class CodeBlock

class CodeBlock extends CKEditor5PluginDefault implements CKEditor5PluginConfigurableInterface {
  use CKEditor5PluginConfigurableTrait;
  
  /**
   * {@inheritdoc}
   */
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    $form['languages'] = [
      '#title' => $this->t('Programming languages'),
      '#type' => 'textarea',
      '#description' => $this->t('A list of programming languages that will be provided in the "Code Block" dropdown. Enter one value per line, in the format key|label. Example: php|PHP.'),
    ];
    if (!empty($this->configuration['languages'])) {
      $as_selectors = '';
      foreach ($this->configuration['languages'] as $language) {
        $as_selectors .= sprintf("%s|%s\n", $language['language'], $language['label']);
      }
      $form['languages']['#default_value'] = $as_selectors;
    }
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
    $form_value = $form_state->getValue('languages');
    [
      $styles,
      $not_parseable_lines,
    ] = self::parseLanguagesFromValue($form_value);
    if (!empty($not_parseable_lines)) {
      $line_numbers = array_keys($not_parseable_lines);
      $form_state->setError($form['languages'], $this->formatPlural(count($not_parseable_lines), 'Line @line-number does not contain a valid value. Enter a valid language key followed by a pipe symbol and a label.', 'Lines @line-numbers do not contain a valid value. Enter a valid language key followed by a pipe symbol and a label.', [
        '@line-number' => reset($line_numbers),
        '@line-numbers' => implode(', ', $line_numbers),
      ]));
    }
    $form_state->setValue('languages', $styles);
  }
  
  /**
   * Parses the line-based (for form) Code Block configuration.
   *
   * @param string $form_value
   *   A string containing >=1 lines with on each line a language key and label.
   *
   * @return array
   *   The parsed equivalent: a list of arrays with each containing:
   *   - label: the label after the pipe symbol, with whitespace trimmed
   *   - language: the key for the language
   */
  protected static function parseLanguagesFromValue(string $form_value) : array {
    $not_parseable_lines = [];
    $lines = explode("\n", $form_value);
    $languages = [];
    foreach ($lines as $line) {
      if (empty(trim($line))) {
        continue;
      }
      // Parse the line.
      [
        $language,
        $label,
      ] = array_map('trim', explode('|', $line));
      $languages[] = [
        'label' => $label,
        'language' => $language,
      ];
    }
    return [
      $languages,
      $not_parseable_lines,
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
    $this->configuration['languages'] = $form_state->getValue('languages');
  }
  
  /**
   * {@inheritdoc}
   */
  public function defaultConfiguration() {
    return [
      'languages' => [
        [
          'language' => 'plaintext',
          'label' => 'Plain text',
        ],
        [
          'language' => 'c',
          'label' => 'C',
        ],
        [
          'language' => 'cs',
          'label' => 'C#',
        ],
        [
          'language' => 'cpp',
          'label' => 'C++',
        ],
        [
          'language' => 'css',
          'label' => 'CSS',
        ],
        [
          'language' => 'diff',
          'label' => 'Diff',
        ],
        [
          'language' => 'html',
          'label' => 'HTML',
        ],
        [
          'language' => 'java',
          'label' => 'Java',
        ],
        [
          'language' => 'javascript',
          'label' => 'JavaScript',
        ],
        [
          'language' => 'php',
          'label' => 'PHP',
        ],
        [
          'language' => 'python',
          'label' => 'Python',
        ],
        [
          'language' => 'ruby',
          'label' => 'Ruby',
        ],
        [
          'language' => 'typescript',
          'label' => 'TypeScript',
        ],
        [
          'language' => 'xml',
          'label' => 'XML',
        ],
      ],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDynamicPluginConfig(array $static_plugin_config, EditorInterface $editor) : array {
    return [
      'codeBlock' => [
        'languages' => $this->configuration['languages'],
      ],
    ];
  }

}