class ViewsData

class ViewsData {
    
    /**
     * The base cache ID to use.
     *
     * @var string
     */
    protected $baseCid = 'views_data';
    
    /**
     * The cache backend to use.
     *
     * @var \Drupal\Core\Cache\CacheBackendInterface
     */
    protected $cacheBackend;
    
    /**
     * Table data storage.
     *
     * This is used for explicitly requested tables.
     *
     * @var array
     */
    protected $storage = [];
    
    /**
     * All table storage data loaded from cache.
     *
     * This is used when all data has been loaded from the cache to prevent
     * further cache get calls when rebuilding all data or for single tables.
     *
     * @var array
     */
    protected $allStorage = [];
    
    /**
     * Whether the data has been fully loaded in this request.
     *
     * @var bool
     */
    protected $fullyLoaded = FALSE;
    
    /**
     * Whether or not to skip data caching and rebuild data each time.
     *
     * @var bool
     */
    protected $skipCache = FALSE;
    
    /**
     * The current language code.
     *
     * @var string
     */
    protected $langcode;
    
    /**
     * Stores a module manager to invoke hooks.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * Constructs this ViewsData object.
     *
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   The cache backend to use.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config
     *   The configuration factory object to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler class to use for invoking hooks.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     */
    public function __construct(CacheBackendInterface $cache_backend, ConfigFactoryInterface $config, ModuleHandlerInterface $module_handler, LanguageManagerInterface $language_manager) {
        $this->cacheBackend = $cache_backend;
        $this->moduleHandler = $module_handler;
        $this->languageManager = $language_manager;
        $this->langcode = $this->languageManager
            ->getCurrentLanguage()
            ->getId();
        $this->skipCache = $config->get('views.settings')
            ->get('skip_cache');
    }
    
    /**
     * Gets all table data.
     *
     * @see https://www.drupal.org/node/2723553
     *
     * @return array
     *   An array of table data.
     */
    public function getAll() {
        if (!$this->fullyLoaded) {
            $this->allStorage = $this->getData();
        }
        // Set storage from allStorage outside of the fullyLoaded check to prevent
        // cache calls on requests that have requested all data to get a single
        // tables data. Make sure $this->storage is populated in this case.
        $this->storage = $this->allStorage;
        return $this->allStorage;
    }
    
    /**
     * Gets data for a particular table, or all tables.
     *
     * @param string|null $key
     *   The key of the cache entry to retrieve. Defaults to NULL, this will
     *   return all table data. NULL $key deprecated in Drupal 8.2.x and will be
     *   removed in 9.0.0. Use getAll() instead.
     *
     * @see https://www.drupal.org/node/2723553
     * @see https://www.drupal.org/node/3090442
     *
     * @return array
     *   An array of table data.
     */
    public function get($key = NULL) {
        if (!$key) {
            @trigger_error('Calling get() without the $key argument is deprecated in drupal:8.2.0 and is required in drupal:9.0.0. See https://www.drupal.org/node/3090442', E_USER_DEPRECATED);
            return $this->getAll();
        }
        if (!isset($this->storage[$key])) {
            // Prepare a cache ID for get and set.
            $cid = $this->baseCid . ':' . $key;
            $from_cache = FALSE;
            if ($data = $this->cacheGet($cid)) {
                $this->storage[$key] = $data->data;
                $from_cache = TRUE;
            }
            elseif (!$this->fullyLoaded) {
                $this->allStorage = $this->getData();
            }
            if (!$from_cache) {
                if (!isset($this->allStorage[$key])) {
                    // Write an empty cache entry if no information for that table
                    // exists to avoid repeated cache get calls for this table and
                    // prevent loading all tables unnecessarily.
                    $this->storage[$key] = [];
                    $this->allStorage[$key] = [];
                }
                else {
                    $this->storage[$key] = $this->allStorage[$key];
                }
                // Create a cache entry for the requested table.
                $this->cacheSet($cid, $this->allStorage[$key]);
            }
        }
        return $this->storage[$key];
    }
    
    /**
     * Gets data from the cache backend.
     *
     * @param string $cid
     *   The cache ID to return.
     *
     * @return mixed
     *   The cached data, if any. This will immediately return FALSE if the
     *   $skipCache property is TRUE.
     */
    protected function cacheGet($cid) {
        if ($this->skipCache) {
            return FALSE;
        }
        return $this->cacheBackend
            ->get($this->prepareCid($cid));
    }
    
    /**
     * Sets data to the cache backend.
     *
     * @param string $cid
     *   The cache ID to set.
     * @param mixed $data
     *   The data that will be cached.
     */
    protected function cacheSet($cid, $data) {
        return $this->cacheBackend
            ->set($this->prepareCid($cid), $data, Cache::PERMANENT, [
            'views_data',
            'config:core.extension',
        ]);
    }
    
    /**
     * Prepares the cache ID by appending a language code.
     *
     * @param string $cid
     *   The cache ID to prepare.
     *
     * @return string
     *   The prepared cache ID.
     */
    protected function prepareCid($cid) {
        return $cid . ':' . $this->langcode;
    }
    
    /**
     * Gets all data invoked by hook_views_data().
     *
     * This is requested from the cache before being rebuilt.
     *
     * @return array
     *   An array of all data.
     */
    protected function getData() {
        $this->fullyLoaded = TRUE;
        if ($data = $this->cacheGet($this->baseCid)) {
            return $data->data;
        }
        else {
            $modules = $this->moduleHandler
                ->getImplementations('views_data');
            $data = [];
            foreach ($modules as $module) {
                $views_data = $this->moduleHandler
                    ->invoke($module, 'views_data');
                // Set the provider key for each base table.
                foreach ($views_data as &$table) {
                    if (isset($table['table']) && !isset($table['table']['provider'])) {
                        $table['table']['provider'] = $module;
                    }
                }
                $data = NestedArray::mergeDeep($data, $views_data);
            }
            $this->moduleHandler
                ->alter('views_data', $data);
            $this->processEntityTypes($data);
            // Keep a record with all data.
            $this->cacheSet($this->baseCid, $data);
            return $data;
        }
    }
    
    /**
     * Links tables with 'entity type' to respective generic entity-type tables.
     *
     * @param array $data
     *   The array of data to alter entity data for, passed by reference.
     */
    protected function processEntityTypes(array &$data) {
        foreach ($data as $table_name => $table_info) {
            // Add in a join from the entity-table if an entity-type is given.
            if (!empty($table_info['table']['entity type'])) {
                $entity_table = 'views_entity_' . $table_info['table']['entity type'];
                $data[$entity_table]['table']['join'][$table_name] = [
                    'left_table' => $table_name,
                ];
                $data[$entity_table]['table']['entity type'] = $table_info['table']['entity type'];
                // Copy over the default table group if we have none yet.
                if (!empty($table_info['table']['group']) && empty($data[$entity_table]['table']['group'])) {
                    $data[$entity_table]['table']['group'] = $table_info['table']['group'];
                }
            }
        }
    }
    
    /**
     * Fetches a list of all base tables available.
     *
     * @return array
     *   An array of base table data keyed by table name. Each item contains the
     *   following keys:
     *     - title: The title label for the base table.
     *     - help: The help text for the base table.
     *     - weight: The weight of the base table.
     */
    public function fetchBaseTables() {
        $tables = [];
        foreach ($this->getAll() as $table => $info) {
            if (!empty($info['table']['base'])) {
                $tables[$table] = [
                    'title' => $info['table']['base']['title'],
                    'help' => !empty($info['table']['base']['help']) ? $info['table']['base']['help'] : '',
                    'weight' => !empty($info['table']['base']['weight']) ? $info['table']['base']['weight'] : 0,
                ];
            }
        }
        // Sorts by the 'weight' and then by 'title' element.
        uasort($tables, function ($a, $b) {
            if ($a['weight'] != $b['weight']) {
                return $a['weight'] < $b['weight'] ? -1 : 1;
            }
            if ($a['title'] != $b['title']) {
                return $a['title'] < $b['title'] ? -1 : 1;
            }
            return 0;
        });
        return $tables;
    }
    
    /**
     * Clears the class storage and cache.
     */
    public function clear() {
        $this->storage = [];
        $this->allStorage = [];
        $this->fullyLoaded = FALSE;
        Cache::invalidateTags([
            'views_data',
        ]);
    }

}