class ConditionFundamentals

abstract class ConditionFundamentals {
    
    /**
     * Array of conditions.
     *
     * @var array
     */
    protected $conditions = [];
    
    /**
     * The conjunction of this condition group.
     *
     * The value is one of the following:
     * - AND (default)
     * - OR
     *
     * @var string
     */
    protected $conjunction;
    
    /**
     * The query this condition belongs to.
     *
     * @var \Drupal\Core\Entity\Query\QueryInterface
     */
    protected $query;
    
    /**
     * List of potential namespaces of the classes belonging to this condition.
     *
     * @var array
     */
    protected $namespaces = [];
    
    /**
     * Constructs a Condition object.
     *
     * @param string $conjunction
     *   The operator to use to combine conditions: 'AND' or 'OR'.
     * @param QueryInterface $query
     *   The entity query this condition belongs to.
     * @param array $namespaces
     *   List of potential namespaces of the classes belonging to this condition.
     */
    public function __construct($conjunction, QueryInterface $query, $namespaces = []) {
        $this->conjunction = $conjunction;
        $this->query = $query;
        $this->namespaces = $namespaces;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConjunction() {
        return $this->conjunction;
    }
    
    /**
     * {@inheritdoc}
     */
    public function count() {
        return count($this->conditions);
    }
    
    /**
     * {@inheritdoc}
     */
    public function &conditions() {
        return $this->conditions;
    }
    
    /**
     * Implements the magic __clone function.
     *
     * Makes sure condition groups are cloned as well.
     */
    public function __clone() {
        foreach ($this->conditions as $key => $condition) {
            if ($condition['field'] instanceof ConditionInterface) {
                $this->conditions[$key]['field'] = clone $condition['field'];
            }
        }
    }

}