--- /dev/null
+<?php
+
+namespace Drupal\content_moderation;
+
+use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\workflows\Transition;
+
+/**
+ * Validates whether a certain state transition is allowed.
+ */
+class StateTransitionValidation implements StateTransitionValidationInterface {
+
+ /**
+ * The moderation information service.
+ *
+ * @var \Drupal\content_moderation\ModerationInformationInterface
+ */
+ protected $moderationInfo;
+
+ /**
+ * Stores the possible state transitions.
+ *
+ * @var array
+ */
+ protected $possibleTransitions = [];
+
+ /**
+ * Constructs a new StateTransitionValidation.
+ *
+ * @param \Drupal\content_moderation\ModerationInformationInterface $moderation_info
+ * The moderation information service.
+ */
+ public function __construct(ModerationInformationInterface $moderation_info) {
+ $this->moderationInfo = $moderation_info;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getValidTransitions(ContentEntityInterface $entity, AccountInterface $user) {
+ $workflow = $this->moderationInfo->getWorkflowForEntity($entity);
+ $current_state = $entity->moderation_state->value ? $workflow->getState($entity->moderation_state->value) : $workflow->getTypePlugin()->getInitialState($workflow, $entity);
+
+ return array_filter($current_state->getTransitions(), function(Transition $transition) use ($workflow, $user) {
+ return $user->hasPermission('use ' . $workflow->id() . ' transition ' . $transition->id());
+ });
+ }
+
+}