class FilterPluginCollection

class FilterPluginCollection extends DefaultLazyPluginCollection {
    
    /**
     * All possible filter plugin IDs.
     *
     * @var array
     */
    protected $definitions;
    
    /**
     * {@inheritdoc}
     *
     * @return \Drupal\filter\Plugin\FilterInterface
     */
    public function &get($instance_id) {
        return parent::get($instance_id);
    }
    
    /**
     * Retrieves filter definitions and creates an instance for each filter.
     *
     * This is exclusively used for the text format administration page, on which
     * all available filter plugins are exposed, regardless of whether the current
     * text format has an active instance.
     *
     * @todo Refactor text format administration to actually construct/create and
     *   destruct/remove actual filter plugin instances, using a library approach
     *   à la blocks.
     */
    public function getAll() {
        // Retrieve all available filter plugin definitions.
        if (!$this->definitions) {
            $this->definitions = $this->manager
                ->getDefinitions();
            // Do not allow the null filter to be used directly, only as a fallback.
            unset($this->definitions['filter_null']);
        }
        // Ensure that there is an instance of all available filters.
        // Note that getDefinitions() are keyed by $plugin_id. $instance_id is the
        // $plugin_id for filters, since a single filter plugin can only exist once
        // in a format.
        foreach ($this->definitions as $plugin_id => $definition) {
            if (!isset($this->pluginInstances[$plugin_id])) {
                $this->initializePlugin($plugin_id);
            }
        }
        return $this->pluginInstances;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function initializePlugin($instance_id) {
        // Filters have a 1:1 relationship to text formats and can be added and
        // instantiated at any time.
        // @todo $configuration is the whole filter plugin instance configuration,
        //   as contained in the text format configuration. The default
        //   configuration is the filter plugin definition. Configuration should not
        //   be contained in definitions. Move into a FilterBase::init() method.
        $configuration = $this->manager
            ->getDefinition($instance_id);
        // Merge the actual configuration into the default configuration.
        if (isset($this->configurations[$instance_id])) {
            $configuration = NestedArray::mergeDeep($configuration, $this->configurations[$instance_id]);
        }
        $this->configurations[$instance_id] = $configuration;
        parent::initializePlugin($instance_id);
    }
    
    /**
     * {@inheritdoc}
     */
    public function sort() {
        $this->getAll();
        return parent::sort();
    }
    
    /**
     * {@inheritdoc}
     */
    public function sortHelper($aID, $bID) {
        $a = $this->get($aID);
        $b = $this->get($bID);
        if ($a->status != $b->status) {
            return !empty($a->status) ? -1 : 1;
        }
        if ($a->weight != $b->weight) {
            return $a->weight < $b->weight ? -1 : 1;
        }
        if ($a->provider != $b->provider) {
            return strnatcasecmp($a->provider, $b->provider);
        }
        return parent::sortHelper($aID, $bID);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConfiguration() {
        $configuration = parent::getConfiguration();
        // Remove configuration if it matches the defaults. In self::getAll(), we
        // load all available filters, in addition to the enabled filters stored in
        // configuration. In order to prevent those from bleeding through to the
        // stored configuration, remove all filters that match the default values.
        // Because filters are disabled by default, this will never remove the
        // configuration of an enabled filter.
        foreach ($configuration as $instance_id => $instance_config) {
            $default_config = [];
            $default_config['id'] = $instance_id;
            $default_config += $this->get($instance_id)
                ->defaultConfiguration();
            if ($default_config === $instance_config) {
                unset($configuration[$instance_id]);
            }
        }
        return $configuration;
    }

}