class PluginBase

abstract class PluginBase extends ComponentPluginBase implements ContainerFactoryPluginInterface, ViewsPluginInterface, DependentPluginInterface, TrustedCallbackInterface {
    
    /**
     * Include negotiated languages when listing languages.
     *
     * @see \Drupal\views\Plugin\views\PluginBase::listLanguages()
     */
    const INCLUDE_NEGOTIATED = 16;
    
    /**
     * Include entity row languages when listing languages.
     *
     * @see \Drupal\views\Plugin\views\PluginBase::listLanguages()
     */
    const INCLUDE_ENTITY = 32;
    
    /**
     * Query string to indicate the site default language.
     *
     * @see \Drupal\Core\Language\LanguageInterface::LANGCODE_DEFAULT
     */
    const VIEWS_QUERY_LANGUAGE_SITE_DEFAULT = '***LANGUAGE_site_default***';
    
    /**
     * Options for this plugin will be held here.
     *
     * @var array
     */
    public $options = [];
    
    /**
     * The top object of a view.
     *
     * @var \Drupal\views\ViewExecutable
     */
    public $view = NULL;
    
    /**
     * The display object this plugin is for.
     *
     * For display plugins this is empty.
     *
     * @todo find a better description
     *
     * @var \Drupal\views\Plugin\views\display\DisplayPluginBase
     */
    public $displayHandler;
    
    /**
     * Plugins's definition
     *
     * @var array
     */
    public $definition;
    
    /**
     * Denotes whether the plugin has an additional options form.
     *
     * @var bool
     */
    protected $usesOptions = FALSE;
    
    /**
     * Stores the render API renderer.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * Constructs a PluginBase object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->definition = $plugin_definition + $configuration;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition);
    }
    
    /**
     * {@inheritdoc}
     */
    public function init(ViewExecutable $view, DisplayPluginBase $display, array &$options = NULL) {
        $this->view = $view;
        $this->setOptionDefaults($this->options, $this->defineOptions());
        $this->displayHandler = $display;
        $this->unpackOptions($this->options, $options);
    }
    
    /**
     * Information about options for all kinds of purposes will be held here.
     * @code
     * 'option_name' => array(
     *  - 'default' => default value,
     *  - 'contains' => (optional) array of items this contains, with its own
     *      defaults, etc. If contains is set, the default will be ignored and
     *      assumed to be array().
     *  ),
     * @endcode
     *
     * @return array
     *   Returns the options of this handler/plugin.
     */
    protected function defineOptions() {
        return [];
    }
    
    /**
     * Fills up the options of the plugin with defaults.
     *
     * @param array $storage
     *   An array which stores the actual option values of the plugin.
     * @param array $options
     *   An array which describes the options of a plugin. Each element is an
     *   associative array containing:
     *   - default: The default value of one option. Should be translated to the
     *     interface text language selected for page if translatable.
     *   - (optional) contains: An array which describes the available options
     *     under the key. If contains is set, the default will be ignored and
     *     assumed to be an empty array.
     *   - (optional) 'bool': TRUE if the value is boolean, else FALSE.
     */
    protected function setOptionDefaults(array &$storage, array $options) {
        foreach ($options as $option => $definition) {
            if (isset($definition['contains'])) {
                $storage[$option] = [];
                $this->setOptionDefaults($storage[$option], $definition['contains']);
            }
            else {
                $storage[$option] = $definition['default'];
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function filterByDefinedOptions(array &$storage) {
        $this->doFilterByDefinedOptions($storage, $this->defineOptions());
    }
    
    /**
     * Do the work to filter out stored options depending on the defined options.
     *
     * @param array $storage
     *   The stored options.
     * @param array $options
     *   The defined options.
     */
    protected function doFilterByDefinedOptions(array &$storage, array $options) {
        foreach ($storage as $key => $sub_storage) {
            if (!isset($options[$key])) {
                unset($storage[$key]);
            }
            if (isset($options[$key]['contains'])) {
                $this->doFilterByDefinedOptions($storage[$key], $options[$key]['contains']);
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function unpackOptions(&$storage, $options, $definition = NULL, $all = TRUE, $check = TRUE) {
        if ($check && !is_array($options)) {
            return;
        }
        if (!isset($definition)) {
            $definition = $this->defineOptions();
        }
        foreach ($options as $key => $value) {
            if (is_array($value)) {
                // Ignore arrays with no definition.
                if (!$all && empty($definition[$key])) {
                    continue;
                }
                if (!isset($storage[$key]) || !is_array($storage[$key])) {
                    $storage[$key] = [];
                }
                // If we're just unpacking our known options, and we're dropping an
                // unknown array (as might happen for a dependent plugin fields) go
                // ahead and drop that in.
                if (!$all && isset($definition[$key]) && !isset($definition[$key]['contains'])) {
                    $storage[$key] = $value;
                    continue;
                }
                $this->unpackOptions($storage[$key], $value, isset($definition[$key]['contains']) ? $definition[$key]['contains'] : [], $all, FALSE);
            }
            elseif ($all || !empty($definition[$key])) {
                $storage[$key] = $value;
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function destroy() {
        unset($this->view, $this->display, $this->query);
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        // Some form elements belong in a fieldset for presentation, but can't
        // be moved into one because of the $form_state->getValues() hierarchy. Those
        // elements can add a #fieldset => 'fieldset_name' property, and they'll
        // be moved to their fieldset during pre_render.
        $form['#pre_render'][] = [
            get_class($this),
            'preRenderAddFieldsetMarkup',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public static function trustedCallbacks() {
        return [
            'preRenderAddFieldsetMarkup',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateOptionsForm(&$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitOptionsForm(&$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function query() {
    }
    
    /**
     * {@inheritdoc}
     */
    public function themeFunctions() {
        return $this->view
            ->buildThemeFunctions($this->definition['theme']);
    }
    
    /**
     * {@inheritdoc}
     */
    public function validate() {
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function summaryTitle() {
        return $this->t('Settings');
    }
    
    /**
     * {@inheritdoc}
     */
    public function pluginTitle() {
        // Short_title is optional so its defaults to an empty string.
        if (!empty($this->definition['short_title'])) {
            return $this->definition['short_title'];
        }
        return $this->definition['title'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function usesOptions() {
        return $this->usesOptions;
    }
    
    /**
     * {@inheritdoc}
     */
    public function globalTokenReplace($string = '', array $options = []) {
        return \Drupal::token()->replace($string, [
            'view' => $this->view,
        ], $options);
    }
    
    /**
     * Replaces Views' tokens in a given string. The resulting string will be
     * sanitized with Xss::filterAdmin.
     *
     * @param $text
     *   Unsanitized string with possible tokens.
     * @param $tokens
     *   Array of token => replacement_value items.
     *
     * @return string
     */
    protected function viewsTokenReplace($text, $tokens) {
        if (!strlen($text)) {
            // No need to run filterAdmin on an empty string.
            return '';
        }
        if (empty($tokens)) {
            return Xss::filterAdmin($text);
        }
        $twig_tokens = [];
        foreach ($tokens as $token => $replacement) {
            // Twig wants a token replacement array stripped of curly-brackets.
            // Some Views tokens come with curly-braces, others do not.
            // @todo: https://www.drupal.org/node/2544392
            if (strpos($token, '{{') !== FALSE) {
                // Twig wants a token replacement array stripped of curly-brackets.
                $token = trim(str_replace([
                    '{{',
                    '}}',
                ], '', $token));
            }
            // Check for arrays in Twig tokens. Internally these are passed as
            // dot-delimited strings, but need to be turned into associative arrays
            // for parsing.
            if (strpos($token, '.') === FALSE) {
                // We need to validate tokens are valid Twig variables. Twig uses the
                // same variable naming rules as PHP.
                // @see http://php.net/manual/language.variables.basics.php
                assert(preg_match('/^[a-zA-Z_\\x7f-\\xff][a-zA-Z0-9_\\x7f-\\xff]*$/', $token) === 1, 'Tokens need to be valid Twig variables.');
                $twig_tokens[$token] = $replacement;
            }
            else {
                $parts = explode('.', $token);
                $top = array_shift($parts);
                assert(preg_match('/^[a-zA-Z_\\x7f-\\xff][a-zA-Z0-9_\\x7f-\\xff]*$/', $top) === 1, 'Tokens need to be valid Twig variables.');
                $token_array = [
                    array_pop($parts) => $replacement,
                ];
                foreach (array_reverse($parts) as $key) {
                    // The key could also be numeric (array index) so allow that.
                    assert(is_numeric($key) || preg_match('/^[a-zA-Z_\\x7f-\\xff][a-zA-Z0-9_\\x7f-\\xff]*$/', $key) === 1, 'Tokens need to be valid Twig variables.');
                    $token_array = [
                        $key => $token_array,
                    ];
                }
                if (!isset($twig_tokens[$top])) {
                    $twig_tokens[$top] = [];
                }
                $twig_tokens[$top] += $token_array;
            }
        }
        if ($twig_tokens) {
            // Use the unfiltered text for the Twig template, then filter the output.
            // Otherwise, Xss::filterAdmin could remove valid Twig syntax before the
            // template is parsed.
            $build = [
                '#type' => 'inline_template',
                '#template' => $text,
                '#context' => $twig_tokens,
                '#post_render' => [
                    function ($children, $elements) {
                        return Xss::filterAdmin($children);
                    },
                ],
            ];
            // Currently you cannot attach assets to tokens with
            // Renderer::renderPlain(). This may be unnecessarily limiting. Consider
            // using Renderer::executeInRenderContext() instead.
            // @todo: https://www.drupal.org/node/2566621
            return (string) $this->getRenderer()
                ->renderPlain($build);
        }
        else {
            return Xss::filterAdmin($text);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAvailableGlobalTokens($prepared = FALSE, array $types = []) {
        $info = \Drupal::token()->getInfo();
        // Site and view tokens should always be available.
        $types += [
            'site',
            'view',
        ];
        $available = array_intersect_key($info['tokens'], array_flip($types));
        // Construct the token string for each token.
        if ($prepared) {
            $prepared = [];
            foreach ($available as $type => $tokens) {
                foreach (array_keys($tokens) as $token) {
                    $prepared[$type][] = "[{$type}:{$token}]";
                }
            }
            return $prepared;
        }
        return $available;
    }
    
    /**
     * {@inheritdoc}
     */
    public function globalTokenForm(&$form, FormStateInterface $form_state) {
        $token_items = [];
        foreach ($this->getAvailableGlobalTokens() as $type => $tokens) {
            $item = [
                '#markup' => $type,
                'children' => [],
            ];
            foreach ($tokens as $name => $info) {
                $item['children'][$name] = "[{$type}:{$name}]" . ' - ' . $info['name'] . ': ' . $info['description'];
            }
            $token_items[$type] = $item;
        }
        $form['global_tokens'] = [
            '#type' => 'details',
            '#title' => $this->t('Available global token replacements'),
        ];
        $form['global_tokens']['list'] = [
            '#theme' => 'item_list',
            '#items' => $token_items,
            '#attributes' => [
                'class' => [
                    'global-tokens',
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public static function preRenderAddFieldsetMarkup(array $form) {
        foreach (Element::children($form) as $key) {
            $element = $form[$key];
            // In our form builder functions, we added an arbitrary #fieldset property
            // to any element that belongs in a fieldset. If this form element has
            // that property, move it into its fieldset.
            if (isset($element['#fieldset']) && isset($form[$element['#fieldset']])) {
                $form[$element['#fieldset']][$key] = $element;
                // Remove the original element this duplicates.
                unset($form[$key]);
            }
        }
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function preRenderFlattenData($form) {
        foreach (Element::children($form) as $key) {
            $element = $form[$key];
            if (!empty($element['#flatten'])) {
                foreach (Element::children($element) as $child_key) {
                    $form[$child_key] = $form[$key][$child_key];
                }
                // All done, remove the now-empty parent.
                unset($form[$key]);
            }
        }
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getProvider() {
        $definition = $this->getPluginDefinition();
        return $definition['provider'];
    }
    
    /**
     * Makes an array of languages, optionally including special languages.
     *
     * @param int $flags
     *   (optional) Flags for which languages to return (additive). Options:
     *   - \Drupal\Core\Language::STATE_ALL (default): All languages
     *     (configurable and default).
     *   - \Drupal\Core\Language::STATE_CONFIGURABLE: Configurable languages.
     *   - \Drupal\Core\Language::STATE_LOCKED: Locked languages.
     *   - \Drupal\Core\Language::STATE_SITE_DEFAULT: Add site default language;
     *     note that this is not included in STATE_ALL.
     *   - \Drupal\views\Plugin\views\PluginBase::INCLUDE_NEGOTIATED: Add
     *     negotiated language types.
     *   - \Drupal\views\Plugin\views\PluginBase::INCLUDE_ENTITY: Add
     *     entity row language types. Note that these are only supported for
     *     display options, not substituted in queries.
     * @param array|null $current_values
     *   The currently-selected options in the list, if available.
     *
     * @return array
     *   An array of language names, keyed by the language code. Negotiated and
     *   special languages have special codes that are substituted in queries by
     *   PluginBase::queryLanguageSubstitutions().
     *   Only configurable languages and languages that are in $current_values are
     *   included in the list.
     */
    protected function listLanguages($flags = LanguageInterface::STATE_ALL, array $current_values = NULL) {
        $manager = \Drupal::languageManager();
        $languages = $manager->getLanguages($flags);
        $list = [];
        // The entity languages should come first, if requested.
        if ($flags & PluginBase::INCLUDE_ENTITY) {
            $list['***LANGUAGE_entity_translation***'] = $this->t('Content language of view row');
            $list['***LANGUAGE_entity_default***'] = $this->t('Original language of content in view row');
        }
        // STATE_SITE_DEFAULT comes in with ID set
        // to LanguageInterface::LANGCODE_SITE_DEFAULT.
        // Since this is not a real language, surround it by '***LANGUAGE_...***',
        // like the negotiated languages below.
        if ($flags & LanguageInterface::STATE_SITE_DEFAULT) {
            $name = $languages[LanguageInterface::LANGCODE_SITE_DEFAULT]->getName();
            // The language name may have already been translated, no need to
            // translate it again.
            // @see Drupal\Core\Language::filterLanguages().
            if (!$name instanceof TranslatableMarkup) {
                $name = $this->t($name);
            }
            $list[PluginBase::VIEWS_QUERY_LANGUAGE_SITE_DEFAULT] = $name;
            // Remove site default language from $languages so it's not added
            // twice with the real languages below.
            unset($languages[LanguageInterface::LANGCODE_SITE_DEFAULT]);
        }
        // Add in negotiated languages, if requested.
        if ($flags & PluginBase::INCLUDE_NEGOTIATED) {
            $types_info = $manager->getDefinedLanguageTypesInfo();
            $types = $manager->getLanguageTypes();
            // We only go through the configured types.
            foreach ($types as $id) {
                if (isset($types_info[$id]['name'])) {
                    $name = $types_info[$id]['name'];
                    // Surround IDs by '***LANGUAGE_...***', to avoid query collisions.
                    $id = '***LANGUAGE_' . $id . '***';
                    $list[$id] = $this->t('@type language selected for page', [
                        '@type' => $name,
                    ]);
                }
            }
            if (!empty($current_values)) {
                foreach ($types_info as $id => $type) {
                    $id = '***LANGUAGE_' . $id . '***';
                    // If this (non-configurable) type is among the current values,
                    // add that option too, so it is not lost. If not among the current
                    // values, skip displaying it to avoid user confusion.
                    if (isset($type['name']) && !isset($list[$id]) && in_array($id, $current_values)) {
                        $list[$id] = $this->t('@type language selected for page', [
                            '@type' => $type['name'],
                        ]);
                    }
                }
            }
        }
        // Add real languages.
        foreach ($languages as $id => $language) {
            $list[$id] = $language->getName();
        }
        return $list;
    }
    
    /**
     * Returns substitutions for Views queries for languages.
     *
     * This is needed so that the language options returned by
     * PluginBase::listLanguages() are able to be used in queries. It is called
     * by the Views module implementation of hook_views_query_substitutions()
     * to get the language-related substitutions.
     *
     * @return array
     *   An array in the format of hook_views_query_substitutions() that gives
     *   the query substitutions needed for the special language types.
     */
    public static function queryLanguageSubstitutions() {
        $changes = [];
        $manager = \Drupal::languageManager();
        // Handle default language.
        $default = $manager->getDefaultLanguage()
            ->getId();
        $changes[PluginBase::VIEWS_QUERY_LANGUAGE_SITE_DEFAULT] = $default;
        // Handle negotiated languages.
        $types = $manager->getDefinedLanguageTypesInfo();
        foreach ($types as $id => $type) {
            if (isset($type['name'])) {
                $changes['***LANGUAGE_' . $id . '***'] = $manager->getCurrentLanguage($id)
                    ->getId();
            }
        }
        return $changes;
    }
    
    /**
     * Returns the render API renderer.
     *
     * @return \Drupal\Core\Render\RendererInterface
     */
    protected function getRenderer() {
        if (!isset($this->renderer)) {
            $this->renderer = \Drupal::service('renderer');
        }
        return $this->renderer;
    }

}