class SelectProfileForm

class SelectProfileForm extends FormBase {
    
    /**
     * The key used in the profile list for the install from config option.
     *
     * This key must not be a valid profile extension name.
     */
    const CONFIG_INSTALL_PROFILE_KEY = '::existing_config::';
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'install_select_profile_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, $install_state = NULL) {
        $form['#title'] = $this->t('Select an installation profile');
        $profiles = [];
        $names = [];
        foreach ($install_state['profiles'] as $profile) {
            
            /** @var \Drupal\Core\Extension\Extension $profile */
            $details = install_profile_info($profile->getName());
            // Don't show hidden profiles. This is used by to hide the testing profile,
            // which only exists to speed up test runs.
            if ($details['hidden'] === TRUE && !drupal_valid_test_ua()) {
                continue;
            }
            $profiles[$profile->getName()] = $details;
            // Determine the name of the profile; default to file name if defined name
            // is unspecified.
            $name = $details['name'] ?? $profile->getName();
            $names[$profile->getName()] = $name;
        }
        // Display radio buttons alphabetically by human-readable name, but always
        // put the core profiles first (if they are present in the filesystem).
        natcasesort($names);
        if (isset($names['minimal'])) {
            // If the expert ("Minimal") core profile is present, put it in front of
            // any non-core profiles rather than including it with them alphabetically,
            // since the other profiles might be intended to group together in a
            // particular way.
            $names = [
                'minimal' => $names['minimal'],
            ] + $names;
        }
        if (isset($names['standard'])) {
            // If the default ("Standard") core profile is present, put it at the very
            // top of the list. This profile will have its radio button pre-selected,
            // so we want it to always appear at the top.
            $names = [
                'standard' => $names['standard'],
            ] + $names;
        }
        // The profile name and description are extracted for translation from the
        // .info file, so we can use $this->t() on them even though they are dynamic
        // data at this point.
        $form['profile'] = [
            '#type' => 'radios',
            '#title' => $this->t('Select an installation profile'),
            '#title_display' => 'invisible',
            '#options' => array_map([
                $this,
                't',
            ], $names),
            '#default_value' => 'standard',
        ];
        foreach (array_keys($names) as $profile_name) {
            $form['profile'][$profile_name]['#description'] = isset($profiles[$profile_name]['description']) ? $this->t($profiles[$profile_name]['description']) : '';
        }
        $config_sync_directory = Settings::get('config_sync_directory');
        if (!empty($config_sync_directory)) {
            $sync = new FileStorage($config_sync_directory);
            $extensions = $sync->read('core.extension');
            $site = $sync->read('system.site');
            if (isset($site['name']) && isset($extensions['profile']) && in_array($extensions['profile'], array_keys($names), TRUE)) {
                // Ensure the profile can be installed from configuration. Install
                // profile's which implement hook_INSTALL() are not supported.
                // @todo https://www.drupal.org/project/drupal/issues/2982052 Remove
                //   this restriction.
                $root = \Drupal::root();
                include_once $root . '/core/includes/install.inc';
                $file = $root . '/' . $install_state['profiles'][$extensions['profile']]->getPath() . "/{$extensions['profile']}.install";
                if (is_file($file)) {
                    require_once $file;
                }
                if (!function_exists($extensions['profile'] . '_install')) {
                    $form['profile']['#options'][static::CONFIG_INSTALL_PROFILE_KEY] = $this->t('Use existing configuration');
                    $form['profile'][static::CONFIG_INSTALL_PROFILE_KEY]['#description'] = [
                        'description' => [
                            '#markup' => $this->t('Install %name using existing configuration.', [
                                '%name' => $site['name'],
                            ]),
                        ],
                        'info' => [
                            '#type' => 'item',
                            '#markup' => $this->t('The configuration from the directory %sync_directory will be used.', [
                                '%sync_directory' => $config_sync_directory,
                            ]),
                            '#wrapper_attributes' => [
                                'class' => [
                                    'messages',
                                    'messages--status',
                                ],
                            ],
                            '#states' => [
                                'visible' => [
                                    ':input[name="profile"]' => [
                                        'value' => static::CONFIG_INSTALL_PROFILE_KEY,
                                    ],
                                ],
                            ],
                        ],
                    ];
                }
            }
        }
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save and continue'),
            '#button_type' => 'primary',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        global $install_state;
        $profile = $form_state->getValue('profile');
        if ($profile === static::CONFIG_INSTALL_PROFILE_KEY) {
            $sync = new FileStorage(Settings::get('config_sync_directory'));
            $profile = $sync->read('core.extension')['profile'];
            $install_state['parameters']['existing_config'] = TRUE;
        }
        $install_state['parameters']['profile'] = $profile;
    }

}