finished the helper function in thumbnail/helpers

ckanext/odsh/pdf_to_thumbnail/helpers.py

-from ckan.lib.helpers import resource_display_name
 
+from ckan.lib.helpers import is_url, url_for
 
 def thumbnail_namespace(filename):
     return "/" + filename
 
-def get_name_from_last_pdf_upload(package):
+def get_download_link_for_thumbnail(package):
     resources = package.get('resources')
     for resource in resources[::-1]:
         url_type =resource.get('url_type')
         mimetype = resource.get('mimetype')
         if url_type == 'upload' and mimetype == 'application/pdf':
-            return resource_display_name(resource)
+            package_id = resource.get('package_id')
+            resource_id = resource.get('id')
+            pre_resource_url = resource.get('url')
+            if is_url(pre_resource_url):
+                url_resource = pre_resource_url
+            else:
+                url_resource = url_for(controller='package',
+                                    action='resource_download',
+                                    id=package_id,
+                                    resource_id=resource_id,
+                                    filename=pre_resource_url,
+                                    qualified = True)
+            
+            
+            return url_resource

ckanext/odsh/pdf_to_thumbnail/plugin.py

@@ -54,5 +54,5 @@ class ThumbnailPlugin(plugins.SingletonPlugin):
         
         return {
                 'thumbnail_namespace':thumbnail_helpers.thumbnail_namespace,
-                'thumbnail_get_name_from_last_pdf_upload':thumbnail_helpers.get_name_from_last_pdf_upload 
+                'thumbail_get_download_link':thumbnail_helpers.get_download_link_for_thumbnail
                 }

ckanext/odsh/templates/package/read.html

@@ -5,7 +5,7 @@
 {% set successor_url = h.collection_get_successor(pkg) %}
 {% set predecessor_url = h.collection_get_predecessor(pkg) %}
 {% set latest_collection_member = h.collection_get_latest_member(pkg) %}
-{% set thumbnail_name = h.thumbnail_get_name_from_last_pdf_upload(pkg) %}
+{% set thumbnail_url = h.thumbail_get_download_link(pkg) %}
 
 {% block breadcrumb_content %}
 {% if pkg %}
@@ -80,7 +80,8 @@
 <section id="dataset-preview">
     <h3>{{ _('Preview') }}:</h3>
     <div class="container-preview-large">
-        <a href="#">
+        <a href="{{ thumbnail_url }}">
+
             <img src= "{{ picture }}" alt= "Vorschau"/>
         </a>
     </div>