] = $attendee_id;
// to:
$ext_att_data_source['attendee_id'] = $ext_attendee_id;