Cleaned up TopicUserSpec, introduces clearing of pinned topics

lib/pinned_check.rb

@@ -0,0 +1,24 @@
+# Helps us determine whether a topic should be displayed as pinned or not,
+# taking into account anonymous users and users who have dismissed it
+class PinnedCheck
+
+  def initialize(topic, topic_user=nil)
+    @topic, @topic_user = topic, topic_user
+  end
+
+  def pinned?
+
+    # If the topic isn't pinned the answer is false
+    return false if @topic.pinned_at.blank?
+
+    # If the user is anonymous or hasn't entered the topic, the value is always true
+    return true if @topic_user.blank?
+
+    # If the user hasn't cleared the pin, it's true
+    return true if @topic_user.cleared_pinned_at.blank?
+
+    # The final check is to see whether the cleared the pin before or after it was last pinned
+    @topic_user.cleared_pinned_at < @topic.pinned_at
+  end
+
+end