specimen

Refactor the code below to improve the security and implement best-practices in terms of Magento coding approaches. Also, please create a module that contains the rewritten controller and (at least) system.xml to specify appropriate default values.

public function postAction() {            
//avoid notices warnings
!isset($_POST['livechat_license_number']) ? $livechat_license_number = '' : $livechat_license_number =   $_POST['livechat_license_number'];
!isset($_POST['livechat_groups']) ? $livechat_groups = '0' : $livechat_groups = $_POST['livechat_groups']; 
!isset($_POST['livechat_params']) ? $livechat_params = '' : $livechat_params = $_POST['livechat_params'];
$config_table = Mage::getSingleton('core/resource')->getTableName('core_config_data');

$read = Mage::getSingleton('core/resource')->getConnection('core_read');
$query = 'SELECT * FROM ' . $config_table;
$query .= ' WHERE scope="default" AND scope_id=0 AND path="livechat/general/license"';
$results = $read->fetchAll($query);

$write = Mage::getSingleton('core/resource')->getConnection('core_write');

//check for existing configurations
if ($row = array_pop($results)) {
       $license_id = $row['config_id'];
      
       $query = 'UPDATE ' . $config_table;
       $query .= ' SET value="' . $livechat_license_number . '"';
       $query .= ' WHERE config_id=' . $license_id;
       $write->query($query);
     
       $query = 'UPDATE ' . $config_table;
       $query .= ' SET value="' . $livechat_groups . '"';
       $query .= ' WHERE config_id=' . ++$license_id;
       $write->query($query);
      
       $query = 'UPDATE ' . $config_table;
       $query .= ' SET value="' . $livechat_params . '"';
       $query .= ' WHERE config_id=' . ++$license_id;
       $write->query($query);
} else {
       $query = 'INSERT INTO ' . $config_table;
       $query .= ' (scope, scope_id, path, value)';
       $query .= ' VALUES ("default", 0, "livechat/general/license", "' . $livechat_license_number . '"),';
       $query .= ' ("default", 0, "livechat/advanced/group", "0"),';
       $query .= ' ("default", 0, "livechat/advanced/params", "")';
       $write->query($query);
}

// Refresh the config.
Mage::getConfig()->cleanCache();
Mage::getConfig()->reinit();

$this->_redirect('*/*/index'); 
}