Merge pull request #7 from LearningLocker/issue/valid_context

Validates context for activity.

src/StatementBase.php

@@ -13,19 +13,38 @@ class StatementBase extends Element {
   ];
   protected $required_props = ['actor', 'verb', 'object'];
 
-  public function validate() {
-    $errors = [];
+  private function validateVoider($errors) {
     $verb_id = $this->getPropValue('verb.id');
     $object_type = $this->getPropValue('object.objectType');
 
     // Validates voider.
-    if (
-      $verb_id === 'http://adlnet.gov/expapi/verbs/voided' &&
-      $object_type !== 'StatementRef'
-    ) {
+    if ($verb_id === 'http://adlnet.gov/expapi/verbs/voided' && $object_type !== 'StatementRef') {
       $errors[] = new Error("`object.objectType` must be `StatementRef` not `$object_type` when voiding");
     }
 
+    return $errors;
+  }
+
+  private function validateContextForActivity($errors) {
+    $object_type = $this->getPropValue('object.objectType');
+    $is_activity = $object_type === 'Activity';
+
+    // Validates context for activity.
+    if ($this->getPropValue('context.revision') !== null && !$is_activity) {
+      $errors[] = new Error("`context.revision` must only be used if `object.objectType` is `Activity` not `$object_type`");
+    }
+    if ($this->getPropValue('context.platform') !== null && !$is_activity) {
+      $errors[] = new Error("`context.platform` must only be used if `object.objectType` is `Activity` not `$object_type`");
+    }
+
+    return $errors;
+  }
+
+  public function validate() {
+    $errors = [];
+    $errors = $this->validateVoider($errors);
+    $errors = $this->validateContextForActivity($errors);
+
     return array_merge($errors, parent::validate());
   }
 }