gistfile1.diff

diff --git a/block_page.services.yml b/block_page.services.yml
index 8df43da..da46708 100644
--- a/block_page.services.yml
+++ b/block_page.services.yml
@@ -12,3 +12,6 @@ services:
   plugin.manager.page_variant:
     class: Drupal\block_page\Plugin\PageVariantManager
     parent: default_plugin_manager
+  context.handler:
+    class: Drupal\block_page\ContextHandler
+    arguments: ['@typed_data_manager']
diff --git a/src/ContextHandler.php b/src/ContextHandler.php
new file mode 100644
index 0000000..3b04290
--- /dev/null
+++ b/src/ContextHandler.php
@@ -0,0 +1,109 @@
+<?php
+/**
+* @file
+* Contains \Drupal\block_page\ContextHandler.php.
+*/
+
+namespace Drupal\block_page;
+
+use Drupal\Component\Plugin\PluginManagerInterface;
+use Drupal\Core\TypedData\DataDefinitionInterface;
+use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\TypedDataManager;
+
+class ContextHandler {
+
+  /**
+  * @var \Drupal\Core\TypedData\TypedDataManager
+  */
+  protected $typed_data;
+
+  public function __construct(TypedDataManager $typed_data) {
+    $this->typed_data = $typed_data;
+  }
+
+  public function checkRequirements(array $contexts, array $requirements) {
+    $results = array();
+    foreach ($requirements as $name => $requirement) {
+      if (!$requirement instanceof DataDefinitionInterface) {
+        // @todo make a custom exception class.
+        throw new \Exception(sprintf('The %s requirement must be an instance of DataDefinitionInterface.', $name));
+      }
+      if ($requirement->isRequired()) {
+        foreach ($contexts as $context_object) {
+          $context = $context_object->getContextDefinition();
+          if (!$context instanceof DataDefinitionInterface) {
+            // @todo make a custom exception class.
+            throw new \Exception('An illegal context was passed, all contexts must be an instance of DataDefinitionInterface.');
+          }
+          if ($requirement->getDataType() == $context->getDataType()) {
+            foreach ($requirement->getConstraints() as $constraint_name => $constraint) {
+              if ($context->getConstraint($constraint_name) != $constraint) {
+                continue 2;
+              }
+            }
+          }
+          $results[$name] = TRUE;
+        }
+      }
+      else {
+        $results[$name] = TRUE;
+      }
+    }
+    return count($requirements) == count($results);
+  }
+
+  public function getAvailablePlugins(array $contexts, PluginManagerInterface $manager) {
+    $plugins = $manager->getDefinitions();
+    $available_plugins = array();
+    foreach ($plugins as $plugin_id => $plugin) {
+      if (isset($plugin['context'])) {
+        $plugin_contexts = $plugin['context'];
+        $requirements = array();
+        foreach ($plugin_contexts as $context_id => $plugin_context) {
+          $definition = $this->typed_data->getDefinition($plugin_context['type']);
+          $definition['type'] = $plugin_context['type'];
+          if (isset($plugin_context['constraints'])) {
+            if (!isset($definition['constraints'])) {
+              $definition['constraints'] = $plugin_context['constraints'];
+            }
+            else {
+              $definition['constraints'] += $plugin_context['constraints'];
+            }
+          }
+          if (!isset($definition['required'])) {
+            $definition['required'] = TRUE;
+          }
+          $requirements[$context_id] = new DataDefinition($definition);
+        }
+        if ($this->checkRequirements($contexts, $requirements)) {
+          $available_plugins[$plugin_id] = $plugin;
+        }
+      }
+      else {
+        $available_plugins[$plugin_id] = $plugin;
+      }
+    }
+    return $available_plugins;
+  }
+
+  public function getValidContexts(array $contexts, DataDefinitionInterface $definition) {
+    $valid = array();
+    foreach ($contexts as $id => $context) {
+      if (!$context instanceof DataDefinitionInterface) {
+        // @todo make a custom exception class.
+        throw new \Exception('An illegal context was passed, all contexts must be an instance of DataDefinitionInterface.');
+      }
+      if ($definition->getDataType() == $context->getDataType()) {
+        foreach ($definition->getConstraints() as $constraint_name => $constraint) {
+          if ($context->getConstraint($constraint_name) != $constraint) {
+            continue 2;
+          }
+        }
+      }
+      $valid[$id] = $context;
+    }
+    return $valid;
+  }
+
+}
diff --git a/src/Controller/BlockPageController.php b/src/Controller/BlockPageController.php
index 072b458..7548911 100644
--- a/src/Controller/BlockPageController.php
+++ b/src/Controller/BlockPageController.php
@@ -95,7 +95,9 @@ class BlockPageController extends ControllerBase {
       '#links' => array(),
     );
     $condition_manager = \Drupal::service('plugin.manager.condition');
-    foreach ($condition_manager->getDefinitions() as $access_id => $access_condition) {
+    $context_handler = \Drupal::service('context.handler');
+    $available_plugins = $context_handler->getAvailablePlugins($block_page->getContextValues(), $condition_manager);
+    foreach ($available_plugins as $access_id => $access_condition) {
       $build['#links'][$access_id] = array(
         'title' => $access_condition['label'],
         'route_name' => 'block_page.access_condition_add',
diff --git a/src/EventSubscriber/CurrentUserContext.php b/src/EventSubscriber/CurrentUserContext.php
index 26db991..cec3773 100644
--- a/src/EventSubscriber/CurrentUserContext.php
+++ b/src/EventSubscriber/CurrentUserContext.php
@@ -9,6 +9,7 @@ namespace Drupal\block_page\EventSubscriber;
 
 use Drupal\block_page\Event\BlockPageContextEvent;
 use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Plugin\Context\Context;
 use Drupal\Core\Session\AccountProxyInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
@@ -52,7 +53,9 @@ class CurrentUserContext implements EventSubscriberInterface {
    */
   public function onBlockPageContext(BlockPageContextEvent $event) {
     $current_user = $this->userStorage->load($this->accountProxy->getAccount()->id());
-    $event->getBlockPage()->setContextValue('current_user', $current_user);
+    $context = new Context(['type' => 'entity', 'constraints' => ['EntityType' => 'user']]);
+    $context->setContextValue($current_user);
+    $event->getBlockPage()->setContextValue('current_user', $context);
   }
 
   /**