🎉 initial commit

Civi/Mailinglistsync/ADGroupMailingList.php

@@ -0,0 +1,237 @@
+<?php /** @noinspection SpellCheckingInspection */
+
+namespace Civi\Mailinglistsync;
+
+use CRM_Mailinglistsync_ExtensionUtil as E;
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+
+class ADGroupMailingList extends GroupMailingList {
+
+  public const LOCATION_TYPE = 'AD_Mailing_List_Address';
+
+  protected string $sid;
+
+  /**
+   * Get an AD mailing list by its SID.
+   *
+   * @params string $sid
+   * @param string $sid
+   *
+   * @return \Civi\Mailinglistsync\ADGroupMailingList|null
+   *
+   * @throws \CRM_Core_Exception
+   * @throws \Civi\API\Exception\UnauthorizedException
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public static function getBySID(string $sid): ?self {
+    $id = static::RELATED_CLASS::get()
+      ->addSelect('id')
+      ->addWhere(static::CUSTOM_GROUP_NAME . '.Active_Directory_SID', '=', $sid)
+      ->execute()
+      ->first()['id'];
+
+    $groups = \CRM_Contact_BAO_Group::getGroups(['id' => $id]);
+    $groupId = array_pop($groups);
+    return $groupId ? new self($groupId) : NULL;
+  }
+
+  /**
+   * Synchronize recipients with a list of SIDs and e-mail addresses.
+   *
+   * @param array $recipients
+   *
+   * @return array A description of the changes made
+   *
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function syncRecipients(array $recipients): array {
+
+    $adGroupMembers = $this->getRecipients();
+
+    // Add new recipients
+    $recipientsAdded = [];
+    foreach ($recipients as $recipient) {
+      if (empty($adGroupMembers[$recipient['sid']] ?? NULL)) {
+        $recipientsAdded[$recipient['sid']] = $this->addRecipient($recipient);
+      }
+    }
+
+    // Remove recipients that are no longer in the list
+    $recipientsRemoved = [];
+    foreach ($adGroupMembers as $adGroupMember) {
+      /* @var \Civi\Mailinglistsync\MailingListRecipient $adGroupMember */
+      if (!in_array($adGroupMember->getSid(), array_column($recipients, 'sid'))) {
+        $recipientsRemoved[$adGroupMember->getSid()] = $this->removeRecipient($adGroupMember);
+      }
+    }
+
+    // Update recipients
+    $recipientsUpdated = [];
+
+    $recipientAttributesMap = [
+      // Map recipient attribute names to method names (get/set)
+      'first_name' => 'FirstName',
+      'last_name' => 'LastName',
+      'email' => 'Email',
+    ];
+
+    foreach ($recipients as $recipient) {
+      $changed = FALSE;
+
+      // Find the group member by SID
+      $adGroupMemberArray = array_filter(
+        $adGroupMembers,
+        fn($adGroupMember) => $adGroupMember->getSid() === $recipient['sid']
+      );
+      $count = count($adGroupMemberArray);
+      if ($count === 0) {
+        continue;
+      }
+      elseif ($count > 1) {
+        throw new MailinglistException(
+          "Multiple recipients with the same SID",
+          MailinglistException::ERROR_CODE_MULTIPLE_RECIPIENTS
+        );
+      }
+      /* @var \Civi\Mailinglistsync\MailingListRecipient $adGroupMember */
+      $adGroupMember = array_pop($adGroupMemberArray);
+
+      // Update attributes if they have changed
+      foreach ($recipientAttributesMap as $attrName => $methodName) {
+        $changed = self::updateRecipient(
+          $adGroupMember,
+          $recipient,
+          $attrName,
+          fn() => $adGroupMember->{"get$methodName"}(),
+          fn($value) => $adGroupMember->{"set$methodName"}($value),
+          $recipientsUpdated,
+        ) || $changed;
+      }
+
+      // Apply changes
+      if ($changed) {
+        $adGroupMember->save();
+      }
+    }
+
+    // Count errors
+    $errorCount = count(array_filter(
+      $recipientsAdded,
+      fn($recipient) => $recipient['is_error']
+    ));
+    $errorCount += count(array_filter(
+      $recipientsRemoved,
+      fn($recipient) => $recipient['is_error']
+    ));
+    $errorCount += count(array_filter(
+      $recipientsUpdated,
+      fn($recipient) => array_filter($recipient, fn($attr) => $attr['is_error'])
+    ));
+
+    return [
+      'error_count' => $errorCount,
+      'recipients_added' => $recipientsAdded,
+      'recipients_removed' => $recipientsRemoved,
+      'recipients_updated' => $recipientsUpdated,
+    ];
+  }
+
+  /**
+   * Get a list of recipients indexed by SID.
+   *
+   * @override GroupMailingList::getRecipients()
+   * @return array
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function getRecipients(): array {
+    $recipients = parent::getRecipients();
+    return array_column($recipients, null, fn($recipient) => $recipient->getSid());
+  }
+
+  private function addRecipient(array $recipient): array {
+    $result = ['recipient' => $recipient];
+
+    try {
+      // Try to find an existing contact
+      $contactSearch = $this->findExistingContact(
+        firstName: $recipient['first_name'],
+        lastName: $recipient['last_name'],
+        email: $recipient['email'],
+      );
+      if ($contactSearch !== NULL) {
+        $result['is_error'] = FALSE;
+        $result['recipient']['contact_id'] = $contactSearch['contact']['id'];
+        $result['recipient']['found_by'] = $contactSearch['found_by'];
+        $result['recipient']['contact_created'] = FALSE;
+        return $result;
+      }
+
+      // Create a new contact if none was found
+      $newRecipient = MailingListRecipient::createContact(
+        firstName: $recipient['first_name'],
+        lastName: $recipient['last_name'],
+        email: $recipient['email'],
+        sid: $recipient['sid'],
+      );
+      $result['is_error'] = FALSE;
+      $result['recipient']['contact_id'] = $newRecipient->getContactId();
+      $result['recipient']['contact_created'] = TRUE;
+      return $result;
+    }
+    catch (MailinglistException $e) {
+      $error = $e->getLogMessage();
+      \Civi::log(E::LONG_NAME)->error($error);
+      $result['is_error'] = TRUE;
+      $result['error_message'] = $error;
+      $result['recipient']['contact_created'] = FALSE;
+      return $result;
+    }
+  }
+
+  /**
+   * Helper function to update recipient data dynamically.
+   * OMG, is this DRY!
+   *
+   * @param \Civi\Mailinglistsync\MailingListRecipient $old
+   * @param array $new
+   * @param string $attributeName
+   * @param callable $getter
+   * @param callable $setter
+   * @param array $changes
+   *
+   * @return bool TRUE if the recipient was updated, FALSE otherwise
+   */
+  private static function updateRecipient(
+    MailingListRecipient $old,
+    array $new,
+    string $attributeName,
+    callable $getter,
+    callable $setter,
+    array &$changes,
+  ): bool {
+    $updated = FALSE;
+    if ($new[$attributeName] !== $getter()) {
+      $error = NULL;
+      $oldValue = $getter();
+      try {
+        $setter($new[$attributeName]);
+        $updated = TRUE;
+      }
+      catch (MailinglistException $e) {
+        \Civi::log(E::LONG_NAME)->error($e->getLogMessage());
+        $error = $e->getLogMessage();
+      }
+      finally {
+        $changes[$old['sid']][$attributeName] = [
+          'is_error' => $error !== NULL,
+          'old' => $oldValue,
+          'new' => $new[$attributeName],
+        ];
+        if ($error !== NULL) {
+          $changes[$old['sid']][$attributeName]['error'] = $error;
+        }
+      }
+    }
+    return $updated;
+  }
+}

Civi/Mailinglistsync/BaseMailingList.php

@@ -0,0 +1,486 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use Civi\API\Exception\UnauthorizedException;
+use Civi\Api4\CustomField;
+use Civi\Core\Lock\NullLock;
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+use CRM_Mailinglistsync_ExtensionUtil as E;
+use Civi\Api4\MockBasicEntity;
+use Civi\Api4\LocationType;
+use Dompdf\Exception;
+
+abstract class BaseMailingList {
+
+  public const GROUP_MAILING_LIST = 'group';
+
+  public const EVENT_MAILING_LIST = 'event';
+
+  public const CUSTOM_GROUP_NAME = 'BASE_Mailing_List';
+
+  protected const RELATED_CLASS = MockBasicEntity::class;
+  protected const RELATED_TYPE = 'base';
+
+  protected MailingListManager $mailingListManager;
+
+  /**
+   * Data to be updated. Use the `save()` method to apply the update.
+   *
+   * @var array
+   */
+  private array $updateData;
+
+  /**
+   * Constructor
+   *
+   * @param int|array|null $entity The entity ID or an array of entity data.
+   *
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  function __construct(int|array $entity = NULL) {
+    $this->updateData = [];
+    if ($entity) {
+      $this->load($entity);
+    }
+    $this->mailingListManager = new MailingListManager();
+  }
+
+  /**
+   * Set related entity directly or load it from the database by passing an ID.
+   *
+   * @param array|int $entity
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  protected function load(array|int $entity): void {
+    if (is_int($entity)) {
+      $id = $entity;
+      try {
+        $entity = static::RELATED_CLASS::get()
+          ->addSelect('*')
+          ->addSelect('custom.*')
+          ->addWhere('id', '=', $id)
+          ->execute()
+          ->first();
+        $this->setEntity($entity);
+      }
+      catch (UnauthorizedException) {
+        $type = static::RELATED_TYPE;
+        throw new MailinglistException(
+          "Could not get $type with id '$id' via API4 due to insufficient permissions",
+          MailinglistException::ERROR_CODE_PERMISSION_DENIED
+        );
+      }
+      catch (\Exception) {
+        $type = static::RELATED_TYPE;
+        throw new MailinglistException(
+          "Could not get $type with id '$id' via API4",
+          $type === self::GROUP_MAILING_LIST ? MailinglistException::ERROR_CODE_GET_GROUP_MAILING_LISTS_FAILED : MailinglistException::ERROR_CODE_GET_EVENT_MAILING_LISTS_FAILED
+        );
+      }
+    }
+    $this->setEntity($entity);
+  }
+
+  /**
+   * Get related custom fields.
+   *
+   * @throws UnauthorizedException
+   * @throws \CRM_Core_Exception
+   */
+  static protected function getCustomFields(): array {
+    return CustomField::get()
+      ->addSelect('*')
+      ->addWhere('custom_group_id:name', '=', static::CUSTOM_GROUP_NAME)
+      ->execute()
+      ->getArrayCopy();
+  }
+
+  /**
+   * Validate e-mail address.
+   *
+   * @param string $emailAddress
+   *
+   * @return bool
+   */
+  static public function validateEmailAddress(string $emailAddress): bool {
+    return (bool) filter_var($emailAddress, FILTER_VALIDATE_EMAIL);
+  }
+
+  /**
+   * Validate custom fields.
+   *
+   * @param array $fields
+   * @param \CRM_Core_Form $form
+   * @param array $errors
+   *
+   * @return bool
+   * @throws \CRM_Core_Exception
+   * @throws \Civi\API\Exception\UnauthorizedException
+   * @throws \Exception
+   */
+  static public function validateCustomFields(array $fields, \CRM_Core_Form $form, array &$errors): bool {
+    $result = TRUE;
+    $customFields = self::getCustomFields();
+    $customValues = [];
+
+    // Determine the entity type
+    if ($form instanceof \CRM_Group_Form_Edit) {
+      $entityId = $form->getEntityId();
+      $type = self::GROUP_MAILING_LIST;
+    }
+    elseif ($form instanceof \CRM_Event_Form_ManageEvent_EventInfo) {
+      $entityId = $form->getEventID(); // It's things like this...
+      $type = self::EVENT_MAILING_LIST;
+    }
+    else {
+      throw new \Exception('Unknown form type');
+    }
+
+    // Translate custom field names
+    foreach ($customFields as $customField) {
+      $fieldId = $customField['id'];
+      $fieldName = "custom_$fieldId";
+      $getCustomField = function() use ($fields, $fieldName) {
+        foreach ($fields as $key => $value) {
+          if (preg_match("/^$fieldName" . "_.*/", $key)) {
+            return ['field_name' => $key, 'value' => $value];
+          }
+        }
+        return NULL;
+      };
+      $customValues[$customField['name']] = $getCustomField();
+    }
+
+    // Validate e-mail address
+    if (!empty($customValues['E_mail_address'])) {
+      if (!self::validateEmailAddress($customValues['E_mail_address']['value'])) {
+        $errors[$customValues['E_mail_address']['field_name']] = E::ts('Invalid e-mail address');
+        $result = FALSE;
+      }
+    }
+
+    // E-mail address must be unique for groups and events
+    if (!empty($customValues['E_mail_address']['value'])) {
+      $emailAddress = $customValues['E_mail_address']['value'];
+      $groupId = self::GROUP_MAILING_LIST === $type ? $entityId : NULL;
+      $eventId = self::EVENT_MAILING_LIST === $type ? $entityId : NULL;
+
+      // Check if the e-mail address is already in use for a group
+      $existingGroup = GroupMailingList::getByEmailAddress($emailAddress, $groupId);
+      if ($existingGroup) {
+        $errors[$customValues['E_mail_address']['field_name']] =
+          E::ts("E-mail address '%1' already in use for group '%2'",
+            [
+              1 => $customValues['E_mail_address']['value'],
+              2 => $existingGroup->getTitle(),
+            ]);
+        $result = FALSE;
+      }
+
+      // Check if the e-mail address is already in use for an event
+      $existingEvent = EventMailingList::getByEmailAddress($emailAddress, $eventId);
+      if ($existingEvent) {
+        $errors[$customValues['E_mail_address']['field_name']] =
+          E::ts("E-mail address '%1' already in use for event '%2'",
+            [
+              1 => $customValues['E_mail_address']['value'],
+              2 => $existingEvent->getTitle(),
+            ]);
+        $result = FALSE;
+      }
+    }
+
+    return $result;
+  }
+
+  /**
+   * Get mailing lists by its e-mail address.
+   *
+   * @param string $emailAddress
+   * @param int|null $excludeId ID to exclude from the search
+   *
+   * @return ?self
+   * @throws \CRM_Core_Exception
+   * @throws \Civi\API\Exception\UnauthorizedException
+   */
+  static public function getByEmailAddress(string $emailAddress, int $excludeId = NULL): ?self {
+    $result = static::RELATED_CLASS::get()
+      ->addSelect('*')
+      ->addSelect('custom.*')
+      ->addWhere(static::CUSTOM_GROUP_NAME . '.E_mail_address', '=', $emailAddress);
+    // If $excludeId is set, exclude it from the search
+    if ($excludeId) {
+      $result->addWhere('id', '!=', $excludeId);
+    }
+    $mailingListData = $result->execute()->first();
+    return !empty($mailingListData) ? new static($mailingListData) : NULL;
+  }
+
+  /**
+   * Returns the related entity.
+   *
+   * @return array
+   */
+  protected abstract function getEntity(): array;
+
+  /**
+   * Set the related entity.
+   *
+   * @param array $value
+   *
+   * @return void
+   */
+  protected abstract function setEntity(array $value): void;
+
+  /**
+   * Check if the group is a mailing list.
+   *
+   * @return bool
+   */
+  public function isMailingList(): bool {
+    return (bool) $this->getEntity()[static::CUSTOM_GROUP_NAME . '.Enable_mailing_list'];
+  }
+
+  /**
+   * Check if the group is an AD mailing list.
+   *
+   * @return bool
+   */
+  public function isADGroup(): bool {
+    return FALSE;
+  }
+
+  /**
+   * Mark changes to be saved via the `save()` method.
+   *
+   * @param array $values
+   */
+  protected function update(array $values): void {
+    $this->updateData += $values;
+  }
+
+  /**
+   * Saves the changes marked using the `update()` method.
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function save(): void {
+    if (empty($this->updateData)) {
+      return;
+    }
+    try {
+      static::RELATED_CLASS::update()
+        ->setValues($this->updateData)
+        ->addWhere('id', '=', $this->getEntity()['id'])
+        ->execute();
+    }
+    catch (\Exception $e) {
+      $type = static::RELATED_TYPE;
+      throw new MailinglistException(
+        "Could not update $type with id '{$this->getEntity()['id']}'\n$e",
+        MailinglistException::ERROR_CODE_UPDATE_ENTITY_FAILED
+      );
+    }
+  }
+
+  /**
+   * Get the e-mail address of the mailing list.
+   *
+   * @return string
+   */
+  public function getEmailAddress(): string {
+    return $this->getEntity()[static::CUSTOM_GROUP_NAME . '.E_mail_address'];
+  }
+
+  /**
+   * Get the title of the mailing list.
+   *
+   * @return string
+   */
+  public function getTitle(): string {
+    return $this->getEntity()['title'];
+  }
+
+  /**
+   * Update the e-mail address of the mailing list.
+   *
+   * @param string $emailAddress
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function updateEmailAddress(string $emailAddress): void {
+    // Validate email address
+    if (ADGroupMailingList::validateEmailAddress($emailAddress)) {
+      throw new MailinglistException(
+        E::ts("Invalid e-mail address '%1'", [1 => $emailAddress]),
+        MailinglistException::ERROR_CODE_INVALID_EMAIL_ADDRESS
+      );
+    }
+    try {
+      static::update([
+        static::CUSTOM_GROUP_NAME . '.E_mail_address' => $emailAddress,
+      ]);
+    }
+    catch (MailinglistException) {
+      $type = static::RELATED_TYPE;
+      throw new MailinglistException(
+        "Could not update e-mail address for $type with id '{$this->getEntity()['id']}'",
+        MailinglistException::ERROR_CODE_UPDATE_EMAIL_ADDRESS_FAILED
+      );
+    }
+  }
+
+  /**
+   * Get the location type name for the mailing list.
+   *
+   * Note: Use the getLocationTypes() from Utils which retrieves an array of
+   * location type IDs and names from cache or database.
+   *
+   * @return string
+   */
+  public static function getLocationTypeName(): string {
+    return static::LOCATION_TYPE;
+  }
+
+  /**
+   * Get a list of recipients.
+   *
+   * @return array E-mail addresses ['john.doe@example.org', ...]
+   */
+  public abstract function getRecipients(): array;
+
+  /**
+   * Returns this mailing lists id.
+   *
+   * @return int
+   */
+  public function getId(): int {
+    return (int) $this->getEntity()['id'];
+  }
+
+  /**
+   * Try to find an existing contact by the given parameters.
+   * First tries to find the contact by the SID, then by the e-mail address
+   * and finally by the first and last name (if restricting tags are set).
+   *
+   * @param string|null $firstName
+   * @param string|null $lastName
+   * @param string|null $email
+   * @param string|null $sid
+   *
+   * @return array|null ['contact' => $contact, 'found_by' => $found_by]
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  protected function findExistingContact(
+    string $firstName = NULL,
+    string $lastName = NULL,
+    string $email = NULL,
+    string $sid = NULL,
+  ): ?array {
+
+    // Get the tags to restrict the search to.
+    $tags = \Civi::settings()->get(E::SHORT_NAME . '_ad_contact_tags');
+
+    // Prepare the get call for reuse.
+    $prepareGetEmail = function () use ($tags,) {
+      $selectFields = [
+        'id',
+        'first_name',
+        'last_name',
+        'email.email',
+        GroupMailingList::CUSTOM_GROUP_NAME . '.Active_Directory_SID'
+      ];
+      $call =  \Civi\Api4\Contact::get()
+        ->addSelect(...$selectFields)
+        ->addJoin('Email AS email', 'LEFT', ['id', '=', 'email.contact_id']);
+      if ($tags) {
+        $call->addJoin('EntityTag AS entity_tag', 'LEFT',
+          ['id', '=', 'entity_tag.entity_id'],
+          ['entity_tag.entity_table', '=', 'civicrm_contact'],
+          ['entity_tag.tag_id', 'IN', $tags]
+        );
+      }
+      return $call;
+    };
+
+    // Try to find the contact by the SID.
+    try {
+      $contact = $prepareGetEmail()
+        ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Active_Directory_SID', '=', $sid)
+        ->execute()
+        ->getArrayCopy();
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        "Could not get contact by SID '$sid': $e",
+        MailinglistException::ERROR_CODE_GET_CONTACT_FAILED,
+      );
+    }
+    if (count($contact) > 1) {
+      throw new MailinglistException(
+        "Multiple contacts with the same SID '$sid' found",
+        MailinglistException::ERROR_CODE_MULTIPLE_CONTACTS_FOUND
+      );
+    }
+    elseif (count($contact) === 1) {
+      return ['contact' => array_pop($contact), 'found_by' => 'sid'];
+    }
+
+    // Try fo find the contact by the e-mail address.
+    try {
+      $contact = $prepareGetEmail()
+        ->addWhere('email', '=', $email)
+        ->execute()
+        ->getArrayCopy();
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        "Could not get contact by e-mail address '$email': $e",
+        MailinglistException::ERROR_CODE_GET_CONTACT_FAILED,
+      );
+    }
+    if (count($contact) > 1) {
+      throw new MailinglistException(
+        "Multiple contacts with the same e-mail address '$email' found",
+        MailinglistException::ERROR_CODE_MULTIPLE_CONTACTS_FOUND
+      );
+    }
+    elseif (count($contact) === 1) {
+      return ['contact' => array_pop($contact), 'found_by' => 'email'];
+    }
+
+    // Try to find the contact by the first and last name and only if the tags are set.
+    if ($tags) {
+      try {
+        $contact = $prepareGetEmail()
+          ->addWhere('first_name', '=', $firstName)
+          ->addWhere('last_name', '=', $lastName)
+          ->execute()
+          ->getArrayCopy();
+      }
+      catch (\Exception $e) {
+        throw new MailinglistException(
+          "Could not get contact by first and last name '$firstName $lastName': $e",
+          MailinglistException::ERROR_CODE_GET_CONTACT_FAILED,
+        );
+      }
+      if (count($contact) > 1) {
+        throw new MailinglistException(
+          "Multiple contacts with the same first and last name found",
+          MailinglistException::ERROR_CODE_MULTIPLE_CONTACTS_FOUND
+        );
+      }
+      elseif (count($contact) === 1) {
+        return ['contact' => array_pop($contact), 'found_by' => 'names'];
+      }
+    }
+
+    // If no contact was found, return NULL.
+    return NULL;
+  }
+}

Civi/Mailinglistsync/EventMailingList.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use CRM_Mailinglistsync_ExtensionUtil as E;
+use Civi\Api4\Event;
+
+class EventMailingList extends BaseMailingList {
+
+  public const CUSTOM_GROUP_NAME = 'Event_Mailing_List';
+
+  public const LOCATION_TYPE = 'Event_Mailing_List_Address';
+
+  protected const RELATED_CLASS = Event::class;
+  protected const RELATED_TYPE = 'event';
+
+  protected array $event;
+
+  /**
+   * Returns the related event.
+   *
+   * @return array
+   */
+  protected function getEntity(): array {
+    return $this->event;
+  }
+
+  /**
+   * Set the related event.
+   *
+   * @param array $value
+   *
+   * @return void
+   */
+  protected function setEntity(array $value): void {
+    $this->event = $value;
+  }
+
+  public function getRecipients(): array {
+    // TODO: Implement getRecipients() method.
+  }
+
+  /**
+   * Get a list of participants status that are enabled for the mailing list.
+   *
+   * @return array
+   */
+  public static function getEnabledParticipantStatus(): array {
+    return MailingListSettings::get(E::SHORT_NAME . '_participant_status');
+  }
+
+  public static function create(array $values): BaseMailingList {
+    // TODO: Implement create() method.
+  }
+
+}

Civi/Mailinglistsync/Exceptions/BaseException.php

@@ -0,0 +1,53 @@
+<?php
+
+namespace Civi\Mailinglistsync\Exceptions;
+
+use CRM_Mailinglistsync_ExtensionUtil as E;
+
+/**
+ * A simple custom exception class that indicates a problem within a class
+ * of the de.propeace.mailinglist extension.
+ */
+class BaseException extends \CRM_Core_Exception {
+
+  /**
+   * @var int|string
+   */
+  protected $code;
+
+  protected string $log_message;
+
+  /**
+   * BaseException Constructor
+   *
+   * @param string $message
+   *  Error message
+   * @param string $error_code
+   *  A meaningful error code
+   */
+  public function __construct(string $message = '', string $error_code = '') {
+    parent::__construct($message, 1);
+    $this->log_message = !empty($message) ? E::LONG_NAME . ': ' . $message : '';
+    $this->code = $error_code;
+  }
+
+  /**
+   * Returns the error message, but with the extension name prefixed.
+   *
+   * @return string
+   */
+  public function getLogMessage(): string {
+    return $this->log_message;
+  }
+
+  /**
+   * Returns the error code.
+   *
+   * @return string
+   */
+  public function getErrorCode(): string {
+    return $this->code;
+  }
+
+}
+

Civi/Mailinglistsync/Exceptions/MailinglistException.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Civi\Mailinglistsync\Exceptions;
+
+/**
+ * A simple custom error indicating a problem with the validation of the
+ * BaseMailingList and its subclasses.
+ */
+class MailinglistException extends BaseException {
+
+  public const ERROR_CODE_PERMISSION_DENIED = 'permission_denied';
+  public const ERROR_CODE_UPDATE_EMAIL_ADDRESS_FAILED = 'update_email_address_failed';
+  public const ERROR_CODE_DELETE_EMAIL_ADDRESS_FAILED = 'delete_email_address_failed';
+  public const ERROR_CODE_GET_RECIPIENTS_FAILED = 'get_recipients_failed';
+  public const ERROR_CODE_GET_LOCATION_TYPES_FAILED = 'get_location_types_failed';
+  public const ERROR_CODE_INVALID_CLASS = 'invalid_class';
+  public const ERROR_CODE_INVALID_EMAIL_ADDRESS = 'invalid_email_address';
+  public const ERROR_CODE_GET_GROUP_MAILING_LISTS_FAILED = 'get_group_mailing_lists_failed';
+  public const ERROR_CODE_GET_AD_GROUP_MAILING_LISTS_FAILED = 'get_group_mailing_lists_failed';
+  public const ERROR_CODE_GET_EVENT_MAILING_LISTS_FAILED = 'get_event_mailing_lists_failed';
+  public const ERROR_CODE_GET_CONTACT_FAILED = 'get_contact_failed';
+  public const ERROR_CODE_CREATE_CONTACT_FAILED = 'create_contact_failed';
+  public const ERROR_CODE_MULTIPLE_CONTACTS_FOUND = 'multiple_contacts_found';
+  public const ERROR_CODE_INVALID_LOCATION_TYPE = 'invalid_location_type';
+  public const ERROR_CODE_GROUP_CREATION_FAILED = 'group_creation_failed';
+  public const ERROR_CODE_UPDATE_ENTITY_FAILED = 'update_entity_failed';
+  public const ERROR_CODE_MULTIPLE_RECIPIENTS = 'multiple_recipients';
+
+
+
+}
+

Civi/Mailinglistsync/Exceptions/MailinglistSyncException.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Civi\Mailinglistsync\Exceptions;
+
+/**
+ * A simple custom error indicating a problem with the validation of the
+ * synchronization of mailing lists.
+ */
+class MailinglistSyncException extends BaseException {
+
+  public const ERROR_CODE_UNSERIALIZE_SINGLETON = 'unserialize_singleton';
+
+}
+

Civi/Mailinglistsync/GroupMailingList.php

@@ -0,0 +1,157 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use Civi\Api4\Contact;
+use Civi\Api4\Group;
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+
+class GroupMailingList extends BaseMailingList {
+
+  public const CUSTOM_GROUP_NAME = 'Group_Mailing_List';
+
+  public const LOCATION_TYPE = 'Mailing_List_Address';
+
+  protected const RELATED_CLASS = Group::class;
+  protected const RELATED_TYPE = 'group';
+
+  protected array $group;
+
+  /**
+   * Returns the related group.
+   *
+   * @return array
+   */
+  protected function getEntity(): array {
+    return $this->group;
+  }
+
+  /**
+   * Create a new GroupMailingList.
+   *
+   * @param string $title
+   * @param string $description
+   * @param string $email
+   * @param string|null $sid
+   *
+   * @return \Civi\Mailinglistsync\GroupMailingList
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public static function createGroup(
+    string $title,
+    string $description,
+    string $email,
+    string $sid = NULL
+  ): self {
+    try {
+      $request = \Civi\Api4\Group::create()
+        ->addValue('title', $title)
+        ->addValue('description', $description)
+        ->addValue(static::CUSTOM_GROUP_NAME . '.Email', $email)
+        ->addValue('is_active', 1);
+
+      // If the group is an AD group, add the AD SID
+      if (!empty($values['sid'])) {
+        $request->addValue(static::CUSTOM_GROUP_NAME . '.SID', $values['sid']);
+      }
+      return new self($request->execute()->getArrayCopy()['id']);
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        "Could not create group\n$e",
+        MailinglistException::ERROR_CODE_GROUP_CREATION_FAILED
+      );
+    }
+  }
+
+  /**
+   * Set the related group.
+   *
+   * @param array $value
+   */
+  protected function setEntity(array $value): void {
+    $this->group = $value;
+  }
+
+  /**
+   * Check if the group is an AD mailing list.
+   * @return bool
+   */
+  public function isADGroup(): bool {
+    return !empty($this->group[static::CUSTOM_GROUP_NAME . '.Active_Directory_UUID']);
+  }
+
+  /**
+   * Get a list of recipients indexed by email address.
+   *
+   * @return array List of recipients (MailListRecipient)
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function getRecipients(): array {
+    try {
+      $recipientData = Contact::get()
+        ->addSelect('id', 'first_name', 'last_name', 'email.email', 'Active_Directory.SID')
+        ->addJoin('Email AS email', 'INNER', ['id', '=', 'email.contact_id'])
+        ->addJoin('GroupContact AS group_contact', 'INNER', ['id', '=', 'group_contact.contact_id'])
+        ->addJoin('LocationType AS location_type', 'INNER', ['email.location_type_id', '=', 'location_type.id'])
+        ->addWhere('group_contact.group_id', '=', $this->group['id'])
+        ->addWhere('location_type.name', '=', static::LOCATION_TYPE)
+        ->addGroupBy('id')
+        ->execute()
+        ->getArrayCopy();
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        "Could not get recipients for group with id '{$this->group['id']}'\n$e",
+        MailinglistException::ERROR_CODE_GET_RECIPIENTS_FAILED
+      );
+    }
+
+    $recipients = [];
+    foreach ($recipientData as $recipient) {
+      $recipients[$recipient['email.email']] = new MailingListRecipient(
+        contact_id: $recipient['id'],
+        first_name: $recipient['first_name'],
+        last_name: $recipient['last_name'],
+        email: $recipient['email.email'],
+        sid: $recipient['Active_Directory.SID'],
+      );
+    }
+
+    return $recipients;
+  }
+
+  /**
+   * Update the title of the group.
+   *
+   * @param string $title
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function updateGroupTitle(string $title): void {
+    $this->update(['title' => $title]);
+  }
+
+  /**
+   * Update the description of the group.
+   *
+   * @return string
+   */
+  public function getGroupDescription(): string {
+    return $this->group['description'];
+  }
+
+  /**
+   * Update the description of the group.
+   *
+   * @param string $description
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function updateGroupDescription(string $description): void {
+    $this->update(['description' => $description]);
+  }
+
+}

Civi/Mailinglistsync/MailingListManager.php

@@ -0,0 +1,98 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use CRM_Mailinglistsync_ExtensionUtil as E;
+
+class MailingListManager {
+
+  /**
+   * Is the mailing list enabled?
+   *
+   * @var bool
+   */
+  private bool $enabled;
+
+  /**
+   * Is logging enabled?
+   *
+   * @var bool
+   */
+  private mixed $logging;
+
+  /**
+   * Host of the mlmmj server
+   *
+   * @var string
+   */
+  private string $mlmmjHost;
+
+  /**
+   * Token for the mlmmj server
+   *
+   * @var string
+   */
+  private string $mlmmjToken;
+
+  /**
+   * Port of the mlmmj server
+   *
+   * @var int
+   */
+  private int $mlmmjPort;
+
+  /**
+   * Host of the dovecot server
+   *
+   * @var string|mixed
+   */
+  private string $dovecotHost;
+
+  /**
+   * Token for the dovecot server
+   *
+   * @var string|mixed
+   */
+  private string $dovecotToken;
+
+  /**
+   * Port of the dovecot server
+   *
+   * @var int
+   */
+  private int $dovecotPort;
+
+  /**
+   * Constructor.
+   *
+   * @throws \Exception
+   */
+  function __construct() {
+    // Load settings
+    $settings = MailingListSettings::get();
+    $this->enabled = $settings[E::SHORT_NAME . '_enable'] ?? FALSE;
+    $this->logging = $settings[E::SHORT_NAME . '_logging'] ?? FALSE;
+    $this->mlmmjHost = $settings[E::SHORT_NAME . '_mlmmj_host'] ??
+      throw new \Exception('No mlmmj host set');
+    $this->mlmmjToken = $settings[E::SHORT_NAME . '_mlmmj_token'] ??
+      throw new \Exception('No mlmmj token set');
+    $this->mlmmjPort = $settings[E::SHORT_NAME . '_mlmmj_port'] ?? 443;
+    $this->dovecotHost = $settings[E::SHORT_NAME . '_dovecot_host'] ??
+      throw new \Exception('No dovecot host set');
+    $this->dovecotToken = $settings[E::SHORT_NAME . '_dovecot_token'] ??
+      throw new \Exception('No dovecot token set');
+    $this->dovecotPort = $settings[E::SHORT_NAME . '_dovecot_port'] ?? 443;
+  }
+
+  function createEmailAddress(string $emailAddress) {} // TODO
+
+  function deleteEmailAddress(string $emailAddress) {} // TODO
+
+  function createMailingList(BaseMailingList $mailingList) {} // TODO
+
+  function deleteMailingList(BaseMailingList $mailingList) {} // TODO
+
+  function updateMailingList(BaseMailingList $mailingList) {} // TODO
+
+
+}

Civi/Mailinglistsync/MailingListRecipient.php

@@ -0,0 +1,335 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+use CRM_Mailinglistsync_ExtensionUtil as E;
+
+class MailingListRecipient {
+
+  protected int $contactId;
+
+  protected string $firstName;
+
+  protected string $lastName;
+
+  protected string $email;
+
+  protected string $sid;
+
+  /**
+   * Data to be updated. Use the `save()` method to apply the update.
+   *
+   * @var array
+   */
+  private $updateData;
+
+  /**
+   * Constructor.
+   *
+   * @param int $contact_id
+   * @param string $first_name
+   * @param string $last_name
+   * @param string $email
+   * @param string|null $sid
+   */
+  public function __construct(
+    int $contact_id,
+    string $first_name,
+    string $last_name,
+    string $email,
+    string $sid = NULL,
+  ) {
+    $this->contactId = $contact_id;
+    $this->firstName = $first_name;
+    $this->lastName = $last_name;
+    $this->email = $email;
+    $this->sid = $sid;
+    $this->updateData = [];
+  }
+
+//  /**
+//   * Get or create a contact.
+//   *
+//   * @param string $fistName
+//   * @param string $lastName
+//   * @param string $email
+//   * @param string $locationType The location type of the email address
+//   *
+//   * @return \Civi\Mailinglistsync\MailingListRecipient
+//   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+//   */
+//  public static function getOrCreate(
+//    string $fistName,
+//    string $lastName,
+//    string $email,
+//    string $locationType,
+//  ): self {
+//
+//    // Verify location type
+//    $locationTypes = [
+//      GroupMailingList::LOCATION_TYPE,
+//      ADGroupMailingList::LOCATION_TYPE,
+//      EventMailingList::LOCATION_TYPE,
+//    ];
+//    if (!in_array($locationType, $locationTypes)) {
+//      throw new MailinglistException(
+//        E::ts('Invalid location type'),
+//        MailinglistException::ERROR_CODE_INVALID_LOCATION_TYPE,
+//      );
+//    }
+//
+//    // Try to get contact
+//    try {
+//      $contact = \Civi\Api4\Contact::get()
+//        ->addSelect('*', 'location_type.*')
+//        ->addJoin('Email AS email', 'LEFT', ['id', '=', 'email.contact_id'])
+//        ->addJoin('LocationType AS location_type', 'LEFT', ['email.location_type_id', '=', 'location_type.id'])
+//        ->addWhere('email.email', '=', $email)
+//        ->addWhere('location_type.name', '=', $locationType)
+//        ->execute()
+//        ->first();
+//    }
+//    catch (\Exception $e) {
+//      throw new MailinglistException(
+//        E::ts('Failed to get contact'),
+//        MailinglistException::ERROR_CODE_GET_CONTACT_FAILED,
+//      );
+//    }
+//
+//    // Create contact if it does not exist
+//    if (empty($contact)) {
+//      try {
+//        $contact = \Civi\Api4\Contact::create(FALSE)
+//          ->addValue('contact_type', 'Individual')
+//          ->addValue('first_name', $fistName)
+//          ->addValue('last_name', $lastName)
+//          ->setChain([
+//            'Email.create',
+//            \Civi\Api4\Email::create(FALSE)
+//              ->addValue('contact_id', '$id')
+//              ->addValue('email', $email)
+//              ->addValue('location_type_id.name', $locationType),
+//          ])
+//          ->execute()
+//          ->first();
+//        array_pop($contact['Email.create']);
+//      }
+//      catch (\Exception $e) {
+//        throw new MailinglistException(
+//          E::ts('Failed to create contact'),
+//          MailinglistException::ERROR_CODE_CREATE_CONTACT_FAILED,
+//        );
+//      }
+//    }
+//
+//    return new static(contact: $contact, email: $email);
+//  }
+
+  /**
+   * Create a new contact and return the recipient.
+   *
+   * @param string $firstName
+   * @param string $lastName
+   * @param string $email
+   * @param string $sid
+   *
+   * @return \Civi\Mailinglistsync\MailingListRecipient
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public static function createContact(
+    string $firstName,
+    string $lastName,
+    string $email,
+    string $sid,
+  ): self {
+
+    // Try to create a new contact
+    try {
+      $contact = \Civi\Api4\Contact::create(FALSE)
+        ->addValue('contact_type', 'Individual')
+        ->addValue('first_name', $firstName)
+        ->addValue('last_name', $lastName)
+        ->setChain([
+          'Email.create',
+          \Civi\Api4\Email::create(FALSE)
+            ->addValue('email', $email)
+            ->addValue('location_type_id.name', 'Main'),
+        ])
+        ->execute();
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts("Failed to create contact: {$e->getMessage()}"),
+        MailinglistException::ERROR_CODE_CREATE_CONTACT_FAILED,
+      );
+    }
+
+    return new static(
+      contact_id: $contact['id'],
+      first_name: $firstName,
+      last_name: $lastName,
+      email: $email,
+      sid: $sid,
+    );
+
+  }
+
+  /**
+   * Get a list of group mailing lists the contact is subscribed to.
+   *
+   * @return array
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function getMailingLists(): array {
+    $mailingLists = [];
+    try {
+      $groups = \Civi\Api4\GroupContact::get()
+        ->addSelect('group_id')
+        ->addWhere('contact_id', '=', $this->getContactId())
+        ->addWhere('status', '=', 'Added')
+        ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Enable_mailing_list', '=', TRUE)
+        ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Active_Directory_SID', 'IS EMPTY')
+        ->execute()
+        ->getArrayCopy();
+    } catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts('Failed to get group mailing lists'),
+        MailinglistException::ERROR_CODE_GET_GROUP_MAILING_LISTS_FAILED,
+      );
+    }
+
+    foreach ($groups as $group) {
+      $mailingList = new GroupMailingList($group['group_id']);
+      if ($mailingList->isADGroup()) {
+        $mailingList = new ADGroupMailingList($group['group_id']); ;
+      }
+      $mailingLists[] = $mailingList;
+    }
+
+    return $mailingLists;
+  }
+
+  /**
+   * Get a list of AD group mailing lists the contact is subscribed to.
+   *
+   * @return array
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function getAdMailingLists(): array {
+    $mailingLists = [];
+    try {
+      $groups = \Civi\Api4\GroupContact::get()
+        ->addSelect('group_id')
+        ->addWhere('contact_id', '=', $this->getContactId())
+        ->addWhere('status', '=', 'Added')
+        ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Enable_mailing_list', '=', TRUE)
+        ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Active_Directory_SID', 'IS NOT EMPTY')
+        ->execute()
+        ->getArrayCopy();
+    } catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts('Failed to get AD group mailing lists'),
+        MailinglistException::ERROR_CODE_GET_AD_GROUP_MAILING_LISTS_FAILED,
+      );
+    }
+
+    foreach ($groups as $group) {
+      $mailingList = new GroupMailingList($group['group_id']);
+      if ($mailingList->isADGroup()) {
+        $mailingList = new ADGroupMailingList($group['group_id']); ;
+      }
+      $mailingLists[] = $mailingList;
+    }
+
+    return $mailingLists;
+  }
+
+  /**
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function getEventMailingLists(): array {
+    $mailingLists = [];
+    try {
+    $groups = \Civi\Api4\Participant::get()
+      ->addSelect('event_id')
+      ->addWhere('contact_id', '=', $this->getContactId())
+      ->addWhere('status_id', 'IN', EventMailingList::getEnabledParticipantStatus())
+      ->addWhere(GroupMailingList::CUSTOM_GROUP_NAME . '.Enable_mailing_list', '=', TRUE)
+      ->execute()
+      ->getArrayCopy();
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts('Failed to get event mailing lists'),
+        MailinglistException::ERROR_CODE_GET_EVENT_MAILING_LISTS_FAILED,
+      );
+    }
+    foreach ($groups as $group) {
+      $mailingList = new EventMailingList($group['group_id']);
+      $mailingLists[] = $mailingList;
+    }
+
+    return $mailingLists;
+  }
+
+  public function getContactId(): int {
+    return $this->contactId;
+  }
+
+  public function getFirstName(): string {
+    return $this->firstName;
+  }
+
+  public function getLastName(): string {
+    return $this->lastName;
+  }
+
+  public function getEmail(): string {
+    return $this->email;
+  }
+
+  public function getSid(): string {
+    return $this->sid;
+  }
+
+  public function setFirstName(string $firstName): void {
+    $this->updateData += ['first_name' => $firstName];
+  }
+
+  public function setLastName(string $lastName): void {
+    $this->updateData += ['last_name' => $lastName];
+  }
+
+  public function setEmail(string $email): void {
+    $this->updateData += ['email' => $email];
+  }
+
+  public function setSid(string $sid): void {
+    $this->updateData += ['sid' => $sid];
+  }
+
+  /**
+   * Save the changes marked using the setter methods.
+   *
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public function save(): void {
+    if (empty($this->updateData)) {
+      return;
+    }
+
+    try {
+      \Civi\Api4\Contact::update()
+        ->setValues($this->updateData)
+        ->addWhere('id', '=', $this->getContactId())
+        ->execute();
+    } catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts("Failed to update contact: {$e->getMessage()}"),
+        MailinglistException::ERROR_CODE_UPDATE_ENTITY_FAILED,
+      );
+    }
+  }
+
+}

Civi/Mailinglistsync/MailingListSettings.php

@@ -0,0 +1,126 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use Civi\Authx\None;
+use CRM_Mailinglistsync_ExtensionUtil as E;
+
+class MailingListSettings {
+
+  public const SETTINGS = [
+    E::SHORT_NAME . '_enable' => [
+      'data_type' => 'boolean',
+    ],
+    E::SHORT_NAME . '_logging' => [
+      'data_type' => 'boolean',
+    ],
+    E::SHORT_NAME . '_mlmmj_host' => [
+      'data_type' => 'string',
+    ],
+    E::SHORT_NAME . '_mlmmj_token' => [
+      'data_type' => 'string',
+    ],
+    E::SHORT_NAME . '_mlmmj_port' => [
+      'data_type' => 'integer',
+      'default_value' => 443,
+    ],
+    E::SHORT_NAME . '_dovecot_host' => [
+      'data_type' => 'string',
+    ],
+    E::SHORT_NAME . '_dovecot_token' => [
+      'data_type' => 'string',
+    ],
+    E::SHORT_NAME . '_dovecot_port' => [
+      'data_type' => 'integer',
+      'default_value' => 443,
+    ],
+    E::SHORT_NAME . '_participant_status' => [
+      'data_type' => 'array',
+    ],
+    E::SHORT_NAME . '_ad_contact_tags' => [
+      'data_type' => 'array',
+    ],
+  ];
+
+  /**
+   * Stores a setting in Civi::settings
+   *
+   * @param array $settings
+   * Expects an array with key => value for the setting
+   */
+  public static function set(array $settings): void {
+    // Remove possibly illegal data from settings
+    $settings = array_intersect_key($settings, self::SETTINGS);
+
+    // Cast settings to the correct datatype
+    foreach ($settings as $key => $value) {
+      if ($value !== '') {
+        settype($settings[$key], self::SETTINGS[$key]['data_type']);
+      } else {
+        $settings[$key] = NULL;
+      }
+    }
+
+    \Civi::settings()->add($settings);
+  }
+
+  /**
+   * Returns a specific value of a setting if the key is passed as parameter.
+   * Else all settings will be returned as associative array.
+   *
+   * @param null $key
+   * The name of the setting or NULL
+   *
+   * @return array|mixed|null
+   */
+  public static function get($key = NULL): mixed {
+    if (!is_null($key)) {
+      return \Civi::settings()->get($key);
+    }
+    else {
+      $settings = [];
+      foreach (array_keys(self::SETTINGS) as $key) {
+        $settings[$key] = \Civi::settings()->get($key) ?? self::SETTINGS[$key]['default_value'] ?? NULL;
+      }
+      return $settings;
+    }
+  }
+
+  /**
+   * Validates the settings.
+   *
+   * @param array $values
+   * @param array $errors
+   *
+   * @return void
+   */
+  public static function validate(array $values, array &$errors): void {
+    // Validate url if synchronization is enabled
+    $url = $values[E::SHORT_NAME . '_mailinglist_mlmmj_host'];
+    if (!empty($values[E::SHORT_NAME . '_mailinglist_mlmmj_enable']) && !filter_var($url, FILTER_VALIDATE_URL)) {
+      $errors[E::SHORT_NAME . '_mailinglist_mlmmj_host'] = E::ts('Invalid URL');
+    }
+
+    // Validate port if synchronization is enabled and port is set
+    $port = $values[E::SHORT_NAME . '_mailinglist_mlmmj_port'] ?? NULL;
+    if (!empty($values[E::SHORT_NAME . '_mailinglist_mlmmj_enable']) && !empty($port)) {
+      if (is_numeric($port)) {
+        $errors[E::SHORT_NAME . '_mailinglist_mlmmj_port'] = E::ts('Port must be a number');
+      }
+      if ($port < 1 || $port > 65535) {
+        $errors[E::SHORT_NAME . '_mailinglist_mlmmj_port'] = E::ts('Port must be between 1 and 65535');
+      }
+    }
+
+    // Require host and token if mlmmj is enabled
+    if (!empty($values[E::SHORT_NAME . '_mailinglist_mlmmj_enable'])) {
+      if (empty($values[E::SHORT_NAME . '_mailinglist_mlmmj_host'])) {
+        $errors[E::SHORT_NAME . '_mailinglist_mlmmj_host'] = E::ts('Host is required');
+      }
+      if (empty($values[E::SHORT_NAME . '_mailinglist_mlmmj_token'])) {
+        $errors[E::SHORT_NAME . '_mailinglist_mlmmj_token'] = E::ts('Token is required');
+      }
+    }
+  }
+
+}

Civi/Mailinglistsync/QueueHelper.php

@@ -0,0 +1,177 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use CRM_Mailinglistsync_ExtensionUtil as E;
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+use Civi\Mailinglistsync\Exceptions\MailinglistSyncException;
+use CRM_Queue_Queue;
+
+class QueueHelper {
+
+  /**
+   * Singleton instances.
+   *
+   * @var array
+   */
+  private static array $instances = [];
+
+  private CRM_Queue_Queue $groupQueue;
+  private CRM_Queue_Queue $eventQueue;
+  private CRM_Queue_Queue $emailQueue;
+
+  private array $groups;
+
+  private array $events;
+
+  private array $emails;
+
+  /**
+   * Protect singleton from being instantiated.
+   */
+  protected function __construct() {
+    // Get queues
+    $this->groupQueue = \Civi::queue(
+      'propeace-mailinglist-group-queue', [
+      'type' => 'SqlParallel',
+      'is_autorun' => FALSE,
+      'reset' => FALSE,
+      'error' => 'drop',
+    ]);
+    $this->eventQueue = \Civi::queue(
+      'propeace-mailinglist-group-queue', [
+      'type' => 'SqlParallel',
+      'is_autorun' => FALSE,
+      'reset' => FALSE,
+      'error' => 'drop',
+    ]);
+    $this->emailQueue = \Civi::queue(
+      'propeace-mailinglist-group-queue', [
+      'type' => 'SqlParallel',
+      'is_autorun' => FALSE,
+      'reset' => FALSE,
+      'error' => 'drop',
+    ]);
+  }
+
+  /**
+   * Protect singleton from being cloned.
+   */
+  protected function __clone() { }
+
+  /**
+   * Protect unserialize method to prevent cloning of the instance.
+   * @throws \Exception
+   */
+  public function __wakeup()
+  {
+    throw new MailinglistSyncException(
+      "Cannot unserialize a singleton.",
+      MailinglistSyncException::ERROR_CODE_UNSERIALIZE_SINGLETON
+    );
+  }
+
+  /**
+   * Returns the singleton instance.
+   *
+   * @return \Civi\Mailinglistsync\QueueHelper
+   */
+  public static function getInstance(): QueueHelper
+  {
+    $cls = static::class;
+    if (!isset(self::$instances[$cls])) {
+      self::$instances[$cls] = new static();
+      \Civi::log()->debug(E::LONG_NAME . ": Created new instance of $cls");
+    }
+
+    return self::$instances[$cls];
+  }
+
+  /**
+   * Getter for the group queue.
+   *
+   * @return \CRM_Queue_Queue
+   */
+  public function getGroupQueue(): CRM_Queue_Queue {
+    return $this->groupQueue;
+  }
+
+  /**
+   * Getter for the event queue.
+   *
+   * @return \CRM_Queue_Queue
+   */
+  public function getEventQueue(): CRM_Queue_Queue {
+    return $this->eventQueue;
+  }
+
+  /**
+   * Getter for the email queue.
+   *
+   * @return \CRM_Queue_Queue
+   */
+  public function getEmailQueue(): CRM_Queue_Queue {
+    return $this->emailQueue;
+  }
+
+  public function getGroups(): array {
+    return $this->groups;
+  }
+
+  public function addToGroups(GroupMailingList $group): void {
+    $this->groups[] = $group;
+  }
+
+  public function getEvents(): array {
+    return $this->events;
+  }
+
+  public function addToEvents(EventMailingList $event): void {
+    $this->events[] = $event;
+  }
+
+  public function getEmails(): array {
+    return $this->emails;
+  }
+
+  public function addToEmails(string $email): void {
+    $this->emails[] = $email;
+  }
+
+  /**
+   * Stores an instance of the given class in the queue helper singleton.
+   * Meant to be passed as callback to the queue.
+   *
+   * @param int $entityId
+   * @param string $class
+   *
+   * @return void
+   * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+   */
+  public static function storeInstance(int $entityId, string $class): void {
+
+    // Throw exception if class is invalid
+    if ($class != GroupMailingList::class &&
+      $class != ADGroupMailingList::class &&
+      $class != EventMailingList::class) {
+      throw new MailinglistException(
+        "Invalid class '$class'",
+        MailinglistException::ERROR_CODE_INVALID_CLASS
+      );
+    }
+
+    // Instantiate the mailing list object
+    $instance = new $class();
+    $instance->load($entityId);
+
+    // Store instance in the queue helper singleton
+    match ($class) {
+      GroupMailingList::class, ADGroupMailingList::class => self::getInstance()->addToGroups($instance),
+      EventMailingList::class => self::getInstance()->addToEvents($instance),
+      default => throw new MailinglistException(
+        "Invalid class '$class'",
+        MailinglistException::ERROR_CODE_INVALID_CLASS
+      ),
+    };
+  }
+}

Civi/Mailinglistsync/Utils.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Civi\Mailinglistsync;
+
+use Civi\Api4\LocationType;
+use Civi\Mailinglistsync\Exceptions\MailinglistException;
+use CRM_Mailinglistsync_ExtensionUtil as E;
+
+/**
+ * Gets the location type IDs for mailing list email-addresses either from
+ * the database or from the cache.
+ *
+ * @return array
+ * @throws \Civi\Mailinglistsync\Exceptions\MailinglistException
+ */
+function getLocationTypes(): array {
+  // Try to get location types from cache
+  $locationTypes = \Civi::cache()->get(E::SHORT_NAME . '_location_types');
+
+  // Get location types from database if not in cache
+  if ($locationTypes === NULL) {
+    $locationTypeNames = [
+      GroupMailingList::getLocationTypeName(),
+      ADGroupMailingList::getLocationTypeName(),
+      EventMailingList::getLocationTypeName(),
+    ];
+    try {
+      $result = LocationType::get()
+        ->addSelect('id', 'name')
+        ->addWhere('name', 'IN', $locationTypeNames)
+        ->execute()
+        ->getArrayCopy();
+      $locationTypes = [];
+      foreach ($result as $locationType) {
+        $locationTypes[$locationType['id']] = $locationType['name'];
+      }
+    }
+    catch (\Exception $e) {
+      throw new MailinglistException(
+        E::ts('Could not get location types'),
+        MailinglistException::ERROR_CODE_GET_LOCATION_TYPES_FAILED,
+      );
+    }
+    // Cache location types
+    \Civi::cache()->set(E::SHORT_NAME . '_location_types', $locationTypes);
+  }
+
+  return $locationTypes;
+}