modules/group_recurring_events_series/group_recurring_events_series.group.permissions.yml

+access group_recurring_events_series overview:
+  title: 'Access group recurring events series overview'
+  description: 'Access the overview of all group recurring events series, regardless of type'

modules/group_recurring_events_series/group_recurring_events_series.info.yml

+name: 'Group recurring events'
+description: 'Enables Group functionality for the Recurring events module'
+package: 'Group'
+type: 'module'
+core_version_requirement: ^9.3 || ^10
+dependencies:
+  - 'recurring_events:recurring_events'
+  - 'group:group'

modules/group_recurring_events_series/group_recurring_events_series.install

+<?php
+
+/**
+ * @file
+ * Install, and update functions for group recurring events series module.
+ */

modules/group_recurring_events_series/group_recurring_events_series.links.action.yml

+group_content.group_recurring_events_series_relate_page:
+  route_name: 'entity.group_content.group_recurring_events_series_relate_page'
+  title: 'Add existing events'
+  appears_on:
+    - 'view.group_recurring_events_series.page_1'
+
+group_content.group_recurring_events_series_add_page:
+  route_name: 'entity.group_content.group_recurring_events_series_add_page'
+  title: 'Add new events'
+  appears_on:
+    - 'view.group_recurring_events_series.page_1'

modules/group_recurring_events_series/group_recurring_events_series.module

+<?php
+
+/**
+ * @file
+ * Enables Group functionality for the Recurring events module.
+ */
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Url;
+use Drupal\recurring_events\Entity\EventSeriesTypeInterface;
+
+/**
+ * Implements hook_ENTITY_TYPE_insert().
+ */
+function group_recurring_events_series_eventseries_type_insert(EventSeriesTypeInterface $eventseries_type) {
+  if (\Drupal::isConfigSyncing()) {
+    return;
+  }
+  \Drupal::service('plugin.manager.group_content_enabler')->clearCachedDefinitions();
+}
+
+/**
+ * Implements hook_entity_operation().
+ */
+function group_recurring_events_series_entity_operation(EntityInterface $entity) {
+  $operations = [];
+
+  if ($entity->getEntityTypeId() == 'group' && \Drupal::moduleHandler()->moduleExists('views')) {
+    /** @var \Drupal\group\Entity\GroupInterface $entity */
+    if ($entity->hasPermission('access group_recurring_events_series overview', \Drupal::currentUser())) {
+      /** @var \Symfony\Component\Routing\RouterInterface $router */
+      $router = \Drupal::service('router.no_access_checks');
+      if ($router->getRouteCollection()->get('view.group_recurring_events_series.page_1') !== NULL) {
+        $operations['recurring_events_series'] = [
+          'title' => t('Events series'),
+          'weight' => 20,
+          'url' => Url::fromRoute('view.group_recurring_events_series.page_1', ['group' => $entity->id()]),
+        ];
+      }
+    }
+  }
+
+  return $operations;
+}
+
+/**
+ * Implements hook_entity_type_build().
+ */
+function group_recurring_events_series_entity_type_build(array &$entity_types) {
+  if (isset($entity_types['eventinstance'])) {
+    $entity_types['eventinstance']->setHandlerClass('access', 'Drupal\group_recurring_events_series\Access\GroupEventInstanceHandler');
+  }
+}

modules/group_recurring_events_series/group_recurring_events_series.routing.yml

+route_callbacks:
+  - '\Drupal\group_recurring_events_series\Routing\GroupEventSeriesRouteProvider::getRoutes'

modules/group_recurring_events_series/src/Access/GroupEventInstanceHandler.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Access;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Session\AccountInterface;
+
+use Drupal\recurring_events\EventInstanceAccessControlHandler;
+
+/**
+ * The GroupEventInstanceHandler class.
+ */
+class GroupEventInstanceHandler extends EventInstanceAccessControlHandler {
+
+  /**
+   * Determine access for the group.
+   */
+  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
+    $result = parent::checkAccess($entity, $operation, $account);
+    if (!$result->isAllowed()) {
+      // Need GroupContentAccessControlHandler not
+      // EventSeriesAccessControlHandler.
+      $manager = \Drupal::service('plugin.manager.group_content_enabler');
+      $type = 'group_recurring_events_series:' . $entity->getType();
+      if ($manager->hasHandler($type, 'access')) {
+        $handler = $manager->getAccessControlHandler($type);
+        $result = $handler->entityAccess($entity->getEventSeries(), $operation, $account, TRUE);
+      }
+    }
+    return $result;
+  }
+
+}

modules/group_recurring_events_series/src/Controller/GroupEventSeriesController.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Controller;
+
+use Drupal\Core\Entity\EntityFormBuilderInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\TempStore\PrivateTempStoreFactory;
+use Drupal\group\Entity\Controller\GroupContentController;
+use Drupal\group\Entity\GroupInterface;
+use Drupal\group\Plugin\GroupContentEnablerManagerInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Returns responses for 'group_recurring_events_series' GroupContent routes.
+ */
+class GroupEventSeriesController extends GroupContentController {
+
+  /**
+   * The group content plugin manager.
+   *
+   * @var \Drupal\group\Plugin\GroupContentEnablerManagerInterface
+   */
+  protected $pluginManager;
+
+  /**
+   * Constructs a new GroupEventSeriesController.
+   *
+   * @param \Drupal\group\Plugin\GroupContentEnablerManagerInterface $plugin_manager
+   *   The group content plugin manager.
+   * @param \Drupal\Core\TempStore\PrivateTempStoreFactory $temp_store_factory
+   *   The private store factory.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\Core\Entity\EntityFormBuilderInterface $entity_form_builder
+   *   The entity form builder.
+   * @param \Drupal\Core\Render\RendererInterface $renderer
+   *   The renderer.
+   */
+  public function __construct(GroupContentEnablerManagerInterface $plugin_manager, PrivateTempStoreFactory $temp_store_factory, EntityTypeManagerInterface $entity_type_manager, EntityFormBuilderInterface $entity_form_builder, RendererInterface $renderer) {
+    parent::__construct($temp_store_factory, $entity_type_manager, $entity_form_builder, $renderer);
+    $this->pluginManager = $plugin_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('plugin.manager.group_content_enabler'),
+      $container->get('tempstore.private'),
+      $container->get('entity_type.manager'),
+      $container->get('entity.form_builder'),
+      $container->get('renderer')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addPage(GroupInterface $group, $create_mode = FALSE) {
+    $build = parent::addPage($group, $create_mode);
+
+    // Do not interfere with redirects.
+    if (!is_array($build)) {
+      return $build;
+    }
+
+    // Overwrite the label and description for all of the displayed bundles.
+    $storage_handler = $this->entityTypeManager->getStorage('eventseries_type');
+    foreach ($this->addPageBundles($group, $create_mode) as $plugin_id => $bundle_name) {
+      if (!empty($build['#bundles'][$bundle_name])) {
+        $plugin = $group->getGroupType()->getContentPlugin($plugin_id);
+        $bundle_label = $storage_handler->load($plugin->getEntityBundle())->label();
+
+        $t_args = ['%eventseries_type' => $bundle_label];
+        $description = $create_mode
+          ? $this->t('Add new content of type %eventseries_type to the group.', $t_args)
+          : $this->t('Add existing content of type %eventseries_type to the group.', $t_args);
+
+        $build['#bundles'][$bundle_name]['label'] = $bundle_label;
+        $build['#bundles'][$bundle_name]['description'] = $description;
+      }
+    }
+
+    return $build;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function addPageBundles(GroupInterface $group, $create_mode) {
+    $bundles = [];
+
+    // Retrieve all group_recurring_events_series plugins for the group's type.
+    $plugin_ids = $this->pluginManager->getInstalledIds($group->getGroupType());
+    foreach ($plugin_ids as $key => $plugin_id) {
+      if (strpos($plugin_id, 'group_recurring_events_series:') !== 0) {
+        unset($plugin_ids[$key]);
+      }
+    }
+
+    // Retrieve all of the responsible group content types, keyed by plugin ID.
+    $storage = $this->entityTypeManager->getStorage('group_content_type');
+    $properties = [
+      'group_type' => $group->bundle(),
+      'content_plugin' => $plugin_ids,
+    ];
+    foreach ($storage->loadByProperties($properties) as $bundle => $group_content_type) {
+      /** @var \Drupal\group\Entity\GroupContentTypeInterface $group_content_type */
+      $bundles[$group_content_type->getContentPluginId()] = $bundle;
+    }
+
+    return $bundles;
+  }
+
+}

modules/group_recurring_events_series/src/Plugin/GroupContentEnabler/GroupEventSeries.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Plugin\GroupContentEnabler;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+use Drupal\group\Entity\GroupInterface;
+use Drupal\group\Plugin\GroupContentEnablerBase;
+use Drupal\recurring_events\Entity\EventSeriesType;
+
+/**
+ * Provides a content enabler for event series.
+ *
+ * @GroupContentEnabler(
+ *   id = "group_recurring_events_series",
+ *   label = @Translation("Group event series"),
+ *   description = @Translation("Adds event series to groups both publicly and privately."),
+ *   entity_type_id = "eventseries",
+ *   entity_access = TRUE,
+ *   reference_label = @Translation("Title"),
+ *   reference_description = @Translation("The title of the event series to add to the group"),
+ *   deriver = "Drupal\group_recurring_events_series\Plugin\GroupContentEnabler\GroupEventSeriesDeriver",
+ *   handlers = {
+ *     "access" = "Drupal\group\Plugin\GroupContentAccessControlHandler",
+ *     "permission_provider" = "Drupal\group_recurring_events_series\Plugin\GroupEventSeriesPermissionProvider",
+ *   }
+ * )
+ */
+class GroupEventSeries extends GroupContentEnablerBase {
+
+  /**
+   * Retrieves the event series type this plugin supports.
+   *
+   * @return \Drupal\recurring_events\Entity\EventSeriesType
+   *   The event series type this plugin supports.
+   */
+  protected function getEventSeriesType() {
+    return EventSeriesType::load($this->getEntityBundle());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getGroupOperations(GroupInterface $group) {
+    $account = \Drupal::currentUser();
+    $plugin_id = $this->getPluginId();
+    $type = $this->getEntityBundle();
+    $operations = [];
+
+    if ($group->hasPermission("create $plugin_id entity", $account)) {
+      $route_params = ['group' => $group->id(), 'plugin_id' => $plugin_id];
+      $operations["group_recurring_events_series-create-$type"] = [
+        'title' => $this->t('Add @type', ['@type' => $this->getEventSeriesType()->label()]),
+        'url' => new Url('entity.group_content.create_form', $route_params),
+        'weight' => 30,
+      ];
+    }
+
+    return $operations;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    $config = parent::defaultConfiguration();
+    $config['entity_cardinality'] = 1;
+    return $config;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildConfigurationForm($form, $form_state);
+
+    // Disable the entity cardinality field as the functionality of this module
+    // relies on a cardinality of 1. We don't just hide it, though, to keep a UI
+    // that's consistent with other content enabler plugins.
+    $info = $this->t("This field has been disabled by the plugin to guarantee the functionality that's expected of it.");
+    $form['entity_cardinality']['#disabled'] = TRUE;
+    $form['entity_cardinality']['#description'] .= '<br /><em>' . $info . '</em>';
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function calculateDependencies() {
+    $dependencies = parent::calculateDependencies();
+    $dependencies['config'][] = 'recurring_events.eventseries_type.' . $this->getEntityBundle();
+    return $dependencies;
+  }
+
+}

modules/group_recurring_events_series/src/Plugin/GroupContentEnabler/GroupEventSeriesDeriver.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Plugin\GroupContentEnabler;
+
+use Drupal\Component\Plugin\Derivative\DeriverBase;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\recurring_events\Entity\EventSeriesType;
+
+/**
+ * Provides a deriver for group event series entities.
+ */
+class GroupEventSeriesDeriver extends DeriverBase {
+
+  use StringTranslationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    $this->derivatives = [];
+
+    foreach (EventSeriesType::loadMultiple() as $name => $eventseries_type) {
+      $label = $eventseries_type->label();
+
+      $this->derivatives[$name] = [
+        'entity_bundle' => $name,
+        'label' => $this->t('Group event series (@type)', ['@type' => $label]),
+        'description' => $this->t('Adds %type content to groups both publicly and privately.', ['%type' => $label]),
+      ] + $base_plugin_definition;
+    }
+
+    return $this->derivatives;
+  }
+
+}

modules/group_recurring_events_series/src/Plugin/GroupEventSeriesPermissionProvider.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Plugin;
+
+use Drupal\group\Plugin\GroupContentPermissionProvider;
+
+/**
+ * Provides group permissions for events series GroupContent entities.
+ */
+class GroupEventSeriesPermissionProvider extends GroupContentPermissionProvider {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getEntityViewUnpublishedPermission($scope = 'any') {
+    if ($scope === 'any') {
+      // Backwards compatible permission name for 'any' scope.
+      return "view unpublished $this->pluginId entity";
+    }
+    return parent::getEntityViewUnpublishedPermission($scope);
+  }
+
+}

modules/group_recurring_events_series/src/Routing/GroupEventSeriesRouteProvider.php

+<?php
+
+namespace Drupal\group_recurring_events_series\Routing;
+
+use Drupal\recurring_events\Entity\EventSeriesType;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Provides routes for group_recurring_events_series group content.
+ */
+class GroupEventSeriesRouteProvider {
+
+  /**
+   * Provides the shared collection route for group event series plugins.
+   */
+  public function getRoutes() {
+    $routes = $plugin_ids = $permissions_add = $permissions_create = [];
+
+    foreach (EventSeriesType::loadMultiple() as $name => $eventseries_type) {
+      $plugin_id = "group_recurring_events_series:$name";
+
+      $plugin_ids[] = $plugin_id;
+      $permissions_add[] = "create $plugin_id content";
+      $permissions_create[] = "create $plugin_id entity";
+    }
+
+    // If there are no event series types yet, we cannot have any plugin IDs
+    // and should therefore exit early because we cannot have any routes for
+    // them either.
+    if (empty($plugin_ids)) {
+      return $routes;
+    }
+
+    $routes['entity.group_content.group_recurring_events_series_relate_page'] = new Route('group/{group}/eventseries/add');
+    $routes['entity.group_content.group_recurring_events_series_relate_page']
+      ->setDefaults([
+        '_title' => 'Add existing content',
+        '_controller' => '\Drupal\group_recurring_events_series\Controller\GroupEventSeriesController::addPage',
+      ])
+      ->setRequirement('_group_permission', implode('+', $permissions_add))
+      ->setRequirement('_group_installed_content', implode('+', $plugin_ids))
+      ->setOption('_group_operation_route', TRUE);
+
+    $routes['entity.group_content.group_recurring_events_series_add_page'] = new Route('group/{group}/eventseries/create');
+    $routes['entity.group_content.group_recurring_events_series_add_page']
+      ->setDefaults([
+        '_title' => 'Add new content',
+        '_controller' => '\Drupal\group_recurring_events_series\Controller\GroupEventSeriesController::addPage',
+        'create_mode' => TRUE,
+      ])
+      ->setRequirement('_group_permission', implode('+', $permissions_create))
+      ->setRequirement('_group_installed_content', implode('+', $plugin_ids))
+      ->setOption('_group_operation_route', TRUE);
+
+    return $routes;
+  }
+
+}

modules/recurring_events_ical/config/schema/recurring_events_ical.event_ical_mapping.schema.yml

+recurring_events_ical.event_ical_mapping.*:
+  type: config_entity
+  label: 'Event iCal property mapping'
+  mapping:
+    id:
+      type: string
+      label: 'ID'
+    label:
+      type: label
+      label: 'Type'
+    properties:
+      type: sequence
+      label: 'Properties'
+      sequence:
+        type: recurring_events_ical.ical_property.[%key]

modules/recurring_events_ical/config/schema/recurring_events_ical.ical_property.schema.yml

+recurring_events_ical.ical_property.summary:
+  type: string
+  label: 'SUMMARY'
+recurring_events_ical.ical_property.contact:
+  type: string
+  label: 'CONTACT'
+  nullable: true
+recurring_events_ical.ical_property.description:
+  type: string
+  label: 'DESCRIPTION'
+  nullable: true
+recurring_events_ical.ical_property.geo:
+  type: string
+  label: 'GEO'
+  nullable: true
+recurring_events_ical.ical_property.location:
+  type: string
+  label: 'LOCATION'
+  nullable: true
+recurring_events_ical.ical_property.priority:
+  type: string
+  label: 'PRIORITY'
+  nullable: true
+recurring_events_ical.ical_property.url:
+  type: string
+  label: 'URL'
+  nullable: true

modules/recurring_events_ical/recurring_events_ical.info.yml

+name: 'Recurring Events iCalendar'
+type: module
+description: 'Provides the ability to export recurring events as iCalendar files'
+core_version_requirement: ^9.3 || ^10
+package: 'Recurring Events'
+configure: entity.event_ical_mapping.collection
+dependencies:
+  - recurring_events:recurring_events
+  - token:token

modules/recurring_events_ical/recurring_events_ical.links.action.yml

+entity.event_ical_mapping.add_form:
+  route_name: 'entity.event_ical_mapping.add_form'
+  title: 'Add iCalendar property mapping'
+  appears_on:
+    - entity.event_ical_mapping.collection

modules/recurring_events_ical/recurring_events_ical.links.menu.yml

+# iCal property mapping configuration page.
+entity.event_ical_mapping.collection:
+  title: 'Event iCalendar Property Mapping'
+  description: 'Configure event instance tokens to populate iCalendar properties.'
+  route_name: entity.event_ical_mapping.collection
+  parent: events.admin.overview
+  weight: 4

modules/recurring_events_ical/recurring_events_ical.module

+<?php
+
+/**
+ * @file
+ * Contains recurring_events_ical.module.
+ */
+
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Implements hook_entity_base_field_info_alter().
+ */
+function recurring_events_ical_entity_base_field_info_alter(&$fields, EntityTypeInterface $entity_type) {
+  if ($entity_type->id() === 'eventseries' || $entity_type->id() === 'eventinstance') {
+    $fields['event_ical_link'] = BaseFieldDefinition::create('event_ical_link')
+      ->setName('event_ical_link')
+      ->setLabel(t('Event iCalendar Link'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\recurring_events_ical\Field\EventICalLinkItemList')
+      ->setTargetEntityTypeId($entity_type->id())
+      ->setDisplayConfigurable('form', FALSE)
+      ->setDisplayConfigurable('view', TRUE)
+      ->setDisplayOptions('view', [
+        'label' => 'hidden',
+        'weight' => 10,
+      ]);
+  }
+}
+
+/**
+ * Implements hook_entity_type_alter().
+ */
+function recurring_events_ical_entity_type_alter(array &$entity_types) {
+  /** @var \Drupal\Core\Entity\EntityTypeInterface[] $entity_types */
+  $entity_types['eventseries']->setLinkTemplate('ical', $entity_types['eventseries']->getLinkTemplate('canonical') . '/ical');
+  $entity_types['eventinstance']->setLinkTemplate('ical', $entity_types['eventinstance']->getLinkTemplate('canonical') . '/ical');
+}
+
+/**
+ * Implements hook_config_schema_info_alter().
+ */
+function recurring_events_ical_config_schema_info_alter(&$definitions) {
+  foreach (['eventseries', 'eventinstance'] as $entity_type) {
+    $definitions["recurring_events.$entity_type.config"]['mapping']['ical_link_title'] = [
+      'type' => 'string',
+      'label' => 'iCalendar link title',
+    ];
+  }
+}
+
+/**
+ * Implements hook_form_FORM_ID_alter() for 'eventseries_settings'.
+ */
+function recurring_events_ical_form_eventseries_settings_alter(&$form, FormStateInterface $form_state, $form_id) {
+  _recurring_events_ical_settings($form, 'eventseries');
+  $form['#submit'][] = 'recurring_events_ical_form_eventseries_settings_submit';
+}
+
+/**
+ * Implements hook_form_FORM_ID_alter() for 'eventinstance_settings'.
+ */
+function recurring_events_ical_form_eventinstance_settings_alter(&$form, FormStateInterface $form_state, $form_id) {
+  _recurring_events_ical_settings($form, 'eventinstance');
+  $form['#submit'][] = 'recurring_events_ical_form_eventinstance_settings_submit';
+}
+
+/**
+ * Helper function to add the iCalendar settings fields to a form.
+ *
+ * @param array &$form
+ *   Nested array of form elements that comprise the form.
+ * @param string $entity_type
+ *   The type of event entity, either 'eventseries' or 'eventinstance'.
+ */
+function _recurring_events_ical_settings(array &$form, string $entity_type) {
+  $config = \Drupal::config("recurring_events.$entity_type.config");
+
+  /** @var \Drupal\token\TokenEntityMapperInterface $token_entity_mapper */
+  $token_entity_mapper = \Drupal::service('token.entity_mapper');
+  $token_types[$entity_type] = $token_entity_mapper->getTokenTypeForEntityType($entity_type);
+
+  $form['ical'] = [
+    '#type' => 'details',
+    '#title' => t('iCalendar'),
+    '#open' => TRUE,
+  ];
+  $form['ical']['ical_link_title'] = [
+    '#type' => 'textfield',
+    '#title' => t('iCalendar Link Title'),
+    '#description' => t('Link text for the Event iCalendar Link field.'),
+    '#size' => 65,
+    '#maxlength' => 1280,
+    '#element_validate' => ['token_element_validate'],
+    '#after_build' => ['token_element_validate'],
+    '#token_types' => $token_types,
+    '#default_value' => $config->get('ical_link_title') ?? t('Download as iCal'),
+  ];
+  $form['ical']['token_browser'] = [
+    '#theme' => 'token_tree_link',
+    '#token_types' => $token_types,
+    '#global_types' => TRUE,
+    '#show_nested' => TRUE,
+  ];
+}
+
+/**
+ * Additional submission handler for the eventseries_settings form.
+ *
+ * @param array &$form
+ *   Nested array of form elements that comprise the form.
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
+ *   The form state.
+ */
+function recurring_events_ical_form_eventseries_settings_submit(array &$form, FormStateInterface $form_state) {
+  \Drupal::configFactory()->getEditable('recurring_events.eventseries.config')
+    ->set('ical_link_title', $form_state->getValue('ical_link_title'))
+    ->save();
+}
+
+/**
+ * Additional submission handler for the eventinstance_settings form.
+ *
+ * @param array &$form
+ *   Nested array of form elements that comprise the form.
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
+ *   The form state.
+ */
+function recurring_events_ical_form_eventinstance_settings_submit(array &$form, FormStateInterface $form_state) {
+  \Drupal::configFactory()->getEditable('recurring_events.eventinstance.config')
+    ->set('ical_link_title', $form_state->getValue('ical_link_title'))
+    ->save();
+}

modules/recurring_events_ical/recurring_events_ical.routing.yml

+# iCal property mapping configuration
+entity.event_ical_mapping.collection:
+  path: '/admin/structure/events/ical'
+  defaults:
+    _entity_list: 'event_ical_mapping'
+    _title: 'iCalendar'
+  requirements:
+    _permission: 'administer eventinstance types'
+
+entity.event_ical_mapping.add_form:
+  path: '/admin/structure/events/ical/add'
+  defaults:
+    _entity_form: 'event_ical_mapping.add'
+    _title: 'Add iCalendar property mapping'
+  requirements:
+    _permission: 'administer eventinstance types'
+
+entity.event_ical_mapping.edit_form:
+  path: '/admin/structure/events/ical/{event_ical_mapping}'
+  defaults:
+    _entity_form: 'event_ical_mapping.edit'
+    _title: 'Edit iCalendar property mapping'
+  requirements:
+    _permission: 'administer eventinstance types'
+
+entity.event_ical_mapping.delete_form:
+  path: '/admin/structure/events/ical/{event_ical_mapping}/delete'
+  defaults:
+    _entity_form: 'event_ical_mapping.delete'
+    _title: 'Delete iCalendar property mapping'
+  requirements:
+    _permission: 'administer eventinstance types'
+
+# iCalendar download on EventSeries
+entity.eventseries.ical:
+  path: '/events/series/{eventseries}/ical'
+  defaults:
+    _controller: '\Drupal\recurring_events_ical\Controller\EventExportController::series'
+  requirements:
+    _entity_access: 'eventseries.view'
+    eventseries: \d+
+  options:
+    parameters:
+      eventseries:
+        type: entity:eventseries
+
+# iCalendar download on EventInstance
+entity.eventinstance.ical:
+  path: '/events/{eventinstance}/ical'
+  defaults:
+    _controller: '\Drupal\recurring_events_ical\Controller\EventExportController::instance'
+  requirements:
+    _entity_access: 'eventinstance.view'
+    eventinstance: \d+
+  options:
+    parameters:
+      eventinstance:
+        type: entity:eventinstance