<?php

declare(strict_types=1);

namespace Models;
use Models\Model;

/**
 * This class should be extended to add functionalities to
 * fetch, clear and save item cache.
 */
abstract class CacheModel extends Model
{


    /**
     * Obtain a data structure from the database using a filter.
     *
     * @param array $filter Filter to retrieve the modeled element.
     *
     * @return array The modeled element data structure stored into the DB.
     * @throws \Exception When the data cannot be retrieved from the DB.
     *
     * @abstract
     */
    abstract protected static function fetchCachedData(array $filter);


    /**
     * Stores the data structure obtained.
     *
     * @param array $filter Filter to retrieve the modeled element.
     *
     * @return array The modeled element data structure stored into the DB.
     * @throws \Exception When the data cannot be retrieved from the DB.
     *
     * @abstract
     */
    abstract protected static function saveCachedData(array $filter, array $data): bool;


    /**
     * Deletes previous data that are not useful.
     *
     * @param array $filter Filter to retrieve the modeled element.
     *
     * @return array The modeled element data structure stored into the DB.
     * @throws \Exception When the data cannot be retrieved from the DB.
     *
     * @abstract
     */
    abstract protected static function clearCachedData(array $filter): int;


    /**
     * Obtain a model's instance from the database using a filter.
     *
     * @param array $filter Filter to retrieve the modeled element.
     *
     * @return self A modeled element's instance.
     *
     * @overrides Model::fromDB.
     */
    public static function fromDB(array $filter): Model
    {
        global $config;

        if ($filter['cache_expiration'] != 0) {
            // Obtain the item's data from cache.
            $cacheData = static::fetchCachedData($filter);
            if ($cacheData === null) {
                // Delete expired data cache.
                static::clearCachedData(
                    [
                        'vc_item_id' => $filter['id'],
                        'vc_id'      => $filter['id_layout'],
                        'user_id'    => $config['id_user'],
                    ]
                );
                // Obtain the item's data from the database.
                $data = static::fetchDataFromDB($filter);
                // Save the item's data in cache.
                static::saveCachedData(
                    [
                        'vc_item_id' => $filter['id'],
                        'vc_id'      => $filter['id_layout'],
                        'user_id'    => $config['id_user'],
                    ],
                    $data
                );
                return static::fromArray($data);
            } else {
                $data = \io_safe_output(\json_decode(\base64_decode($cacheData['data']), true));
                return static::fromArray($data);
            }
        } else {
            return static::fromArray(static::fetchDataFromDB($filter));
        }
    }


}