class Slideshow

class Slideshow extends StylePluginBase {
    
    /**
     * Does the style plugin allows to use style plugins.
     *
     * @var bool
     */
    protected $usesRowPlugin = TRUE;
    
    /**
     * Does the style plugin support custom css class for the rows.
     *
     * @var bool
     */
    protected $usesRowClass = TRUE;
    
    /**
     * Does the style plugin support grouping of rows.
     *
     * @var bool
     */
    protected $usesGrouping = FALSE;
    
    /**
     * Does the style plugin for itself support to add fields to it's output.
     *
     * This option only makes sense on style plugins without row plugins, like
     * for example table.
     *
     * @var bool
     */
    protected $usesFields = TRUE;
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['row_class_custom'] = [
            'default' => '',
        ];
        $options['row_class_default'] = [
            'default' => TRUE,
        ];
        $options['slideshow_type'] = [
            'default' => 'views_slideshow_cycle',
        ];
        $options['slideshow_skin'] = [
            'default' => 'default',
        ];
        $typeManager = \Drupal::service('plugin.manager.views_slideshow.slideshow_type');
        foreach ($typeManager->getDefinitions() as $id => $definition) {
            $instance = $typeManager->createInstance($id, []);
            $options[$id] = $instance->defaultConfiguration();
        }
        $widgetTypeManager = \Drupal::service('plugin.manager.views_slideshow.widget_type');
        $widgetTypes = $widgetTypeManager->getDefinitions();
        foreach ([
            'top',
            'bottom',
        ] as $location) {
            foreach ($widgetTypes as $widgetTypeId => $widgetTypeDefinition) {
                $options['widgets']['contains'][$location]['contains'][$widgetTypeId]['contains'] = $widgetTypeManager->createInstance($widgetTypeId, [])
                    ->defaultConfiguration();
            }
        }
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        // Wrap all the form elements to help style the form.
        $form['views_slideshow_wrapper'] = [
            '#markup' => '<div id="views-slideshow-form-wrapper">',
        ];
        // Skins.
        $form['slideshow_skin_header'] = [
            '#markup' => '<h2>' . $this->t('Style') . '</h2>',
        ];
        
        /**
         * @var \Drupal\Component\Plugin\PluginManagerInterface
         */
        $skinManager = \Drupal::service('plugin.manager.views_slideshow.slideshow_skin');
        // Get all skins to create the option list.
        $skins = [];
        foreach ($skinManager->getDefinitions() as $id => $definition) {
            $skins[$id] = $definition['label'];
        }
        asort($skins);
        // Create the drop down box so users can choose an available skin.
        $form['slideshow_skin'] = [
            '#type' => 'select',
            '#title' => $this->t('Skin'),
            '#options' => $skins,
            '#default_value' => $this->options['slideshow_skin'],
            '#description' => $this->t('Select the skin to use for this display.  Skins allow for easily swappable layouts of things like next/prev links and thumbnails.  Note that not all skins support all widgets, so a combination of skins and widgets may lead to unpredictable results in layout.'),
        ];
        // Slides.
        $form['slides_header'] = [
            '#markup' => '<h2>' . $this->t('Slides') . '</h2>',
        ];
        // Get all slideshow types.
        $typeManager = \Drupal::service('plugin.manager.views_slideshow.slideshow_type');
        $types = $typeManager->getDefinitions();
        if ($types) {
            // Build our slideshow options for the form.
            $slideshow_options = [];
            foreach ($types as $id => $definition) {
                $slideshow_options[$id] = $definition['label'];
            }
            $form['slideshow_type'] = [
                '#type' => 'select',
                '#title' => $this->t('Slideshow Type'),
                '#options' => $slideshow_options,
                '#default_value' => $this->options['slideshow_type'],
            ];
            // @todo check if default values are properly passed to the buildConfigurationForm().
            foreach ($types as $id => $definition) {
                $configuration = [];
                if (!empty($this->options[$id])) {
                    $configuration = $this->options[$id];
                }
                $instance = $typeManager->createInstance($id, $configuration);
                $form[$id] = [
                    '#type' => 'fieldset',
                    '#title' => $this->t('@module options', [
                        '@module' => $definition['label'],
                    ]),
                    '#collapsible' => TRUE,
                    '#attributes' => [
                        'class' => [
                            $id,
                        ],
                    ],
                    '#states' => [
                        'visible' => [
                            ':input[name="style_options[slideshow_type]"]' => [
                                'value' => $id,
                            ],
                        ],
                    ],
                ];
                $form = $instance->buildConfigurationForm($form, $form_state);
            }
        }
        else {
            $form['enable_module'] = [
                '#markup' => $this->t('There is no Views Slideshow plugin enabled. Go to the @modules and enable a Views Slideshow plugin module. For example Views Slideshow Cycle.', [
                    '@modules' => Link::fromTextAndUrl($this->t('Modules Page'), Url::fromRoute('system.modules_list'))
                        ->toString(),
                ]),
            ];
        }
        // Widgets.
        // @todo Improve the UX by using Ajax.
        $form['widgets_header'] = [
            '#markup' => '<h2>' . $this->t('Widgets') . '</h2>',
        ];
        // Define the available locations.
        $location = [
            'top' => $this->t('Top'),
            'bottom' => $this->t('Bottom'),
        ];
        // Loop through all locations so we can add header for each location.
        foreach ($location as $location_id => $location_name) {
            $form['widgets'][$location_id]['header'] = [
                '#markup' => '<h3>' . $this->t('@location Widgets', [
                    '@location' => $location_name,
                ]) . '</h3>',
            ];
        }
        
        /**
         * @var \Drupal\Component\Plugin\PluginManagerInterface
         */
        $widgetTypeManager = \Drupal::service('plugin.manager.views_slideshow.widget_type');
        // Get all widgets types that are registered.
        $widgets = $widgetTypeManager->getDefinitions();
        if (!empty($widgets)) {
            // Build our weight values by number of widgets.
            $weights = [];
            for ($i = 1; $i <= count($widgets); $i++) {
                $weights[$i] = $i;
            }
            // Loop through our widgets and locations to build our form values for
            // each widget.
            foreach ($widgets as $widget_id => $widget_info) {
                // Determine if this widget type is compatible with any slideshow type.
                $compatible_slideshows = [];
                foreach ($types as $slideshow_id => $slideshow_info) {
                    if ($widgetTypeManager->createInstance($widget_id, [])
                        ->checkCompatiblity($slideshow_info)) {
                        $compatible_slideshows[] = $slideshow_id;
                    }
                }
                // Display the widget config form only if the widget type is compatible
                // with at least one slideshow type.
                if (!empty($compatible_slideshows)) {
                    foreach ($location as $location_id => $location_name) {
                        // Use Widget Checkbox.
                        $form['widgets'][$location_id][$widget_id]['enable'] = [
                            '#type' => 'checkbox',
                            '#title' => $widget_info['label'],
                            '#default_value' => $this->options['widgets'][$location_id][$widget_id]['enable'],
                            '#description' => $this->t('Should @name be rendered at the @location of the slides.', [
                                '@name' => $widget_info['label'],
                                '@location' => $location_name,
                            ]),
                            '#dependency' => [
                                'edit-style-options-slideshow-type' => $compatible_slideshows,
                            ],
                        ];
                        // Need to wrap this so it indents correctly.
                        $form['widgets'][$location_id][$widget_id]['wrapper'] = [
                            '#markup' => '<div class="vs-dependent">',
                        ];
                        // Widget weight.
                        // We check to see if the default value is greater than the number
                        // of widgets just in case a widget has been removed and the form
                        // hasn't been saved again.
                        $weight = isset($this->options['widgets'][$location_id][$widget_id]['weight']) ? $this->options['widgets'][$location_id][$widget_id]['weight'] : 0;
                        if ($weight > count($widgets)) {
                            $weight = count($widgets);
                        }
                        $form['widgets'][$location_id][$widget_id]['weight'] = [
                            '#type' => 'select',
                            '#title' => $this->t('Weight of the @name', [
                                '@name' => $widget_info['label'],
                            ]),
                            '#default_value' => $weight,
                            '#options' => $weights,
                            '#description' => $this->t('Determines in what order the @name appears. A lower weight will cause the @name to be above higher weight items.', [
                                '@name' => $widget_info['label'],
                            ]),
                            '#prefix' => '<div class="vs-dependent">',
                            '#suffix' => '</div>',
                            '#states' => [
                                'visible' => [
                                    ':input[name="style_options[widgets][' . $location_id . '][' . $widget_id . '][enable]"]' => [
                                        'checked' => TRUE,
                                    ],
                                ],
                            ],
                        ];
                        // Build the appropriate array for the states API.
                        $widget_dependency = 'style_options[widgets][' . $location_id . '][' . $widget_id . ']';
                        // Get the current configuration of this widget type.
                        $configuration = [];
                        if (!empty($this->options['widgets'][$location_id][$widget_id])) {
                            $configuration = $this->options['widgets'][$location_id][$widget_id];
                        }
                        $configuration['dependency'] = $widget_dependency;
                        $instance = $widgetTypeManager->createInstance($widget_id, $configuration);
                        // Get the configuration form of this widget type.
                        $form['widgets'][$location_id][$widget_id] = $instance->buildConfigurationForm($form['widgets'][$location_id][$widget_id], $form_state);
                        // Close the vs-dependent wrapper.
                        $form['widgets'][$location_id][$widget_id]['wrapper_close'] = [
                            '#markup' => '</div>',
                        ];
                    }
                }
            }
        }
        // Browse locations and remove the header if no widget is available.
        foreach ($location as $location_id => $location_name) {
            // If no widget is available, the only key is "header".
            if (count(array_keys($form['widgets'][$location_id])) == 1) {
                unset($form['widgets'][$location_id]);
            }
        }
        // Remove the widget section header if there is no widget available.
        if (empty($form['widgets'])) {
            unset($form['widgets']);
            unset($form['widgets_header']);
        }
        $form['views_slideshow_wrapper_close'] = [
            '#markup' => '</div>',
        ];
        // Add a library to style the form.
        $form['#attached']['library'] = [
            'views_slideshow/form',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateOptionsForm(&$form, FormStateInterface $form_state) {
        // Validate all slideshow type plugins values.
        $typeManager = \Drupal::service('plugin.manager.views_slideshow.slideshow_type');
        foreach ($typeManager->getDefinitions() as $id => $definition) {
            $type = $typeManager->createInstance($id);
            $type->validateConfigurationForm($form, $form_state);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitOptionsForm(&$form, FormStateInterface $form_state) {
        // Submit all slideshow type plugins values.
        $typeManager = \Drupal::service('plugin.manager.views_slideshow.slideshow_type');
        foreach ($typeManager->getDefinitions() as $id => $definition) {
            $type = $typeManager->createInstance($id);
            $type->submitConfigurationForm($form, $form_state);
        }
    }

}