[Solved] How to create a view filter which display nodes if “field1” – “field2” < $amount

Baud Asks: How to create a view filter which display nodes if “field1” – “field2” < $amount
I have a content type with 2 fields: field1 and field2

I would like to create a view filter which display node based on a calculation on those two fields.

The filter should display only nodes if field1 - field2 is lower then a given amount.

Here is my try: At the end of the code, I don’t know how to create the query

Code:
 class Myfilter extends FilterPluginBase implements ContainerFactoryPluginInterface {

  protected ViewsHandlerManager $joinHandler;

  private int $amount;

  public function __construct(array $configuration, $plugin_id, $plugin_definition, RouteMatchInterface $route_match, ViewsHandlerManager $join_handler) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->joinHandler = $join_handler;
    $this->amount = 0;
    if (($node = $route_match->getParameter('node')) && ($node->bundle()=='my_bundle')) {
      $this->amount = $node->get('field_inv_amount')->value;
    }

  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration, $plugin_id, $plugin_definition,
      $container->get('current_route_match'),
      $container->get('plugin.manager.views.join')
    );
  }

  public function query() {
    //parent::query();
    
    $fields = [
      'field1',
      'field2',
    ];
    foreach ($fields as $field) {
      $table_field_name = 'node__' . $field;
      $configuration = [
        'table' => $table_field_name,
        'field' => 'nid',
        'left_table' => 'node_field_data',
        'left_field' => 'nid',
        'operator' => '=',
      ];
      $join = $this->joinHandler->createInstance('standard', $configuration);
      $this->query->addRelationship($table_field_name, $join, 'node_field_data');
    }
    // I am stuck here... field1-field2 should be < $this->amount
    $this->query->addWhere( ???? );
  }

}

Any hint will be appreciated

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