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'],
            ],
        ];
    }

}