class BlockHooks

class BlockHooks {
    
    /**
     * Implements hook_help().
     */
    public function help($route_name, RouteMatchInterface $route_match) {
        switch ($route_name) {
            case 'help.page.block':
                $block_content = \Drupal::moduleHandler()->moduleExists('block_content') ? Url::fromRoute('help.page', [
                    'name' => 'block_content',
                ])->toString() : '#';
                $output = '';
                $output .= '<h2>' . t('About') . '</h2>';
                $output .= '<p>' . t('The Block module allows you to place blocks in regions of your installed themes, and configure block settings. For more information, see the <a href=":blocks-documentation">online documentation for the Block module</a>.', [
                    ':blocks-documentation' => 'https://www.drupal.org/documentation/modules/block/',
                ]) . '</p>';
                $output .= '<h2>' . t('Uses') . '</h2>';
                $output .= '<dl>';
                $output .= '<dt>' . t('Placing and moving blocks') . '</dt>';
                $output .= '<dd>' . t('You can place a new block in a region by selecting <em>Place block</em> on the <a href=":blocks">Block layout page</a>. Once a block is placed, it can be moved to a different region by drag-and-drop or by using the <em>Region</em> drop-down list, and then clicking <em>Save blocks</em>.', [
                    ':blocks' => Url::fromRoute('block.admin_display')->toString(),
                ]) . '</dd>';
                $output .= '<dt>' . t('Toggling between different themes') . '</dt>';
                $output .= '<dd>' . t('Blocks are placed and configured specifically for each theme. The Block layout page opens with the default theme, but you can toggle to other installed themes.') . '</dd>';
                $output .= '<dt>' . t('Demonstrating block regions for a theme') . '</dt>';
                $output .= '<dd>' . t('You can see where the regions are for the current theme by clicking the <em>Demonstrate block regions</em> link on the <a href=":blocks">Block layout page</a>. Regions are specific to each theme.', [
                    ':blocks' => Url::fromRoute('block.admin_display')->toString(),
                ]) . '</dd>';
                $output .= '<dt>' . t('Configuring block settings') . '</dt>';
                $output .= '<dd>' . t('To change the settings of an individual block click on the <em>Configure</em> link on the <a href=":blocks">Block layout page</a>. The available options vary depending on the module that provides the block. For all blocks you can change the block title and toggle whether to display it.', [
                    ':blocks' => Url::fromRoute('block.admin_display')->toString(),
                ]) . '</dd>';
                $output .= '<dt>' . t('Controlling visibility') . '</dt>';
                $output .= '<dd>' . t('You can control the visibility of a block by restricting it to specific pages, content types, and/or roles by setting the appropriate options under <em>Visibility settings</em> of the block configuration.') . '</dd>';
                $output .= '<dt>' . t('Adding content blocks') . '</dt>';
                $output .= '<dd>' . t('You can add content blocks, if the <em>Block Content</em> module is installed. For more information, see the <a href=":blockcontent-help">Block Content help page</a>.', [
                    ':blockcontent-help' => $block_content,
                ]) . '</dd>';
                $output .= '</dl>';
                return $output;
        }
        if ($route_name == 'block.admin_display' || $route_name == 'block.admin_display_theme') {
            $demo_theme = $route_match->getParameter('theme') ?: \Drupal::config('system.theme')->get('default');
            $themes = \Drupal::service('theme_handler')->listInfo();
            $output = '<p>' . t('Block placement is specific to each theme on your site. Changes will not be saved until you click <em>Save blocks</em> at the bottom of the page.') . '</p>';
            $output .= '<p>' . Link::fromTextAndUrl(t('Demonstrate block regions (@theme)', [
                '@theme' => $themes[$demo_theme]->info['name'],
            ]), Url::fromRoute('block.admin_demo', [
                'theme' => $demo_theme,
            ]))
                ->toString() . '</p>';
            return $output;
        }
    }
    
    /**
     * Implements hook_theme().
     */
    public function theme() : array {
        return [
            'block' => [
                'render element' => 'elements',
            ],
        ];
    }
    
    /**
     * Implements hook_page_top().
     */
    public function pageTop(array &$page_top) {
        if (\Drupal::routeMatch()->getRouteName() === 'block.admin_demo') {
            $theme = \Drupal::theme()->getActiveTheme()
                ->getName();
            $page_top['backlink'] = [
                '#type' => 'link',
                '#title' => t('Exit block region demonstration'),
                '#options' => [
                    'attributes' => [
                        'class' => [
                            'block-demo-backlink',
                        ],
                    ],
                ],
                '#weight' => -10,
            ];
            if (\Drupal::config('system.theme')->get('default') == $theme) {
                $page_top['backlink']['#url'] = Url::fromRoute('block.admin_display');
            }
            else {
                $page_top['backlink']['#url'] = Url::fromRoute('block.admin_display_theme', [
                    'theme' => $theme,
                ]);
            }
        }
    }
    
    /**
     * Implements hook_modules_installed().
     *
     * @see block_themes_installed()
     */
    public function modulesInstalled($modules) {
        // block_themes_installed() does not call block_theme_initialize() during site
        // installation because block configuration can be optional or provided by the
        // profile. Now, when the profile is installed, this configuration exists,
        // call block_theme_initialize() for all installed themes.
        $profile = \Drupal::installProfile();
        if (in_array($profile, $modules, TRUE)) {
            foreach (\Drupal::service('theme_handler')->listInfo() as $theme => $data) {
                block_theme_initialize($theme);
            }
        }
    }
    
    /**
     * Implements hook_rebuild().
     */
    public function rebuild() {
        foreach (\Drupal::service('theme_handler')->listInfo() as $theme => $data) {
            if ($data->status) {
                $regions = system_region_list($theme);
                
                /** @var \Drupal\block\BlockInterface[] $blocks */
                $blocks = \Drupal::entityTypeManager()->getStorage('block')
                    ->loadByProperties([
                    'theme' => $theme,
                ]);
                foreach ($blocks as $block_id => $block) {
                    // Disable blocks in invalid regions.
                    if (!isset($regions[$block->getRegion()])) {
                        if ($block->status()) {
                            \Drupal::messenger()->addWarning(t('The block %info was assigned to the invalid region %region and has been disabled.', [
                                '%info' => $block_id,
                                '%region' => $block->getRegion(),
                            ]));
                        }
                        $block->setRegion(system_default_region($theme))
                            ->disable()
                            ->save();
                    }
                }
            }
        }
    }
    
    /**
     * Implements hook_ENTITY_TYPE_delete() for user_role entities.
     *
     * Removes deleted role from blocks that use it.
     */
    public function userRoleDelete($role) {
        foreach (Block::loadMultiple() as $block) {
            
            /** @var \Drupal\block\BlockInterface $block */
            $visibility = $block->getVisibility();
            if (isset($visibility['user_role']['roles'][$role->id()])) {
                unset($visibility['user_role']['roles'][$role->id()]);
                $block->setVisibilityConfig('user_role', $visibility['user_role']);
                $block->save();
            }
        }
    }
    
    /**
     * Implements hook_ENTITY_TYPE_delete() for menu entities.
     */
    public function menuDelete(Menu $menu) {
        if (!$menu->isSyncing()) {
            foreach (Block::loadMultiple() as $block) {
                if ($block->getPluginId() == 'system_menu_block:' . $menu->id()) {
                    $block->delete();
                }
            }
        }
    }
    
    /**
     * Implements hook_ENTITY_TYPE_delete() for 'configurable_language'.
     *
     * Delete the potential block visibility settings of the deleted language.
     */
    public function configurableLanguageDelete(ConfigurableLanguageInterface $language) {
        // Remove the block visibility settings for the deleted language.
        foreach (Block::loadMultiple() as $block) {
            
            /** @var \Drupal\block\BlockInterface $block */
            $visibility = $block->getVisibility();
            if (isset($visibility['language']['langcodes'][$language->id()])) {
                unset($visibility['language']['langcodes'][$language->id()]);
                $block->setVisibilityConfig('language', $visibility['language']);
                $block->save();
            }
        }
    }
    
    /**
     * Implements hook_block_build_BASE_BLOCK_ID_alter().
     */
    public function blockBuildLocalActionsBlockAlter(array &$build, BlockPluginInterface $block) {
        $build['#lazy_builder_preview'] = [
            '#type' => 'container',
            '#attributes' => [
                'class' => [
                    'invisible',
                ],
            ],
            'actions' => [
                '#theme' => 'menu_local_action',
                '#link' => [
                    'title' => t('Add'),
                    'url' => Url::fromUserInput('#'),
                ],
            ],
        ];
    }

}