CakePHP3 IsUniqueInContextRule

IsUniqueInContext.php

<?php
namespace App\Model\Rule;

use Cake\Datasource\EntityInterface;
use Cake\ORM\TableRegistry;

/**
 * Checks if a list of fields from an entity are unique in the table given a context where they can be duplicates
 */
class IsUniqueInContext
{

    /**
     * The list of fields to check
     *
     * @var array
     */
    protected $_fields;

    /**
     * The options to use.
     *
     * @var array
     */
    protected $_options;

    /**
     * Constructor.
     *
     * ### Options
     *
     * - `context` Set context list of fields in which duplications are okay.
     *
     * @param array $fields The list of fields to check uniqueness for
     * @param array $options The additional options for this rule.
     */
    public function __construct(array $fields, array $options = [])
    {
        $this->_fields = $fields;
        $this->_options = $options + ['context' => []];
        $this->_options['context'] = (array)$this->_options['context'];
    }

    public function __invoke(EntityInterface $entity, array $options)
    {
        $table = $options['repository'];
        $query = $table->find();
        foreach ($this->_fields as $field) {
            $query = $query->where([$field => $entity->get($field)]);
        }
        foreach ($this->_options['context'] as $contextField) {
            $query = $query->where(['NOT' => [$contextField => $entity->get($contextField)]]);
        }
        $wouldBeUnique = $query->count() === 0;
        return $wouldBeUnique;
    }
}