<?php

namespace Drupalgcl_tag_cloudPluginBlock;

use DrupalComponentUtilityUrlHelper;
use DrupalCoreBlockBlockBase;
use DrupalCoreFormFormStateInterface;
use DrupalCorePluginContainerFactoryPluginInterface;
use DrupalCoreUrl;
use DrupaltaxonomyEntityVocabulary;
use DrupaltaxonomyTermStorageInterface;
use SymfonyComponentDependencyInjectionContainerInterface;

/**
 * Provides a 'TagCloudBlock' block.
 *
 * @Block(
 *  id = "gcl_tag_cloud_block",
 *  admin_label = @Translation("Tag cloud block"),
 * )
 */
class TagCloudBlock extends BlockBase implements ContainerFactoryPluginInterface {

  protected $term_storage;
  protected $token_service;

  public function __construct(array $configuration, $plugin_id, $plugin_definition, TermStorageInterface $term_storage, $token_service) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->term_storage = $term_storage;
    $this->token_service = $token_service;
  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition){
return new static(
  $configuration,
  $plugin_id,
  $plugin_definition,
  $container->get('entity.manager')->getStorage("taxonomy_term"),
  $container->get('token')
);
  }

  /**
   * {@inheritdoc}
   */
  public function blockForm($form, FormStateInterface $form_state) {
    $form = parent::blockForm($form, $form_state);

    // Get the configurations.
    $config = $this->getConfiguration();

    $vocabularies = Vocabulary::loadMultiple();
    $vocabulary_options = [];
    foreach ($vocabularies as $vocabulary) {
      $vid = $vocabulary->get('vid');
      $name = $vocabulary->get('name');
      $vocabulary_options[$vid] = $name;
    }

    $form['vocabularies'] = [
      '#type' => 'checkboxes',
      '#options' => $vocabulary_options,
      '#title' => t('Vocabularies'),
      '#required' => TRUE,
      '#default_value' => $config['vocabularies'],
    ];

    $form['redirect_url'] = [
      '#type' => 'textfield',
      '#title' => t('Redirect url'),
      '#required' => FALSE,
      '#default_value' => isset($config['redirect_url']) ? $config['redirect_url'] : 'tags/',
    ];
    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function blockValidate($form, FormStateInterface $form_state) {
    $redirect_url = $form_state->getValue('redirect_url');
    if (UrlHelper::isExternal($redirect_url)) {
      $form_state->setErrorByName('redirect_url', t('External link is not allowed for redirect url.'));
    }
  }

  /**
   * {@inheritdoc}
   */
  public function blockSubmit($form, FormStateInterface $form_state) {
    $this->setConfigurationValue('vocabularies', $form_state->getValue('vocabularies'));
    $this->setConfigurationValue('redirect_url', $form_state->getValue('redirect_url'));
  }


  /**
   * {@inheritdoc}
   */
  public function build() {
    $config = $this->getConfiguration();

    $vocabularies_selected = $config['vocabularies'];
    $terms = [];
    foreach ($vocabularies_selected as $vid) {
      $vocabulary_terms = $this->term_storage->loadTree($vid);
      foreach ($vocabulary_terms as $term) {
        $term = $this->term_storage->load($term->tid);
        $url = $this->token_service->replace(
          $config['redirect_url'],
          ['term' => $term]
        );
        $terms[$term->id()] = [
          'name' => $term->getName(),
          'url' => $url . $term->id(),
        ];
      }
    }

    $build = [];
    $build['gcl_tag_cloud_block'] = [
      '#theme' => 'gcl_tag_cloud_block',
      '#tags' => $terms,
    ];

    return $build;
  }
}

<h2>Tag Cloud</h2>
{% for term_id, term in tags %}
    <a href="{{ term.url }}">{{ term.name }}</a>
    <br>
{% endfor %}