class NegotiationUrlForm

class NegotiationUrlForm extends ConfigFormBase {
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * Constructs a new NegotiationUrlForm object.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The factory for configuration objects.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     */
    public function __construct(ConfigFactoryInterface $config_factory, LanguageManagerInterface $language_manager) {
        parent::__construct($config_factory);
        $this->languageManager = $language_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('config.factory'), $container->get('language_manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'language_negotiation_configure_url_form';
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getEditableConfigNames() {
        return [
            'language.negotiation',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        global $base_url;
        $config = $this->config('language.negotiation');
        $form['language_negotiation_url_part'] = [
            '#title' => $this->t('Part of the URL that determines language'),
            '#type' => 'radios',
            '#options' => [
                LanguageNegotiationUrl::CONFIG_PATH_PREFIX => $this->t('Path prefix'),
                LanguageNegotiationUrl::CONFIG_DOMAIN => $this->t('Domain'),
            ],
            '#default_value' => $config->get('url.source'),
        ];
        $form['prefix'] = [
            '#type' => 'details',
            '#tree' => TRUE,
            '#title' => $this->t('Path prefix configuration'),
            '#open' => TRUE,
            '#description' => $this->t('Language codes or other custom text to use as a path prefix for URL language detection. For the selected fallback language, this value may be left blank. <strong>Modifying this value may break existing URLs. Use with caution in a production environment.</strong> Example: Specifying "deutsch" as the path prefix code for German results in URLs like "example.com/deutsch/contact".'),
            '#states' => [
                'visible' => [
                    ':input[name="language_negotiation_url_part"]' => [
                        'value' => (string) LanguageNegotiationUrl::CONFIG_PATH_PREFIX,
                    ],
                ],
            ],
        ];
        $form['domain'] = [
            '#type' => 'details',
            '#tree' => TRUE,
            '#title' => $this->t('Domain configuration'),
            '#open' => TRUE,
            '#description' => $this->t('The domain names to use for these languages. <strong>Modifying this value may break existing URLs. Use with caution in a production environment.</strong> Example: Specifying "de.example.com" as language domain for German will result in a URL like "http://de.example.com/contact".'),
            '#states' => [
                'visible' => [
                    ':input[name="language_negotiation_url_part"]' => [
                        'value' => (string) LanguageNegotiationUrl::CONFIG_DOMAIN,
                    ],
                ],
            ],
        ];
        $languages = $this->languageManager
            ->getLanguages();
        $prefixes = $config->get('url.prefixes');
        $domains = $config->get('url.domains');
        foreach ($languages as $langcode => $language) {
            $t_args = [
                '%language' => $language->getName(),
                '%langcode' => $language->getId(),
            ];
            $form['prefix'][$langcode] = [
                '#type' => 'textfield',
                '#title' => $language->isDefault() ? $this->t('%language (%langcode) path prefix (Default language)', $t_args) : $this->t('%language (%langcode) path prefix', $t_args),
                '#maxlength' => 64,
                '#default_value' => $prefixes[$langcode] ?? '',
                '#field_prefix' => $base_url . '/',
            ];
            $form['domain'][$langcode] = [
                '#type' => 'textfield',
                '#title' => $this->t('%language (%langcode) domain', [
                    '%language' => $language->getName(),
                    '%langcode' => $language->getId(),
                ]),
                '#maxlength' => 128,
                '#default_value' => $domains[$langcode] ?? '',
            ];
        }
        $form_state->setRedirect('language.negotiation');
        return parent::buildForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        $languages = $this->languageManager
            ->getLanguages();
        // Count repeated values for uniqueness check.
        $count = array_count_values($form_state->getValue('prefix'));
        $default_langcode = $this->config('language.negotiation')
            ->get('selected_langcode');
        if ($default_langcode == LanguageInterface::LANGCODE_SITE_DEFAULT) {
            $default_langcode = $this->languageManager
                ->getDefaultLanguage()
                ->getId();
        }
        foreach ($languages as $langcode => $language) {
            $value = $form_state->getValue([
                'prefix',
                $langcode,
            ]);
            if ($value === '') {
                if (!($default_langcode == $langcode) && $form_state->getValue('language_negotiation_url_part') == LanguageNegotiationUrl::CONFIG_PATH_PREFIX) {
                    // Throw a form error if the prefix is blank for a non-default language,
                    // although it is required for selected negotiation type.
                    $form_state->setErrorByName("prefix][{$langcode}", $this->t('The prefix may only be left blank for the <a href=":url">selected detection fallback language.</a>', [
                        ':url' => Url::fromRoute('language.negotiation_selected')->toString(),
                    ]));
                }
            }
            elseif (strpos($value, '/') !== FALSE) {
                // Throw a form error if the string contains a slash,
                // which would not work.
                $form_state->setErrorByName("prefix][{$langcode}", $this->t('The prefix may not contain a slash.'));
            }
            elseif (isset($count[$value]) && $count[$value] > 1) {
                // Throw a form error if there are two languages with the same
                // domain/prefix.
                $form_state->setErrorByName("prefix][{$langcode}", $this->t('The prefix for %language, %value, is not unique.', [
                    '%language' => $language->getName(),
                    '%value' => $value,
                ]));
            }
        }
        // Count repeated values for uniqueness check.
        $count = array_count_values($form_state->getValue('domain'));
        foreach ($languages as $langcode => $language) {
            $value = $form_state->getValue([
                'domain',
                $langcode,
            ]);
            if ($value === '') {
                if ($form_state->getValue('language_negotiation_url_part') == LanguageNegotiationUrl::CONFIG_DOMAIN) {
                    // Throw a form error if the domain is blank for a non-default language,
                    // although it is required for selected negotiation type.
                    $form_state->setErrorByName("domain][{$langcode}", $this->t('The domain may not be left blank for %language.', [
                        '%language' => $language->getName(),
                    ]));
                }
            }
            elseif (isset($count[$value]) && $count[$value] > 1) {
                // Throw a form error if there are two languages with the same
                // domain/domain.
                $form_state->setErrorByName("domain][{$langcode}", $this->t('The domain for %language, %value, is not unique.', [
                    '%language' => $language->getName(),
                    '%value' => $value,
                ]));
            }
        }
        // Domain names should not contain protocol and/or ports.
        foreach ($languages as $langcode => $language) {
            $value = $form_state->getValue([
                'domain',
                $langcode,
            ]);
            if (!empty($value)) {
                // Ensure we have exactly one protocol when checking the hostname.
                $host = 'http://' . str_replace([
                    'http://',
                    'https://',
                ], '', $value);
                if (parse_url($host, PHP_URL_HOST) != $value) {
                    $form_state->setErrorByName("domain][{$langcode}", $this->t('The domain for %language may only contain the domain name, not a trailing slash, protocol and/or port.', [
                        '%language' => $language->getName(),
                    ]));
                }
            }
        }
        parent::validateForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        // Save selected format (prefix or domain).
        $this->config('language.negotiation')
            ->set('url.source', $form_state->getValue('language_negotiation_url_part'))
            ->set('url.prefixes', $form_state->getValue('prefix'))
            ->set('url.domains', $form_state->getValue('domain'))
            ->save();
        parent::submitForm($form, $form_state);
    }

}