cbr-1.0.0/src/Services/SimilarityCalculator.php

<?

namespace Drupal\cbr\Services;

use Drupal\cbr\Plugin\Field\FieldType\CBRFieldInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Database\Connection;


/**
 * Similarity calculator service.
 * Calculates similarity between two cases.
 */
class SimilarityCalculator
{

    protected $database;

    function __construct(Connection $database)
    {
        $this->database = $database;
    }

    /**
     * Calculate similarity between two cases.
     * @param $entity1 The first case.
     * @param $entity2 The second case.
     * @return float The similarity [0-1] between the two cases.
     */
    function calculate(EntityInterface $entity1, EntityInterface $entity2): float
    {
        $similarity = 0;
        $sum_weight = 0;
        /* @var FieldItemListInterface $field_item */
        foreach ($entity1->getFields(false) as $field_item) {
            if ($field_item->first() !== null && $field_item->first() instanceof CBRFieldInterface) {

                /* @var FieldConfig $field_config */
                $field_config = $field_item->getFieldDefinition()->getConfig($entity1->bundle());
                $weight = $field_config->getThirdPartySetting('cbr', 'weight', 1);

                /* @var CBRFieldInterface $field1 */
                $field1 = $field_item->first();
                $value1 = $field1->getValueForSimilarityCalculation($field_config);

                /* @var CBRFieldInterface $field1 */
                $field2 = $entity2->get($field_item->getName())->first();
                if ($field2 != null) {
                    $value2 = $field2->getValueForSimilarityCalculation($field_config);
                    $similarity += $field1->calculateSimilarity($value1, $value2, $field_config) * $weight;
                }
                $sum_weight += $weight;
            }
        }
        //Normalize similarity to [0-1]
        if ($sum_weight != 0) {
            $similarity = $similarity / $sum_weight;
        } else {
            $similarity = 0;
        }
        return $similarity;
    }

    /**
     * Save similarity and remove cases from caclulation queue.
     * @param $nid1 The first case id.
     * @param $nid2 The second case id.
     * @param $similarity The similarity [0-1] between the two cases.
     */
    function saveSimilarity($nid1, $nid2, $similarity)
    {
        //Save similarity
        $merge_query = $this->database->merge('cbr_similarity');
        $merge_query->key(['nid1' => $nid1, 'nid2' => $nid2]);
        $merge_query->fields(['similarity' => $similarity]);
        $merge_query->execute();

        //Remove from calculation queue
        $delete_query = $this->database->delete('cbr_calculation_queue');
        $delete_query->condition('nid', $nid1);
        $delete_query->execute();
    }
}