don't link cover to google books if own cover

core/models.py

@@ -1121,6 +1121,12 @@ class Work(models.Model):
     def openlibrary_url(self):
         return "http://openlibrary.org" + self.openlibrary_id
     
+    def uses_google_cover(self):
+        if self.preferred_edition and self.preferred_edition.cover_image:
+            return False
+        else: 
+            return self.googlebooks_id
+    
     def cover_image_small(self):
         if self.preferred_edition and self.preferred_edition.cover_image_small():
             return self.preferred_edition.cover_image_small()

frontend/templates/work.html

@@ -71,7 +71,7 @@
                 <div class="js-maincol-inner">
                     <div id="content-block">
                         <div class="book-detail">
-                            {% if work.googlebooks_id %}
+                            {% if work.uses_google_cover %}
                                 <div id="book-detail-img">
                                     <a href="{{ work.googlebooks_url }}">
                                     <img src="{{ work.cover_image_thumbnail }}" alt="Find {{ work.title }} at Google Books" title="Find {{ work.title }} at Google Books" width="131" height="192" /></a>