<?php
/**
 * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
 *
 * Copyright (C) 2019 - 2022 Jan Böhmer (https://github.com/jbtronics)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

declare(strict_types=1);

namespace App\Services\Trees;

use App\Entity\Base\AbstractStructuralDBElement;
use App\Repository\StructuralDBElementRepository;
use App\Services\UserSystem\UserCacheKeyGenerator;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Contracts\Cache\ItemInterface;
use Symfony\Contracts\Cache\TagAwareCacheInterface;

/**
 *  This service gives you a flat list containing all structured entities in the order of the structure.
 */
class NodesListBuilder
{
    protected EntityManagerInterface $em;
    protected TagAwareCacheInterface $cache;
    protected UserCacheKeyGenerator $keyGenerator;

    public function __construct(EntityManagerInterface $em, TagAwareCacheInterface $treeCache, UserCacheKeyGenerator $keyGenerator)
    {
        $this->em = $em;
        $this->keyGenerator = $keyGenerator;
        $this->cache = $treeCache;
    }

    /**
     * Gets a flattened hierarchical tree. Useful for generating option lists.
     * In difference to the Repository Function, the results here are cached.
     *
     * @param string                           $class_name the class name of the entity you want to retrieve
     * @param AbstractStructuralDBElement|null $parent     This entity will be used as root element. Set to null, to use global root
     *
     * @return AbstractStructuralDBElement[] a flattened list containing the tree elements
     */
    public function typeToNodesList(string $class_name, ?AbstractStructuralDBElement $parent = null): array
    {
        $parent_id = null !== $parent ? $parent->getID() : '0';
        // Backslashes are not allowed in cache keys
        $secure_class_name = str_replace('\\', '_', $class_name);
        $key = 'list_'.$this->keyGenerator->generateKey().'_'.$secure_class_name.$parent_id;

        return $this->cache->get($key, function (ItemInterface $item) use ($class_name, $parent, $secure_class_name) {
            // Invalidate when groups, a element with the class or the user changes
            $item->tag(['groups', 'tree_list', $this->keyGenerator->generateKey(), $secure_class_name]);
            /** @var StructuralDBElementRepository $repo */
            $repo = $this->em->getRepository($class_name);

            return $repo->toNodesList($parent);
        });
    }

    /**
     * Returns a flattened list of all (recursive) children elements of the given AbstractStructuralDBElement.
     * The value is cached for performance reasons.
     *
     * @template T of AbstractStructuralDBElement
     * @param  T $element
     * @return T[]
     */
    public function getChildrenFlatList(AbstractStructuralDBElement $element): array
    {
        return $this->typeToNodesList(get_class($element), $element);
    }
}