[FIX] website_blog: next post looping when last post

The next post button at the bottom of an article was stuck when getting to
the last page. A cookie storing the *all* the visited posts was used
to determine the next one according to a non-stored (so not working) and
unexpected criteria 'ranking'. Also could get articles from other blog.

Instead of this whole broken logic, simple loop through articles by classic
order and go back to first one when at the end.
Better looping algorithm can be used in master where ranking is stored.
Fixes #3097, opw 614559

addons/website_blog/controllers/main.py

@@ -199,17 +199,12 @@ def blog_post(self, blog, blog_post, tag_id=None, page=1, enable_editor=None, **
         tags = tag_obj.browse(cr, uid, tag_obj.search(cr, uid, [], context=context), context=context)
 
         # Find next Post
-        visited_blogs = request.httprequest.cookies.get('visited_blogs') or ''
-        visited_ids = filter(None, visited_blogs.split(','))
-        visited_ids = map(lambda x: int(x), visited_ids)
-        if blog_post.id not in visited_ids:
-            visited_ids.append(blog_post.id)
-        next_post_id = blog_post_obj.search(cr, uid, [
-            ('id', 'not in', visited_ids),
-        ], order='ranking desc', limit=1, context=context)
-        if not next_post_id:
-            next_post_id = blog_post_obj.search(cr, uid, [('id', '!=', blog.id)], order='ranking desc', limit=1, context=context)
-        next_post = next_post_id and blog_post_obj.browse(cr, uid, next_post_id[0], context=context) or False
+        all_post_ids = blog_post_obj.search(cr, uid, [('blog_id', '=', blog.id)], context=context)
+        # should always return at least the current post
+        current_blog_post_index = all_post_ids.index(blog_post.id)
+        next_post_id = all_post_ids[0 if current_blog_post_index == len(all_post_ids) - 1 \
+                            else current_blog_post_index + 1]
+        next_post = next_post_id and blog_post_obj.browse(cr, uid, next_post_id, context=context) or False
 
         values = {
             'tags': tags,
@@ -227,7 +222,6 @@ def blog_post(self, blog, blog_post, tag_id=None, page=1, enable_editor=None, **
             'comments': comments,
         }
         response = request.website.render("website_blog.blog_post_complete", values)
-        response.set_cookie('visited_blogs', ','.join(map(str, visited_ids)))
 
         request.session[request.session_id] = request.session.get(request.session_id, [])
         if not (blog_post.id in request.session[request.session_id]):