class.ExcPeerReviewDistribution.php

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<?php

declare(strict_types=1);

namespace ILIAS\Exercise\PeerReview;

class ExcPeerReviewDistribution
{
    protected array $user_ids = [];
    protected array $user_order = [];
    protected int $num_assignments;

    public function __construct(array $user_ids, int $num_assignments)
    {
        $this->user_ids = array_values($user_ids);  // ensure numerical indexing

        // we cannot assign more users to a single user than count($user_ids) - 1
        $num_assignments = min($num_assignments, count($user_ids) - 1);

        // we cannot create a negative number of assignments
        $num_assignments = max($num_assignments, 0);

        $this->num_assignments = $num_assignments;
        $this->initDistribution();
    }

    protected function initDistribution(): void
    {
        $this->user_order = $this->randomUserOrder($this->user_ids);
    }

    protected function randomUserOrder(array $user_ids): array
    {
        $order = [];
        while (count($user_ids) > 0) {
            $next = rand(0, count($user_ids) - 1);
            $order[] = $user_ids[$next];
            unset($user_ids[$next]);
            $user_ids = array_values($user_ids);    // re-index
        }
        return $order;
    }

    public function getUserOrder(): array
    {
        return $this->user_order;
    }

    public function getPeersOfRater(int $user_id): array
    {
        $peers = [];
        $key = array_search($user_id, $this->user_order);
        if ($key === false) {
            return [];
        }
        for ($j = 1; $j <= $this->num_assignments; $j++) {
            $peer_key = ($key + $j) % (count($this->user_order));
            $peers[] = $this->user_order[$peer_key];
        }
        return $peers;
    }
}